[msan] Convert vector shadow to scalar before zext

[thurstond]

zext does not allow converting vector shadow to scalar, so we must manually convert it prior to calling zext in materializeOneCheck, for which the 'ConvertedShadow' parameter isn't actually guaranteed to be scalar (1). Note that it is safe/no-op to call convertShadowToScalar on a shadow that is already scalar.

In contrast, the storeOrigin function already converts the (potentially vector) shadow to scalar; we add a comment to note why it is load bearing.

(1) In materializeInstructionChecks():
"// Disable combining in some cases. TrackOrigins checks each shadow to pick
// correct origin.
bool Combine = !MS.TrackOrigins;
...
if (!Combine) {
materializeOneCheck(IRB, ConvertedShadow, ShadowData.Origin);
continue;
}"

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Thurston Dang (thurstond)

Changes

zext does not allow converting vector shadow to scalar, so we must
manually convert it prior to calling zext in materializeOneCheck,
for which the 'convertedShadow' parameter isn't actually guaranteed
to be scalar.

In contrast, the storeOrigin function already converts the (potentially vector) shadow to scalar; we add a comment to note that it is load bearing.

---

Full diff: https://github.com/llvm/llvm-project/pull/96722.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp (+3)

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index f11c1c5933327..442db32025337 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1283,6 +1283,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     const DataLayout &DL = F.getParent()->getDataLayout();
     const Align OriginAlignment = std::max(kMinOriginAlignment, Alignment);
     TypeSize StoreSize = DL.getTypeStoreSize(Shadow->getType());
+    // ZExt cannot convert between vector and scalar
     Value *ConvertedShadow = convertShadowToScalar(Shadow, IRB);
     if (auto *ConstantShadow = dyn_cast<Constant>(ConvertedShadow)) {
       if (!ClCheckConstantShadow || ConstantShadow->isZeroValue()) {
@@ -1398,6 +1399,8 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     if (instrumentWithCalls(ConvertedShadow) &&
         SizeIndex < kNumberOfAccessSizes && !MS.CompileKernel) {
       FunctionCallee Fn = MS.MaybeWarningFn[SizeIndex];
+      // ZExt cannot convert between vector and scalar
+      ConvertedShadow = convertShadowToScalar(ConvertedShadow, IRB);
       Value *ConvertedShadow2 =
           IRB.CreateZExt(ConvertedShadow, IRB.getIntNTy(8 * (1 << SizeIndex)));
       CallBase *CB = IRB.CreateCall(

[vitalybuka]

Tests is needed