DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Implementation

Mercurial (cdf352f02ac4)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* JS script descriptor. */

#ifndef vm_JSScript_h
#define vm_JSScript_h

#include "mozilla/ArrayUtils.h"
#include "mozilla/Atomics.h"
#include "mozilla/Maybe.h"
#include "mozilla/MaybeOneOf.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/RefPtr.h"
#include "mozilla/Span.h"
#include "mozilla/Tuple.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Utf8.h"
#include "mozilla/Variant.h"

#include <type_traits>  // std::is_same
#include <utility>      // std::move

#include "jstypes.h"

#include "frontend/BinASTRuntimeSupport.h"
#include "frontend/NameAnalysisTypes.h"
#include "frontend/SourceNotes.h"  // SrcNote
#include "gc/Barrier.h"
#include "gc/Rooting.h"
#include "jit/IonCode.h"
#include "js/CompileOptions.h"
#include "js/UbiNode.h"
#include "js/UniquePtr.h"
#include "js/Utility.h"
#include "util/StructuredSpewer.h"
#include "vm/BigIntType.h"
#include "vm/BytecodeIterator.h"
#include "vm/BytecodeLocation.h"
#include "vm/BytecodeUtil.h"
#include "vm/JSAtom.h"
#include "vm/NativeObject.h"
#include "vm/Scope.h"
#include "vm/Shape.h"
#include "vm/SharedImmutableStringsCache.h"
#include "vm/SharedStencil.h"
#include "vm/Time.h"

namespace JS {
struct ScriptSourceInfo;
template <typename UnitT>
class SourceText;
}  // namespace JS

namespace js {

namespace coverage {
class LCovSource;
}  // namespace coverage

namespace jit {
class AutoKeepJitScripts;
struct BaselineScript;
struct IonScriptCounts;
class JitScript;
}  // namespace jit

class AutoSweepJitScript;
class ModuleObject;
class RegExpObject;
class ScriptSourceHolder;
class SourceCompressionTask;
class Shape;
class DebugAPI;
class DebugScript;

namespace frontend {
struct CompilationInfo;
class FunctionIndex;
class FunctionBox;
class ModuleSharedContext;
class ScriptStencil;
}  // namespace frontend

class ScriptCounts {
 public:
  typedef mozilla::Vector<PCCounts, 0, SystemAllocPolicy> PCCountsVector;

  inline ScriptCounts();
  inline explicit ScriptCounts(PCCountsVector&& jumpTargets);
  inline ScriptCounts(ScriptCounts&& src);
  inline ~ScriptCounts();

  inline ScriptCounts& operator=(ScriptCounts&& src);

  // Return the counter used to count the number of visits. Returns null if
  // the element is not found.
  PCCounts* maybeGetPCCounts(size_t offset);
  const PCCounts* maybeGetPCCounts(size_t offset) const;

  // PCCounts are stored at jump-target offsets. This function looks for the
  // previous PCCount which is in the same basic block as the current offset.
  PCCounts* getImmediatePrecedingPCCounts(size_t offset);

  // Return the counter used to count the number of throws. Returns null if
  // the element is not found.
  const PCCounts* maybeGetThrowCounts(size_t offset) const;

  // Throw counts are stored at the location of each throwing
  // instruction. This function looks for the previous throw count.
  //
  // Note: if the offset of the returned count is higher than the offset of
  // the immediate preceding PCCount, then this throw happened in the same
  // basic block.
  const PCCounts* getImmediatePrecedingThrowCounts(size_t offset) const;

  // Return the counter used to count the number of throws. Allocate it if
  // none exists yet. Returns null if the allocation failed.
  PCCounts* getThrowCounts(size_t offset);

  size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf);

 private:
  friend class ::JSScript;
  friend struct ScriptAndCounts;

  // This sorted array is used to map an offset to the number of times a
  // branch got visited.
  PCCountsVector pcCounts_;

  // This sorted vector is used to map an offset to the number of times an
  // instruction throw.
  PCCountsVector throwCounts_;

  // Information about any Ion compilations for the script.
  jit::IonScriptCounts* ionCounts_;
};

// The key of these side-table hash maps are intentionally not traced GC
// references to JSScript. Instead, we use bare pointers and manually fix up
// when objects could have moved (see Zone::fixupScriptMapsAfterMovingGC) and
// remove when the realm is destroyed (see Zone::clearScriptCounts and
// Zone::clearScriptNames). They essentially behave as weak references, except
// that the references are not cleared early by the GC. They must be non-strong
// references because the tables are kept at the Zone level and otherwise the
// table keys would keep scripts alive, thus keeping Realms alive, beyond their
// expected lifetimes. However, We do not use actual weak references (e.g. as
// used by WeakMap tables provided in gc/WeakMap.h) because they would be
// collected before the calls to the JSScript::finalize function which are used
// to aggregate code coverage results on the realm.
//
// Note carefully, however, that there is an exceptional case for which we *do*
// want the JSScripts to be strong references (and thus traced): when the
// --dump-bytecode command line option or the PCCount JSFriend API is used,
// then the scripts for all counts must remain alive. See
// Zone::traceScriptTableRoots() for more details.
//
// TODO: Clean this up by either aggregating coverage results in some other
// way, or by tweaking sweep ordering.
using UniqueScriptCounts = js::UniquePtr<ScriptCounts>;
using ScriptCountsMap = HashMap<BaseScript*, UniqueScriptCounts,
                                DefaultHasher<BaseScript*>, SystemAllocPolicy>;

// The 'const char*' for the function name is a pointer within the LCovSource's
// LifoAlloc and will be discarded at the same time.
using ScriptLCovEntry = mozilla::Tuple<coverage::LCovSource*, const char*>;
using ScriptLCovMap = HashMap<BaseScript*, ScriptLCovEntry,
                              DefaultHasher<BaseScript*>, SystemAllocPolicy>;

#ifdef MOZ_VTUNE
using ScriptVTuneIdMap = HashMap<BaseScript*, uint32_t,
                                 DefaultHasher<BaseScript*>, SystemAllocPolicy>;
#endif

using UniqueDebugScript = js::UniquePtr<DebugScript, JS::FreePolicy>;
using DebugScriptMap = HashMap<BaseScript*, UniqueDebugScript,
                               DefaultHasher<BaseScript*>, SystemAllocPolicy>;

class ScriptSource;

struct ScriptSourceChunk {
  ScriptSource* ss = nullptr;
  uint32_t chunk = 0;

  ScriptSourceChunk() = default;

  ScriptSourceChunk(ScriptSource* ss, uint32_t chunk) : ss(ss), chunk(chunk) {
    MOZ_ASSERT(valid());
  }

  bool valid() const { return ss != nullptr; }

  bool operator==(const ScriptSourceChunk& other) const {
    return ss == other.ss && chunk == other.chunk;
  }
};

struct ScriptSourceChunkHasher {
  using Lookup = ScriptSourceChunk;

  static HashNumber hash(const ScriptSourceChunk& ssc) {
    return mozilla::AddToHash(DefaultHasher<ScriptSource*>::hash(ssc.ss),
                              ssc.chunk);
  }
  static bool match(const ScriptSourceChunk& c1, const ScriptSourceChunk& c2) {
    return c1 == c2;
  }
};

template <typename Unit>
using EntryUnits = mozilla::UniquePtr<Unit[], JS::FreePolicy>;

// The uncompressed source cache contains *either* UTF-8 source data *or*
// UTF-16 source data.  ScriptSourceChunk implies a ScriptSource that
// contains either UTF-8 data or UTF-16 data, so the nature of the key to
// Map below indicates how each SourceData ought to be interpreted.
using SourceData = mozilla::UniquePtr<void, JS::FreePolicy>;

template <typename Unit>
inline SourceData ToSourceData(EntryUnits<Unit> chars) {
  static_assert(std::is_same<SourceData::DeleterType,
                             typename EntryUnits<Unit>::DeleterType>::value,
                "EntryUnits and SourceData must share the same deleter "
                "type, that need not know the type of the data being freed, "
                "for the upcast below to be safe");
  return SourceData(chars.release());
}

class UncompressedSourceCache {
  using Map = HashMap<ScriptSourceChunk, SourceData, ScriptSourceChunkHasher,
                      SystemAllocPolicy>;

 public:
  // Hold an entry in the source data cache and prevent it from being purged on
  // GC.
  class AutoHoldEntry {
    UncompressedSourceCache* cache_ = nullptr;
    ScriptSourceChunk sourceChunk_ = {};
    SourceData data_ = nullptr;

   public:
    explicit AutoHoldEntry() = default;

    ~AutoHoldEntry() {
      if (cache_) {
        MOZ_ASSERT(sourceChunk_.valid());
        cache_->releaseEntry(*this);
      }
    }

    template <typename Unit>
    void holdUnits(EntryUnits<Unit> units) {
      MOZ_ASSERT(!cache_);
      MOZ_ASSERT(!sourceChunk_.valid());
      MOZ_ASSERT(!data_);

      data_ = ToSourceData(std::move(units));
    }

   private:
    void holdEntry(UncompressedSourceCache* cache,
                   const ScriptSourceChunk& sourceChunk) {
      // Initialise the holder for a specific cache and script source.
      // This will hold on to the cached source chars in the event that
      // the cache is purged.
      MOZ_ASSERT(!cache_);
      MOZ_ASSERT(!sourceChunk_.valid());
      MOZ_ASSERT(!data_);

      cache_ = cache;
      sourceChunk_ = sourceChunk;
    }

    void deferDelete(SourceData data) {
      // Take ownership of source chars now the cache is being purged. Remove
      // our reference to the ScriptSource which might soon be destroyed.
      MOZ_ASSERT(cache_);
      MOZ_ASSERT(sourceChunk_.valid());
      MOZ_ASSERT(!data_);

      cache_ = nullptr;
      sourceChunk_ = ScriptSourceChunk();

      data_ = std::move(data);
    }

    const ScriptSourceChunk& sourceChunk() const { return sourceChunk_; }
    friend class UncompressedSourceCache;
  };

 private:
  UniquePtr<Map> map_ = nullptr;
  AutoHoldEntry* holder_ = nullptr;

 public:
  UncompressedSourceCache() = default;

  template <typename Unit>
  const Unit* lookup(const ScriptSourceChunk& ssc, AutoHoldEntry& asp);

  bool put(const ScriptSourceChunk& ssc, SourceData data, AutoHoldEntry& asp);

  void purge();

  size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf);

 private:
  void holdEntry(AutoHoldEntry& holder, const ScriptSourceChunk& ssc);
  void releaseEntry(AutoHoldEntry& holder);
};

template <typename Unit>
struct SourceTypeTraits;

template <>
struct SourceTypeTraits<mozilla::Utf8Unit> {
  using CharT = char;
  using SharedImmutableString = js::SharedImmutableString;

  static const mozilla::Utf8Unit* units(const SharedImmutableString& string) {
    // Casting |char| data to |Utf8Unit| is safe because |Utf8Unit|
    // contains a |char|.  See the long comment in |Utf8Unit|'s definition.
    return reinterpret_cast<const mozilla::Utf8Unit*>(string.chars());
  }

  static char* toString(const mozilla::Utf8Unit* units) {
    auto asUnsigned =
        const_cast<unsigned char*>(mozilla::Utf8AsUnsignedChars(units));
    return reinterpret_cast<char*>(asUnsigned);
  }

  static UniqueChars toCacheable(EntryUnits<mozilla::Utf8Unit> str) {
    // The cache only stores strings of |char| or |char16_t|, and right now
    // it seems best not to gunk up the cache with |Utf8Unit| too.  So
    // cache |Utf8Unit| strings by interpreting them as |char| strings.
    char* chars = toString(str.release());
    return UniqueChars(chars);
  }
};

template <>
struct SourceTypeTraits<char16_t> {
  using CharT = char16_t;
  using SharedImmutableString = js::SharedImmutableTwoByteString;

  static const char16_t* units(const SharedImmutableString& string) {
    return string.chars();
  }

  static char16_t* toString(const char16_t* units) {
    return const_cast<char16_t*>(units);
  }

  static UniqueTwoByteChars toCacheable(EntryUnits<char16_t> str) {
    return UniqueTwoByteChars(std::move(str));
  }
};

// Synchronously compress the source of |script|, for testing purposes.
extern MOZ_MUST_USE bool SynchronouslyCompressSource(
    JSContext* cx, JS::Handle<BaseScript*> script);

// Retrievable source can be retrieved using the source hook (and therefore
// need not be XDR'd, can be discarded if desired because it can always be
// reconstituted later, etc.).
enum class SourceRetrievable { Yes, No };

// [SMDOC] ScriptSource
//
// This class abstracts over the source we used to compile from. The current
// representation may transition to different modes in order to save memory.
// Abstractly the source may be one of UTF-8, UTF-16, or BinAST. The data
// itself may be unavailable, retrieveable-using-source-hook, compressed, or
// uncompressed. If source is retrieved or decompressed for use, we may update
// the ScriptSource to hold the result.
class ScriptSource {
  // NOTE: While ScriptSources may be compressed off thread, they are only
  // modified by the main thread, and all members are always safe to access
  // on the main thread.

