review request (M): 6912064: type profiles need to be more thorough for dynamic language support
john.r.rose at oracle.com
Thu Jul 15 20:36:50 PDT 2010
I got a pre-review for 6912064 in January. These changes still work well; I just used them successfully with a performance tuning experiment.
There was a corner case bug which required an additional 'stopped()' check in graphKit. Here's the update:
The four lines in this file starting "// Profile disagrees with this path." are new:
That is the only difference from January.
Any further comments on this change set?
FTR, here is the previous communication. (Yes, it's been a while.)
From: John Rose <John.Rose at Sun.COM>
Date: January 26, 2010 7:14:13 PM PST
To: Vladimir Kozlov <Vladimir.Kozlov at Sun.COM>
Cc: Igor Veresov <Igor.Veresov at Sun.COM>, hotspot-compiler-dev compiler <hotspot-compiler-dev at openjdk.java.net>
Subject: Re: for pre-review (M): 6912064: type profiles need to be more thorough for dynamic language support
On Jan 26, 2010, at 6:59 PM, Vladimir Kozlov wrote:
> Then why you generate the klass check with uncommon trap for instanceof
> for cases when profiling shows that it will fail?
For code like this:
if (x instanceof String)
else if (x instanceof Number)
If the 'x' is always an Integer, I want to fold all the tests up from the first instanceof, not the second.
The profile will show when 'x' is of a monomorphic type. That is more interesting than whether the first check happens to go true or false.
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