[X86][SSE] Reapplied: Improve vector ZERO_EXTEND by combining to ZERO_EXTEND_VECTOR_INREG

Generalise the existing SIGN_EXTEND to SIGN_EXTEND_VECTOR_INREG combine to support zero extension as well and get rid of a lot of unnecessary ANY_EXTEND + mask patterns.

Reapplied with a fix for PR26870 (avoid premature use of TargetConstant in ZERO_EXTEND_VECTOR_INREG expansion).

Differential Revision: http://reviews.llvm.org/D17691

llvm-svn: 263159

1 files changed, 18 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index fd47bb30246..b7c468a9579 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -273,6 +273,7 @@ namespace {
     SDValue visitANY_EXTEND(SDNode *N);
     SDValue visitSIGN_EXTEND_INREG(SDNode *N);
     SDValue visitSIGN_EXTEND_VECTOR_INREG(SDNode *N);
+    SDValue visitZERO_EXTEND_VECTOR_INREG(SDNode *N);
     SDValue visitTRUNCATE(SDNode *N);
     SDValue visitBITCAST(SDNode *N);
     SDValue visitBUILD_PAIR(SDNode *N);
@@ -1396,6 +1397,7 @@ SDValue DAGCombiner::visit(SDNode *N) {
   case ISD::ANY_EXTEND:         return visitANY_EXTEND(N);
   case ISD::SIGN_EXTEND_INREG:  return visitSIGN_EXTEND_INREG(N);
   case ISD::SIGN_EXTEND_VECTOR_INREG: return visitSIGN_EXTEND_VECTOR_INREG(N);
+  case ISD::ZERO_EXTEND_VECTOR_INREG: return visitZERO_EXTEND_VECTOR_INREG(N);
   case ISD::TRUNCATE:           return visitTRUNCATE(N);
   case ISD::BITCAST:            return visitBITCAST(N);
   case ISD::BUILD_PAIR:         return visitBUILD_PAIR(N);
@@ -5722,7 +5724,8 @@ static SDNode *tryToFoldExtendOfConstant(SDNode *N, const TargetLowering &TLI,
   EVT VT = N->getValueType(0);
 
   assert((Opcode == ISD::SIGN_EXTEND || Opcode == ISD::ZERO_EXTEND ||
-         Opcode == ISD::ANY_EXTEND || Opcode == ISD::SIGN_EXTEND_VECTOR_INREG)
+         Opcode == ISD::ANY_EXTEND || Opcode == ISD::SIGN_EXTEND_VECTOR_INREG ||
+         Opcode == ISD::ZERO_EXTEND_VECTOR_INREG)
          && "Expected EXTEND dag node in input!");
 
   // fold (sext c1) -> c1
@@ -7000,6 +7003,20 @@ SDValue DAGCombiner::visitSIGN_EXTEND_VECTOR_INREG(SDNode *N) {
   return SDValue();
 }
 
+SDValue DAGCombiner::visitZERO_EXTEND_VECTOR_INREG(SDNode *N) {
+  SDValue N0 = N->getOperand(0);
+  EVT VT = N->getValueType(0);
+
+  if (N0.getOpcode() == ISD::UNDEF)
+    return DAG.getUNDEF(VT);
+
+  if (SDNode *Res = tryToFoldExtendOfConstant(N, TLI, DAG, LegalTypes,
+                                              LegalOperations))
+    return SDValue(Res, 0);
+
+  return SDValue();
+}
+
 SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   EVT VT = N->getValueType(0);