[llvm] [PowerPC] improve performance on the isNan and !isNan function in case of -ffp-model=strict (PR #204170)

[zhijian lin via llvm-commits]

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diggerlin wrote:

the code  setOperationAction(ISD::IS_FPCLASS, MVT::ppcf128, Custom);
only when 
if (Subtarget.hasP9Vector()) && Subtarget.useCRBits()) is true.

so the for non-P9 the MVT::ppcf128 is not customized. 



https://github.com/llvm/llvm-project/pull/204170