Re-committing changes from r76825 to BumpPtrAllocator with a fix and tests for

an off-by-one error.

llvm-svn: 76891

1 files changed, 95 insertions, 0 deletions

diff --git a/llvm/unittests/Support/AllocatorTest.cpp b/llvm/unittests/Support/AllocatorTest.cpp
index e69de29bb2d..cc3296a8d01 100644
--- a/llvm/unittests/Support/AllocatorTest.cpp
+++ b/llvm/unittests/Support/AllocatorTest.cpp
@@ -0,0 +1,95 @@
+//===- llvm/unittest/Support/AllocatorTest.cpp - BumpPtrAllocator tests ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Allocator.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(AllocatorTest, Basics) {
+  BumpPtrAllocator Alloc;
+  int *a = (int*)Alloc.Allocate(sizeof(int), 0);
+  int *b = (int*)Alloc.Allocate(sizeof(int) * 10, 0);
+  int *c = (int*)Alloc.Allocate(sizeof(int), 0);
+  *a = 1;
+  b[0] = 2;
+  b[9] = 2;
+  *c = 3;
+  EXPECT_EQ(1, *a);
+  EXPECT_EQ(2, b[0]);
+  EXPECT_EQ(2, b[9]);
+  EXPECT_EQ(3, *c);
+  EXPECT_EQ(1U, Alloc.GetNumSlabs());
+}
+
+// Allocate enough bytes to create three slabs.
+TEST(AllocatorTest, ThreeSlabs) {
+  BumpPtrAllocator Alloc(4096, 4096);
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(1U, Alloc.GetNumSlabs());
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(2U, Alloc.GetNumSlabs());
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(3U, Alloc.GetNumSlabs());
+}
+
+// Allocate enough bytes to create two slabs, reset the allocator, and do it
+// again.
+TEST(AllocatorTest, TestReset) {
+  BumpPtrAllocator Alloc(4096, 4096);
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(1U, Alloc.GetNumSlabs());
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(2U, Alloc.GetNumSlabs());
+  Alloc.Reset();
+  EXPECT_EQ(1U, Alloc.GetNumSlabs());
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(1U, Alloc.GetNumSlabs());
+  Alloc.Allocate(3000, 0);
+  EXPECT_EQ(2U, Alloc.GetNumSlabs());
+}
+
+// Test some allocations at varying alignments.
+TEST(AllocatorTest, TestAlignment) {
+  BumpPtrAllocator Alloc;
+  uintptr_t a;
+  a = (uintptr_t)Alloc.Allocate(1, 2);
+  EXPECT_EQ(0U, a & 1);
+  a = (uintptr_t)Alloc.Allocate(1, 4);
+  EXPECT_EQ(0U, a & 3);
+  a = (uintptr_t)Alloc.Allocate(1, 8);
+  EXPECT_EQ(0U, a & 7);
+  a = (uintptr_t)Alloc.Allocate(1, 16);
+  EXPECT_EQ(0U, a & 15);
+  a = (uintptr_t)Alloc.Allocate(1, 32);
+  EXPECT_EQ(0U, a & 31);
+  a = (uintptr_t)Alloc.Allocate(1, 64);
+  EXPECT_EQ(0U, a & 63);
+  a = (uintptr_t)Alloc.Allocate(1, 128);
+  EXPECT_EQ(0U, a & 127);
+}
+
+// Test allocating just over the slab size.  This tests a bug where before the
+// allocator incorrectly calculated the buffer end pointer.
+TEST(AllocatorTest, TestOverflow) {
+  BumpPtrAllocator Alloc(4096, 4096);
+
+  // Fill the slab right up until the end pointer.
+  Alloc.Allocate(4096 - sizeof(MemSlab), 0);
+  EXPECT_EQ(1U, Alloc.GetNumSlabs());
+
+  // If we dont't allocate a new slab, then we will have overflowed.
+  Alloc.Allocate(1, 0);
+  EXPECT_EQ(2U, Alloc.GetNumSlabs());
+}
+
+}  // anonymous namespace