[PATCH] D81969: [SVE] Fix invalid usages of getNumElements in ShuffleVectorInstruction

[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.

Fix invalid usages of getNumElements identified by test case
LLVM.Transforms/InstCombine::vscale_extractelement.ll.

changesLength: Since the length of the llvm::SmallVector shufflemask
is related to the minimum number of elements in a scalable vector, it is
fine to just get the Min field of the ElementCount

isIdentityWithExtract: Since it is not possible to express the mask
needed for this pattern for scalable vectors, we can just bail before
calling getNumElements()


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D81969

Files:
  llvm/include/llvm/IR/Instructions.h
  llvm/lib/IR/Instructions.cpp


Index: llvm/lib/IR/Instructions.cpp
===================================================================
--- llvm/lib/IR/Instructions.cpp
+++ llvm/lib/IR/Instructions.cpp
@@ -2205,8 +2205,14 @@
 bool ShuffleVectorInst::isIdentityWithExtract() const {
   if (isa<UndefValue>(Op<2>()))
     return false;
-  int NumOpElts = cast<VectorType>(Op<0>()->getType())->getNumElements();
-  int NumMaskElts = getType()->getNumElements();
+
+  // FIXME: Not currently possible to express a shuffle mask for a scalable
+  // vector for this case
+  if (isa<ScalableVectorType>(getType()))
+    return false;
+
+  int NumOpElts = cast<FixedVectorType>(Op<0>()->getType())->getNumElements();
+  int NumMaskElts = cast<FixedVectorType>(getType())->getNumElements();
   if (NumMaskElts >= NumOpElts)
     return false;
 
Index: llvm/include/llvm/IR/Instructions.h
===================================================================
--- llvm/include/llvm/IR/Instructions.h
+++ llvm/include/llvm/IR/Instructions.h
@@ -1977,7 +1977,7 @@
   ///           shufflevector <4 x n> A, <4 x n> B, <1,2,3,4,5>
   bool changesLength() const {
     unsigned NumSourceElts =
-        cast<VectorType>(Op<0>()->getType())->getNumElements();
+        cast<VectorType>(Op<0>()->getType())->getElementCount().Min;
     unsigned NumMaskElts = ShuffleMask.size();
     return NumSourceElts != NumMaskElts;
   }


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