[llvm] [RISCV][ISelLowering] Use Zicond for FP selects on Zfinx/Zdinx (PR #169299)

[via llvm-commits]

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@@ -9555,6 +9555,36 @@ SDValue RISCVTargetLowering::lowerSELECT(SDValue Op, SelectionDAG &DAG) const {
   if (SDValue V = lowerSelectToBinOp(Op.getNode(), DAG, Subtarget))
     return V;
 
+  // When there is no cost for GPR <-> FGPR, we can use zicond select for
+  // floating value when CondV is int type
+  bool FPinGPR = Subtarget.hasStdExtZfinx() || Subtarget.hasStdExtZdinx();
+  bool UseZicondForFPSel = Subtarget.hasStdExtZicond() && FPinGPR &&
+                           VT.isFloatingPoint() &&
+                           CondV.getValueType().isInteger();
+  if (UseZicondForFPSel) {
+    MVT XLenIntVT = Subtarget.getXLenVT();
+
+    auto CastToInt = [&](SDValue V) -> SDValue {
+      if (VT == MVT::f32 && Subtarget.is64Bit()) {
+        return DAG.getNode(RISCVISD::FMV_X_ANYEXTW_RV64, DL, XLenIntVT, V);
+      }
+      return DAG.getBitcast(XLenIntVT, V);
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fennecJ wrote:

You're right. The original implementation caused issues with f16. I've added explicit handling for MVT::f16 to ensure it generates the correct FMV nodes. Thanks for the review.

https://github.com/llvm/llvm-project/pull/169299