interpreter/RegisterFile.h

   1 /*
   2  * Copyright (C) 2008, 2009 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 "Collector.h"
  33 #include "ExecutableAllocator.h"
  34 #include "Register.h"
  35 #include "WeakGCPtr.h"
  36 #include <stdio.h>
  37 #include <wtf/Noncopyable.h>
  38 #include <wtf/VMTags.h>
  39
  40 #if HAVE(MMAP)
  41 #include <errno.h>
  42 #include <sys/mman.h>
  43 #endif
  44
  45 namespace JSC {
  46
  47 /*
  48     A register file is a stack of register frames. We represent a register
  49     frame by its offset from "base", the logical first entry in the register
  50     file. The bottom-most register frame's offset from base is 0.
  51
  52     In a program where function "a" calls function "b" (global code -> a -> b),
  53     the register file might look like this:
  54
  55     |       global frame     |        call frame      |        call frame      |     spare capacity     |
  56     -----------------------------------------------------------------------------------------------------
  57     |  0 |  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 | 10 | 11 | 12 | 13 | 14 |    |    |    |    |    | <-- index in buffer
  58     -----------------------------------------------------------------------------------------------------
  59     | -3 | -2 | -1 |  0 |  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 | 10 | 11 |    |    |    |    |    | <-- index relative to base
  60     -----------------------------------------------------------------------------------------------------
  61     |    <-globals | temps-> |  <-vars | temps->      |                 <-vars |
  62        ^              ^                   ^                                       ^
  63        |              |                   |                                       |
  64      buffer    base (frame 0)          frame 1                                 frame 2
  65
  66     Since all variables, including globals, are accessed by negative offsets
  67     from their register frame pointers, to keep old global offsets correct, new
  68     globals must appear at the beginning of the register file, shifting base
  69     to the right.
  70
  71     If we added one global variable to the register file depicted above, it
  72     would look like this:
  73
  74     |         global frame        |<                                                                    >
  75     ------------------------------->                                                                    <
  76     |  0 |  1 |  2 |  3 |  4 |  5 |<                             >snip<                                 > <-- index in buffer
  77     ------------------------------->                                                                    <
  78     | -4 | -3 | -2 | -1 |  0 |  1 |<                                                                    > <-- index relative to base
  79     ------------------------------->                                                                    <
  80     |         <-globals | temps-> |
  81        ^                   ^
  82        |                   |
  83      buffer         base (frame 0)
  84
  85     As you can see, global offsets relative to base have stayed constant,
  86     but base itself has moved. To keep up with possible changes to base,
  87     clients keep an indirect pointer, so their calculations update
  88     automatically when base changes.
  89
  90     For client simplicity, the RegisterFile measures size and capacity from
  91     "base", not "buffer".
  92 */
  93
  94     class JSGlobalObject;
  95
  96     class RegisterFile : public Noncopyable {
  97         friend class JIT;
  98     public:
  99         enum CallFrameHeaderEntry {
 100             CallFrameHeaderSize = 8,
 101
 102             CodeBlock = -8,
 103             ScopeChain = -7,
 104             CallerFrame = -6,
 105             ReturnPC = -5, // This is either an Instruction* or a pointer into JIT generated code stored as an Instruction*.
 106             ReturnValueRegister = -4,
 107             ArgumentCount = -3,
 108             Callee = -2,
 109             OptionalCalleeArguments = -1,
 110         };
 111
 112         enum { ProgramCodeThisRegister = -CallFrameHeaderSize - 1 };
 113         enum { ArgumentsRegister = 0 };
 114
 115         static const size_t defaultCapacity = 524288;
 116         static const size_t defaultMaxGlobals = 8192;
 117         static const size_t commitSize = 1 << 14;
 118         // Allow 8k of excess registers before we start trying to reap the registerfile
 119         static const ptrdiff_t maxExcessCapacity = 8 * 1024;
 120
 121         RegisterFile(size_t capacity = defaultCapacity, size_t maxGlobals = defaultMaxGlobals);
 122         ~RegisterFile();
 123
 124         Register* start() const { return m_start; }
 125         Register* end() const { return m_end; }
 126         size_t size() const { return m_end - m_start; }
 127
 128         void setGlobalObject(JSGlobalObject*);
 129         bool clearGlobalObject(JSGlobalObject*);
 130         JSGlobalObject* globalObject();
 131
 132         bool grow(Register* newEnd);
 133         void shrink(Register* newEnd);
 134
 135         void setNumGlobals(size_t numGlobals) { m_numGlobals = numGlobals; }
 136         int numGlobals() const { return m_numGlobals; }
 137         size_t maxGlobals() const { return m_maxGlobals; }
 138
 139         Register* lastGlobal() const { return m_start - m_numGlobals; }
 140
 141         void markGlobals(MarkStack& markStack, Heap* heap) { heap->markConservatively(markStack, lastGlobal(), m_start); }
 142         void markCallFrames(MarkStack& markStack, Heap* heap) { heap->markConservatively(markStack, m_start, m_end); }
 143
 144     private:
 145         void releaseExcessCapacity();
 146         size_t m_numGlobals;
 147         const size_t m_maxGlobals;
 148         Register* m_start;
 149         Register* m_end;
 150         Register* m_max;
 151         Register* m_buffer;
 152         Register* m_maxUsed;
 153
 154 #if HAVE(VIRTUALALLOC)
 155         Register* m_commitEnd;
 156 #endif
 157
 158         WeakGCPtr<JSGlobalObject> m_globalObject; // The global object whose vars are currently stored in the register file.