  friend class SourceCompressionTask;
  friend bool SynchronouslyCompressSource(JSContext* cx,
                                          JS::Handle<BaseScript*> script);

 private:
  // Common base class of the templated variants of PinnedUnits<T>.
  class PinnedUnitsBase {
   protected:
    PinnedUnitsBase** stack_ = nullptr;
    PinnedUnitsBase* prev_ = nullptr;

    ScriptSource* source_;

    explicit PinnedUnitsBase(ScriptSource* source) : source_(source) {}
  };

 public:
  // Any users that wish to manipulate the char buffer of the ScriptSource
  // needs to do so via PinnedUnits for GC safety. A GC may compress
  // ScriptSources. If the source were initially uncompressed, then any raw
  // pointers to the char buffer would now point to the freed, uncompressed
  // chars. This is analogous to Rooted.
  template <typename Unit>
  class PinnedUnits : public PinnedUnitsBase {
    const Unit* units_;

   public:
    PinnedUnits(JSContext* cx, ScriptSource* source,
                UncompressedSourceCache::AutoHoldEntry& holder, size_t begin,
                size_t len);

    ~PinnedUnits();

    const Unit* get() const { return units_; }

    const typename SourceTypeTraits<Unit>::CharT* asChars() const {
      return SourceTypeTraits<Unit>::toString(get());
    }
  };

 private:
  // Missing source text that isn't retrievable using the source hook.  (All
  // ScriptSources initially begin in this state.  Users that are compiling
  // source text will overwrite |data| to store a different state.)
  struct Missing {};

  // Source that can be retrieved using the registered source hook.  |Unit|
  // records the source type so that source-text coordinates in functions and
  // scripts that depend on this |ScriptSource| are correct.
  template <typename Unit>
  struct Retrievable {
    // The source hook and script URL required to retrieve source are stored
    // elsewhere, so nothing is needed here.  It'd be better hygiene to store
    // something source-hook-like in each |ScriptSource| that needs it, but that
    // requires reimagining a source-hook API that currently depends on source
    // hooks being uniquely-owned pointers...
  };

  // Uncompressed source text. Templates distinguish if we are interconvertable
  // to |Retrievable| or not.
  template <typename Unit>
  class UncompressedData {
    typename SourceTypeTraits<Unit>::SharedImmutableString string_;

   public:
    explicit UncompressedData(
        typename SourceTypeTraits<Unit>::SharedImmutableString str)
        : string_(std::move(str)) {}

    const Unit* units() const { return SourceTypeTraits<Unit>::units(string_); }

    size_t length() const { return string_.length(); }
  };

  template <typename Unit, SourceRetrievable CanRetrieve>
  class Uncompressed : public UncompressedData<Unit> {
    using Base = UncompressedData<Unit>;

   public:
    using Base::Base;
  };

  // Compressed source text. Templates distinguish if we are interconvertable
  // to |Retrievable| or not.
  template <typename Unit>
  struct CompressedData {
    // Single-byte compressed text, regardless whether the original text
    // was single-byte or two-byte.
    SharedImmutableString raw;
    size_t uncompressedLength;

    CompressedData(SharedImmutableString raw, size_t uncompressedLength)
        : raw(std::move(raw)), uncompressedLength(uncompressedLength) {}
  };

  template <typename Unit, SourceRetrievable CanRetrieve>
  struct Compressed : public CompressedData<Unit> {
    using Base = CompressedData<Unit>;

   public:
    using Base::Base;
  };

  // BinAST source.
  struct BinAST {
    SharedImmutableString string;
    UniquePtr<frontend::BinASTSourceMetadata> metadata;

    BinAST(SharedImmutableString&& str,
           UniquePtr<frontend::BinASTSourceMetadata> metadata)
        : string(std::move(str)), metadata(std::move(metadata)) {}
  };

  // The set of currently allowed encoding modes.
  using SourceType =
      mozilla::Variant<Compressed<mozilla::Utf8Unit, SourceRetrievable::Yes>,
                       Uncompressed<mozilla::Utf8Unit, SourceRetrievable::Yes>,
                       Compressed<mozilla::Utf8Unit, SourceRetrievable::No>,
                       Uncompressed<mozilla::Utf8Unit, SourceRetrievable::No>,
                       Compressed<char16_t, SourceRetrievable::Yes>,
                       Uncompressed<char16_t, SourceRetrievable::Yes>,
                       Compressed<char16_t, SourceRetrievable::No>,
                       Uncompressed<char16_t, SourceRetrievable::No>,
                       Retrievable<mozilla::Utf8Unit>, Retrievable<char16_t>,
                       Missing, BinAST>;

  //
  // Start of fields.
  //

  mozilla::Atomic<uint32_t, mozilla::ReleaseAcquire> refs = {};

  // An id for this source that is unique across the process. This can be used
  // to refer to this source from places that don't want to hold a strong
  // reference on the source itself.
  //
  // This is a 32 bit ID and could overflow, in which case the ID will not be
  // unique anymore.
  uint32_t id_ = 0;

  // Source data (as a mozilla::Variant).
  SourceType data = SourceType(Missing());

  // If the GC calls triggerConvertToCompressedSource with PinnedUnits present,
  // the first PinnedUnits (that is, bottom of the stack) will install the
  // compressed chars upon destruction.
  //
  // Retrievability isn't part of the type here because uncompressed->compressed
  // transitions must preserve existing retrievability.
  PinnedUnitsBase* pinnedUnitsStack_ = nullptr;
  mozilla::MaybeOneOf<CompressedData<mozilla::Utf8Unit>,
                      CompressedData<char16_t>>
      pendingCompressed_;

  // The filename of this script.
  mozilla::Maybe<SharedImmutableString> filename_;

  // If this ScriptSource was generated by a code-introduction mechanism such
  // as |eval| or |new Function|, the debugger needs access to the "raw"
  // filename of the top-level script that contains the eval-ing code.  To
  // keep track of this, we must preserve the original outermost filename (of
  // the original introducer script), so that instead of a filename of
  // "foo.js line 30 > eval line 10 > Function", we can obtain the original
  // raw filename of "foo.js".
  //
  // In the case described above, this field will be set to to the original raw
  // filename from above, otherwise it will be mozilla::Nothing.
  mozilla::Maybe<SharedImmutableString> introducerFilename_;

  mozilla::Maybe<SharedImmutableTwoByteString> displayURL_;
  mozilla::Maybe<SharedImmutableTwoByteString> sourceMapURL_;

  // The bytecode cache encoder is used to encode only the content of function
  // which are delazified.  If this value is not nullptr, then each delazified
  // function should be recorded before their first execution.
  // This value is logically owned by the canonical ScriptSourceObject, and
  // will be released in the canonical SSO's finalizer.
  UniquePtr<XDRIncrementalEncoder> xdrEncoder_ = nullptr;

  // Instant at which the first parse of this source ended, or null
  // if the source hasn't been parsed yet.
  //
  // Used for statistics purposes, to determine how much time code spends
  // syntax parsed before being full parsed, to help determine whether
  // our syntax parse vs. full parse heuristics are correct.
  mozilla::TimeStamp parseEnded_;

  // A string indicating how this source code was introduced into the system.
  // This is a constant, statically allocated C string, so does not need memory
  // management.
  const char* introductionType_ = nullptr;

  // Bytecode offset in caller script that generated this code.  This is
  // present for eval-ed code, as well as "new Function(...)"-introduced
  // scripts.
  mozilla::Maybe<uint32_t> introductionOffset_;

  // If this source is for Function constructor, the position of ")" after
  // parameter list in the source.  This is used to get function body.
  // 0 for other cases.
  uint32_t parameterListEnd_ = 0;

  // Line number within the file where this source starts.
  uint32_t startLine_ = 0;

  // See: CompileOptions::mutedErrors.
  bool mutedErrors_ = false;

  // Set to true if parser saw  asmjs directives.
  bool containsAsmJS_ = false;

  //
  // End of fields.
  //

  // How many ids have been handed out to sources.
  static mozilla::Atomic<uint32_t, mozilla::SequentiallyConsistent> idCount_;

  template <typename Unit>
  const Unit* chunkUnits(JSContext* cx,
                         UncompressedSourceCache::AutoHoldEntry& holder,
                         size_t chunk);

  // Return a string containing the chars starting at |begin| and ending at
  // |begin + len|.
  //
  // Warning: this is *not* GC-safe! Any chars to be handed out must use
  // PinnedUnits. See comment below.
  template <typename Unit>
  const Unit* units(JSContext* cx, UncompressedSourceCache::AutoHoldEntry& asp,
                    size_t begin, size_t len);

 public:
  // When creating a JSString* from TwoByte source characters, we don't try to
  // to deflate to Latin1 for longer strings, because this can be slow.
  static const size_t SourceDeflateLimit = 100;

  explicit ScriptSource() : id_(++idCount_) {}

  void finalizeGCData();
  ~ScriptSource();

  void incref() { refs++; }
  void decref() {
    MOZ_ASSERT(refs != 0);
    if (--refs == 0) {
      js_delete(this);
    }
  }
  MOZ_MUST_USE bool initFromOptions(JSContext* cx,
                                    const JS::ReadOnlyCompileOptions& options);

  /**
   * The minimum script length (in code units) necessary for a script to be
   * eligible to be compressed.
   */
  static constexpr size_t MinimumCompressibleLength = 256;

  mozilla::Maybe<SharedImmutableString> getOrCreateStringZ(JSContext* cx,
                                                           UniqueChars&& str);
  mozilla::Maybe<SharedImmutableTwoByteString> getOrCreateStringZ(
      JSContext* cx, UniqueTwoByteChars&& str);

 private:
  class LoadSourceMatcher;

 public:
  // Attempt to load usable source for |ss| -- source text on which substring
  // operations and the like can be performed.  On success return true and set
  // |*loaded| to indicate whether usable source could be loaded; otherwise
  // return false.
  static bool loadSource(JSContext* cx, ScriptSource* ss, bool* loaded);

  // Assign source data from |srcBuf| to this recently-created |ScriptSource|.
  template <typename Unit>
  MOZ_MUST_USE bool assignSource(JSContext* cx,
                                 const JS::ReadOnlyCompileOptions& options,
                                 JS::SourceText<Unit>& srcBuf);

  bool hasSourceText() const {
    return hasUncompressedSource() || hasCompressedSource();
  }
  bool hasBinASTSource() const { return data.is<BinAST>(); }

  void setBinASTSourceMetadata(frontend::BinASTSourceMetadata* metadata) {
    MOZ_ASSERT(hasBinASTSource());
    data.as<BinAST>().metadata.reset(metadata);
  }
  frontend::BinASTSourceMetadata* binASTSourceMetadata() const {
    MOZ_ASSERT(hasBinASTSource());
    return data.as<BinAST>().metadata.get();
  }

 private:
  template <typename Unit>
  struct UncompressedDataMatcher {
    template <SourceRetrievable CanRetrieve>
    const UncompressedData<Unit>* operator()(
        const Uncompressed<Unit, CanRetrieve>& u) {
      return &u;
    }

    template <typename T>
    const UncompressedData<Unit>* operator()(const T&) {
      MOZ_CRASH(
          "attempting to access uncompressed data in a ScriptSource not "
          "containing it");
      return nullptr;
    }
  };

 public:
  template <typename Unit>
  const UncompressedData<Unit>* uncompressedData() {
    return data.match(UncompressedDataMatcher<Unit>());
  }

 private:
  template <typename Unit>
  struct CompressedDataMatcher {
    template <SourceRetrievable CanRetrieve>
    const CompressedData<Unit>* operator()(
        const Compressed<Unit, CanRetrieve>& c) {
      return &c;
    }

    template <typename T>
    const CompressedData<Unit>* operator()(const T&) {
      MOZ_CRASH(
          "attempting to access compressed data in a ScriptSource not "
          "containing it");
      return nullptr;
    }
  };

 public:
  template <typename Unit>
  const CompressedData<Unit>* compressedData() {
    return data.match(CompressedDataMatcher<Unit>());
  }

 private:
  struct BinASTDataMatcher {
    void* operator()(const BinAST& b) {
      return const_cast<char*>(b.string.chars());
    }

    void notBinAST() { MOZ_CRASH("ScriptSource isn't backed by BinAST data"); }

    template <typename T>
    void* operator()(const T&) {
      notBinAST();
      return nullptr;
    }
  };

 public:
  void* binASTData() { return data.match(BinASTDataMatcher()); }

 private:
  struct HasUncompressedSource {
    template <typename Unit, SourceRetrievable CanRetrieve>
    bool operator()(const Uncompressed<Unit, CanRetrieve>&) {
      return true;
    }

    template <typename Unit, SourceRetrievable CanRetrieve>
    bool operator()(const Compressed<Unit, CanRetrieve>&) {
      return false;
    }

    template <typename Unit>
    bool operator()(const Retrievable<Unit>&) {
      return false;
    }

