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cranelift: simplify fneg(fneg(x)) to x #6034

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merged 1 commit into from
Mar 17, 2023
Merged

cranelift: simplify fneg(fneg(x)) to x #6034

merged 1 commit into from
Mar 17, 2023

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Kmeakin
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@Kmeakin Kmeakin commented Mar 16, 2023

algebraic.isle includes rewrites for cancelling fnegs when used as arguments to fma, but not for fneg cancelling itself

cfallin
cfallin approved these changes Mar 16, 2023
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Thanks!

(For completeness, I believe this is safe even on FP because the sign bit is separate from all others, so we have e.g. NaN and -NaN, and inf and -inf; everything is negatable, I think, and so this identity holds.)

@cfallin cfallin enabled auto-merge March 16, 2023 20:14
@cfallin cfallin added this pull request to the merge queue Mar 16, 2023
@alexcrichton alexcrichton removed this pull request from the merge queue due to a manual request Mar 16, 2023
@alexcrichton alexcrichton added this pull request to the merge queue Mar 16, 2023
@github-actions github-actions bot added the cranelift Issues related to the Cranelift code generator label Mar 16, 2023
Merged via the queue into bytecodealliance:main with commit d479951 Mar 17, 2023
@Kmeakin Kmeakin deleted the double-fneg branch March 17, 2023 01:56
@jameysharp jameysharp mentioned this pull request Apr 5, 2023
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@Kmeakin @cfallin @alexcrichton