lebedev.ri added a comment. In D104854#2957529 <https://reviews.llvm.org/D104854#2957529>, @spatel wrote:
> In D104854#2957471 <https://reviews.llvm.org/D104854#2957471>, @sepavloff > wrote: > >> In D104854#2957423 <https://reviews.llvm.org/D104854#2957423>, @spatel wrote: >> >>> Is it intentional that we are not canonicalizing the intrinsic call back to >>> `fcmp uno` in the default FP environment? >> >> It is lowered to unordered comparison by default. Changing `llvm.isnan` to >> `fcmp uno` somewhere in IR would make it possible to optimize out the latter >> if fast-math mode is on. Preserving semantics of `isnan` when fast-math is >> in effect was one of the goals of this change. > > I understand that the codegen was supposed to be no worse, but the difference > in IR causes optimizer regressions like: > https://llvm.org/PR51556 > > If we want this intrinsic (and its siblings that haven't been created yet) to > survive through IR, then we have to enhance IR passes to recognize the new > patterns. > It would be easier to do this in steps: (1) create the intrinsic only if not > in the default FP env, (2) update IR analysis/passes to recognize the > intrinsic, (3) create the intrinsic in the default FP env with no FMF, (4) > create the intrinsic always. +1, but right now i'm not sold on the behavior of not optimizing away NaN checks in no-NaN's mode. At least that part should be reconciled now. It *might* be an improvement, but it caters to expectations of one group while catering away from the documentation and existing expectations of other groups. This shouldn't be decided in a review, it should be driven by an RFC. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D104854/new/ https://reviews.llvm.org/D104854 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