    bool operator()(const BinAST&) { return false; }

    bool operator()(const Missing&) { return false; }
  };

 public:
  bool hasUncompressedSource() const {
    return data.match(HasUncompressedSource());
  }

 private:
  template <typename Unit>
  struct IsUncompressed {
    template <SourceRetrievable CanRetrieve>
    bool operator()(const Uncompressed<Unit, CanRetrieve>&) {
      return true;
    }

    template <typename T>
    bool operator()(const T&) {
      return false;
    }
  };

 public:
  template <typename Unit>
  bool isUncompressed() const {
    return data.match(IsUncompressed<Unit>());
  }

 private:
  struct HasCompressedSource {
    template <typename Unit, SourceRetrievable CanRetrieve>
    bool operator()(const Compressed<Unit, CanRetrieve>&) {
      return true;
    }

    template <typename T>
    bool operator()(const T&) {
      return false;
    }
  };

 public:
  bool hasCompressedSource() const { return data.match(HasCompressedSource()); }

 private:
  template <typename Unit>
  struct IsCompressed {
    template <SourceRetrievable CanRetrieve>
    bool operator()(const Compressed<Unit, CanRetrieve>&) {
      return true;
    }

    template <typename T>
    bool operator()(const T&) {
      return false;
    }
  };

 public:
  template <typename Unit>
  bool isCompressed() const {
    return data.match(IsCompressed<Unit>());
  }

 private:
  template <typename Unit>
  struct SourceTypeMatcher {
    template <template <typename C, SourceRetrievable R> class Data,
              SourceRetrievable CanRetrieve>
    bool operator()(const Data<Unit, CanRetrieve>&) {
      return true;
    }

    template <template <typename C, SourceRetrievable R> class Data,
              typename NotUnit, SourceRetrievable CanRetrieve>
    bool operator()(const Data<NotUnit, CanRetrieve>&) {
      return false;
    }

    bool operator()(const Retrievable<Unit>&) {
      MOZ_CRASH("source type only applies where actual text is available");
      return false;
    }

    template <typename NotUnit>
    bool operator()(const Retrievable<NotUnit>&) {
      return false;
    }

    bool operator()(const BinAST&) {
      MOZ_CRASH("doesn't make sense to ask source type of BinAST data");
      return false;
    }

    bool operator()(const Missing&) {
      MOZ_CRASH("doesn't make sense to ask source type when missing");
      return false;
    }
  };

 public:
  template <typename Unit>
  bool hasSourceType() const {
    return data.match(SourceTypeMatcher<Unit>());
  }

 private:
  struct UncompressedLengthMatcher {
    template <typename Unit, SourceRetrievable CanRetrieve>
    size_t operator()(const Uncompressed<Unit, CanRetrieve>& u) {
      return u.length();
    }

    template <typename Unit, SourceRetrievable CanRetrieve>
    size_t operator()(const Compressed<Unit, CanRetrieve>& u) {
      return u.uncompressedLength;
    }

    template <typename Unit>
    size_t operator()(const Retrievable<Unit>&) {
      MOZ_CRASH("ScriptSource::length on a missing-but-retrievable source");
      return 0;
    }

    size_t operator()(const BinAST& b) { return b.string.length(); }

    size_t operator()(const Missing& m) {
      MOZ_CRASH("ScriptSource::length on a missing source");
      return 0;
    }
  };

 public:
  size_t length() const {
    MOZ_ASSERT(hasSourceText() || hasBinASTSource());
    return data.match(UncompressedLengthMatcher());
  }

  JSLinearString* substring(JSContext* cx, size_t start, size_t stop);
  JSLinearString* substringDontDeflate(JSContext* cx, size_t start,
                                       size_t stop);

  MOZ_MUST_USE bool appendSubstring(JSContext* cx, js::StringBuffer& buf,
                                    size_t start, size_t stop);

  void setParameterListEnd(uint32_t parameterListEnd) {
    parameterListEnd_ = parameterListEnd;
  }

  bool isFunctionBody() { return parameterListEnd_ != 0; }
  JSLinearString* functionBodyString(JSContext* cx);

  void addSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf,
                              JS::ScriptSourceInfo* info) const;

 private:
  // Overwrites |data| with the uncompressed data from |source|.
  //
  // This function asserts nothing about |data|.  Users should use assertions to
  // double-check their own understandings of the |data| state transition being
  // performed.
  template <typename Unit>
  MOZ_MUST_USE bool setUncompressedSourceHelper(JSContext* cx,
                                                EntryUnits<Unit>&& source,
                                                size_t length,
                                                SourceRetrievable retrievable);

 public:
  // Initialize a fresh |ScriptSource| with unretrievable, uncompressed source.
  template <typename Unit>
  MOZ_MUST_USE bool initializeUnretrievableUncompressedSource(
      JSContext* cx, EntryUnits<Unit>&& source, size_t length);

  // Set the retrieved source for a |ScriptSource| whose source was recorded as
  // missing but retrievable.
  template <typename Unit>
  MOZ_MUST_USE bool setRetrievedSource(JSContext* cx, EntryUnits<Unit>&& source,
                                       size_t length);

  MOZ_MUST_USE bool tryCompressOffThread(JSContext* cx);

  // *Trigger* the conversion of this ScriptSource from containing uncompressed
  // |Unit|-encoded source to containing compressed source.  Conversion may not
  // be complete when this function returns: it'll be delayed if there's ongoing
  // use of the uncompressed source via |PinnedUnits|, in which case conversion
  // won't occur until the outermost |PinnedUnits| is destroyed.
  //
  // Compressed source is in bytes, no matter that |Unit| might be |char16_t|.
  // |sourceLength| is the length in code units (not bytes) of the uncompressed
  // source.
  template <typename Unit>
  void triggerConvertToCompressedSource(SharedImmutableString compressed,
                                        size_t sourceLength);

  // Initialize a fresh ScriptSource as containing unretrievable compressed
  // source of the indicated original encoding.
  template <typename Unit>
  MOZ_MUST_USE bool initializeWithUnretrievableCompressedSource(
      JSContext* cx, UniqueChars&& raw, size_t rawLength, size_t sourceLength);

#if defined(JS_BUILD_BINAST)

  /*
   * Do not take ownership of the given `buf`. Store the canonical, shared
   * and de-duplicated version. If there is no extant shared version of
   * `buf`, make a copy.
   */
  MOZ_MUST_USE bool setBinASTSourceCopy(JSContext* cx, const uint8_t* buf,
                                        size_t len);

  const uint8_t* binASTSource();

#endif /* JS_BUILD_BINAST */

 private:
  void performTaskWork(SourceCompressionTask* task);

  struct TriggerConvertToCompressedSourceFromTask {
    ScriptSource* const source_;
    SharedImmutableString& compressed_;

    TriggerConvertToCompressedSourceFromTask(ScriptSource* source,
                                             SharedImmutableString& compressed)
        : source_(source), compressed_(compressed) {}

    template <typename Unit, SourceRetrievable CanRetrieve>
    void operator()(const Uncompressed<Unit, CanRetrieve>&) {
      source_->triggerConvertToCompressedSource<Unit>(std::move(compressed_),
                                                      source_->length());
    }

    template <typename Unit, SourceRetrievable CanRetrieve>
    void operator()(const Compressed<Unit, CanRetrieve>&) {
      MOZ_CRASH(
          "can't set compressed source when source is already compressed -- "
          "ScriptSource::tryCompressOffThread shouldn't have queued up this "
          "task?");
    }

    template <typename Unit>
    void operator()(const Retrievable<Unit>&) {
      MOZ_CRASH("shouldn't compressing unloaded-but-retrievable source");
    }

    void operator()(const BinAST&) {
      MOZ_CRASH("doesn't make sense to set compressed source for BinAST data");
    }

    void operator()(const Missing&) {
      MOZ_CRASH(
          "doesn't make sense to set compressed source for missing source -- "
          "ScriptSource::tryCompressOffThread shouldn't have queued up this "
          "task?");
    }
  };

  template <typename Unit>
  void convertToCompressedSource(SharedImmutableString compressed,
                                 size_t uncompressedLength);

  template <typename Unit>
  void performDelayedConvertToCompressedSource();

  void triggerConvertToCompressedSourceFromTask(
      SharedImmutableString compressed);

 private:
  // It'd be better to make this function take <XDRMode, Unit>, as both
  // specializations of this function contain nested Unit-parametrized
  // helper classes that do everything the function needs to do.  But then
  // we'd need template function partial specialization to hold XDRMode
  // constant while varying Unit, so that idea's no dice.
  template <XDRMode mode>
  MOZ_MUST_USE XDRResult xdrUnretrievableUncompressedSource(
      XDRState<mode>* xdr, uint8_t sourceCharSize, uint32_t uncompressedLength);

 public:
  const char* filename() const {
    return filename_ ? filename_.ref().chars() : nullptr;
  }
  MOZ_MUST_USE bool setFilename(JSContext* cx, const char* filename);
  MOZ_MUST_USE bool setFilename(JSContext* cx, UniqueChars&& filename);

  const char* introducerFilename() const {
    return introducerFilename_ ? introducerFilename_.ref().chars() : filename();
  }
  MOZ_MUST_USE bool setIntroducerFilename(JSContext* cx, const char* filename);
  MOZ_MUST_USE bool setIntroducerFilename(JSContext* cx,
                                          UniqueChars&& filename);

  bool hasIntroductionType() const { return introductionType_; }
  const char* introductionType() const {
    MOZ_ASSERT(hasIntroductionType());
    return introductionType_;
  }

  uint32_t id() const { return id_; }

  // Display URLs
  MOZ_MUST_USE bool setDisplayURL(JSContext* cx, const char16_t* url);
  MOZ_MUST_USE bool setDisplayURL(JSContext* cx, UniqueTwoByteChars&& url);
  bool hasDisplayURL() const { return displayURL_.isSome(); }
  const char16_t* displayURL() { return displayURL_.ref().chars(); }

  // Source maps
  MOZ_MUST_USE bool setSourceMapURL(JSContext* cx, const char16_t* url);
  MOZ_MUST_USE bool setSourceMapURL(JSContext* cx, UniqueTwoByteChars&& url);
  bool hasSourceMapURL() const { return sourceMapURL_.isSome(); }
  const char16_t* sourceMapURL() { return sourceMapURL_.ref().chars(); }

  bool mutedErrors() const { return mutedErrors_; }

  uint32_t startLine() const { return startLine_; }

  bool hasIntroductionOffset() const { return introductionOffset_.isSome(); }
  uint32_t introductionOffset() const { return introductionOffset_.value(); }
  void setIntroductionOffset(uint32_t offset) {
    MOZ_ASSERT(!hasIntroductionOffset());
    MOZ_ASSERT(offset <= (uint32_t)INT32_MAX);
    introductionOffset_.emplace(offset);
  }

  bool containsAsmJS() const { return containsAsmJS_; }
  void setContainsAsmJS() { containsAsmJS_ = true; }

  // Return wether an XDR encoder is present or not.
  bool hasEncoder() const { return bool(xdrEncoder_); }

  // Create a new XDR encoder, and encode the top-level JSScript. The result
  // of the encoding would be available in the |buffer| provided as argument,
  // as soon as |xdrFinalize| is called and all xdr function calls returned
  // successfully.
  bool xdrEncodeTopLevel(JSContext* cx, HandleScript script);

  // Encode a delazified JSFunction.  In case of errors, the XDR encoder is
  // freed and the |buffer| provided as argument to |xdrEncodeTopLevel| is
  // considered undefined.
  //
  // The |sourceObject| argument is the object holding the current
  // ScriptSource.
  bool xdrEncodeFunction(JSContext* cx, HandleFunction fun,
                         HandleScriptSourceObject sourceObject);

  // Linearize the encoded content in the |buffer| provided as argument to
  // |xdrEncodeTopLevel|, and free the XDR encoder.  In case of errors, the
  // |buffer| is considered undefined.
  bool xdrFinalizeEncoder(JS::TranscodeBuffer& buffer);

  const mozilla::TimeStamp parseEnded() const { return parseEnded_; }
  // Inform `this` source that it has been fully parsed.
  void recordParseEnded() {
    MOZ_ASSERT(parseEnded_.IsNull());
    parseEnded_ = ReallyNow();
  }

 private:
  template <typename Unit,
            template <typename U, SourceRetrievable CanRetrieve> class Data,
            XDRMode mode>
  static void codeRetrievable(ScriptSource* ss);

  template <typename Unit, XDRMode mode>
  static MOZ_MUST_USE XDRResult codeUncompressedData(XDRState<mode>* const xdr,
                                                     ScriptSource* const ss);

  template <typename Unit, XDRMode mode>
  static MOZ_MUST_USE XDRResult codeCompressedData(XDRState<mode>* const xdr,
                                                   ScriptSource* const ss);

  template <XDRMode mode>
  static MOZ_MUST_USE XDRResult codeBinASTData(XDRState<mode>* const xdr,
                                               ScriptSource* const ss);

  template <typename Unit, XDRMode mode>
  static void codeRetrievableData(ScriptSource* ss);

  template <XDRMode mode>
  static MOZ_MUST_USE XDRResult xdrData(XDRState<mode>* const xdr,
                                        ScriptSource* const ss);

 public:
  template <XDRMode mode>
  static MOZ_MUST_USE XDRResult
  XDR(XDRState<mode>* xdr, const mozilla::Maybe<JS::CompileOptions>& options,
      MutableHandle<ScriptSourceHolder> ss);

  void trace(JSTracer* trc);
};

class ScriptSourceHolder {
  ScriptSource* ss;

 public:
  ScriptSourceHolder() : ss(nullptr) {}
  explicit ScriptSourceHolder(ScriptSource* ss) : ss(ss) { ss->incref(); }
  ~ScriptSourceHolder() {
    if (ss) {
      ss->decref();
    }
  }
  void reset(ScriptSource* newss) {
    // incref before decref just in case ss == newss.
    if (newss) {
      newss->incref();
    }
    if (ss) {
      ss->decref();
    }
    ss = newss;
  }
  ScriptSource* get() const { return ss; }

  void trace(JSTracer* trc) { ss->trace(trc); }
};

