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      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), 0);
     21   int *b = (int*)Alloc.Allocate(sizeof(int) * 10, 0);
     22   int *c = (int*)Alloc.Allocate(sizeof(int), 0);
     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 
     34 // Allocate enough bytes to create three slabs.
     35 TEST(AllocatorTest, ThreeSlabs) {
     36   BumpPtrAllocator Alloc(4096, 4096);
     37   Alloc.Allocate(3000, 0);
     38   EXPECT_EQ(1U, Alloc.GetNumSlabs());
     39   Alloc.Allocate(3000, 0);
     40   EXPECT_EQ(2U, Alloc.GetNumSlabs());
     41   Alloc.Allocate(3000, 0);
     42   EXPECT_EQ(3U, Alloc.GetNumSlabs());
     43 }
     44 
     45 // Allocate enough bytes to create two slabs, reset the allocator, and do it
     46 // again.
     47 TEST(AllocatorTest, TestReset) {
     48   BumpPtrAllocator Alloc(4096, 4096);
     49   Alloc.Allocate(3000, 0);
     50   EXPECT_EQ(1U, Alloc.GetNumSlabs());
     51   Alloc.Allocate(3000, 0);
     52   EXPECT_EQ(2U, Alloc.GetNumSlabs());
     53   Alloc.Reset();
     54   EXPECT_EQ(1U, Alloc.GetNumSlabs());
     55   Alloc.Allocate(3000, 0);
     56   EXPECT_EQ(1U, Alloc.GetNumSlabs());
     57   Alloc.Allocate(3000, 0);
     58   EXPECT_EQ(2U, Alloc.GetNumSlabs());
     59 }
     60 
     61 // Test some allocations at varying alignments.
     62 TEST(AllocatorTest, TestAlignment) {
     63   BumpPtrAllocator Alloc;
     64   uintptr_t a;
     65   a = (uintptr_t)Alloc.Allocate(1, 2);
     66   EXPECT_EQ(0U, a & 1);
     67   a = (uintptr_t)Alloc.Allocate(1, 4);
     68   EXPECT_EQ(0U, a & 3);
     69   a = (uintptr_t)Alloc.Allocate(1, 8);
     70   EXPECT_EQ(0U, a & 7);
     71   a = (uintptr_t)Alloc.Allocate(1, 16);
     72   EXPECT_EQ(0U, a & 15);
     73   a = (uintptr_t)Alloc.Allocate(1, 32);
     74   EXPECT_EQ(0U, a & 31);
     75   a = (uintptr_t)Alloc.Allocate(1, 64);
     76   EXPECT_EQ(0U, a & 63);
     77   a = (uintptr_t)Alloc.Allocate(1, 128);
     78   EXPECT_EQ(0U, a & 127);
     79 }
     80 
     81 // Test allocating just over the slab size.  This tests a bug where before the
     82 // allocator incorrectly calculated the buffer end pointer.
     83 TEST(AllocatorTest, TestOverflow) {
     84   BumpPtrAllocator Alloc(4096, 4096);
     85 
     86   // Fill the slab right up until the end pointer.
     87   Alloc.Allocate(4096 - sizeof(MemSlab), 0);
     88   EXPECT_EQ(1U, Alloc.GetNumSlabs());
     89 
     90   // If we don't allocate a new slab, then we will have overflowed.
     91   Alloc.Allocate(1, 0);
     92   EXPECT_EQ(2U, Alloc.GetNumSlabs());
     93 }
     94 
     95 // Test allocating with a size larger than the initial slab size.
     96 TEST(AllocatorTest, TestSmallSlabSize) {
     97   BumpPtrAllocator Alloc(128);
     98 
     99   Alloc.Allocate(200, 0);
    100   EXPECT_EQ(2U, Alloc.GetNumSlabs());
    101 }
    102 
    103 // Mock slab allocator that returns slabs aligned on 4096 bytes.  There is no
    104 // easy portable way to do this, so this is kind of a hack.
    105 class MockSlabAllocator : public SlabAllocator {
    106   MemSlab *LastSlab;
    107 
    108 public:
    109   virtual ~MockSlabAllocator() { }
    110 
    111   virtual MemSlab *Allocate(size_t Size) {
    112     // Allocate space for the alignment, the slab, and a void* that goes right
    113     // before the slab.
    114     size_t Alignment = 4096;
    115     void *MemBase = malloc(Size + Alignment - 1 + sizeof(void*));
    116 
    117     // Make the slab.
    118     MemSlab *Slab = (MemSlab*)(((uintptr_t)MemBase+sizeof(void*)+Alignment-1) &
    119                                ~(uintptr_t)(Alignment - 1));
    120     Slab->Size = Size;
    121     Slab->NextPtr = 0;
    122 
    123     // Hold a pointer to the base so we can free the whole malloced block.
    124     ((void**)Slab)[-1] = MemBase;
    125 
    126     LastSlab = Slab;
    127     return Slab;
    128   }
    129 
    130   virtual void Deallocate(MemSlab *Slab) {
    131     free(((void**)Slab)[-1]);
    132   }
    133 
    134   MemSlab *GetLastSlab() {
    135     return LastSlab;
    136   }
    137 };
    138 
    139 // Allocate a large-ish block with a really large alignment so that the
    140 // allocator will think that it has space, but after it does the alignment it
    141 // will not.
    142 TEST(AllocatorTest, TestBigAlignment) {
    143   MockSlabAllocator SlabAlloc;
    144   BumpPtrAllocator Alloc(4096, 4096, SlabAlloc);
    145   uintptr_t Ptr = (uintptr_t)Alloc.Allocate(3000, 2048);
    146   MemSlab *Slab = SlabAlloc.GetLastSlab();
    147   EXPECT_LE(Ptr + 3000, ((uintptr_t)Slab) + Slab->Size);
    148 }
    149 
    150 }  // anonymous namespace
    151