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Re: Compiler Analysis: 3.3, 3.4, or tree-ssa?


Matt Fago wrote:
The -O1, -O2, and -O3 options are general-purpose choices for producing good code in general circumstances.

Are they? How is this determined?

I'll amend my statement...


"The -O1, -O2, and -O3 options *SHOULD BE* general-purpose choices for producing good code in general circumstances."

I think Acovea might allow the flags implied by these options to be chosen in a more quantitative way. Obviously Acovia should give better results when used with a specific code of interest.

I note that on some experiments, -O2 and -O3 produce *slower* code than does -O1; and in several cases, Acovea finds options sets that produce code which runs in 40% less time than it does when compiled with any of the predefined optimization sets.


We could define variations on the -O?? theme... -Ofp, for example, that optimizes for floating-point applications.

--
Scott Robert Ladd
Coyote Gulch Productions (http://www.coyotegulch.com)
Software Invention for High-Performance Computing


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