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

[Krzysztof Parzyszek]

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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