[llvm] r367461 - [SCCP] Update condition to avoid overflow.
Alina Sbirlea via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 31 11:22:22 PDT 2019
Author: asbirlea
Date: Wed Jul 31 11:22:22 2019
New Revision: 367461
URL: http://llvm.org/viewvc/llvm-project?rev=367461&view=rev
Log:
[SCCP] Update condition to avoid overflow.
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
Added:
llvm/trunk/test/Transforms/SCCP/ubsan_overflow.ll
Modified:
llvm/trunk/lib/Analysis/ConstantFolding.cpp
Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=367461&r1=367460&r2=367461&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Wed Jul 31 11:22:22 2019
@@ -544,7 +544,7 @@ Constant *FoldReinterpretLoadFromConstPt
int64_t InitializerSize = DL.getTypeAllocSize(GV->getInitializer()->getType());
// 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);
// If we're not accessing anything in this constant, the result is undefined.
Added: llvm/trunk/test/Transforms/SCCP/ubsan_overflow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SCCP/ubsan_overflow.ll?rev=367461&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SCCP/ubsan_overflow.ll (added)
+++ llvm/trunk/test/Transforms/SCCP/ubsan_overflow.ll Wed Jul 31 11:22:22 2019
@@ -0,0 +1,13 @@
+; RUN: opt -sccp -S %s | FileCheck %s
+
+ at 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
+}
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