jit/ExecutableAllocator.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  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef ExecutableAllocator_h
  27 #define ExecutableAllocator_h
  28
  29 #if ENABLE(ASSEMBLER)
  30
  31 #include <wtf/Assertions.h>
  32 #include <wtf/PassRefPtr.h>
  33 #include <wtf/RefCounted.h>
  34 #include <wtf/Vector.h>
  35
  36 #include <limits>
  37
  38 #define JIT_ALLOCATOR_PAGE_SIZE (ExecutableAllocator::pageSize)
  39 #define JIT_ALLOCATOR_LARGE_ALLOC_SIZE (ExecutableAllocator::pageSize * 4)
  40
  41 namespace JSC {
  42
  43 class ExecutablePool : public RefCounted<ExecutablePool> {
  44 private:
  45     struct Allocation {
  46         char* pages;
  47         size_t size;
  48     };
  49     typedef Vector<Allocation, 2> AllocationList;
  50
  51 public:
  52     static PassRefPtr<ExecutablePool> create(size_t n)
  53     {
  54         return adoptRef(new ExecutablePool(n));
  55     }
  56
  57     void* alloc(size_t n)
  58     {
  59         ASSERT(m_freePtr <= m_end);
  60
  61         // Round 'n' up to a multiple of word size; if all allocations are of
  62         // word sized quantities, then all subsequent allocations will be aligned.
  63         n = roundUpAllocationSize(n, sizeof(void*));
  64
  65         if (static_cast<ptrdiff_t>(n) < (m_end - m_freePtr)) {
  66             void* result = m_freePtr;
  67             m_freePtr += n;
  68             return result;
  69         }
  70
  71         // Insufficient space to allocate in the existing pool
  72         // so we need allocate into a new pool
  73         return poolAllocate(n);
  74     }
  75
  76     ~ExecutablePool()
  77     {
  78         AllocationList::const_iterator end = m_pools.end();
  79         for (AllocationList::const_iterator ptr = m_pools.begin(); ptr != end; ++ptr)
  80             ExecutablePool::systemRelease(*ptr);
  81     }
  82
  83     size_t available() const { return (m_pools.size() > 1) ? 0 : m_end - m_freePtr; }
  84
  85 private:
  86     static Allocation systemAlloc(size_t n);
  87     static void systemRelease(const Allocation& alloc);
  88
  89     inline size_t roundUpAllocationSize(size_t request, size_t granularity)
  90     {
  91         if ((std::numeric_limits<size_t>::max() - granularity) <= request)
  92             CRASH(); // Allocation is too large
  93
  94         // Round up to next page boundary
  95         size_t size = request + (granularity - 1);
  96         size = size & ~(granularity - 1);
  97         ASSERT(size >= request);
  98         return size;
  99     }
 100
 101     ExecutablePool(size_t n);
 102
 103     void* poolAllocate(size_t n);
 104
 105     char* m_freePtr;
 106     char* m_end;
 107     AllocationList m_pools;
 108 };
 109
 110 class ExecutableAllocator {
 111 public:
 112     static size_t pageSize;
 113     ExecutableAllocator()
 114     {
 115         if (!pageSize)
 116             intializePageSize();
 117         m_smallAllocationPool = ExecutablePool::create(JIT_ALLOCATOR_LARGE_ALLOC_SIZE);
 118     }
 119
 120     PassRefPtr<ExecutablePool> poolForSize(size_t n)
 121     {
 122         // Try to fit in the existing small allocator
 123         if (n < m_smallAllocationPool->available())
 124             return m_smallAllocationPool;
 125
 126         // If the request is large, we just provide a unshared allocator
 127         if (n > JIT_ALLOCATOR_LARGE_ALLOC_SIZE)
 128             return ExecutablePool::create(n);
 129
 130         // Create a new allocator
 131         RefPtr<ExecutablePool> pool = ExecutablePool::create(JIT_ALLOCATOR_LARGE_ALLOC_SIZE);
 132
 133         // If the new allocator will result in more free space than in
 134         // the current small allocator, then we will use it instead
 135         if ((pool->available() - n) > m_smallAllocationPool->available())
 136             m_smallAllocationPool = pool;
 137         return pool.release();
 138     }
 139
 140 private:
 141     RefPtr<ExecutablePool> m_smallAllocationPool;
 142     static void intializePageSize();
 143 };
 144
 145 inline ExecutablePool::ExecutablePool(size_t n)
 146 {
 147     size_t allocSize = roundUpAllocationSize(n, JIT_ALLOCATOR_PAGE_SIZE);
 148     Allocation mem = systemAlloc(allocSize);
 149     m_pools.append(mem);
 150     m_freePtr = mem.pages;
 151     if (!m_freePtr)
 152         CRASH(); // Failed to allocate
 153     m_end = m_freePtr + allocSize;
 154 }
 155
 156 inline void* ExecutablePool::poolAllocate(size_t n)
 157 {
 158     size_t allocSize = roundUpAllocationSize(n, JIT_ALLOCATOR_PAGE_SIZE);
 159
 160     Allocation result = systemAlloc(allocSize);
 161     if (!result.pages)
 162         CRASH(); // Failed to allocate
 163
 164     ASSERT(m_end >= m_freePtr);
 165     if ((allocSize - n) > static_cast<size_t>(m_end - m_freePtr)) {
 166         // Replace allocation pool
 167         m_freePtr = result.pages + n;
 168         m_end = result.pages + allocSize;
 169     }
 170
 171     m_pools.append(result);
 172     return result.pages;
 173 }
 174
 175 }
 176
 177 #endif // ENABLE(ASSEMBLER)
 178
 179 #endif // !defined(ExecutableAllocator)