// [SMDOC] ScriptSourceObject
//
// ScriptSourceObject stores the ScriptSource and GC pointers related to it.
//
// ScriptSourceObjects can be cloned when we clone the JSScript (in order to
// execute the script in a different compartment). In this case we create a new
// SSO that stores (a wrapper for) the original SSO in its "canonical slot".
// The canonical SSO is always used for the private, introductionScript,
// element, elementAttributeName slots. This means their accessors may return an
// object in a different compartment, hence the "unwrapped" prefix.
//
// Note that we don't clone the SSO when cloning the script for a different
// realm in the same compartment, so sso->realm() does not necessarily match the
// script's realm.
//
// We need ScriptSourceObject (instead of storing these GC pointers in the
// ScriptSource itself) to properly account for cross-zone pointers: the
// canonical SSO will be stored in the wrapper map if necessary so GC will do
// the right thing.
class ScriptSourceObject : public NativeObject {
  static const JSClassOps classOps_;

  static ScriptSourceObject* createInternal(JSContext* cx, ScriptSource* source,
                                            HandleObject canonical);

  bool isCanonical() const {
    return &getReservedSlot(CANONICAL_SLOT).toObject() == this;
  }
  ScriptSourceObject* unwrappedCanonical() const;

 public:
  static const JSClass class_;

  static void trace(JSTracer* trc, JSObject* obj);
  static void finalize(JSFreeOp* fop, JSObject* obj);

  static ScriptSourceObject* create(JSContext* cx, ScriptSource* source);
  static ScriptSourceObject* clone(JSContext* cx, HandleScriptSourceObject sso);

  // Initialize those properties of this ScriptSourceObject whose values
  // are provided by |options|, re-wrapping as necessary.
  static bool initFromOptions(JSContext* cx, HandleScriptSourceObject source,
                              const JS::ReadOnlyCompileOptions& options);

  static bool initElementProperties(JSContext* cx,
                                    HandleScriptSourceObject source,
                                    HandleObject element,
                                    HandleString elementAttrName);

  bool hasSource() const { return !getReservedSlot(SOURCE_SLOT).isUndefined(); }
  ScriptSource* source() const {
    return static_cast<ScriptSource*>(getReservedSlot(SOURCE_SLOT).toPrivate());
  }

  JSObject* unwrappedElement() const {
    return unwrappedCanonical()->getReservedSlot(ELEMENT_SLOT).toObjectOrNull();
  }
  const Value& unwrappedElementAttributeName() const {
    const Value& v =
        unwrappedCanonical()->getReservedSlot(ELEMENT_PROPERTY_SLOT);
    MOZ_ASSERT(!v.isMagic());
    return v;
  }
  BaseScript* unwrappedIntroductionScript() const {
    Value value =
        unwrappedCanonical()->getReservedSlot(INTRODUCTION_SCRIPT_SLOT);
    if (value.isUndefined()) {
      return nullptr;
    }
    return value.toGCThing()->as<BaseScript>();
  }

  void setPrivate(JSRuntime* rt, const Value& value);

  Value canonicalPrivate() const {
    Value value = getReservedSlot(PRIVATE_SLOT);
    MOZ_ASSERT_IF(!isCanonical(), value.isUndefined());
    return value;
  }

 private:
  enum {
    SOURCE_SLOT = 0,
    CANONICAL_SLOT,
    ELEMENT_SLOT,
    ELEMENT_PROPERTY_SLOT,
    INTRODUCTION_SCRIPT_SLOT,
    PRIVATE_SLOT,
    RESERVED_SLOTS
  };
};

enum class GeneratorKind : bool { NotGenerator, Generator };
enum class FunctionAsyncKind : bool { SyncFunction, AsyncFunction };

// ScriptWarmUpData represents a pointer-sized field in BaseScript that stores
// one of the following using low-bit tags:
//
// * The enclosing BaseScript. This is only used while this script is lazy and
//   its containing script is also lazy. This outer script must be compiled
//   before the current script can in order to correctly build the scope chain.
//
// * The enclosing Scope. This is only used while this script is lazy and its
//   containing script is compiled. This is the outer scope chain that will be
//   used to compile this scipt.
//
// * The script's warm-up count. This is only used until the script has a
//   JitScript. The Baseline Interpreter and JITs use the warm-up count stored
//   in JitScript.
//
// * A pointer to the JitScript, when the script is warm enough for the Baseline
//   Interpreter.
//
class ScriptWarmUpData {
  uintptr_t data_ = ResetState();

 private:
  static constexpr uintptr_t NumTagBits = 2;
  static constexpr uint32_t MaxWarmUpCount = UINT32_MAX >> NumTagBits;

 public:
  // Public only for the JITs.
  static constexpr uintptr_t TagMask = (1 << NumTagBits) - 1;
  static constexpr uintptr_t JitScriptTag = 0;
  static constexpr uintptr_t EnclosingScriptTag = 1;
  static constexpr uintptr_t EnclosingScopeTag = 2;
  static constexpr uintptr_t WarmUpCountTag = 3;

 private:
  // A gc-safe value to clear to.
  constexpr uintptr_t ResetState() { return 0 | WarmUpCountTag; }

  template <uintptr_t Tag>
  inline void setTaggedPtr(void* ptr) {
    static_assert(Tag <= TagMask, "Tag must fit in TagMask");
    MOZ_ASSERT((uintptr_t(ptr) & TagMask) == 0);
    data_ = uintptr_t(ptr) | Tag;
  }

  template <typename T, uintptr_t Tag>
  inline T getTaggedPtr() const {
    static_assert(Tag <= TagMask, "Tag must fit in TagMask");
    MOZ_ASSERT((data_ & TagMask) == Tag);
    return reinterpret_cast<T>(data_ & ~TagMask);
  }

  void setWarmUpCount(uint32_t count) {
    if (count > MaxWarmUpCount) {
      count = MaxWarmUpCount;
    }
    data_ = (uintptr_t(count) << NumTagBits) | WarmUpCountTag;
  }

 public:
  void trace(JSTracer* trc);

  bool isEnclosingScript() const {
    return (data_ & TagMask) == EnclosingScriptTag;
  }
  bool isEnclosingScope() const {
    return (data_ & TagMask) == EnclosingScopeTag;
  }
  bool isWarmUpCount() const { return (data_ & TagMask) == WarmUpCountTag; }
  bool isJitScript() const { return (data_ & TagMask) == JitScriptTag; }

  // NOTE: To change type safely, 'clear' the old tagged value and then 'init'
  //       the new one. This will notify the GC appropriately.

  BaseScript* toEnclosingScript() const {
    return getTaggedPtr<BaseScript*, EnclosingScriptTag>();
  }
  inline void initEnclosingScript(BaseScript* enclosingScript);
  inline void clearEnclosingScript();

  Scope* toEnclosingScope() const {
    return getTaggedPtr<Scope*, EnclosingScopeTag>();
  }
  inline void initEnclosingScope(Scope* enclosingScope);
  inline void clearEnclosingScope();

  uint32_t toWarmUpCount() const {
    MOZ_ASSERT(isWarmUpCount());
    return data_ >> NumTagBits;
  }
  void resetWarmUpCount(uint32_t count) {
    MOZ_ASSERT(isWarmUpCount());
    setWarmUpCount(count);
  }
  void incWarmUpCount(uint32_t amount) {
    MOZ_ASSERT(isWarmUpCount());
    data_ += uintptr_t(amount) << NumTagBits;
  }

  jit::JitScript* toJitScript() const {
    return getTaggedPtr<jit::JitScript*, JitScriptTag>();
  }
  void initJitScript(jit::JitScript* jitScript) {
    MOZ_ASSERT(isWarmUpCount());
    setTaggedPtr<JitScriptTag>(jitScript);
  }
  void clearJitScript() {
    MOZ_ASSERT(isJitScript());
    data_ = ResetState();
  }
} JS_HAZ_GC_POINTER;

static_assert(sizeof(ScriptWarmUpData) == sizeof(uintptr_t),
              "JIT code depends on ScriptWarmUpData being pointer-sized");

struct FieldInitializers {
  static constexpr uint32_t MaxInitializers = INT32_MAX;

#ifdef DEBUG
  bool valid = false;
#endif

  // This struct will eventually have a vector of constant values for optimizing
  // field initializers.
  uint32_t numFieldInitializers = 0;

  explicit FieldInitializers(uint32_t numFieldInitializers)
      :
#ifdef DEBUG
        valid(true),
#endif
        numFieldInitializers(numFieldInitializers) {
  }

  static FieldInitializers Invalid() { return FieldInitializers(); }

 private:
  FieldInitializers() = default;
};

// [SMDOC] - JSScript data layout (unshared)
//
// PrivateScriptData stores variable-length data associated with a script.
// Abstractly a PrivateScriptData consists of all these arrays:
//
//   * A non-empty array of GCCellPtr in gcthings()
//
// Accessing this array just requires calling the appropriate public
// Span-computing function.
class alignas(uintptr_t) PrivateScriptData final {
  uint32_t ngcthings = 0;

  js::FieldInitializers fieldInitializers_ = js::FieldInitializers::Invalid();

  // Translate an offset into a concrete pointer.
  template <typename T>
  T* offsetToPointer(size_t offset) {
    uintptr_t base = reinterpret_cast<uintptr_t>(this);
    uintptr_t elem = base + offset;
    return reinterpret_cast<T*>(elem);
  }

  // Helpers for creating initializing trailing data
  template <typename T>
  void initElements(size_t offset, size_t length);

  // Size to allocate
  static size_t AllocationSize(uint32_t ngcthings);

  // Initialize header and PackedSpans
  explicit PrivateScriptData(uint32_t ngcthings);

 public:
  static constexpr size_t offsetOfGCThings() {
    return sizeof(PrivateScriptData);
  }

  // Accessors for typed array spans.
  mozilla::Span<JS::GCCellPtr> gcthings() {
    size_t offset = offsetOfGCThings();
    return mozilla::MakeSpan(offsetToPointer<JS::GCCellPtr>(offset), ngcthings);
  }

  void setFieldInitializers(FieldInitializers fieldInitializers) {
    fieldInitializers_ = fieldInitializers;
  }
  const FieldInitializers& getFieldInitializers() { return fieldInitializers_; }

  // Allocate a new PrivateScriptData. Headers and GCPtrs are initialized.
  static PrivateScriptData* new_(JSContext* cx, uint32_t ngcthings);

  template <XDRMode mode>
  static MOZ_MUST_USE XDRResult XDR(js::XDRState<mode>* xdr,
                                    js::HandleScript script,
                                    js::HandleScriptSourceObject sourceObject,
                                    js::HandleScope scriptEnclosingScope,
                                    js::HandleObject funOrMod);

  // Clone src script data into dst script.
  static bool Clone(JSContext* cx, js::HandleScript src, js::HandleScript dst,
                    js::MutableHandle<JS::GCVector<js::Scope*>> scopes);

  static bool InitFromStencil(JSContext* cx, js::HandleScript script,
                              const js::frontend::ScriptStencil& stencil);

  void trace(JSTracer* trc);

  size_t allocationSize() const;

  // PrivateScriptData has trailing data so isn't copyable or movable.
  PrivateScriptData(const PrivateScriptData&) = delete;
  PrivateScriptData& operator=(const PrivateScriptData&) = delete;
};

// Script data that is shareable across a JSRuntime.
class RuntimeScriptData final {
  // This class is reference counted as follows: each pointer from a JSScript
  // counts as one reference plus there may be one reference from the shared
  // script data table.
  mozilla::Atomic<uint32_t, mozilla::SequentiallyConsistent> refCount_ = {};

  uint32_t natoms_ = 0;

  js::UniquePtr<ImmutableScriptData> isd_ = nullptr;

  // NOTE: The raw bytes of this structure are used for hashing so use explicit
  // padding values as needed for predicatable results across compilers.

  friend class ::JSScript;

 private:
  // Layout of trailing arrays.
  size_t atomOffset() const { return offsetOfAtoms(); }