 159     };
 160
 161     // FIXME: Add a generic getpagesize() to WTF, then move this function to WTF as well.
 162     inline bool isPageAligned(size_t size) { return size != 0 && size % (8 * 1024) == 0; }
 163
 164     inline RegisterFile::RegisterFile(size_t capacity, size_t maxGlobals)
 165         : m_numGlobals(0)
 166         , m_maxGlobals(maxGlobals)
 167         , m_start(0)
 168         , m_end(0)
 169         , m_max(0)
 170         , m_buffer(0)
 171     {
 172         // Verify that our values will play nice with mmap and VirtualAlloc.
 173         ASSERT(isPageAligned(maxGlobals));
 174         ASSERT(isPageAligned(capacity));
 175
 176         size_t bufferLength = (capacity + maxGlobals) * sizeof(Register);
 177     #if HAVE(MMAP)
 178         m_buffer = static_cast<Register*>(mmap(0, bufferLength, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, VM_TAG_FOR_REGISTERFILE_MEMORY, 0));
 179         if (m_buffer == MAP_FAILED) {
 180 #if OS(WINCE)
 181             fprintf(stderr, "Could not allocate register file: %d\n", GetLastError());
 182 #else
 183             fprintf(stderr, "Could not allocate register file: %d\n", errno);
 184 #endif
 185             CRASH();
 186         }
 187     #elif HAVE(VIRTUALALLOC)
 188         m_buffer = static_cast<Register*>(VirtualAlloc(0, roundUpAllocationSize(bufferLength, commitSize), MEM_RESERVE, PAGE_READWRITE));
 189         if (!m_buffer) {
 190 #if OS(WINCE)
 191             fprintf(stderr, "Could not allocate register file: %d\n", GetLastError());
 192 #else
 193             fprintf(stderr, "Could not allocate register file: %d\n", errno);
 194 #endif
 195             CRASH();
 196         }
 197         size_t committedSize = roundUpAllocationSize(maxGlobals * sizeof(Register), commitSize);
 198         void* commitCheck = VirtualAlloc(m_buffer, committedSize, MEM_COMMIT, PAGE_READWRITE);
 199         if (commitCheck != m_buffer) {
 200 #if OS(WINCE)
 201             fprintf(stderr, "Could not allocate register file: %d\n", GetLastError());
 202 #else
 203             fprintf(stderr, "Could not allocate register file: %d\n", errno);
 204 #endif
 205             CRASH();
 206         }
 207         m_commitEnd = reinterpret_cast<Register*>(reinterpret_cast<char*>(m_buffer) + committedSize);
 208     #else
 209         /*
 210          * If neither MMAP nor VIRTUALALLOC are available - use fastMalloc instead.
 211          *
 212          * Please note that this is the fallback case, which is non-optimal.
 213          * If any possible, the platform should provide for a better memory
 214          * allocation mechanism that allows for "lazy commit" or dynamic
 215          * pre-allocation, similar to mmap or VirtualAlloc, to avoid waste of memory.
 216          */
 217         m_buffer = static_cast<Register*>(fastMalloc(bufferLength));
 218     #endif
 219         m_start = m_buffer + maxGlobals;
 220         m_end = m_start;
 221         m_maxUsed = m_end;
 222         m_max = m_start + capacity;
 223     }
 224
 225     inline void RegisterFile::shrink(Register* newEnd)
 226     {
 227         if (newEnd >= m_end)
 228             return;
 229         m_end = newEnd;
 230         if (m_end == m_start && (m_maxUsed - m_start) > maxExcessCapacity)
 231             releaseExcessCapacity();
 232     }
 233
 234     inline bool RegisterFile::grow(Register* newEnd)
 235     {
 236         if (newEnd < m_end)
 237             return true;
 238
 239         if (newEnd > m_max)
 240             return false;
 241
 242 #if !HAVE(MMAP) && HAVE(VIRTUALALLOC)
 243         if (newEnd > m_commitEnd) {
 244             size_t size = roundUpAllocationSize(reinterpret_cast<char*>(newEnd) - reinterpret_cast<char*>(m_commitEnd), commitSize);
 245             if (!VirtualAlloc(m_commitEnd, size, MEM_COMMIT, PAGE_READWRITE)) {
 246 #if OS(WINCE)
 247                 fprintf(stderr, "Could not allocate register file: %d\n", GetLastError());
 248 #else
 249                 fprintf(stderr, "Could not allocate register file: %d\n", errno);
 250 #endif
 251                 CRASH();
 252             }
 253             m_commitEnd = reinterpret_cast<Register*>(reinterpret_cast<char*>(m_commitEnd) + size);
 254         }
 255 #endif
 256
 257         if (newEnd > m_maxUsed)
 258             m_maxUsed = newEnd;
 259
 260         m_end = newEnd;
 261         return true;
 262     }
 263
 264 } // namespace JSC
 265
 266 #endif // RegisterFile_h