[LLVMdev] [cfe-dev] RFC: Codifying (but not formalizing) the optimization levels in LLVM and Clang

Krzysztof Parzyszek
Sat, 19 Jan 2013 17:18:17 -0000

On 1/19/2013 1:55 AM, Chandler Carruth wrote:
>
> -ffast-math is *totally* different from these attributes, and in fact
> -ffast-math is specifically not modeled as a function attribute because
> it changes the fundamental semantics of an operation.

It's not different at all.  The user may want to compile parts of the
program with -ffast-math, and parts without it.  Same thing applies to
vectorization, parallelization, or any aggressive optimizations that
could result in small imprecisions (e.g. reassociation).  When LTO is
introduced, the inlining code will be faced with these decisions.

-Krzysztof


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