[llvm] [RISCV]: Implemented softening of `FCANONICALIZE` (PR #169234)

[Kevin Per via llvm-commits]

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@@ -311,6 +313,12 @@ SDValue DAGTypeLegalizer::SoftenFloatRes_FABS(SDNode *N) {
   return DAG.getNode(ISD::AND, SDLoc(N), NVT, Op, Mask);
 }
 
+SDValue DAGTypeLegalizer::SoftenFloatRes_FCANONICALIZE(SDNode *N) {
+  return SoftenFloatRes_Unary(
+      N, GetFPLibCall(N->getValueType(0), RTLIB::FMIN_F32, RTLIB::FMIN_F64,
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kper wrote:

hmmm, I see

I changed it now

> This function should always be implementable as multiplication by 1.0, provided that the compiler does not constant fold the operation. Likewise, division by 1.0 and llvm.minnum(x, x) are possible implementations. Addition with -0.0 is also sufficient provided that the rounding mode is not -Infinity.
https://llvm.org/docs/LangRef.html#llvm-canonicalize-intrinsic

Since, I wasn't sure whether mul * 1.0, etc gets folded, I mapped it to `llvm.minnum(x, x)`

https://github.com/llvm/llvm-project/pull/169234