On Jun 17, 2011, at 10:21 AM, Tom Rodriguez wrote:

>> 
>> Sorry, I was thinking recording which branch of the GWT is taken and 
>> storing them in the GWT.
>> Two GWTs should not share the same metadata.
> 
> This is the major problem with GWT/selectAlternative.  Previously when GWT 
> was bytecodes we at least had a chance to get some profile information on 
> which way the branch was likely to go but with the ricochet frame version we 
> have no knowledge so each side of the if has equal probability.  The were no 
> guarantees that the GWT would always be used as a fast/slow idiom but in 
> practice it was so we used to get good data.  We'll have to find someway to 
> capture profiles for this if we can to treat fast/slow in a more aggressive 
> way.

selectAlternative has a branch profile.  As long as GWT is being used as 
expected (for fast/slow splits), selectAlternative will have a fast/slow 
profile, just like the original GWT invokers.

The PROB_FAIR in CallGenerator::for_method_handle_inline could be made 
"smarter", by feeding from the control inputs of the Phi; that would be a good 
start.

-- John
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