[TargetLowering] Use ISD::FSHR in expandFixedPointMul

Replace OR(SHL,SRL) pattern with ISD::FSHR (legalization expands this later if necessary) - this helps with the scale == 0 'undefined' drop-through case that was discussed on D55720.

llvm-svn: 353546

1 files changed, 2 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index c8b66d05a01..0f343f5989f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5512,9 +5512,6 @@ TargetLowering::expandFixedPointMul(SDNode *Node, SelectionDAG &DAG) const {
   // are scaled. The result is given to us in 2 halves, so we only want part of
   // both in the result.
   EVT ShiftTy = getShiftAmountTy(VT, DAG.getDataLayout());
-  Lo = DAG.getNode(ISD::SRL, dl, VT, Lo, DAG.getConstant(Scale, dl, ShiftTy));
-  Hi = DAG.getNode(
-      ISD::SHL, dl, VT, Hi,
-      DAG.getConstant(VT.getScalarSizeInBits() - Scale, dl, ShiftTy));
-  return DAG.getNode(ISD::OR, dl, VT, Lo, Hi);
+  return DAG.getNode(ISD::FSHR, dl, VT, Hi, Lo,
+                     DAG.getConstant(Scale, dl, ShiftTy));
 }