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Re: [PATCH] Improve cost computations in IVOPTS


> assuming that compile time and memory consumption are not significantly
> affected by this (and other similar) changes -- ivopts tries rather hard
> to avoid folding things and creating new expressions in the phase of the
> computation of the costs, as I used to run into problems with memory
> requirements otherwise.

Note that the pass already folds during cost computation (strip_offset_1).
That's pretty much unavoidable I think, otherwise the discrepancy would be too 
big between the computed costs and the costs of the generated expressions.

I've tested the change on a big Ada application (x86) and on GCC itself 
(x86-64, both individual files and bootstrap), compilation times are not 
affected.  The binaries are all slightly smaller.  Memory consumption is 
harder to evaluate but doesn't seem to vary much either for the cases I've 
looked at.

FWIW this brings about measurable improvements on x86 at run time for our 
Ada performance testsuite (from a few percents up to 10 for specific tests).

-- 
Eric Botcazou


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