[llvm] [msan] Convert vector shadow to scalar before zext (PR #96722)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Thurston Dang (thurstond)

<details>
<summary>Changes</summary>

    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
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(

``````````

</details>


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