[LLVMdev] Using LLVM to serialize object state -- and performance

Paul J. Lucas paul at lucasmail.org
Wed Nov 7 07:12:56 PST 2012

On Nov 6, 2012, at 11:49 AM, "Kaylor, Andrew" <andrew.kaylor at intel.com> wrote:

> I think you may have gone beyond what I understand in how the legacy JIT code works.  It looks like the call to addGlobalMapping should short-circuit the named function look up that I described ...

Well, I first look for the function by name and, if I didn't find it, then I call addGlobalMapping().  But that's not where the time is going.  Here:


is a call graph generated by kcachegrind.  I still don't understand all the numbers (and this PDF seems not to include commas where it should), but if you look at the left fork, the bottom two ovals, "Schedule..." is called 16K times and "setHeightToAtLeas..." is called 37K times.  On the right fork, RAGreed... is called 35K times.

Those are far too many calls to *anything* for a simple sequence of "call" LLVM instructions.  Something seems horribly wrong.

- Paul

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