[llvm] [PowerPC] Forbid f128 SELECT_CC optimized into fsel (PR #71497)

[Qiu Chaofan via llvm-commits]

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@@ -8080,7 +8080,8 @@ SDValue PPCTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
   // For more information, see section F.3 of the 2.06 ISA specification.
   // With ISA 3.0
   if ((!DAG.getTarget().Options.NoInfsFPMath && !Flags.hasNoInfs()) ||
-      (!DAG.getTarget().Options.NoNaNsFPMath && !Flags.hasNoNaNs()))
+      (!DAG.getTarget().Options.NoNaNsFPMath && !Flags.hasNoNaNs()) ||
+      ResVT == MVT::f128)
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ecnelises wrote:

yes, we don't have instruction for `ppc_fp128` fsel. The motivating case exists from https://github.com/llvm/llvm-project/commit/097a95f2df4666df74909ab1d3bcc0c1824ace86 , which sets `select_cc f128` as custom, while we don't have that lowering for `ppc_fp128`.

https://github.com/llvm/llvm-project/pull/71497