PPC: Improve code generation for mixed-precision reciprocal sqrt

The DAGCombine logic that recognized a/sqrt(b) and transformed it into
a multiplication by the reciprocal sqrt did not handle cases where the
sqrt and the division were separated by an fpext or fptrunc.

llvm-svn: 178801

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index e33d2cc7165..8195f5eb050 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -6849,6 +6849,33 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
         return DAG.getNode(ISD::FMUL, dl, N->getValueType(0),
                            N->getOperand(0), RV);
       }
+    } else if (N->getOperand(1).getOpcode() == ISD::FP_EXTEND &&
+               N->getOperand(1).getOperand(0).getOpcode() == ISD::FSQRT) {
+      SDValue RV =
+        DAGCombineFastRecipFSQRT(N->getOperand(1).getOperand(0).getOperand(0),
+                                 DCI);
+      if (RV.getNode() != 0) {
+        DCI.AddToWorklist(RV.getNode());
+        RV = DAG.getNode(ISD::FP_EXTEND, N->getOperand(1).getDebugLoc(),
+                         N->getValueType(0), RV);
+        DCI.AddToWorklist(RV.getNode());
+        return DAG.getNode(ISD::FMUL, dl, N->getValueType(0),
+                           N->getOperand(0), RV);
+      }
+    } else if (N->getOperand(1).getOpcode() == ISD::FP_ROUND &&
+               N->getOperand(1).getOperand(0).getOpcode() == ISD::FSQRT) {
+      SDValue RV =
+        DAGCombineFastRecipFSQRT(N->getOperand(1).getOperand(0).getOperand(0),
+                                 DCI);
+      if (RV.getNode() != 0) {
+        DCI.AddToWorklist(RV.getNode());
+        RV = DAG.getNode(ISD::FP_ROUND, N->getOperand(1).getDebugLoc(),
+                         N->getValueType(0), RV,
+                         N->getOperand(1).getOperand(1));
+        DCI.AddToWorklist(RV.getNode());
+        return DAG.getNode(ISD::FMUL, dl, N->getValueType(0),
+                           N->getOperand(0), RV);
+      }
     }
 
     SDValue RV = DAGCombineFastRecip(N->getOperand(1), DCI);