  // Size to allocate.
  static size_t AllocationSize(uint32_t natoms);

  template <typename T>
  void initElements(size_t offset, size_t length);

  // Initialize to GC-safe state.
  explicit RuntimeScriptData(uint32_t natoms);

 public:
  // Hash over the contents of RuntimeScriptData and its ImmutableScriptData.
  struct Hasher;

  static RuntimeScriptData* new_(JSContext* cx, uint32_t natoms);

  uint32_t refCount() const { return refCount_; }
  void AddRef() { refCount_++; }
  void Release() {
    MOZ_ASSERT(refCount_ != 0);
    uint32_t remain = --refCount_;
    if (remain == 0) {
      isd_ = nullptr;
      js_free(this);
    }
  }

  uint32_t natoms() const { return natoms_; }
  GCPtrAtom* atoms() {
    uintptr_t base = reinterpret_cast<uintptr_t>(this);
    return reinterpret_cast<GCPtrAtom*>(base + atomOffset());
  }

  mozilla::Span<const GCPtrAtom> atomsSpan() const {
    uintptr_t base = reinterpret_cast<uintptr_t>(this);
    const GCPtrAtom* p =
        reinterpret_cast<const GCPtrAtom*>(base + atomOffset());
    return mozilla::MakeSpan(p, natoms_);
  }

  static constexpr size_t offsetOfAtoms() { return sizeof(RuntimeScriptData); }

  static constexpr size_t offsetOfISD() {
    return offsetof(RuntimeScriptData, isd_);
  }

  void traceChildren(JSTracer* trc);

  template <XDRMode mode>
  static MOZ_MUST_USE XDRResult XDR(js::XDRState<mode>* xdr,
                                    js::HandleScript script);

  // Mark this RuntimeScriptData for use in a new zone.
  void markForCrossZone(JSContext* cx);

  static bool InitFromStencil(JSContext* cx, js::HandleScript script,
                              js::frontend::ScriptStencil& stencil);

  size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) {
    return mallocSizeOf(this) + mallocSizeOf(isd_.get());
  }

  // RuntimeScriptData has trailing data so isn't copyable or movable.
  RuntimeScriptData(const RuntimeScriptData&) = delete;
  RuntimeScriptData& operator=(const RuntimeScriptData&) = delete;
};

// Matches RuntimeScriptData objects that have the same atoms as well as
// contain the same bytes in their ImmutableScriptData.
struct RuntimeScriptData::Hasher {
  using Lookup = RefPtr<RuntimeScriptData>;

  static HashNumber hash(const Lookup& l) {
    mozilla::Span<const uint8_t> immutableData = l->isd_->immutableData();

    HashNumber h =
        mozilla::HashBytes(immutableData.data(), immutableData.size());
    return mozilla::AddToHash(
        h, mozilla::HashBytes(l->atoms(), l->natoms() * sizeof(GCPtrAtom)));
  }

  static bool match(RuntimeScriptData* entry, const Lookup& lookup) {
    return (entry->atomsSpan() == lookup->atomsSpan()) &&
           (entry->isd_->immutableData() == lookup->isd_->immutableData());
  }
};

using RuntimeScriptDataTable =
    HashSet<RuntimeScriptData*, RuntimeScriptData::Hasher, SystemAllocPolicy>;

// Range of characters in scriptSource which contains a script's source,
// that is, the range used by the Parser to produce a script.
//
// For most functions the fields point to the following locations.
//
//   function * f(a, b) { return a + b; }
//   ^          ^                        ^
//   |          |                        |
//   |          sourceStart              sourceEnd
//   |                                   |
//   toStringStart                       toStringEnd
//
// For the special case of class constructors, the spec requires us to use an
// alternate definition of toStringStart / toStringEnd.
//
//   class C { constructor() { this.field = 42; } }
//   ^         ^                                 ^ ^
//   |         |                                 | `---------`
//   |         sourceStart                       sourceEnd   |
//   |                                                       |
//   toStringStart                                           toStringEnd
//
// NOTE: These are counted in Code Units from the start of the script source.
struct SourceExtent {
  SourceExtent() = default;

  SourceExtent(uint32_t sourceStart, uint32_t sourceEnd, uint32_t toStringStart,
               uint32_t toStringEnd, uint32_t lineno, uint32_t column)
      : sourceStart(sourceStart),
        sourceEnd(sourceEnd),
        toStringStart(toStringStart),
        toStringEnd(toStringEnd),
        lineno(lineno),
        column(column) {}

  uint32_t sourceStart = 0;
  uint32_t sourceEnd = 0;
  uint32_t toStringStart = 0;
  uint32_t toStringEnd = 0;

  // Line and column of |sourceStart_| position.
  uint32_t lineno = 0;
  uint32_t column = 0;  // Count of Code Points
};

// [SMDOC] Script Representation (js::BaseScript)
//
// A "script" corresponds to a JavaScript function or a top-level (global, eval,
// module) body that will be executed using SpiderMonkey bytecode. Note that
// special forms such as asm.js do not use bytecode or the BaseScript type.
//
// BaseScript may be generated directly from the parser/emitter, or by cloning
// or deserializing another script. Cloning is typically used when a script is
// needed in multiple realms and we would like to avoid re-compiling.
//
// A single script may be shared by multiple JSFunctions in a realm when those
// function objects are used as closure. In this case, a single JSFunction is
// considered canonical (and often does not escape to script directly).
//
// A BaseScript may be in "lazy" form where the parser performs a syntax-only
// parse and saves minimal information. These lazy scripts must be recompiled
// from the source (generating bytecode) before they can execute in a process
// called "delazification". On GC memory pressure, a fully-compiled script may
// be converted back into lazy form by "relazification".
//
// A fully-initialized BaseScript can be identified with `hasBytecode()` and
// will have bytecode and set of GC-things such as scopes, inner-functions, and
// object/string literals. This is referred to as a "non-lazy" script.
//
// A lazy script has either an enclosing script or scope. Each script needs to
// know its enclosing scope in order to be fully compiled. If the parent is
// still lazy we track that script and will need to compile it first to know our
// own enclosing scope. This is because scope objects are not created until full
// compilation and bytecode generation.
//
//
// # Script Warm-Up #
//
// A script evolves its representation over time. As it becomes "hotter" we
// attach a stack of additional data-structures generated by the JITs to
// speed-up execution. This evolution may also be run in reverse, in order to
// reduce memory usage.
//
//              +-------------------------------------+
//              | ScriptSource                        |
//              |   Provides:   Source                |
//              |   Engine:     Parser                |
//              +-------------------------------------+
//                                v
//              +-------------------------------------+
//              | BaseScript                          |
//              |   Provides:   SourceExtent/Bindings |
//              |   Engine:     CompileLazyFunction   |
//              +-------------------------------------+
//                                v
//              +-------------------------------------+
//              | RuntimeScriptData                   |
//              |   Provides:   Bytecode              |
//              |   Engine:     Interpreter           |
//              +-------------------------------------+
//                                v
//              +-------------------------------------+
//              | JitScript                           |
//              |   Provides:   Inline Caches (ICs)   |
//              |   Engine:     BaselineInterpreter   |
//              +-------------------------------------+
//                                v
//              +-------------------------------------+
//              | BaselineScript                      |
//              |   Provides:   Native Code           |
//              |   Engine:     Baseline              |
//              +-------------------------------------+
//                                v
//              +-------------------------------------+
//              | IonScript                           |
//              |   Provides:   Optimized Native Code |
//              |   Engine:     IonMonkey             |
//              +-------------------------------------+
//
// NOTE: Scripts may be directly created with bytecode and skip the lazy script
//       form. This is always the case for top-level scripts.
class BaseScript : public gc::TenuredCell {
 public:
  // The definition of flags is shared with the frontend for consistency.
  using ImmutableFlags = ImmutableScriptFlagsEnum;
  using MutableFlags = MutableScriptFlagsEnum;

 protected:
  // Pointer to baseline->method()->raw(), ion->method()->raw(), a wasm jit
  // entry, the JIT's EnterInterpreter stub, or the lazy link stub. Must be
  // non-null (except on no-jit builds).
  uint8_t* jitCodeRaw_ = nullptr;

  // Object that determines what Realm this script is compiled for. For function
  // scripts this is the canonical function, otherwise it is the GlobalObject of
  // the realm.
  const GCPtrObject functionOrGlobal_ = {};

  // The ScriptSourceObject for this script. This is always same-compartment
  // with this script, but may be a clone if the original source object is in a
  // different compartment.
  const GCPtr<ScriptSourceObject*> sourceObject_ = {};

  // Position of the function in the source buffer. Both in terms of line/column
  // and code-unit offset.
  SourceExtent extent_ = {};

  // Immutable flags are a combination of parser options and bytecode
  // characteristics. These flags are preserved when serializing or copying this
  // script. These flags are static after script initialization with the key
  // exception that delazification / relazification may modify a subset of them.
  ImmutableScriptFlags immutableFlags_ = {};

  // Mutable flags store transient information used by subsystems such as the
  // debugger and the JITs. These flags are *not* preserved when serializing or
  // cloning since they are based on runtime state.
  MutableScriptFlags mutableFlags_ = {};

  // Variable-length data owned by this script. This stores one of:
  //    - GC pointers that bytecode references.
  //    - Inner-functions and bindings generated by syntax parse.
  //    - Nullptr, if no bytecode or inner functions.
  // This is updated as script is delazified and relazified.
  PrivateScriptData* data_ = nullptr;

  // Shareable script data. This includes runtime-wide atom pointers, bytecode,
  // and various script note structures. If the script is currently lazy, this
  // will be nullptr.
  RefPtr<js::RuntimeScriptData> sharedData_ = {};

  // Multi-purpose value that changes type as the script warms up from lazy form
  // to interpreted-bytecode to JITs. See: ScriptWarmUpData type for more info.
  ScriptWarmUpData warmUpData_ = {};

  // End of fields.

  BaseScript(uint8_t* stubEntry, JSObject* functionOrGlobal,
             ScriptSourceObject* sourceObject, SourceExtent extent,
             uint32_t immutableFlags)
      : jitCodeRaw_(stubEntry),
        functionOrGlobal_(functionOrGlobal),
        sourceObject_(sourceObject),
        extent_(extent),
        immutableFlags_(immutableFlags) {
    MOZ_ASSERT(functionOrGlobal->compartment() == sourceObject->compartment());
    MOZ_ASSERT(extent_.toStringStart <= extent_.sourceStart);
    MOZ_ASSERT(extent_.sourceStart <= extent_.sourceEnd);
    MOZ_ASSERT(extent_.sourceEnd <= extent_.toStringEnd);
  }

 public:
  static BaseScript* New(JSContext* cx, js::HandleObject functionOrGlobal,
                         js::HandleScriptSourceObject sourceObject,
                         const js::SourceExtent& extent,
                         uint32_t immutableFlags);

  // Create a lazy BaseScript without initializing any gc-things.
  static BaseScript* CreateRawLazy(JSContext* cx, uint32_t ngcthings,
                                   HandleFunction fun,
                                   HandleScriptSourceObject sourceObject,
                                   const SourceExtent& extent,
                                   uint32_t immutableFlags);

  // Create a lazy BaseScript and initialize gc-things with provided
  // closedOverBindings and innerFunctions.
  static BaseScript* CreateLazy(
      JSContext* cx, const frontend::CompilationInfo& compilationInfo,
      HandleFunction fun, HandleScriptSourceObject sourceObject,
      const frontend::AtomVector& closedOverBindings,
      const Vector<frontend::FunctionIndex>& innerFunctionIndexes,
      const SourceExtent& extent, uint32_t immutableFlags);

  uint8_t* jitCodeRaw() const { return jitCodeRaw_; }
  bool isUsingInterpreterTrampoline(JSRuntime* rt) const;

  // Canonical function for the script, if it has a function. For top-level
  // scripts this is nullptr.
  JSFunction* function() const {
    if (functionOrGlobal_->is<JSFunction>()) {
      return &functionOrGlobal_->as<JSFunction>();
    }
    return nullptr;
  }

  JS::Realm* realm() const { return functionOrGlobal_->nonCCWRealm(); }
  JS::Compartment* compartment() const {
    return functionOrGlobal_->compartment();
  }
  JS::Compartment* maybeCompartment() const { return compartment(); }
  inline JSPrincipals* principals() const;

  ScriptSourceObject* sourceObject() const { return sourceObject_; }
  ScriptSource* scriptSource() const { return sourceObject()->source(); }
  ScriptSource* maybeForwardedScriptSource() const;

  bool mutedErrors() const { return scriptSource()->mutedErrors(); }

  const char* filename() const { return scriptSource()->filename(); }
  const char* maybeForwardedFilename() const {
    return maybeForwardedScriptSource()->filename();
  }

  bool isBinAST() const { return scriptSource()->hasBinASTSource(); }

  uint32_t sourceStart() const { return extent_.sourceStart; }
  uint32_t sourceEnd() const { return extent_.sourceEnd; }
  uint32_t sourceLength() const {
    return extent_.sourceEnd - extent_.sourceStart;
  }
  uint32_t toStringStart() const { return extent_.toStringStart; }
  uint32_t toStringEnd() const { return extent_.toStringEnd; }
  SourceExtent extent() const { return extent_; }

