interpreter/RegisterFile.h

   1 /*
   2  * Copyright (C) 2008 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright
  11  *     notice, this list of conditions and the following disclaimer in the
  12  *     documentation and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  14  *     its contributors may be used to endorse or promote products derived
  15  *     from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef RegisterFile_h
  30 #define RegisterFile_h
  31
  32 #include "Register.h"
  33 #include "Collector.h"
  34 #include <wtf/Noncopyable.h>
  35
  36 #if HAVE(MMAP)
  37 #include <errno.h>
  38 #include <stdio.h>
  39 #include <sys/mman.h>
  40 #endif
  41
  42 namespace JSC {
  43
  44 /*
  45     A register file is a stack of register frames. We represent a register
  46     frame by its offset from "base", the logical first entry in the register
  47     file. The bottom-most register frame's offset from base is 0.
  48
  49     In a program where function "a" calls function "b" (global code -> a -> b),
  50     the register file might look like this:
  51
  52     |       global frame     |        call frame      |        call frame      |     spare capacity     |
  53     -----------------------------------------------------------------------------------------------------
  54     |  0 |  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 | 10 | 11 | 12 | 13 | 14 |    |    |    |    |    | <-- index in buffer
  55     -----------------------------------------------------------------------------------------------------
  56     | -3 | -2 | -1 |  0 |  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 | 10 | 11 |    |    |    |    |    | <-- index relative to base
  57     -----------------------------------------------------------------------------------------------------
  58     |    <-globals | temps-> |  <-vars | temps->      |                 <-vars |
  59        ^              ^                   ^                                       ^
  60        |              |                   |                                       |
  61      buffer    base (frame 0)          frame 1                                 frame 2
  62
  63     Since all variables, including globals, are accessed by negative offsets
  64     from their register frame pointers, to keep old global offsets correct, new
  65     globals must appear at the beginning of the register file, shifting base
  66     to the right.
  67
  68     If we added one global variable to the register file depicted above, it
  69     would look like this:
  70
  71     |         global frame        |<                                                                    >
  72     ------------------------------->                                                                    <
  73     |  0 |  1 |  2 |  3 |  4 |  5 |<                             >snip<                                 > <-- index in buffer
  74     ------------------------------->                                                                    <
  75     | -4 | -3 | -2 | -1 |  0 |  1 |<                                                                    > <-- index relative to base
  76     ------------------------------->                                                                    <
  77     |         <-globals | temps-> |
  78        ^                   ^
  79        |                   |
  80      buffer         base (frame 0)
  81
  82     As you can see, global offsets relative to base have stayed constant,
  83     but base itself has moved. To keep up with possible changes to base,
  84     clients keep an indirect pointer, so their calculations update
  85     automatically when base changes.
  86
  87     For client simplicity, the RegisterFile measures size and capacity from
  88     "base", not "buffer".
  89 */
  90
  91     class JSGlobalObject;
  92
  93     class RegisterFile : Noncopyable {
  94         friend class JIT;
  95     public:
  96         enum CallFrameHeaderEntry {
  97             CallFrameHeaderSize = 8,
  98
  99             CodeBlock = -8,
 100             ScopeChain = -7,
 101             CallerFrame = -6,
 102             ReturnPC = -5, // This is either an Instruction* or a pointer into JIT generated code stored as an Instruction*.
