llvm/unittests/Support/AllocatorTest.cpp

   1 //===- llvm/unittest/Support/AllocatorTest.cpp - BumpPtrAllocator tests ---===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/Support/Allocator.h"
  10 #include "gtest/gtest.h"
  11 #include <cstdlib>
  12
  13 using namespace llvm;
  14
  15 namespace {
  16
  17 TEST(AllocatorTest, Basics) {
  18   BumpPtrAllocator Alloc;
  19   int *a = (int*)Alloc.Allocate(sizeof(int), alignof(int));
  20   int *b = (int*)Alloc.Allocate(sizeof(int) * 10, alignof(int));
  21   int *c = (int*)Alloc.Allocate(sizeof(int), alignof(int));
  22   *a = 1;
  23   b[0] = 2;
  24   b[9] = 2;
  25   *c = 3;
  26   EXPECT_EQ(1, *a);
  27   EXPECT_EQ(2, b[0]);
  28   EXPECT_EQ(2, b[9]);
  29   EXPECT_EQ(3, *c);
  30   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  31
  32   BumpPtrAllocator Alloc2 = std::move(Alloc);
  33   EXPECT_EQ(0U, Alloc.GetNumSlabs());
  34   EXPECT_EQ(1U, Alloc2.GetNumSlabs());
  35
  36   // Make sure the old pointers still work. These are especially interesting
  37   // under ASan or Valgrind.
  38   EXPECT_EQ(1, *a);
  39   EXPECT_EQ(2, b[0]);
  40   EXPECT_EQ(2, b[9]);
  41   EXPECT_EQ(3, *c);
  42
  43   Alloc = std::move(Alloc2);
  44   EXPECT_EQ(0U, Alloc2.GetNumSlabs());
  45   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  46 }
  47
  48 // Allocate enough bytes to create three slabs.
  49 TEST(AllocatorTest, ThreeSlabs) {
  50   BumpPtrAllocator Alloc;
  51   Alloc.Allocate(3000, 1);
  52   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  53   Alloc.Allocate(3000, 1);
  54   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  55   Alloc.Allocate(3000, 1);
  56   EXPECT_EQ(3U, Alloc.GetNumSlabs());
  57 }
  58
  59 // Allocate enough bytes to create two slabs, reset the allocator, and do it
  60 // again.
  61 TEST(AllocatorTest, TestReset) {
  62   BumpPtrAllocator Alloc;
  63
  64   // Allocate something larger than the SizeThreshold=4096.
  65   (void)Alloc.Allocate(5000, 1);
  66   Alloc.Reset();
  67   // Calling Reset should free all CustomSizedSlabs.
  68   EXPECT_EQ(0u, Alloc.GetNumSlabs());
  69
  70   Alloc.Allocate(3000, 1);
  71   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  72   Alloc.Allocate(3000, 1);
  73   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  74   Alloc.Reset();
  75   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  76   Alloc.Allocate(3000, 1);
  77   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  78   Alloc.Allocate(3000, 1);
  79   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  80 }
  81
  82 // Test some allocations at varying alignments.
  83 TEST(AllocatorTest, TestAlignment) {
  84   BumpPtrAllocator Alloc;
  85   uintptr_t a;
  86   a = (uintptr_t)Alloc.Allocate(1, 2);
  87   EXPECT_EQ(0U, a & 1);
  88   a = (uintptr_t)Alloc.Allocate(1, 4);
  89   EXPECT_EQ(0U, a & 3);
  90   a = (uintptr_t)Alloc.Allocate(1, 8);
  91   EXPECT_EQ(0U, a & 7);
  92   a = (uintptr_t)Alloc.Allocate(1, 16);
  93   EXPECT_EQ(0U, a & 15);
  94   a = (uintptr_t)Alloc.Allocate(1, 32);
  95   EXPECT_EQ(0U, a & 31);
  96   a = (uintptr_t)Alloc.Allocate(1, 64);
  97   EXPECT_EQ(0U, a & 63);
  98   a = (uintptr_t)Alloc.Allocate(1, 128);
  99   EXPECT_EQ(0U, a & 127);
 100 }
 101
 102 // Test allocating just over the slab size.  This tests a bug where before the
 103 // allocator incorrectly calculated the buffer end pointer.
 104 TEST(AllocatorTest, TestOverflow) {
 105   BumpPtrAllocator Alloc;
 106
 107   // Fill the slab right up until the end pointer.
 108   Alloc.Allocate(4096, 1);
 109   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 110
 111   // If we don't allocate a new slab, then we will have overflowed.
 112   Alloc.Allocate(1, 1);
 113   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 114 }
 115
 116 // Test allocating with a size larger than the initial slab size.
 117 TEST(AllocatorTest, TestSmallSlabSize) {
 118   BumpPtrAllocator Alloc;
 119
 120   Alloc.Allocate(8000, 1);
 121   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 122 }
 123
 124 // Test requesting alignment that goes past the end of the current slab.
 125 TEST(AllocatorTest, TestAlignmentPastSlab) {
 126   BumpPtrAllocator Alloc;
 127   Alloc.Allocate(4095, 1);
 128
 129   // Aligning the current slab pointer is likely to move it past the end of the
 130   // slab, which would confuse any unsigned comparisons with the difference of
 131   // the end pointer and the aligned pointer.