  MOZ_MUST_USE bool appendSourceDataForToString(JSContext* cx,
                                                js::StringBuffer& buf);

#if defined(JS_BUILD_BINAST)
  // Set the position of the function in the source code.
  //
  // BinAST file format can put lazy functions after the entire tree, and in
  // that case BaseScript::CreateLazy will be called with dummy values for those
  // positions, and then once it reaches to the lazy function part, this
  // function is called to set those positions to correct value.
  void setPositions(uint32_t sourceStart, uint32_t sourceEnd,
                    uint32_t toStringStart, uint32_t toStringEnd) {
    MOZ_ASSERT(toStringStart <= sourceStart);
    MOZ_ASSERT(sourceStart <= sourceEnd);
    MOZ_ASSERT(sourceEnd <= toStringEnd);

    extent_.sourceStart = sourceStart;
    extent_.sourceEnd = sourceEnd;
    extent_.toStringStart = toStringStart;
    extent_.toStringEnd = toStringEnd;
  }

  void setColumn(uint32_t column) { extent_.column = column; }
#endif

  void setToStringEnd(uint32_t toStringEnd) {
    MOZ_ASSERT(extent_.toStringStart <= toStringEnd);
    MOZ_ASSERT(extent_.toStringEnd >= extent_.sourceEnd);
    extent_.toStringEnd = toStringEnd;
  }

  uint32_t lineno() const { return extent_.lineno; }
  uint32_t column() const { return extent_.column; }

 public:
  ImmutableScriptFlags immutableFlags() const { return immutableFlags_; }

  void addToImmutableFlags(const ImmutableScriptFlags& flags) {
    immutableFlags_ |= flags;
  }

  // ImmutableFlags accessors.
  MOZ_MUST_USE bool hasFlag(ImmutableFlags flag) const {
    return immutableFlags_.hasFlag(flag);
  }
  void setFlag(ImmutableFlags flag, bool b = true) {
    immutableFlags_.setFlag(flag, b);
  }
  void clearFlag(ImmutableFlags flag) { immutableFlags_.clearFlag(flag); }

  // MutableFlags accessors.
  MOZ_MUST_USE bool hasFlag(MutableFlags flag) const {
    return mutableFlags_.hasFlag(flag);
  }
  void setFlag(MutableFlags flag, bool b = true) {
    mutableFlags_.setFlag(flag, b);
  }
  void clearFlag(MutableFlags flag) { mutableFlags_.clearFlag(flag); }
  // Specific flag accessors

#define FLAG_GETTER(enumName, enumEntry, lowerName) \
 public:                                            \
  bool lowerName() const { return hasFlag(enumName::enumEntry); }

#define FLAG_GETTER_SETTER(enumName, enumEntry, setterLevel, lowerName, name) \
setterLevel:                                                                  \
  void set##name() { setFlag(enumName::enumEntry); }                          \
  void set##name(bool b) { setFlag(enumName::enumEntry, b); }                 \
  void clear##name() { clearFlag(enumName::enumEntry); }                      \
                                                                              \
 public:                                                                      \
  bool lowerName() const { return hasFlag(enumName::enumEntry); }

#define IMMUTABLE_FLAG_GETTER(lowerName, name) \
  FLAG_GETTER(ImmutableFlags, name, lowerName)
#define IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(lowerName, name) \
  FLAG_GETTER_SETTER(ImmutableFlags, name, public, lowerName, name)
#define MUTABLE_FLAG_GETTER(lowerName, name) \
  FLAG_GETTER(MutableFlags, name, lowerName)
#define MUTABLE_FLAG_GETTER_SETTER(lowerName, name) \
  FLAG_GETTER_SETTER(MutableFlags, name, public, lowerName, name)

  IMMUTABLE_FLAG_GETTER(noScriptRval, NoScriptRval)
  IMMUTABLE_FLAG_GETTER(selfHosted, SelfHosted)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(treatAsRunOnce, TreatAsRunOnce)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(forceStrict, ForceStrict)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(strict, Strict)
  IMMUTABLE_FLAG_GETTER(hasNonSyntacticScope, HasNonSyntacticScope)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(bindingsAccessedDynamically,
                                      BindingsAccessedDynamically)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(funHasExtensibleScope,
                                      FunHasExtensibleScope)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(hasCallSiteObj, HasCallSiteObj)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(hasModuleGoal, HasModuleGoal)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(functionHasThisBinding,
                                      FunctionHasThisBinding)
  // FunctionHasExtraBodyVarScope: custom logic below.
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(hasMappedArgsObj, HasMappedArgsObj)
  IMMUTABLE_FLAG_GETTER(hasInnerFunctions, HasInnerFunctions)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(needsHomeObject, NeedsHomeObject)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(isDerivedClassConstructor,
                                      IsDerivedClassConstructor)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(isLikelyConstructorWrapper,
                                      IsLikelyConstructorWrapper)
  IMMUTABLE_FLAG_GETTER(isGenerator, IsGenerator)
  IMMUTABLE_FLAG_GETTER(isAsync, IsAsync)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(hasRest, HasRest)
  IMMUTABLE_FLAG_GETTER(argumentsHasVarBinding, ArgumentsHasVarBinding)
  IMMUTABLE_FLAG_GETTER(isForEval, IsForEval)
  IMMUTABLE_FLAG_GETTER(isModule, IsModule)
  IMMUTABLE_FLAG_GETTER(needsFunctionEnvironmentObjects,
                        NeedsFunctionEnvironmentObjects)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(shouldDeclareArguments,
                                      ShouldDeclareArguments)
  IMMUTABLE_FLAG_GETTER(isFunction, IsFunction)
  IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC(hasDirectEval, HasDirectEval)
  IMMUTABLE_FLAG_GETTER(alwaysNeedsArgsObj, AlwaysNeedsArgsObj)

  MUTABLE_FLAG_GETTER_SETTER(hasRunOnce, HasRunOnce)
  MUTABLE_FLAG_GETTER_SETTER(hasBeenCloned, HasBeenCloned)
  MUTABLE_FLAG_GETTER_SETTER(hasScriptCounts, HasScriptCounts)
  MUTABLE_FLAG_GETTER_SETTER(hasDebugScript, HasDebugScript)
  MUTABLE_FLAG_GETTER_SETTER(allowRelazify, AllowRelazify)
  MUTABLE_FLAG_GETTER_SETTER(failedBoundsCheck, FailedBoundsCheck)
  MUTABLE_FLAG_GETTER_SETTER(failedShapeGuard, FailedShapeGuard)
  MUTABLE_FLAG_GETTER_SETTER(hadFrequentBailouts, HadFrequentBailouts)
  MUTABLE_FLAG_GETTER_SETTER(hadOverflowBailout, HadOverflowBailout)
  MUTABLE_FLAG_GETTER_SETTER(uninlineable, Uninlineable)
  MUTABLE_FLAG_GETTER_SETTER(invalidatedIdempotentCache,
                             InvalidatedIdempotentCache)
  MUTABLE_FLAG_GETTER_SETTER(failedLexicalCheck, FailedLexicalCheck)
  MUTABLE_FLAG_GETTER_SETTER(needsArgsAnalysis, NeedsArgsAnalysis)
  // NeedsArgsObj: custom logic below.
  MUTABLE_FLAG_GETTER_SETTER(spewEnabled, SpewEnabled)

#undef IMMUTABLE_FLAG_GETTER
#undef IMMUTABLE_FLAG_GETTER_SETTER_PUBLIC
#undef MUTABLE_FLAG_GETTER
#undef MUTABLE_FLAG_GETTER_SETTER
#undef FLAG_GETTER
#undef FLAG_GETTER_SETTER

  GeneratorKind generatorKind() const {
    return isGenerator() ? GeneratorKind::Generator
                         : GeneratorKind::NotGenerator;
  }

  void setGeneratorKind(GeneratorKind kind) {
    // A script only gets its generator kind set as part of initialization,
    // so it can only transition from NotGenerator.
    MOZ_ASSERT(!isGenerator());
    if (kind == GeneratorKind::Generator) {
      setFlag(ImmutableFlags::IsGenerator);
    }
  }

  FunctionAsyncKind asyncKind() const {
    return isAsync() ? FunctionAsyncKind::AsyncFunction
                     : FunctionAsyncKind::SyncFunction;
  }

  void setAsyncKind(FunctionAsyncKind kind) {
    if (kind == FunctionAsyncKind::AsyncFunction) {
      setFlag(ImmutableFlags::IsAsync);
    }
  }

  frontend::ParseGoal parseGoal() const {
    return hasModuleGoal() ? frontend::ParseGoal::Module
                           : frontend::ParseGoal::Script;
  }

  bool hasEnclosingScript() const { return warmUpData_.isEnclosingScript(); }
  BaseScript* enclosingScript() const {
    return warmUpData_.toEnclosingScript();
  }
  void setEnclosingScript(BaseScript* enclosingScript);

  // Returns true is the script has an enclosing scope but no bytecode. It is
  // ready for delazification.
  // NOTE: The enclosing script must have been successfully compiled at some
  // point for the enclosing scope to exist. That script may have since been
  // GC'd, but we kept the scope live so we can still compile ourselves.
  bool isReadyForDelazification() const {
    return warmUpData_.isEnclosingScope();
  }

  Scope* enclosingScope() const {
    MOZ_ASSERT(!warmUpData_.isEnclosingScript(),
               "Enclosing scope is not computed yet");

    if (warmUpData_.isEnclosingScope()) {
      return warmUpData_.toEnclosingScope();
    }

    MOZ_ASSERT(data_, "Script doesn't seem to be compiled");

    size_t outermostScopeIndex = 0;
    return gcthings()[outermostScopeIndex].as<Scope>().enclosing();
  }
  void setEnclosingScope(Scope* enclosingScope);
  Scope* releaseEnclosingScope();

  bool hasJitScript() const { return warmUpData_.isJitScript(); }
  jit::JitScript* jitScript() const {
    MOZ_ASSERT(hasJitScript());
    return warmUpData_.toJitScript();
  }
  jit::JitScript* maybeJitScript() const {
    return hasJitScript() ? jitScript() : nullptr;
  }

  inline bool hasBaselineScript() const;
  inline bool hasIonScript() const;

  bool hasPrivateScriptData() const { return data_ != nullptr; }

  // Update data_ pointer while also informing GC MemoryUse tracking.
  void swapData(UniquePtr<PrivateScriptData>& other);

  mozilla::Span<const JS::GCCellPtr> gcthings() const {
    return data_ ? data_->gcthings() : mozilla::Span<JS::GCCellPtr>();
  }

  void setFieldInitializers(FieldInitializers fieldInitializers) {
    MOZ_ASSERT(data_);
    data_->setFieldInitializers(fieldInitializers);
  }
  const FieldInitializers& getFieldInitializers() const {
    MOZ_ASSERT(data_);
    return data_->getFieldInitializers();
  }

  RuntimeScriptData* sharedData() const { return sharedData_; }
  void initSharedData(RuntimeScriptData* data) {
    MOZ_ASSERT(sharedData_ == nullptr);
    sharedData_ = data;
  }
  void freeSharedData() { sharedData_ = nullptr; }

  // NOTE: Script only has bytecode if JSScript::fullyInitFromStencil completes
  // successfully.
  bool hasBytecode() const {
    if (sharedData_) {
      MOZ_ASSERT(data_);
      MOZ_ASSERT(warmUpData_.isWarmUpCount() || warmUpData_.isJitScript());
      return true;
    }
    return false;
  }

 public:
  static const JS::TraceKind TraceKind = JS::TraceKind::Script;

  void traceChildren(JSTracer* trc);
  void finalize(JSFreeOp* fop);

  size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) {
    return mallocSizeOf(data_);
  }

  inline JSScript* asJSScript();

  template <XDRMode mode>
  static XDRResult XDRLazyScriptData(XDRState<mode>* xdr,
                                     HandleScriptSourceObject sourceObject,
                                     Handle<BaseScript*> lazy,
                                     bool hasFieldInitializer);

  // JIT accessors
  static constexpr size_t offsetOfJitCodeRaw() {
    return offsetof(BaseScript, jitCodeRaw_);
  }
  static constexpr size_t offsetOfPrivateData() {
    return offsetof(BaseScript, data_);
  }
  static constexpr size_t offsetOfSharedData() {
    return offsetof(BaseScript, sharedData_);
  }
  static size_t offsetOfImmutableFlags() {
    static_assert(offsetof(ImmutableScriptFlags, flags_) == 0,
                  "Required for JIT flag access");
    return offsetof(BaseScript, immutableFlags_);
  }
  static constexpr size_t offsetOfMutableFlags() {
    return offsetof(BaseScript, mutableFlags_);
  }
  static constexpr size_t offsetOfWarmUpData() {
    return offsetof(BaseScript, warmUpData_);
  }
};

