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;
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;
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;
85 
86   // Fill the slab right up until the end pointer.
87   Alloc.Allocate(4096, 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;
98 
99   Alloc.Allocate(8000, 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 {
106   static size_t LastSlabSize;
107 
108 public:
109   ~MockSlabAllocator() { }
110 
111   void *Allocate(size_t Size, size_t /*Alignment*/) {
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     // Find the slab start.
118     void *Slab = alignPtr((char *)MemBase + sizeof(void *), Alignment);
119 
120     // Hold a pointer to the base so we can free the whole malloced block.
121     ((void**)Slab)[-1] = MemBase;
122 
123     LastSlabSize = Size;
124     return Slab;
125   }
126 
127   void Deallocate(void *Slab, size_t Size) {
128     free(((void**)Slab)[-1]);
129   }
130 
131   static size_t GetLastSlabSize() { return LastSlabSize; }
132 };
133 
134 size_t MockSlabAllocator::LastSlabSize = 0;
135 
136 // Allocate a large-ish block with a really large alignment so that the
137 // allocator will think that it has space, but after it does the alignment it
138 // will not.
139 TEST(AllocatorTest, TestBigAlignment) {
140   BumpPtrAllocatorImpl<MockSlabAllocator> Alloc;
141 
142   // First allocate a tiny bit to ensure we have to re-align things.
143   (void)Alloc.Allocate(1, 0);
144 
145   // Now the big chunk with a big alignment.
146   (void)Alloc.Allocate(3000, 2048);
147 
148   // We test that the last slab size is not the default 4096 byte slab, but
149   // rather a custom sized slab that is larger.
150   EXPECT_GT(MockSlabAllocator::GetLastSlabSize(), 4096u);
151 }
152 
153 }  // anonymous namespace
154