[llvm] r256476 - [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.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Sun Dec 27 15:33:47 2015
New Revision: 256476

URL: http://llvm.org/viewvc/llvm-project?rev=256476&view=rev
Log:
[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.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp?rev=256476&r1=256475&r2=256476&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp Sun Dec 27 15:33:47 2015
@@ -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
     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(SDVa
   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();