[PATCH] D144534: [DAGCombine] Fold SETCC_OEQ(x, Inf) into IS_FPCLASS

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


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Comment at: llvm/test/CodeGen/AMDGPU/fp-classify.ll:616
+; SI-NEXT:    v_cvt_f32_f16_e64 v1, |s0|
+; SI-NEXT:    v_cmp_class_f32_e32 vcc, v1, v0
 ; SI-NEXT:    v_cndmask_b32_e64 v0, 0, 1, vcc
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qiucf wrote:
> arsenm wrote:
> > The result is the same but I’d somewhat prefer to keep the original isa. The infinity constant is more likely reusable with other uses in the program 
> Fpclass checks are be better if the constant is used one or more times only in such comparison, I think?
These have identical code size and cycles. I think an infinity constant is more likely to appear from unrelated function uses. Plus fcmp is a better canonical form. You should avoid this if you base on only doing the transform if the constant is illegal


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  https://reviews.llvm.org/D144534/new/

https://reviews.llvm.org/D144534