[llvm-dev] [FPEnv] FNEG instruction (original) (raw)
Cameron McInally via llvm-dev llvm-dev at lists.llvm.org
Tue Oct 2 12🔞11 PDT 2018
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On Tue, Oct 2, 2018 at 12:09 PM Kevin Neal <Kevin.Neal at sas.com> wrote:
If we don’t have constrained intrinsics for some of the fp math instructions then aren’t we risking non-strict optimizations?
So far we've only added constrained FP intrinsics for operations that have side effects (i.e. can trap).
The quiet-computational sign-bit operations are special. They never have side effects (i.e. never trap). We have not been able to find a bad transformation for those (i.e. a xform to a trapping operation) other than the FNEG(X) --> FSUB(-0.0, X) transform.
If you can find a transform from one of the quiet-computational operations to a trapping operation, then we should discuss that. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181002/e247607d/attachment.html>
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