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Differential D52272

[InstCombine] Disable strcmp->memcmp transform for MSan.
ClosedPublic

Authored by morehouse on Sep 19 2018, 12:00 PM.

Details

Reviewers
eugenis
xbolva00
Commits
rGe62fc3d0b6ce: [InstCombine] Disable strcmp->memcmp transform for MSan.
rL342582: [InstCombine] Disable strcmp->memcmp transform for MSan.
Summary

The strcmp->memcmp transform can make the resulting memcmp read
uninitialized data, which MSan doesn't like.

Resolves https://github.com/google/sanitizers/issues/993.

Diff Detail

Repository
rL LLVM

Event Timeline

morehouse created this revision.Sep 19 2018, 12:00 PM
Herald added a subscriber: hiraditya. · View Herald TranscriptSep 19 2018, 12:00 PM
Harbormaster completed remote builds in B22857: Diff 166163.Sep 19 2018, 12:00 PM
eugenis accepted this revision.Sep 19 2018, 12:35 PM

LGTM, thanks!

This revision is now accepted and ready to land.Sep 19 2018, 12:35 PM
Closed by commit rL342582: [InstCombine] Disable strcmp->memcmp transform for MSan. (authored by morehouse). · Explain WhySep 19 2018, 12:38 PM
This revision was automatically updated to reflect the committed changes.

Revision Contents

PathSize
llvm/
trunk/
lib/
Transforms/
Utils/
5 lines
test/
Transforms/
InstCombine/
15 lines

Diff 166170

llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp

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static bool canTransformToMemCmp(CallInst *CI, Value *Str, uint64_t Len, static bool canTransformToMemCmp(CallInst *CI, Value *Str, uint64_t Len,
const DataLayout &DL) { const DataLayout &DL) {
if (!isOnlyUsedInComparisonWithZero(CI)) if (!isOnlyUsedInComparisonWithZero(CI))
return false; return false;
if (!isDereferenceableAndAlignedPointer(Str, 1, APInt(64, Len), DL)) if (!isDereferenceableAndAlignedPointer(Str, 1, APInt(64, Len), DL))
return false; return false;
if (CI->getFunction()->hasFnAttribute(Attribute::SanitizeMemory))
return false;
return true; return true;
} }
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
// String and Memory Library Call Optimizations // String and Memory Library Call Optimizations
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
Value *LibCallSimplifier::optimizeStrCat(CallInst *CI, IRBuilder<> &B) { Value *LibCallSimplifier::optimizeStrCat(CallInst *CI, IRBuilder<> &B) {
▲ Show 20 Lines • Show All 2,697 Lines • Show Last 20 Lines

llvm/trunk/test/Transforms/InstCombine/strcmp-memcmp.ll

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; CHECK-NEXT: ret i32 0 ; CHECK-NEXT: ret i32 0
; ;
%string = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i64 0, i64 0 %string = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i64 0, i64 0
%call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 2) %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 2)
tail call void @use(i32 %call) tail call void @use(i32 %call)
ret i32 0 ret i32 0
} }
define i32 @strcmp_memcmp_msan([12 x i8]* dereferenceable (12) %buf) sanitize_memory {
; CHECK-LABEL: @strcmp_memcmp_msan(
; CHECK-NEXT: [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
; CHECK-NEXT: [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
; CHECK-NEXT: [[CONV:%.*]] = zext i1 [[CMP]] to i32
; CHECK-NEXT: ret i32 [[CONV]]
;
%string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
%call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
%cmp = icmp eq i32 %call, 0
%conv = zext i1 %cmp to i32
ret i32 %conv
}
declare i32 @memcmp(i8* nocapture, i8* nocapture, i64) declare i32 @memcmp(i8* nocapture, i8* nocapture, i64)