[msan] Fix select instrumentation.
Select condition shadow was being ignored resulting in false negatives.
This change OR-s sign-extended condition shadow into the result shadow.
llvm-svn: 189785
diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index ae73a2e..f2cf7a7 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1743,9 +1743,12 @@
void visitSelectInst(SelectInst& I) {
IRBuilder<> IRB(&I);
- setShadow(&I, IRB.CreateSelect(I.getCondition(),
- getShadow(I.getTrueValue()), getShadow(I.getFalseValue()),
- "_msprop"));
+ // a = select b, c, d
+ // Sa = (sext Sb) | (select b, Sc, Sd)
+ Value *S = IRB.CreateSelect(I.getCondition(), getShadow(I.getTrueValue()),
+ getShadow(I.getFalseValue()));
+ Value *S2 = IRB.CreateSExt(getShadow(I.getCondition()), S->getType());
+ setShadow(&I, IRB.CreateOr(S, S2, "_msprop"));
if (MS.TrackOrigins) {
// Origins are always i32, so any vector conditions must be flattened.
// FIXME: consider tracking vector origins for app vectors?