[LLVMdev] counting branch frequencies
alastairmurray42 at gmail.com
Wed Sep 19 09:37:55 PDT 2012
On 19/09/12 10:27, Rao, Prashantha wrote:
> Can we not run the -insert-edge-profiling and -profile-loader passes
> at the beginning of the opt? Orthogonal point is, is it worth doing
> any optimizations when -insert-edge-profiling is specified on
> command line?
Yes, we could, and if they were tied into the early pass code it would
prevent a lot of confusion (though the early pass stuff only happens for
-O[1-9] or -std-compile-opts, but I'm sure something could be figured out).
Though for Apala's case (using LLVM 3.1) it would be disastrous as
nothing preserves ProfileInfo. Branch weight metadata (LLVM 3.2
-profile-metadata-loader) would do much better as a lot of effort (not
me, others!) has gone into making sure that the metadata is preserved.
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