[DAGCombiner] rename variables for readability; NFC

PR46406 shows a pattern where we can do better, so try to clean this up
before adding more code.

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a43065e..6a76fc7 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13215,22 +13215,21 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) {
     } else if (N1.getOpcode() == ISD::FMUL) {
       // Look through an FMUL. Even though this won't remove the FDIV directly,
       // it's still worthwhile to get rid of the FSQRT if possible.
-      SDValue SqrtOp;
-      SDValue OtherOp;
+      SDValue Sqrt, Y;
       if (N1.getOperand(0).getOpcode() == ISD::FSQRT) {
-        SqrtOp = N1.getOperand(0);
-        OtherOp = N1.getOperand(1);
+        Sqrt = N1.getOperand(0);
+        Y = N1.getOperand(1);
       } else if (N1.getOperand(1).getOpcode() == ISD::FSQRT) {
-        SqrtOp = N1.getOperand(1);
-        OtherOp = N1.getOperand(0);
+        Sqrt = N1.getOperand(1);
+        Y = N1.getOperand(0);
       }
-      if (SqrtOp.getNode()) {
+      if (Sqrt.getNode()) {
         // We found a FSQRT, so try to make this fold:
-        // x / (y * sqrt(z)) -> x * (rsqrt(z) / y)
-        if (SDValue RV = buildRsqrtEstimate(SqrtOp.getOperand(0), Flags)) {
-          RV = DAG.getNode(ISD::FDIV, SDLoc(N1), VT, RV, OtherOp, Flags);
-          AddToWorklist(RV.getNode());
-          return DAG.getNode(ISD::FMUL, DL, VT, N0, RV, Flags);
+        // X / (Y * sqrt(Z)) -> X * (rsqrt(Z) / Y)
+        if (SDValue Rsqrt = buildRsqrtEstimate(Sqrt.getOperand(0), Flags)) {
+          SDValue Div = DAG.getNode(ISD::FDIV, SDLoc(N1), VT, Rsqrt, Y, Flags);
+          AddToWorklist(Div.getNode());
+          return DAG.getNode(ISD::FMUL, DL, VT, N0, Div, Flags);
         }
       }
     }