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), alignof(int));
  21   int *b = (int*)Alloc.Allocate(sizeof(int) * 10, alignof(int));
  22   int *c = (int*)Alloc.Allocate(sizeof(int), alignof(int));
  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
  65   // Allocate something larger than the SizeThreshold=4096.
  66   (void)Alloc.Allocate(5000, 1);
  67   Alloc.Reset();
  68   // Calling Reset should free all CustomSizedSlabs.
  69   EXPECT_EQ(0u, Alloc.GetNumSlabs());
  70
  71   Alloc.Allocate(3000, 1);
  72   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  73   Alloc.Allocate(3000, 1);
  74   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  75   Alloc.Reset();
  76   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  77   Alloc.Allocate(3000, 1);
  78   EXPECT_EQ(1U, Alloc.GetNumSlabs());
  79   Alloc.Allocate(3000, 1);
  80   EXPECT_EQ(2U, Alloc.GetNumSlabs());
  81 }
  82
  83 // Test some allocations at varying alignments.
  84 TEST(AllocatorTest, TestAlignment) {
  85   BumpPtrAllocator Alloc;
  86   uintptr_t a;
  87   a = (uintptr_t)Alloc.Allocate(1, 2);
  88   EXPECT_EQ(0U, a & 1);
  89   a = (uintptr_t)Alloc.Allocate(1, 4);
  90   EXPECT_EQ(0U, a & 3);
  91   a = (uintptr_t)Alloc.Allocate(1, 8);
  92   EXPECT_EQ(0U, a & 7);
  93   a = (uintptr_t)Alloc.Allocate(1, 16);
  94   EXPECT_EQ(0U, a & 15);
  95   a = (uintptr_t)Alloc.Allocate(1, 32);
  96   EXPECT_EQ(0U, a & 31);
  97   a = (uintptr_t)Alloc.Allocate(1, 64);
  98   EXPECT_EQ(0U, a & 63);
  99   a = (uintptr_t)Alloc.Allocate(1, 128);
 100   EXPECT_EQ(0U, a & 127);
 101 }
 102
 103 // Test allocating just over the slab size.  This tests a bug where before the
 104 // allocator incorrectly calculated the buffer end pointer.
 105 TEST(AllocatorTest, TestOverflow) {
 106   BumpPtrAllocator Alloc;
 107
 108   // Fill the slab right up until the end pointer.
 109   Alloc.Allocate(4096, 1);
 110   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 111
 112   // If we don't allocate a new slab, then we will have overflowed.
 113   Alloc.Allocate(1, 1);
 114   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 115 }
 116
 117 // Test allocating with a size larger than the initial slab size.
 118 TEST(AllocatorTest, TestSmallSlabSize) {
 119   BumpPtrAllocator Alloc;
 120
 121   Alloc.Allocate(8000, 1);
 122   EXPECT_EQ(1U, Alloc.GetNumSlabs());
 123 }
 124
 125 // Test requesting alignment that goes past the end of the current slab.
 126 TEST(AllocatorTest, TestAlignmentPastSlab) {
 127   BumpPtrAllocator Alloc;
 128   Alloc.Allocate(4095, 1);
 129
 130   // Aligning the current slab pointer is likely to move it past the end of the
 131   // slab, which would confuse any unsigned comparisons with the difference of
 132   // the end pointer and the aligned pointer.
 133   Alloc.Allocate(1024, 8192);
 134
 135   EXPECT_EQ(2U, Alloc.GetNumSlabs());
 136 }
 137
 138 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
 139 // easy portable way to do this, so this is kind of a hack.
 140 class MockSlabAllocator {
 141   static size_t LastSlabSize;
 142
 143 public:
 144   ~MockSlabAllocator() { }
 145
 146   void *Allocate(size_t Size, size_t /*Alignment*/) {
 147     // Allocate space for the alignment, the slab, and a void* that goes right
 148     // before the slab.
 149     size_t Alignment = 4096;
 150     void *MemBase = safe_malloc(Size + Alignment - 1 + sizeof(void*));
 151
 152     // Find the slab start.
 153     void *Slab = (void *)alignAddr((char*)MemBase + sizeof(void *), Alignment);
 154
 155     // Hold a pointer to the base so we can free the whole malloced block.
 156     ((void**)Slab)[-1] = MemBase;
 157
 158     LastSlabSize = Size;
 159     return Slab;
 160   }
 161
 162   void Deallocate(void *Slab, size_t Size) {
 163     free(((void**)Slab)[-1]);
 164   }
 165
 166   static size_t GetLastSlabSize() { return LastSlabSize; }
 167 };
 168
 169 size_t MockSlabAllocator::LastSlabSize = 0;
 170
 171 // Allocate a large-ish block with a really large alignment so that the
 172 // allocator will think that it has space, but after it does the alignment it
 173 // will not.
 174 TEST(AllocatorTest, TestBigAlignment) {
 175   BumpPtrAllocatorImpl<MockSlabAllocator> Alloc;
 176
 177   // First allocate a tiny bit to ensure we have to re-align things.
 178   (void)Alloc.Allocate(1, 1);
 179
 180   // Now the big chunk with a big alignment.
 181   (void)Alloc.Allocate(3000, 2048);
 182
 183   // We test that the last slab size is not the default 4096 byte slab, but
 184   // rather a custom sized slab that is larger.
 185   EXPECT_GT(MockSlabAllocator::GetLastSlabSize(), 4096u);
 186 }
 187
 188 }  // anonymous namespace