src/llvm/unittests/Support/AllocatorTest.cpp

   1 //===- llvm/unittest/Support/AllocatorTest.cpp - BumpPtrAllocator tests ---===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #include "llvm/Support/Allocator.h"
  11 #include "gtest/gtest.h"
  12 #include <cstdlib>
  13
  14 using namespace llvm;
  15
  16 namespace {
  17
  18 TEST(AllocatorTest, Basics) {
  19   BumpPtrAllocator Alloc;
  20   int *a = (int*)Alloc.Allocate(sizeof(int), 1);
  21   int *b = (int*)Alloc.Allocate(sizeof(int) * 10, 1);
  22   int *c = (int*)Alloc.Allocate(sizeof(int), 1);
  23   *a = 1;
  24   b[0] = 2;
  25   b[9] = 2;
  26   *c = 3;
  27   EXPECT_EQ(1, *a);
  28   EXPECT_EQ(2, b[0]);
  29   EXPECT_EQ(2, b[9]);
  30   EXPECT_EQ(3, *c);
  31   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  32
  33   BumpPtrAllocator Alloc2 = std::move(Alloc);
  34   EXPECT_EQ(0U, Alloc.GetNumSlabs());
  35   EXPECT_EQ(1U, Alloc2.GetNumSlabs());
  36
  37   // Make sure the old pointers still work. These are especially interesting
  38   // under ASan or Valgrind.
  39   EXPECT_EQ(1, *a);
  40   EXPECT_EQ(2, b[0]);
  41   EXPECT_EQ(2, b[9]);
  42   EXPECT_EQ(3, *c);
  43
  44   Alloc = std::move(Alloc2);
  45   EXPECT_EQ(0U, Alloc2.GetNumSlabs());
  46   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  47 }
  48
  49 // Allocate enough bytes to create three slabs.
  50 TEST(AllocatorTest, ThreeSlabs) {
  51   BumpPtrAllocator Alloc;
  52   Alloc.Allocate(3000, 1);
  53   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  54   Alloc.Allocate(3000, 1);
  55   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  56   Alloc.Allocate(3000, 1);
  57   EXPECT_EQ(3U, Alloc.GetNumSlabs());
  58 }
  59
  60 // Allocate enough bytes to create two slabs, reset the allocator, and do it
  61 // again.
  62 TEST(AllocatorTest, TestReset) {
  63   BumpPtrAllocator Alloc;
  64   Alloc.Allocate(3000, 1);
  65   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  66   Alloc.Allocate(3000, 1);
  67   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  68   Alloc.Reset();
  69   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  70   Alloc.Allocate(3000, 1);
  71   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  72   Alloc.Allocate(3000, 1);
  73   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  74 }
  75
  76 // Test some allocations at varying alignments.
  77 TEST(AllocatorTest, TestAlignment) {
  78   BumpPtrAllocator Alloc;
  79   uintptr_t a;
  80   a = (uintptr_t)Alloc.Allocate(1, 2);
  81   EXPECT_EQ(0U, a & 1);
  82   a = (uintptr_t)Alloc.Allocate(1, 4);
  83   EXPECT_EQ(0U, a & 3);
  84   a = (uintptr_t)Alloc.Allocate(1, 8);
  85   EXPECT_EQ(0U, a & 7);
  86   a = (uintptr_t)Alloc.Allocate(1, 16);
  87   EXPECT_EQ(0U, a & 15);
  88   a = (uintptr_t)Alloc.Allocate(1, 32);
  89   EXPECT_EQ(0U, a & 31);
  90   a = (uintptr_t)Alloc.Allocate(1, 64);
  91   EXPECT_EQ(0U, a & 63);
  92   a = (uintptr_t)Alloc.Allocate(1, 128);
  93   EXPECT_EQ(0U, a & 127);
  94 }
  95
  96 // Test allocating just over the slab size.  This tests a bug where before the
  97 // allocator incorrectly calculated the buffer end pointer.
  98 TEST(AllocatorTest, TestOverflow) {
  99   BumpPtrAllocator Alloc;
 100
 101   // Fill the slab right up until the end pointer.
 102   Alloc.Allocate(4096, 1);
 103   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 104
 105   // If we don't allocate a new slab, then we will have overflowed.
 106   Alloc.Allocate(1, 1);
 107   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 108 }
 109
 110 // Test allocating with a size larger than the initial slab size.
 111 TEST(AllocatorTest, TestSmallSlabSize) {
 112   BumpPtrAllocator Alloc;
 113
 114   Alloc.Allocate(8000, 1);
 115   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 116 }
 117
 118 // Test requesting alignment that goes past the end of the current slab.
 119 TEST(AllocatorTest, TestAlignmentPastSlab) {
 120   BumpPtrAllocator Alloc;
 121   Alloc.Allocate(4095, 1);
 122
 123   // Aligning the current slab pointer is likely to move it past the end of the
 124   // slab, which would confuse any unsigned comparisons with the difference of
 125   // the the end pointer and the aligned pointer.
 126   Alloc.Allocate(1024, 8192);
 127
 128   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 129 }
 130
 131 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
 132 // easy portable way to do this, so this is kind of a hack.
 133 class MockSlabAllocator {
 134   static size_t LastSlabSize;
 135
 136 public:
 137   ~MockSlabAllocator() { }
 138
 139   void *Allocate(size_t Size, size_t /*Alignment*/) {
 140     // Allocate space for the alignment, the slab, and a void* that goes right
 141     // before the slab.
 142     size_t Alignment = 4096;
 143     void *MemBase = malloc(Size + Alignment - 1 + sizeof(void*));
 144
 145     // Find the slab start.
 146     void *Slab = (void *)alignAddr((char*)MemBase + sizeof(void *), Alignment);
 147
 148     // Hold a pointer to the base so we can free the whole malloced block.
 149     ((void**)Slab)[-1] = MemBase;
 150
 151     LastSlabSize = Size;
 152     return Slab;
 153   }
 154
 155   void Deallocate(void *Slab, size_t Size) {
 156     free(((void**)Slab)[-1]);
 157   }
 158
 159   static size_t GetLastSlabSize() { return LastSlabSize; }
 160 };
 161
 162 size_t MockSlabAllocator::LastSlabSize = 0;
 163
 164 // Allocate a large-ish block with a really large alignment so that the
 165 // allocator will think that it has space, but after it does the alignment it
 166 // will not.
 167 TEST(AllocatorTest, TestBigAlignment) {
 168   BumpPtrAllocatorImpl<MockSlabAllocator> Alloc;
 169
 170   // First allocate a tiny bit to ensure we have to re-align things.
 171   (void)Alloc.Allocate(1, 1);
 172
 173   // Now the big chunk with a big alignment.
 174   (void)Alloc.Allocate(3000, 2048);
 175
 176   // We test that the last slab size is not the default 4096 byte slab, but
 177   // rather a custom sized slab that is larger.
 178   EXPECT_GT(MockSlabAllocator::GetLastSlabSize(), 4096u);
 179 }
 180
 181 }  // anonymous namespace