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 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
 138 // easy portable way to do this, so this is kind of a hack.
 139 class MockSlabAllocator {
 140   static size_t LastSlabSize;
 141
 142 public:
 143   ~MockSlabAllocator() { }
 144
 145   void *Allocate(size_t Size, size_t /*Alignment*/) {
 146     // Allocate space for the alignment, the slab, and a void* that goes right
 147     // before the slab.
 148     size_t Alignment = 4096;
 149     void *MemBase = safe_malloc(Size + Alignment - 1 + sizeof(void*));
 150
 151     // Find the slab start.
 152     void *Slab = (void *)alignAddr((char*)MemBase + sizeof(void *), Alignment);
 153
 154     // Hold a pointer to the base so we can free the whole malloced block.
 155     ((void**)Slab)[-1] = MemBase;
 156
 157     LastSlabSize = Size;
 158     return Slab;
 159   }
 160
 161   void Deallocate(void *Slab, size_t Size) {
 162     free(((void**)Slab)[-1]);
 163   }
 164
 165   static size_t GetLastSlabSize() { return LastSlabSize; }
 166 };
 167
 168 size_t MockSlabAllocator::LastSlabSize = 0;
 169
 170 // Allocate a large-ish block with a really large alignment so that the
 171 // allocator will think that it has space, but after it does the alignment it
 172 // will not.
 173 TEST(AllocatorTest, TestBigAlignment) {
 174   BumpPtrAllocatorImpl<MockSlabAllocator> Alloc;
 175
 176   // First allocate a tiny bit to ensure we have to re-align things.
 177   (void)Alloc.Allocate(1, 1);
 178
 179   // Now the big chunk with a big alignment.
 180   (void)Alloc.Allocate(3000, 2048);
 181
 182   // We test that the last slab size is not the default 4096 byte slab, but
 183   // rather a custom sized slab that is larger.
 184   EXPECT_GT(MockSlabAllocator::GetLastSlabSize(), 4096u);
 185 }
 186
 187 }  // anonymous namespace