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 zero-sized allocations.
 103 // In general we don't need to allocate memory for these.
 104 // However Allocate never returns null, so if the first allocation is zero-sized
 105 // we end up creating a slab for it.
 106 TEST(AllocatorTest, TestZero) {
 107   BumpPtrAllocator Alloc;
 108   Alloc.setRedZoneSize(0); // else our arithmetic is all off
 109   EXPECT_EQ(0u, Alloc.GetNumSlabs());
 110   EXPECT_EQ(0u, Alloc.getBytesAllocated());
 111
 112   void *Empty = Alloc.Allocate(0, 1);
 113   EXPECT_NE(Empty, nullptr) << "Allocate is __attribute__((returns_nonnull))";
 114   EXPECT_EQ(1u, Alloc.GetNumSlabs()) << "Allocated a slab to point to";
 115   EXPECT_EQ(0u, Alloc.getBytesAllocated());
 116
 117   void *Large = Alloc.Allocate(4096, 1);
 118   EXPECT_EQ(1u, Alloc.GetNumSlabs());
 119   EXPECT_EQ(4096u, Alloc.getBytesAllocated());
 120   EXPECT_EQ(Empty, Large);
 121
 122   void *Empty2 = Alloc.Allocate(0, 1);
 123   EXPECT_NE(Empty2, nullptr);
 124   EXPECT_EQ(1u, Alloc.GetNumSlabs());
 125   EXPECT_EQ(4096u, Alloc.getBytesAllocated());
 126 }
 127
 128 // Test allocating just over the slab size.  This tests a bug where before the
 129 // allocator incorrectly calculated the buffer end pointer.
 130 TEST(AllocatorTest, TestOverflow) {
 131   BumpPtrAllocator Alloc;
 132
 133   // Fill the slab right up until the end pointer.
 134   Alloc.Allocate(4096, 1);
 135   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 136
 137   // If we don't allocate a new slab, then we will have overflowed.
 138   Alloc.Allocate(1, 1);
 139   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 140 }
 141
 142 // Test allocating with a size larger than the initial slab size.
 143 TEST(AllocatorTest, TestSmallSlabSize) {
 144   BumpPtrAllocator Alloc;
 145
 146   Alloc.Allocate(8000, 1);
 147   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 148 }
 149
 150 // Test requesting alignment that goes past the end of the current slab.
 151 TEST(AllocatorTest, TestAlignmentPastSlab) {
 152   BumpPtrAllocator Alloc;
 153   Alloc.Allocate(4095, 1);
 154
 155   // Aligning the current slab pointer is likely to move it past the end of the
 156   // slab, which would confuse any unsigned comparisons with the difference of
 157   // the end pointer and the aligned pointer.
 158   Alloc.Allocate(1024, 8192);
 159
 160   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 161 }
 162
 163 // Test allocating with a decreased growth delay.
 164 TEST(AllocatorTest, TestFasterSlabGrowthDelay) {
 165   const size_t SlabSize = 4096;
 166   // Decrease the growth delay to double the slab size every slab.
 167   const size_t GrowthDelay = 1;
 168   BumpPtrAllocatorImpl<MallocAllocator, SlabSize, SlabSize, GrowthDelay> Alloc;
 169   // Disable the red zone for this test. The additional bytes allocated for the
 170   // red zone would change the allocation numbers we check below.
 171   Alloc.setRedZoneSize(0);
 172
 173   Alloc.Allocate(SlabSize, 1);
 174   EXPECT_EQ(SlabSize, Alloc.getTotalMemory());
 175   // We hit our growth delay with the previous allocation so the next
 176   // allocation should get a twice as large slab.
 177   Alloc.Allocate(SlabSize, 1);
 178   EXPECT_EQ(SlabSize * 3, Alloc.getTotalMemory());
 179   Alloc.Allocate(SlabSize, 1);
 180   EXPECT_EQ(SlabSize * 3, Alloc.getTotalMemory());
 181
 182   // Both slabs are full again and hit the growth delay again, so the
 183   // next allocation should again get a slab with four times the size of the
 184   // original slab size. In total we now should have a memory size of:
 185   // 1 + 2 + 4 * SlabSize.
 186   Alloc.Allocate(SlabSize, 1);
 187   EXPECT_EQ(SlabSize * 7, Alloc.getTotalMemory());
 188 }
 189
 190 // Test allocating with a increased growth delay.
 191 TEST(AllocatorTest, TestSlowerSlabGrowthDelay) {
 192   const size_t SlabSize = 16;
 193   // Increase the growth delay to only double the slab size every 256 slabs.
 194   const size_t GrowthDelay = 256;
 195   BumpPtrAllocatorImpl<MallocAllocator, SlabSize, SlabSize, GrowthDelay> Alloc;
 196   // Disable the red zone for this test. The additional bytes allocated for the
 197   // red zone would change the allocation numbers we check below.
 198   Alloc.setRedZoneSize(0);
 199
 200   // Allocate 256 slabs. We should keep getting slabs with the original size
 201   // as we haven't hit our growth delay on the last allocation.
 202   for (std::size_t i = 0; i < GrowthDelay; ++i)
 203     Alloc.Allocate(SlabSize, 1);
 204   EXPECT_EQ(SlabSize * GrowthDelay, Alloc.getTotalMemory());
 205   // Allocate another slab. This time we should get another slab allocated
 206   // that is twice as large as the normal slab size.
 207   Alloc.Allocate(SlabSize, 1);
 208   EXPECT_EQ(SlabSize * GrowthDelay + SlabSize * 2, Alloc.getTotalMemory());
 209 }
 210
 211 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
 212 // easy portable way to do this, so this is kind of a hack.
 213 class MockSlabAllocator {
 214   static size_t LastSlabSize;
 215
 216 public:
 217   ~MockSlabAllocator() { }
 218
 219   void *Allocate(size_t Size, size_t /*Alignment*/) {
 220     // Allocate space for the alignment, the slab, and a void* that goes right
 221     // before the slab.
 222     Align Alignment(4096);
 223     void *MemBase = safe_malloc(Size + Alignment.value() - 1 + sizeof(void *));
 224
 225     // Find the slab start.
 226     void *Slab = (void *)alignAddr((char*)MemBase + sizeof(void *), Alignment);
 227
 228     // Hold a pointer to the base so we can free the whole malloced block.
 229     ((void**)Slab)[-1] = MemBase;
 230
 231     LastSlabSize = Size;
 232     return Slab;
 233   }
 234
 235   void Deallocate(void *Slab, size_t /*Size*/, size_t /*Alignment*/) {
 236     free(((void**)Slab)[-1]);
 237   }
 238
 239   static size_t GetLastSlabSize() { return LastSlabSize; }
 240 };
 241
 242 size_t MockSlabAllocator::LastSlabSize = 0;
 243
 244 // Allocate a large-ish block with a really large alignment so that the
 245 // allocator will think that it has space, but after it does the alignment it
 246 // will not.
 247 TEST(AllocatorTest, TestBigAlignment) {
 248   BumpPtrAllocatorImpl<MockSlabAllocator> Alloc;
 249
 250   // First allocate a tiny bit to ensure we have to re-align things.
 251   (void)Alloc.Allocate(1, 1);
 252
 253   // Now the big chunk with a big alignment.
 254   (void)Alloc.Allocate(3000, 2048);
 255
 256   // We test that the last slab size is not the default 4096 byte slab, but
 257   // rather a custom sized slab that is larger.
 258   EXPECT_GT(MockSlabAllocator::GetLastSlabSize(), 4096u);
 259 }
 260
 261 }  // anonymous namespace