[PATCH] D79197: [SVE] Fix invalid usage of getNumElements() in InstCombineMulDivRem

[Christopher Tetreault via Phabricator via llvm-commits]

ctetreau updated this revision to Diff 262172.
ctetreau edited the summary of this revision.
ctetreau added a comment.

address code review issues


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79197/new/

https://reviews.llvm.org/D79197

Files:
  llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  llvm/test/Transforms/InstCombine/udiv-pow2-vscale.ll


Index: llvm/test/Transforms/InstCombine/udiv-pow2-vscale.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/udiv-pow2-vscale.ll
@@ -0,0 +1,27 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+; This vscale udiv with a power-of-2 spalt on the rhs should not crash opt
+
+; CHECK: define <vscale x 2 x i32> @udiv_pow2_vscale()
+define <vscale x 2 x i32> @udiv_pow2_vscale(<vscale x 2 x i32> %lhs) {
+  %splatter = insertelement <vscale x 2 x i32> undef, i32 2, i32 0
+  %rhs = shufflevector <vscale x 2 x i32> %splatter,
+                       <vscale x 2 x i32> undef,
+                       <vscale x 2 x i32> zeroinitializer
+  %res = udiv <vscale x 2 x i32> %lhs, %rhs
+  ret <vscale x 2 x i32> %res
+}
+
+; This fixed width udiv with a power-of-2 splat on the rhs should also not
+; crash, and instcombine should eliminate the udiv
+
+; CHECK-LABEL: define <x 2 x i32> @udiv_pow2_fixed()
+; CHECK-NOT: udiv
+define <2 x i32> @udiv_pow2_fixed(<2 x i32> %lhs) {
+  %splatter = insertelement <2 x i32> undef, i32 2, i32 0
+  %rhs = shufflevector <2 x i32> %splatter,
+                       <2 x i32> undef,
+                       <2 x i32> zeroinitializer
+  %res = udiv <2 x i32> %lhs, %rhs
+  ret <2 x i32> %res
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -96,19 +96,21 @@
 
 /// A helper routine of InstCombiner::visitMul().
 ///
-/// If C is a scalar/vector of known powers of 2, then this function returns
-/// a new scalar/vector obtained from logBase2 of C.
+/// If C is a scalar/fixed width vector of known powers of 2, then this
+/// function returns a new scalar/fixed width vector obtained from logBase2
+/// of C.
 /// Return a null pointer otherwise.
 static Constant *getLogBase2(Type *Ty, Constant *C) {
   const APInt *IVal;
   if (match(C, m_APInt(IVal)) && IVal->isPowerOf2())
     return ConstantInt::get(Ty, IVal->logBase2());
 
-  if (!Ty->isVectorTy())
+  // FIXME: We can extract pow of 2 of splat constant for scalable vectors.
+  if (!isa<FixedVectorType>(Ty))
     return nullptr;
 
   SmallVector<Constant *, 4> Elts;
-  for (unsigned I = 0, E = cast<VectorType>(Ty)->getNumElements(); I != E;
+  for (unsigned I = 0, E = cast<FixedVectorType>(Ty)->getNumElements(); I != E;
        ++I) {
     Constant *Elt = C->getAggregateElement(I);
     if (!Elt)


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