/*
 * NB: after a successful XDR_DECODE, XDRScript callers must do any required
 * subsequent set-up of owning function or script object and then call
 * CallNewScriptHook.
 */
template <XDRMode mode>
XDRResult XDRScript(XDRState<mode>* xdr, HandleScope enclosingScope,
                    HandleScriptSourceObject sourceObject,
                    HandleObject funOrMod, MutableHandleScript scriptp);

template <XDRMode mode>
XDRResult XDRLazyScript(XDRState<mode>* xdr, HandleScope enclosingScope,
                        HandleScriptSourceObject sourceObject,
                        HandleFunction fun, MutableHandle<BaseScript*> lazy);

/*
 * Code any constant value.
 */
template <XDRMode mode>
XDRResult XDRScriptConst(XDRState<mode>* xdr, MutableHandleValue vp);

extern void SweepScriptData(JSRuntime* rt);

} /* namespace js */

namespace JS {

// Define a GCManagedDeletePolicy to allow deleting type outside of normal
// sweeping.
template <>
struct DeletePolicy<js::PrivateScriptData>
    : public js::GCManagedDeletePolicy<js::PrivateScriptData> {};

} /* namespace JS */

class JSScript : public js::BaseScript {
 private:
  template <js::XDRMode mode>
  friend js::XDRResult js::XDRScript(js::XDRState<mode>* xdr,
                                     js::HandleScope enclosingScope,
                                     js::HandleScriptSourceObject sourceObject,
                                     js::HandleObject funOrMod,
                                     js::MutableHandleScript scriptp);

  template <js::XDRMode mode>
  friend js::XDRResult js::RuntimeScriptData::XDR(js::XDRState<mode>* xdr,
                                                  js::HandleScript script);

  friend bool js::RuntimeScriptData::InitFromStencil(
      JSContext* cx, js::HandleScript script,
      js::frontend::ScriptStencil& stencil);

  template <js::XDRMode mode>
  friend js::XDRResult js::PrivateScriptData::XDR(
      js::XDRState<mode>* xdr, js::HandleScript script,
      js::HandleScriptSourceObject sourceObject,
      js::HandleScope scriptEnclosingScope, js::HandleObject funOrMod);

  friend bool js::PrivateScriptData::Clone(
      JSContext* cx, js::HandleScript src, js::HandleScript dst,
      js::MutableHandle<JS::GCVector<js::Scope*>> scopes);

  friend bool js::PrivateScriptData::InitFromStencil(
      JSContext* cx, js::HandleScript script,
      const js::frontend::ScriptStencil& stencil);

 private:
  using js::BaseScript::BaseScript;

 public:
  static JSScript* Create(JSContext* cx, js::HandleObject functionOrGlobal,
                          js::HandleScriptSourceObject sourceObject,
                          js::SourceExtent extent,
                          js::ImmutableScriptFlags flags);

  // NOTE: This should only be used while delazifying.
  static JSScript* CastFromLazy(js::BaseScript* lazy) {
    return static_cast<JSScript*>(lazy);
  }

  // NOTE: If you use createPrivateScriptData directly instead of via
  // fullyInitFromStencil, you are responsible for notifying the debugger
  // after successfully creating the script.
  static bool createPrivateScriptData(JSContext* cx,
                                      JS::Handle<JSScript*> script,
                                      uint32_t ngcthings);

 public:
  static bool fullyInitFromStencil(
      JSContext* cx, js::frontend::CompilationInfo& compilationInfo,
      js::HandleScript script, js::frontend::ScriptStencil& stencil);

#ifdef DEBUG
 private:
  // Assert that jump targets are within the code array of the script.
  void assertValidJumpTargets() const;
#endif

 public:
  js::ImmutableScriptData* immutableScriptData() const {
    return sharedData_->isd_.get();
  }

  // Script bytecode is immutable after creation.
  jsbytecode* code() const {
    if (!sharedData_) {
      return nullptr;
    }
    return immutableScriptData()->code();
  }

  bool hasForceInterpreterOp() const {
    // JSOp::ForceInterpreter, if present, must be the first op.
    MOZ_ASSERT(length() >= 1);
    return JSOp(*code()) == JSOp::ForceInterpreter;
  }

  js::AllBytecodesIterable allLocations() {
    return js::AllBytecodesIterable(this);
  }

  js::BytecodeLocation location() { return js::BytecodeLocation(this, code()); }

  size_t length() const {
    MOZ_ASSERT(sharedData_);
    return immutableScriptData()->codeLength();
  }

  jsbytecode* codeEnd() const { return code() + length(); }

  jsbytecode* lastPC() const {
    jsbytecode* pc = codeEnd() - js::JSOpLength_RetRval;
    MOZ_ASSERT(JSOp(*pc) == JSOp::RetRval);
    return pc;
  }

  bool containsPC(const jsbytecode* pc) const {
    return pc >= code() && pc < codeEnd();
  }

  bool contains(const js::BytecodeLocation& loc) const {
    return containsPC(loc.toRawBytecode());
  }

  size_t pcToOffset(const jsbytecode* pc) const {
    MOZ_ASSERT(containsPC(pc));
    return size_t(pc - code());
  }

  jsbytecode* offsetToPC(size_t offset) const {
    MOZ_ASSERT(offset < length());
    return code() + offset;
  }

  size_t mainOffset() const { return immutableScriptData()->mainOffset; }

  // The fixed part of a stack frame is comprised of vars (in function and
  // module code) and block-scoped locals (in all kinds of code).
  size_t nfixed() const { return immutableScriptData()->nfixed; }

  // Number of fixed slots reserved for slots that are always live. Only
  // nonzero for function or module code.
  size_t numAlwaysLiveFixedSlots() const {
    if (bodyScope()->is<js::FunctionScope>()) {
      return bodyScope()->as<js::FunctionScope>().nextFrameSlot();
    }
    if (bodyScope()->is<js::ModuleScope>()) {
      return bodyScope()->as<js::ModuleScope>().nextFrameSlot();
    }
    return 0;
  }

  // Calculate the number of fixed slots that are live at a particular bytecode.
  size_t calculateLiveFixed(jsbytecode* pc);

  size_t nslots() const { return immutableScriptData()->nslots; }

  unsigned numArgs() const {
    if (bodyScope()->is<js::FunctionScope>()) {
      return bodyScope()
          ->as<js::FunctionScope>()
          .numPositionalFormalParameters();
    }
    return 0;
  }

  inline js::Shape* initialEnvironmentShape() const;

  bool functionHasParameterExprs() const {
    // Only functions have parameters.
    js::Scope* scope = bodyScope();
    if (!scope->is<js::FunctionScope>()) {
      return false;
    }
    return scope->as<js::FunctionScope>().hasParameterExprs();
  }

  bool functionAllowsParameterRedeclaration() const {
    // Parameter redeclaration is only allowed for non-strict functions with
    // simple parameter lists, which are neither arrow nor method functions. We
    // don't have a flag at hand to test the function kind, but we can still
    // test if the function is non-strict and has a simple parameter list by
    // checking |hasMappedArgsObj()|. (Mapped arguments objects are only
    // created for non-strict functions with simple parameter lists.)
    return hasMappedArgsObj();
  }

  // If there are more than MaxBytecodeTypeSets JOF_TYPESET ops in the script,
  // the first MaxBytecodeTypeSets - 1 JOF_TYPESET ops have their own TypeSet
  // and all other JOF_TYPESET ops share the last TypeSet.
  static constexpr size_t MaxBytecodeTypeSets = UINT16_MAX;
  static_assert(sizeof(js::ImmutableScriptData::numBytecodeTypeSets) == 2,
                "MaxBytecodeTypeSets must match sizeof(numBytecodeTypeSets)");

  size_t numBytecodeTypeSets() const {
    return immutableScriptData()->numBytecodeTypeSets;
  }

  size_t numICEntries() const { return immutableScriptData()->numICEntries; }

  size_t funLength() const { return immutableScriptData()->funLength; }

  void cacheForEval() {
    MOZ_ASSERT(isForEval());
    // IsEvalCacheCandidate will make sure that there's nothing in this
    // script that would prevent reexecution even if isRunOnce is
    // true.  So just pretend like we never ran this script.
    clearFlag(MutableFlags::HasRunOnce);
  }

  bool argumentsAliasesFormals() const {
    return argumentsHasVarBinding() && hasMappedArgsObj();
  }

  /*
   * As an optimization, even when argumentsHasVarBinding, the function
   * prologue may not need to create an arguments object. This is determined by
   * needsArgsObj which is set by AnalyzeArgumentsUsage. When !needsArgsObj,
   * the prologue may simply write MagicValue(JS_OPTIMIZED_ARGUMENTS) to
   * 'arguments's slot and any uses of 'arguments' will be guaranteed to handle
   * this magic value. To avoid spurious arguments object creation, we maintain
   * the invariant that needsArgsObj is only called after the script has been
   * analyzed.
   */
  inline bool ensureHasAnalyzedArgsUsage(JSContext* cx);
  bool needsArgsObj() const {
    MOZ_ASSERT(!needsArgsAnalysis());
    return hasFlag(MutableFlags::NeedsArgsObj);
  }
  void setNeedsArgsObj(bool needsArgsObj);
  static void argumentsOptimizationFailed(JSContext* cx,
                                          js::HandleScript script);

  // Update the the arguments analysis flags based on the frontend
  // derived information.
  void resetArgsUsageAnalysis();

  /*
   * Arguments access (via JSOp::*Arg* opcodes) must access the canonical
   * location for the argument. If an arguments object exists AND it's mapped
   * ('arguments' aliases formals), then all access must go through the
   * arguments object. Otherwise, the local slot is the canonical location for
   * the arguments. Note: if a formal is aliased through the scope chain, then
   * script->formalIsAliased and JSOp::*Arg* opcodes won't be emitted at all.
   */
  bool argsObjAliasesFormals() const {
    return needsArgsObj() && hasMappedArgsObj();
  }

  void updateJitCodeRaw(JSRuntime* rt);

  bool isRelazifiable() const {
    // A script may not be relazifiable if parts of it can be entrained in
    // interesting ways:
    //  - Scripts with inner-functions or direct-eval (which can add
    //    inner-functions) should not be relazified as their Scopes may be part
    //    of another scope-chain.
    //  - Generators and async functions may be re-entered in complex ways so
    //    don't discard bytecode. The JIT resume code assumes this.
    //  - Functions with template literals must always return the same object
    //    instance so must not discard it by relazifying.
    return !hasInnerFunctions() && !hasDirectEval() && !isGenerator() &&
           !isAsync() && !hasCallSiteObj();
  }

  js::ModuleObject* module() const {
    if (bodyScope()->is<js::ModuleScope>()) {
      return bodyScope()->as<js::ModuleScope>().module();
    }
    return nullptr;
  }

  bool isGlobalCode() const { return bodyScope()->is<js::GlobalScope>(); }

  // Returns true if the script may read formal arguments on the stack
  // directly, via lazy arguments or a rest parameter.
  bool mayReadFrameArgsDirectly();

  static JSLinearString* sourceData(JSContext* cx, JS::HandleScript script);

  void setDefaultClassConstructorSpan(uint32_t start, uint32_t end,
                                      unsigned line, unsigned column);

#ifdef MOZ_VTUNE
  // Unique Method ID passed to the VTune profiler. Allows attribution of
  // different jitcode to the same source script.
  uint32_t vtuneMethodID();
#endif

 public:
  /* Return whether this is a 'direct eval' script in a function scope. */
  bool isDirectEvalInFunction() const {
    if (!isForEval()) {
      return false;
    }
    return bodyScope()->hasOnChain(js::ScopeKind::Function);
  }

  /*
   * Return whether this script is a top-level script.
   *
   * If we evaluate some code which contains a syntax error, then we might
   * produce a JSScript which has no associated bytecode. Testing with
   * |code()| filters out this kind of scripts.
   *
   * If this script has a function associated to it, then it is not the
   * top-level of a file.
   */
  bool isTopLevel() { return code() && !isFunction(); }

