[PATCH] D79053: [SVE] Fix invalid use of VectorType::getNumElements() in Value Tracking

[Christopher Tetreault via Phabricator via llvm-commits]

ctetreau created this revision.
Herald added subscribers: llvm-commits, psnobl, rkruppe, hiraditya, kristof.beyls, tschuett.
Herald added a reviewer: rengolin.
Herald added a reviewer: efriedma.
Herald added a project: LLVM.
ctetreau added reviewers: sdesmalen, c-rhodes.

Remove invalid usage of VectorType::getNumElements in computeKnownBits
identified by test Clang::CodeGen/aarch64-sve-intrinsics/acle_sve_ext.c.
It is not possible to know at compile time the bits of a scalable
vector, so we cast to fixed width and do not call it if the vector is
scalable


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79053

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/lib/Analysis/ValueTracking.cpp


Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -207,10 +207,11 @@
 static void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
                              const Query &Q) {
   Type *Ty = V->getType();
+  assert(!isa<ScalableVectorType>(Ty) &&
+         "Cannot compute known bits of scalable vector");
+  auto *FVTy = dyn_cast<FixedVectorType>(Ty);
   APInt DemandedElts =
-      Ty->isVectorTy()
-          ? APInt::getAllOnesValue(cast<VectorType>(Ty)->getNumElements())
-          : APInt(1, 1);
+      FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
   computeKnownBits(V, DemandedElts, Known, Depth, Q);
 }
 
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5622,7 +5622,8 @@
 
   // In general, it is possible for computeKnownBits to determine all bits in a
   // value even when the operands are not all constants.
-  if (!Result && I->getType()->isIntOrIntVectorTy()) {
+  if (!Result && I->getType()->isIntOrIntVectorTy() &&
+      !isa<ScalableVectorType>(I->getType())) {
     KnownBits Known = computeKnownBits(I, Q.DL, /*Depth*/ 0, Q.AC, I, Q.DT, ORE);
     if (Known.isConstant())
       Result = ConstantInt::get(I->getType(), Known.getConstant());


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