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[SCCP] Update condition to avoid overflow.

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Summary:
Update condition to remove addition that may cause an overflow.
Resolves PR42814.

Reviewers: sanjoy, RKSimon

Subscribers: jlebar, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65417

llvm-svn: 367461
This commit is contained in:
Alina Sbirlea 2019-07-31 18:22:22 +00:00
parent d2c9e74ca9
commit 73449602de
2 changed files with 14 additions and 1 deletions
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2
lib/Analysis/ConstantFolding.cpp
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@ -544,7 +544,7 @@ Constant *FoldReinterpretLoadFromConstPtr(Constant *C, Type *LoadTy,
int64_t InitializerSize = DL.getTypeAllocSize(GV->getInitializer()->getType()); int64_t InitializerSize = DL.getTypeAllocSize(GV->getInitializer()->getType());
// If we're not accessing anything in this constant, the result is undefined. // If we're not accessing anything in this constant, the result is undefined.
if (Offset + BytesLoaded <= 0) if (Offset <= -1 * static_cast<int64_t>(BytesLoaded))
return UndefValue::get(IntType); return UndefValue::get(IntType);
// If we're not accessing anything in this constant, the result is undefined. // If we're not accessing anything in this constant, the result is undefined.

13
test/Transforms/SCCP/ubsan_overflow.ll Normal file
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@ -0,0 +1,13 @@
; RUN: opt -sccp -S %s | FileCheck %s
@0 = private unnamed_addr constant [16 x i8] c"\01\00\00\00\01\01\00\00\01\01\01\00\01\01\01\01"
; CHECK-LABEL: @foo
define i8 @foo() {
entry:
%0 = add nuw nsw i64 0, -1
%1 = lshr i64 %0, 1
%2 = getelementptr inbounds [4 x [4 x i8]], [4 x [4 x i8]]* bitcast ([16 x i8]* @0 to [4 x [4 x i8]]*), i64 0, i64 0, i64 %1
%3 = load i8, i8* %2, align 1
ret i8 %3
}