InstCombine: Scalarize single use icmp/fcmp
llvm-svn: 348801
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index bc14f10..7ad29a5 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -48,6 +48,8 @@
/// Return true if the value is cheaper to scalarize than it is to leave as a
/// vector operation. isConstant indicates whether we're extracting one known
/// element. If false we're extracting a variable index.
+//
+// FIXME: It's possible to create more instructions that previously existed.
static bool cheapToScalarize(Value *V, bool isConstant) {
if (Constant *C = dyn_cast<Constant>(V)) {
if (isConstant) return true;
@@ -310,6 +312,16 @@
return BinaryOperator::CreateWithCopiedFlags(BO->getOpcode(), E0, E1, BO);
}
+ Value *X, *Y;
+ CmpInst::Predicate Pred;
+ if (match(SrcVec, m_Cmp(Pred, m_Value(X), m_Value(Y))) &&
+ cheapToScalarize(SrcVec, IndexC)) {
+ // extelt (cmp X, Y), Index --> cmp (extelt X, Index), (extelt Y, Index)
+ Value *E0 = Builder.CreateExtractElement(X, Index);
+ Value *E1 = Builder.CreateExtractElement(Y, Index);
+ return CmpInst::Create(cast<CmpInst>(SrcVec)->getOpcode(), Pred, E0, E1);
+ }
+
if (auto *I = dyn_cast<Instruction>(SrcVec)) {
if (auto *IE = dyn_cast<InsertElementInst>(I)) {
// Extracting the inserted element?