[llvm] [RISCV][GISel] Add support for G_IS_FPCLASS in F and D extensions (PR #72000)

[Min-Yih Hsu via llvm-commits]

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@@ -270,6 +279,17 @@ bool RISCVLegalizerInfo::legalizeCustom(LegalizerHelper &Helper,
     return Helper.lower(MI, 0, /* Unused hint type */ LLT()) ==
            LegalizerHelper::Legalized;
   }
+  case TargetOpcode::G_IS_FPCLASS: {
+    // Turn LLVM IR's floating point classes to that in RISCV,
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mshockwave wrote:

Good point. I think right now none of the combiner rules, generic or not, is targeting G_IS_FPCLASS. And I feel like future post-legalizer combiners have to take this in mind.

https://github.com/llvm/llvm-project/pull/72000