  /* Ensure the script has a JitScript. */
  inline bool ensureHasJitScript(JSContext* cx, js::jit::AutoKeepJitScripts&);

  void maybeReleaseJitScript(JSFreeOp* fop);
  void releaseJitScript(JSFreeOp* fop);
  void releaseJitScriptOnFinalize(JSFreeOp* fop);

  inline js::jit::BaselineScript* baselineScript() const;
  inline js::jit::IonScript* ionScript() const;

  inline bool isIonCompilingOffThread() const;
  inline bool canIonCompile() const;
  inline void disableIon();

  inline bool canBaselineCompile() const;
  inline void disableBaselineCompile();

  inline js::GlobalObject& global() const;
  inline bool hasGlobal(const js::GlobalObject* global) const;
  js::GlobalObject& uninlinedGlobal() const;

  uint32_t bodyScopeIndex() const {
    return immutableScriptData()->bodyScopeIndex;
  }

  js::Scope* bodyScope() const { return getScope(bodyScopeIndex()); }

  js::Scope* outermostScope() const {
    // The body scope may not be the outermost scope in the script when
    // the decl env scope is present.
    size_t index = 0;
    return getScope(index);
  }

  bool functionHasExtraBodyVarScope() const {
    bool res = hasFlag(ImmutableFlags::FunctionHasExtraBodyVarScope);
    MOZ_ASSERT_IF(res, functionHasParameterExprs());
    return res;
  }

  js::VarScope* functionExtraBodyVarScope() const {
    MOZ_ASSERT(functionHasExtraBodyVarScope());
    for (JS::GCCellPtr gcThing : gcthings()) {
      if (!gcThing.is<js::Scope>()) {
        continue;
      }
      js::Scope* scope = &gcThing.as<js::Scope>();
      if (scope->kind() == js::ScopeKind::FunctionBodyVar) {
        return &scope->as<js::VarScope>();
      }
    }
    MOZ_CRASH("Function extra body var scope not found");
  }

  bool needsBodyEnvironment() const {
    for (JS::GCCellPtr gcThing : gcthings()) {
      if (!gcThing.is<js::Scope>()) {
        continue;
      }
      js::Scope* scope = &gcThing.as<js::Scope>();
      if (ScopeKindIsInBody(scope->kind()) && scope->hasEnvironment()) {
        return true;
      }
    }
    return false;
  }

  inline js::LexicalScope* maybeNamedLambdaScope() const;

  // Drop script data and reset warmUpData to reference enclosing scope.
  void relazify(JSRuntime* rt);

 private:
  bool createJitScript(JSContext* cx);

  bool createScriptData(JSContext* cx, uint32_t natoms);
  void initImmutableScriptData(js::UniquePtr<js::ImmutableScriptData>&& data) {
    MOZ_ASSERT(!sharedData_->isd_);
    sharedData_->isd_ = std::move(data);
  }
  bool shareScriptData(JSContext* cx);

 public:
  inline uint32_t getWarmUpCount() const;
  inline void incWarmUpCounter(uint32_t amount = 1);
  inline void resetWarmUpCounterForGC();

  void resetWarmUpCounterToDelayIonCompilation();

  unsigned getWarmUpResetCount() const {
    constexpr uint32_t MASK = uint32_t(MutableFlags::WarmupResets_MASK);
    return mutableFlags_ & MASK;
  }
  void incWarmUpResetCounter() {
    constexpr uint32_t MASK = uint32_t(MutableFlags::WarmupResets_MASK);
    uint32_t newCount = getWarmUpResetCount() + 1;
    if (newCount <= MASK) {
      mutableFlags_ &= ~MASK;
      mutableFlags_ |= newCount;
    }
  }
  void resetWarmUpResetCounter() {
    constexpr uint32_t MASK = uint32_t(MutableFlags::WarmupResets_MASK);
    mutableFlags_ &= ~MASK;
  }

 public:
  bool initScriptCounts(JSContext* cx);
  js::ScriptCounts& getScriptCounts();
  js::PCCounts* maybeGetPCCounts(jsbytecode* pc);
  const js::PCCounts* maybeGetThrowCounts(jsbytecode* pc);
  js::PCCounts* getThrowCounts(jsbytecode* pc);
  uint64_t getHitCount(jsbytecode* pc);
  void incHitCount(jsbytecode* pc);  // Used when we bailout out of Ion.
  void addIonCounts(js::jit::IonScriptCounts* ionCounts);
  js::jit::IonScriptCounts* getIonCounts();
  void releaseScriptCounts(js::ScriptCounts* counts);
  void destroyScriptCounts();
  void resetScriptCounts();

  jsbytecode* main() const { return code() + mainOffset(); }

  js::BytecodeLocation mainLocation() const {
    return js::BytecodeLocation(this, main());
  }

  js::BytecodeLocation endLocation() const {
    return js::BytecodeLocation(this, codeEnd());
  }

  js::BytecodeLocation offsetToLocation(uint32_t offset) const {
    return js::BytecodeLocation(this, offsetToPC(offset));
  }

  void addSizeOfJitScript(mozilla::MallocSizeOf mallocSizeOf,
                          size_t* sizeOfJitScript,
                          size_t* sizeOfBaselineFallbackStubs) const;

  mozilla::Span<const js::TryNote> trynotes() const {
    return immutableScriptData()->tryNotes();
  }

  mozilla::Span<const js::ScopeNote> scopeNotes() const {
    return immutableScriptData()->scopeNotes();
  }

  mozilla::Span<const uint32_t> resumeOffsets() const {
    return immutableScriptData()->resumeOffsets();
  }

  uint32_t tableSwitchCaseOffset(jsbytecode* pc, uint32_t caseIndex) const {
    MOZ_ASSERT(containsPC(pc));
    MOZ_ASSERT(JSOp(*pc) == JSOp::TableSwitch);
    uint32_t firstResumeIndex = GET_RESUMEINDEX(pc + 3 * JUMP_OFFSET_LEN);
    return resumeOffsets()[firstResumeIndex + caseIndex];
  }
  jsbytecode* tableSwitchCasePC(jsbytecode* pc, uint32_t caseIndex) const {
    return offsetToPC(tableSwitchCaseOffset(pc, caseIndex));
  }

  bool hasLoops();

  uint32_t numNotes() const {
    MOZ_ASSERT(sharedData_);
    return immutableScriptData()->noteLength();
  }
  js::SrcNote* notes() const {
    MOZ_ASSERT(sharedData_);
    return immutableScriptData()->notes();
  }

  size_t natoms() const {
    MOZ_ASSERT(sharedData_);
    return sharedData_->natoms();
  }
  js::GCPtrAtom* atoms() const {
    MOZ_ASSERT(sharedData_);
    return sharedData_->atoms();
  }

  js::GCPtrAtom& getAtom(size_t index) const {
    MOZ_ASSERT(index < natoms());
    return atoms()[index];
  }

  js::GCPtrAtom& getAtom(jsbytecode* pc) const {
    MOZ_ASSERT(containsPC(pc) && containsPC(pc + sizeof(uint32_t)));
    MOZ_ASSERT(js::JOF_OPTYPE((JSOp)*pc) == JOF_ATOM);
    return getAtom(GET_UINT32_INDEX(pc));
  }

  js::PropertyName* getName(size_t index) {
    return getAtom(index)->asPropertyName();
  }

  js::PropertyName* getName(jsbytecode* pc) const {
    return getAtom(pc)->asPropertyName();
  }

  JSObject* getObject(size_t index) const {
    MOZ_ASSERT(gcthings()[index].asCell()->isTenured());
    return &gcthings()[index].as<JSObject>();
  }

  JSObject* getObject(jsbytecode* pc) const {
    MOZ_ASSERT(containsPC(pc) && containsPC(pc + sizeof(uint32_t)));
    return getObject(GET_UINT32_INDEX(pc));
  }

  js::Scope* getScope(size_t index) const {
    return &gcthings()[index].as<js::Scope>();
  }

  js::Scope* getScope(jsbytecode* pc) const {
    // This method is used to get a scope directly using a JSOp with an
    // index. To search through ScopeNotes to look for a Scope using pc,
    // use lookupScope.
    MOZ_ASSERT(containsPC(pc) && containsPC(pc + sizeof(uint32_t)));
    MOZ_ASSERT(js::JOF_OPTYPE(JSOp(*pc)) == JOF_SCOPE,
               "Did you mean to use lookupScope(pc)?");
    return getScope(GET_UINT32_INDEX(pc));
  }

  inline JSFunction* getFunction(size_t index) const;
  inline JSFunction* getFunction(jsbytecode* pc) const;

  inline js::RegExpObject* getRegExp(size_t index) const;
  inline js::RegExpObject* getRegExp(jsbytecode* pc) const;

  js::BigInt* getBigInt(size_t index) const {
    MOZ_ASSERT(gcthings()[index].asCell()->isTenured());
    return &gcthings()[index].as<js::BigInt>();
  }

  js::BigInt* getBigInt(jsbytecode* pc) const {
    MOZ_ASSERT(containsPC(pc));
    MOZ_ASSERT(js::JOF_OPTYPE(JSOp(*pc)) == JOF_BIGINT);
    return getBigInt(GET_UINT32_INDEX(pc));
  }

  // The following 3 functions find the static scope just before the
  // execution of the instruction pointed to by pc.

  js::Scope* lookupScope(jsbytecode* pc) const;

  js::Scope* innermostScope(jsbytecode* pc) const;
  js::Scope* innermostScope() const { return innermostScope(main()); }

  /*
   * The isEmpty method tells whether this script has code that computes any
   * result (not return value, result AKA normal completion value) other than
   * JSVAL_VOID, or any other effects.
   */
  bool isEmpty() const {
    if (length() > 3) {
      return false;
    }

    jsbytecode* pc = code();
    if (noScriptRval() && JSOp(*pc) == JSOp::False) {
      ++pc;
    }
    return JSOp(*pc) == JSOp::RetRval;
  }

  bool formalIsAliased(unsigned argSlot);
  bool formalLivesInArgumentsObject(unsigned argSlot);

  // See comment above 'debugMode' in Realm.h for explanation of
  // invariants of debuggee compartments, scripts, and frames.
  inline bool isDebuggee() const;

  // A helper class to prevent relazification of the given function's script
  // while it's holding on to it.  This class automatically roots the script.
  class AutoDelazify;
  friend class AutoDelazify;

  class AutoDelazify {
    JS::RootedScript script_;
    JSContext* cx_;
    bool oldAllowRelazify_ = false;

   public:
    explicit AutoDelazify(JSContext* cx, JS::HandleFunction fun = nullptr)
        : script_(cx), cx_(cx) {
      holdScript(fun);
    }

    ~AutoDelazify() { dropScript(); }

    void operator=(JS::HandleFunction fun) {
      dropScript();
      holdScript(fun);
    }

    operator JS::HandleScript() const { return script_; }
    explicit operator bool() const { return script_; }

   private:
    void holdScript(JS::HandleFunction fun);
    void dropScript();
  };
};

namespace js {

struct ScriptAndCounts {
  /* This structure is stored and marked from the JSRuntime. */
  JSScript* script;
  ScriptCounts scriptCounts;

  inline explicit ScriptAndCounts(JSScript* script);
  inline ScriptAndCounts(ScriptAndCounts&& sac);

  const PCCounts* maybeGetPCCounts(jsbytecode* pc) const {
    return scriptCounts.maybeGetPCCounts(script->pcToOffset(pc));
  }
  const PCCounts* maybeGetThrowCounts(jsbytecode* pc) const {
    return scriptCounts.maybeGetThrowCounts(script->pcToOffset(pc));
  }

  jit::IonScriptCounts* getIonCounts() const { return scriptCounts.ionCounts_; }

  void trace(JSTracer* trc) {
    TraceRoot(trc, &script, "ScriptAndCounts::script");
  }
};

extern JS::UniqueChars FormatIntroducedFilename(JSContext* cx,
                                                const char* filename,
                                                unsigned lineno,
                                                const char* introducer);

struct GSNCache;

const js::SrcNote* GetSrcNote(GSNCache& cache, JSScript* script,
                              jsbytecode* pc);

extern const js::SrcNote* GetSrcNote(JSContext* cx, JSScript* script,
                                     jsbytecode* pc);

extern jsbytecode* LineNumberToPC(JSScript* script, unsigned lineno);

extern JS_FRIEND_API unsigned GetScriptLineExtent(JSScript* script);

} /* namespace js */

namespace js {

extern unsigned PCToLineNumber(JSScript* script, jsbytecode* pc,
                               unsigned* columnp = nullptr);

extern unsigned PCToLineNumber(unsigned startLine, SrcNote* notes,
                               jsbytecode* code, jsbytecode* pc,
                               unsigned* columnp = nullptr);

/*
 * This function returns the file and line number of the script currently
 * executing on cx. If there is no current script executing on cx (e.g., a
 * native called directly through JSAPI (e.g., by setTimeout)), nullptr and 0
 * are returned as the file and line.
 */
extern void DescribeScriptedCallerForCompilation(
    JSContext* cx, MutableHandleScript maybeScript, const char** file,
    unsigned* linenop, uint32_t* pcOffset, bool* mutedErrors);

/*
 * Like DescribeScriptedCallerForCompilation, but this function avoids looking
 * up the script/pc and the full linear scan to compute line number.
 */
extern void DescribeScriptedCallerForDirectEval(
    JSContext* cx, HandleScript script, jsbytecode* pc, const char** file,
    unsigned* linenop, uint32_t* pcOffset, bool* mutedErrors);

JSScript* CloneScriptIntoFunction(JSContext* cx, HandleScope enclosingScope,
                                  HandleFunction fun, HandleScript src,
                                  Handle<ScriptSourceObject*> sourceObject);

JSScript* CloneGlobalScript(JSContext* cx, ScopeKind scopeKind,
                            HandleScript src);

} /* namespace js */

namespace JS {
namespace ubi {

template <>
class Concrete<JSScript> : public Concrete<js::BaseScript> {};

}  // namespace ubi
}  // namespace JS

#endif /* vm_JSScript_h */