 132   Alloc.Allocate(1024, 8192);
 133
 134   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 135 }
 136
 137 // Test allocating with a decreased growth delay.
 138 TEST(AllocatorTest, TestFasterSlabGrowthDelay) {
 139   const size_t SlabSize = 4096;
 140   // Decrease the growth delay to double the slab size every slab.
 141   const size_t GrowthDelay = 1;
 142   BumpPtrAllocatorImpl<MallocAllocator, SlabSize, SlabSize, GrowthDelay> Alloc;
 143   // Disable the red zone for this test. The additional bytes allocated for the
 144   // red zone would change the allocation numbers we check below.
 145   Alloc.setRedZoneSize(0);
 146
 147   Alloc.Allocate(SlabSize, 1);
 148   EXPECT_EQ(SlabSize, Alloc.getTotalMemory());
 149   // We hit our growth delay with the previous allocation so the next
 150   // allocation should get a twice as large slab.
 151   Alloc.Allocate(SlabSize, 1);
 152   EXPECT_EQ(SlabSize * 3, Alloc.getTotalMemory());
 153   Alloc.Allocate(SlabSize, 1);
 154   EXPECT_EQ(SlabSize * 3, Alloc.getTotalMemory());
 155
 156   // Both slabs are full again and hit the growth delay again, so the
 157   // next allocation should again get a slab with four times the size of the
 158   // original slab size. In total we now should have a memory size of:
 159   // 1 + 2 + 4 * SlabSize.
 160   Alloc.Allocate(SlabSize, 1);
 161   EXPECT_EQ(SlabSize * 7, Alloc.getTotalMemory());
 162 }
 163
 164 // Test allocating with a increased growth delay.
 165 TEST(AllocatorTest, TestSlowerSlabGrowthDelay) {
 166   const size_t SlabSize = 16;
 167   // Increase the growth delay to only double the slab size every 256 slabs.
 168   const size_t GrowthDelay = 256;
 169   BumpPtrAllocatorImpl<MallocAllocator, SlabSize, SlabSize, GrowthDelay> Alloc;
 170   // Disable the red zone for this test. The additional bytes allocated for the
 171   // red zone would change the allocation numbers we check below.
 172   Alloc.setRedZoneSize(0);
 173
 174   // Allocate 256 slabs. We should keep getting slabs with the original size
 175   // as we haven't hit our growth delay on the last allocation.
 176   for (std::size_t i = 0; i < GrowthDelay; ++i)
 177     Alloc.Allocate(SlabSize, 1);
 178   EXPECT_EQ(SlabSize * GrowthDelay, Alloc.getTotalMemory());
 179   // Allocate another slab. This time we should get another slab allocated
 180   // that is twice as large as the normal slab size.
 181   Alloc.Allocate(SlabSize, 1);
 182   EXPECT_EQ(SlabSize * GrowthDelay + SlabSize * 2, Alloc.getTotalMemory());
 183 }
 184
 185 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
 186 // easy portable way to do this, so this is kind of a hack.
 187 class MockSlabAllocator {
 188   static size_t LastSlabSize;
 189
 190 public:
 191   ~MockSlabAllocator() { }
 192
 193   void *Allocate(size_t Size, size_t /*Alignment*/) {
 194     // Allocate space for the alignment, the slab, and a void* that goes right
 195     // before the slab.
 196     Align Alignment(4096);
 197     void *MemBase = safe_malloc(Size + Alignment.value() - 1 + sizeof(void *));
 198
 199     // Find the slab start.
 200     void *Slab = (void *)alignAddr((char*)MemBase + sizeof(void *), Alignment);
 201
 202     // Hold a pointer to the base so we can free the whole malloced block.
 203     ((void**)Slab)[-1] = MemBase;
 204
 205     LastSlabSize = Size;
 206     return Slab;
 207   }
 208
 209   void Deallocate(void *Slab, size_t /*Size*/, size_t /*Alignment*/) {
 210     free(((void**)Slab)[-1]);
 211   }
 212
 213   static size_t GetLastSlabSize() { return LastSlabSize; }
 214 };
 215
 216 size_t MockSlabAllocator::LastSlabSize = 0;
 217
 218 // Allocate a large-ish block with a really large alignment so that the
 219 // allocator will think that it has space, but after it does the alignment it
 220 // will not.
 221 TEST(AllocatorTest, TestBigAlignment) {
 222   BumpPtrAllocatorImpl<MockSlabAllocator> Alloc;
 223
 224   // First allocate a tiny bit to ensure we have to re-align things.
 225   (void)Alloc.Allocate(1, 1);
 226
 227   // Now the big chunk with a big alignment.
 228   (void)Alloc.Allocate(3000, 2048);
 229
 230   // We test that the last slab size is not the default 4096 byte slab, but
 231   // rather a custom sized slab that is larger.
 232   EXPECT_GT(MockSlabAllocator::GetLastSlabSize(), 4096u);
 233 }
 234
 235 }  // anonymous namespace