[llvm] [X86][GlobalIsel] Support IS_FP_CLASS intrinsic 1/4 (PR #151084)

[Evgenii Kudriashov via llvm-commits]

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@@ -853,10 +857,236 @@ bool X86LegalizerInfo::legalizeGETROUNDING(MachineInstr &MI,
   auto RetValTrunc = MIRBuilder.buildZExtOrTrunc(DstTy, RetVal);
 
   MIRBuilder.buildCopy(Dst, RetValTrunc);
+  MI.eraseFromParent();
+  return true;
+}
+
+bool X86LegalizerInfo::expandFPClassTestForF32OrF64(
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e-kud wrote:

It looks like a rewritten version of `LegalizerHelper::lowerISFPCLASS`, do we have something x86 specific here?

https://github.com/llvm/llvm-project/pull/151084