[PATCH] D82329: [SVE] Fix invalid Scalable to fixed width vetor type demotion in LLT

[Christopher Tetreault via Phabricator via llvm-commits]

ctetreau created this revision.
Herald added subscribers: llvm-commits, psnobl, rkruppe, hiraditya, tschuett.
Herald added a reviewer: efriedma.
Herald added a project: LLVM.

getLLTForType calls LLT::vector(Ty->getNumElements(), ScalarTy) for
fixed width and scalable vectors, losing information on the scalability
of the input vector. Rather than miscompile, return an invalid LLT for
scalable vectors.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D82329

Files:
  llvm/lib/CodeGen/LowLevelType.cpp


Index: llvm/lib/CodeGen/LowLevelType.cpp
===================================================================
--- llvm/lib/CodeGen/LowLevelType.cpp
+++ llvm/lib/CodeGen/LowLevelType.cpp
@@ -18,7 +18,7 @@
 using namespace llvm;
 
 LLT llvm::getLLTForType(Type &Ty, const DataLayout &DL) {
-  if (auto VTy = dyn_cast<VectorType>(&Ty)) {
+  if (auto VTy = dyn_cast<FixedVectorType>(&Ty)) {
     auto NumElements = VTy->getNumElements();
     LLT ScalarTy = getLLTForType(*VTy->getElementType(), DL);
     if (NumElements == 1)


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