[SelectionDAG] Teach LegalizeVectorOps to not unroll CTLZ_ZERO_UNDEF and CTTZ_ZERO_UNDEF if the non-ZERO_UNDEF form is legal or custom. Will be used to simplify X86 code in a follow on commit.

llvm-svn: 256476

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 4bd0b6b518a..f61f631e2ff 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -106,6 +106,7 @@ class VectorLegalizer {
   SDValue ExpandStore(SDValue Op);
   SDValue ExpandFNEG(SDValue Op);
   SDValue ExpandBITREVERSE(SDValue Op);
+  SDValue ExpandCTLZ_CTTZ_ZERO_UNDEF(SDValue Op);
 
   /// \brief Implements vector promotion.
   ///
@@ -719,6 +720,9 @@ SDValue VectorLegalizer::Expand(SDValue Op) {
     return UnrollVSETCC(Op);
   case ISD::BITREVERSE:
     return ExpandBITREVERSE(Op);
+  case ISD::CTLZ_ZERO_UNDEF:
+  case ISD::CTTZ_ZERO_UNDEF:
+    return ExpandCTLZ_CTTZ_ZERO_UNDEF(Op);
   default:
     return DAG.UnrollVectorOp(Op.getNode());
   }
@@ -1022,6 +1026,16 @@ SDValue VectorLegalizer::ExpandFNEG(SDValue Op) {
   return DAG.UnrollVectorOp(Op.getNode());
 }
 
+SDValue VectorLegalizer::ExpandCTLZ_CTTZ_ZERO_UNDEF(SDValue Op) {
+  // If the non-ZERO_UNDEF version is supported we can let LegalizeDAG handle.
+  unsigned Opc = Op.getOpcode() == ISD::CTLZ_ZERO_UNDEF ? ISD::CTLZ : ISD::CTTZ;
+  if (TLI.isOperationLegalOrCustom(Opc, Op.getValueType()))
+    return Op;
+
+  // Otherwise go ahead and unroll.
+  return DAG.UnrollVectorOp(Op.getNode());
+}
+
 SDValue VectorLegalizer::UnrollVSETCC(SDValue Op) {
   EVT VT = Op.getValueType();
   unsigned NumElems = VT.getVectorNumElements();