[llvm] [LoongArch] Custom legalizing ConstantFP to avoid float loads (PR #158050)

[via llvm-commits]

================
@@ -549,10 +551,58 @@ SDValue LoongArchTargetLowering::LowerOperation(SDValue Op,
   case ISD::VECREDUCE_UMAX:
   case ISD::VECREDUCE_UMIN:
     return lowerVECREDUCE(Op, DAG);
+  case ISD::ConstantFP:
+    return lowerConstantFP(Op, DAG);
   }
   return SDValue();
 }
 
+SDValue LoongArchTargetLowering::lowerConstantFP(SDValue Op,
+                                                 SelectionDAG &DAG) const {
+  EVT VT = Op.getValueType();
+  ConstantFPSDNode *CFP = cast<ConstantFPSDNode>(Op);
+  const APFloat &FPVal = CFP->getValueAPF();
+  SDLoc DL(CFP);
+
+  assert((VT == MVT::f32 && Subtarget.hasBasicF()) ||
+         (VT == MVT::f64 && Subtarget.hasBasicD()));
+
+  // If value is 0.0 or -0.0, just ignore it.
+  if (FPVal.isZero())
+    return SDValue();
+
+  // If lsx enabled, use cheaper 'vldi' instruction if possible.
+  if (Subtarget.hasExtLSX() && isFPImmVLDILegal(FPVal, VT))
----------------
heiher wrote:

```suggestion
  if (isFPImmVLDILegal(FPVal, VT))
```

https://github.com/llvm/llvm-project/pull/158050