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.

Header

Mercurial (fbecf6c8a86f)

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
/* -*- Mode: C++; c-basic-offset: 4; indent-tabs-mode: t; tab-width: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is [Open Source Virtual Machine.].
 *
 * The Initial Developer of the Original Code is
 * Adobe System Incorporated.
 * Portions created by the Initial Developer are Copyright (C) 2004-2006
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Adobe AS3 Team
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "MMgc.h"

//#define TESTING_MARKSTACK
#define MARKSTACK_ALLOWANCE  1

namespace MMgc
{
#ifdef TESTING_MARKSTACK
	static int markstack_allowance = 2*MARKSTACK_ALLOWANCE;		// Two stacks!
#endif

	static inline void* AllocStackSegment(size_t nbytes, bool mustSucceed)
	{
#ifdef TESTING_MARKSTACK
		if (markstack_allowance == 0)
			return NULL;
		--markstack_allowance;
#endif
		nbytes = (nbytes + 4095) & ~4095;
		return FixedMalloc::GetFixedMalloc()->Alloc(nbytes, mustSucceed ? kNone : kCanFail);
	}

	static inline void FreeStackSegment(void* p)
	{
#ifdef TESTING_MARKSTACK
		++markstack_allowance;
#endif
		FixedMalloc::GetFixedMalloc()->Free(p);
	}
	
	GCMarkStack::GCMarkStack()
		: m_base(NULL)
		, m_top(NULL)
		, m_limit(NULL)
		, m_topSegment(NULL)
		, m_hiddenCount(0)
		, m_extraSegment(NULL)
#ifdef MMGC_MARKSTACK_DEPTH
		, m_maxDepth(0)
#endif
	{
		PushSegment(true);
		GCAssert(Invariants());
	}

	GCMarkStack::~GCMarkStack()
	{
		while (m_topSegment != NULL)
			PopSegment();
		if (m_extraSegment)
			FreeStackSegment(m_extraSegment);
	}

	void GCMarkStack::Clear()
	{
		// Clear out the elements
		while (m_topSegment->m_prev != NULL)
			PopSegment();
		m_top = m_base;

		// Discard the cached segment
		if (m_extraSegment != NULL) {
			FreeStackSegment(m_extraSegment);
			m_extraSegment = NULL;
		}
		GCAssert(Invariants());
	}

	bool GCMarkStack::PushSegment(bool mustSucceed)
	{
		GCAssert(sizeof(GCStackSegment) <= 4096);
		GCAssert(m_top == m_limit);
		if (m_extraSegment == NULL) {
			void *memory = AllocStackSegment(sizeof(GCStackSegment), mustSucceed);
			if (memory == NULL)
				return false;
			m_extraSegment = new (memory) GCStackSegment();
		}
		if (m_topSegment != NULL)
			m_hiddenCount += kMarkStackItems;
		GCStackSegment* seg = m_extraSegment;
		m_extraSegment = NULL;
		seg->m_prev = m_topSegment;
		m_topSegment = seg;
		m_base = m_topSegment->m_items;
		m_limit = m_base + kMarkStackItems;
		m_top = m_base;
		return true;
	}

	void GCMarkStack::PopSegment()
	{
		m_hiddenCount -= kMarkStackItems;
		GCStackSegment* seg = m_topSegment;
		m_topSegment = seg->m_prev;
		m_base = m_topSegment->m_items;
		m_limit = m_base + kMarkStackItems;
		m_top = m_limit;
		if (m_extraSegment == NULL) {
			seg->m_prev = NULL;
			m_extraSegment = seg;
		}
		else
			FreeStackSegment(seg);
	}

	bool GCMarkStack::TransferOneFullSegmentFrom(GCMarkStack& other)
	{
		GCAssert(other.EntirelyFullSegments() > 0);
		GCStackSegment* seg;

		if (other.m_topSegment->m_prev == NULL) {
			// Picking off the only segment
			GCAssert(other.m_top == other.m_limit);
			seg = other.m_topSegment;
			other.m_topSegment = NULL;
			other.m_base = NULL;
			other.m_top = NULL;
			other.m_limit = NULL;
			if (!other.PushSegment()) {
				// Oops: couldn't push it, so undo.  We're out of memory but we
				// don't want to signal OOM here, we want to recover, signal failure,
				// and let the caller handle it.
				other.m_topSegment = seg;
				other.m_base = seg->m_items;
				other.m_top = other.m_limit = other.m_base + kMarkStackItems;
				return false;
			}
		}
		else {
			// Picking off the one below the top always
			seg = other.m_topSegment->m_prev;
			other.m_topSegment->m_prev = seg->m_prev;
			other.m_hiddenCount -= kMarkStackItems;
		}

		// Insert it below our top segment
		seg->m_prev = m_topSegment->m_prev;
		m_topSegment->m_prev = seg;
		m_hiddenCount += kMarkStackItems;

		// Special case that occurs if a segment was inserted into an empty stack.
		if (m_top == m_base)
			PopSegment();
		GCAssert(Invariants());
		GCAssert(other.Invariants());
		return true;
	}
	
#ifdef _DEBUG
	bool GCMarkStack::Invariants()
	{
		GCAssert(m_base+kMarkStackItems == m_limit);
		GCAssert(m_top >= m_base);
		GCAssert(m_top <= m_limit);
		GCAssert(m_topSegment->m_prev == NULL || m_top > m_base);
		uint32_t hc = 0;
		uint32_t ns = 0;
		for ( GCStackSegment* seg=m_topSegment->m_prev ; seg != NULL ; seg = seg->m_prev ) {
			hc += kMarkStackItems;
			ns++;
		}
		GCAssert(ns == EntirelyFullSegments() || (m_top == m_limit && ns+1 == EntirelyFullSegments()));
		GCAssert(hc == m_hiddenCount);
		GCAssert(Count() == hc + (m_top - m_base));
		return true;
	}
#endif
}