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[asan] small optimization: do not emit "x+0" instructions

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155701 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Kostya Serebryany 2012-04-27 10:04:53 +00:00
parent 4d2f077df1
commit 3f119989c3
1 changed files with 4 additions and 3 deletions
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7
lib/Transforms/Instrumentation/AddressSanitizer.cpp
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@ -363,11 +363,12 @@ void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
size_t Granularity = 1 << MappingScale;
if (TypeSize < 8 * Granularity) {
// Addr & (Granularity - 1)
Value *Lower3Bits = IRB2.CreateAnd(
Value *LastAccessedByte = IRB2.CreateAnd(
AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
// (Addr & (Granularity - 1)) + size - 1
Value *LastAccessedByte = IRB2.CreateAdd(
Lower3Bits, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
if (TypeSize / 8 > 1)
LastAccessedByte = IRB2.CreateAdd(
LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
// (uint8_t) ((Addr & (Granularity-1)) + size - 1)
LastAccessedByte = IRB2.CreateIntCast(
LastAccessedByte, IRB.getInt8Ty(), false);