[X86][SSE] Don't get target shuffle operands prematurely.

PerformShuffleCombine should be usable by unary and binary target shuffles, but was attempting to get the first two operands whatever the instruction type. Since these are only used for VECTOR_SHUFFLE instructions for one particular combine I've moved them inside the relevant if statement.

llvm-svn: 261727

1 files changed, 7 insertions, 4 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index c4829fbbbfb..36e3e5a9016 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -24431,8 +24431,6 @@ static SDValue PerformShuffleCombine(SDNode *N, SelectionDAG &DAG,
                                      TargetLowering::DAGCombinerInfo &DCI,
                                      const X86Subtarget &Subtarget) {
   SDLoc dl(N);
-  SDValue N0 = N->getOperand(0);
-  SDValue N1 = N->getOperand(1);
   EVT VT = N->getValueType(0);
 
   // Don't create instructions with illegal types after legalize types has run.
@@ -24464,8 +24462,13 @@ static SDValue PerformShuffleCombine(SDNode *N, SelectionDAG &DAG,
   // potentially need to be further expanded (or custom lowered) into a
   // less optimal sequence of dag nodes.
   if (!DCI.isBeforeLegalize() && DCI.isBeforeLegalizeOps() &&
-      N1.getOpcode() == ISD::UNDEF && N0.hasOneUse() &&
-      N0.getOpcode() == ISD::BITCAST) {
+      N->getOpcode() == ISD::VECTOR_SHUFFLE &&
+      N->getOperand(0).getOpcode() == ISD::BITCAST &&
+      N->getOperand(1).getOpcode() == ISD::UNDEF &&
+      N->getOperand(0).hasOneUse()) {
+    SDValue N0 = N->getOperand(0);
+    SDValue N1 = N->getOperand(1);
+
     SDValue BC0 = N0.getOperand(0);
     EVT SVT = BC0.getValueType();
     unsigned Opcode = BC0.getOpcode();