[llvm-dev] defaults for FP contraction [e.g. fused multiply-add]: suggestion and patch to be slightly more aggressive and to make Clang`s optimization settings closer to having the same meaning as when they are given to GCC [at least for "-O3"]

Abe Skolnik via llvm-dev llvm-dev at lists.llvm.org
Fri Sep 9 15:21:56 PDT 2016

On 09/09/2016 04:31 PM, Stephen Canon wrote:

> Gating this on -Owhatever is dangerous, .  We should simply default to the pragma “on” state universally.

Why so?  [honestly asking, not arguing]

My guess: b/c we don`t want programs to give different results when compiled at different 
"-O<...>" settings with the exception of "-Ofast".

At any rate, the above change is trivial to apply to my recent proposed patch: just remove the 
"&& (Res.getCodeGenOpts().OptimizationLevel >= 3)" part of the condition.



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