 103             ReturnValueRegister = -4,
 104             ArgumentCount = -3,
 105             Callee = -2,
 106             OptionalCalleeArguments = -1,
 107         };
 108
 109         enum { ProgramCodeThisRegister = -CallFrameHeaderSize - 1 };
 110         enum { ArgumentsRegister = 0 };
 111
 112         static const size_t defaultCapacity = 524288;
 113         static const size_t defaultMaxGlobals = 8192;
 114         static const size_t allocationSize = 1 << 14;
 115         static const size_t allocationSizeMask = allocationSize - 1;
 116
 117         RegisterFile(size_t capacity = defaultCapacity, size_t maxGlobals = defaultMaxGlobals)
 118             : m_numGlobals(0)
 119             , m_maxGlobals(maxGlobals)
 120             , m_start(0)
 121             , m_end(0)
 122             , m_max(0)
 123             , m_buffer(0)
 124             , m_globalObject(0)
 125         {
 126             size_t bufferLength = (capacity + maxGlobals) * sizeof(Register);
 127 #if HAVE(MMAP)
 128             m_buffer = static_cast<Register*>(mmap(0, bufferLength, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0));
 129             if (m_buffer == MAP_FAILED) {
 130                 fprintf(stderr, "Could not allocate register file: %d\n", errno);
 131                 CRASH();
 132             }
 133 #elif HAVE(VIRTUALALLOC)
 134             // Ensure bufferLength is a multiple of allocation size
 135             bufferLength = (bufferLength + allocationSizeMask) & ~allocationSizeMask;
 136             m_buffer = static_cast<Register*>(VirtualAlloc(0, bufferLength, MEM_RESERVE, PAGE_READWRITE));
 137             if (!m_buffer) {
 138                 fprintf(stderr, "Could not allocate register file: %d\n", errno);
 139                 CRASH();
 140             }
 141             int initialAllocation = (maxGlobals * sizeof(Register) + allocationSizeMask) & ~allocationSizeMask;
 142             void* commitCheck = VirtualAlloc(m_buffer, initialAllocation, MEM_COMMIT, PAGE_READWRITE);
 143             if (commitCheck != m_buffer) {
 144                 fprintf(stderr, "Could not allocate register file: %d\n", errno);
 145                 CRASH();
 146             }
 147             m_maxCommitted = reinterpret_cast<Register*>(reinterpret_cast<char*>(m_buffer) + initialAllocation);
 148 #else
 149             #error "Don't know how to reserve virtual memory on this platform."
 150 #endif
 151             m_start = m_buffer + maxGlobals;
 152             m_end = m_start;
 153             m_max = m_start + capacity;
 154         }
 155
 156         ~RegisterFile();
 157
 158         Register* start() const { return m_start; }
 159         Register* end() const { return m_end; }
 160         size_t size() const { return m_end - m_start; }
 161
 162         void setGlobalObject(JSGlobalObject* globalObject) { m_globalObject = globalObject; }
 163         JSGlobalObject* globalObject() { return m_globalObject; }
 164
 165         void shrink(Register* newEnd)
 166         {
 167             if (newEnd < m_end)
 168                 m_end = newEnd;
 169         }
 170
 171         bool grow(Register* newEnd)
 172         {
 173             if (newEnd > m_end) {
 174                 if (newEnd > m_max)
 175                     return false;
 176 #if !HAVE(MMAP) && HAVE(VIRTUALALLOC)
 177                 if (newEnd > m_maxCommitted) {
 178                     ptrdiff_t additionalAllocation = ((reinterpret_cast<char*>(newEnd)  - reinterpret_cast<char*>(m_maxCommitted)) + allocationSizeMask) & ~allocationSizeMask;
 179                     if (!VirtualAlloc(m_maxCommitted, additionalAllocation, MEM_COMMIT, PAGE_READWRITE)) {
 180                         fprintf(stderr, "Could not allocate register file: %d\n", errno);
 181                         CRASH();
 182                     }
 183                     m_maxCommitted = reinterpret_cast<Register*>(reinterpret_cast<char*>(m_maxCommitted) + additionalAllocation);
 184                 }
 185 #endif
 186                 m_end = newEnd;
 187             }
 188             return true;
 189         }
 190
 191         void setNumGlobals(size_t numGlobals) { m_numGlobals = numGlobals; }
 192         int numGlobals() const { return m_numGlobals; }
 193         size_t maxGlobals() const { return m_maxGlobals; }
 194
 195         Register* lastGlobal() const { return m_start - m_numGlobals; }
 196
 197         void markGlobals(Heap* heap) { heap->markConservatively(lastGlobal(), m_start); }
 198         void markCallFrames(Heap* heap) { heap->markConservatively(m_start, m_end); }
 199
 200     private:
 201         size_t m_numGlobals;
 202         const size_t m_maxGlobals;
 203         Register* m_start;
 204         Register* m_end;
 205         Register* m_max;
 206         Register* m_buffer;
 207 #if HAVE(VIRTUALALLOC)
 208         Register* m_maxCommitted;
 209 #endif
 210
 211         JSGlobalObject* m_globalObject; // The global object whose vars are currently stored in the register file.
 212     };
 213
 214 } // namespace JSC
 215
 216 #endif // RegisterFile_h