[LLVMdev] Indirect call site profiling

Philip Reames listmail at philipreames.com
Mon Oct 27 09:31:48 PDT 2014

On 10/24/2014 05:26 PM, betulb at codeaurora.org wrote:
> Hi All,
> We've been working on enhancing LLVM's instrumentation based profiling by
> adding indirect call target profiling support. Our goal is to add
> instrumentation around indirect call sites, so that we may track the
> frequently taken target addresses and their call frequencies.
Just to make sure I understand what're you describing, you're doing 
value profiling specifically for the target address of an indirect call 
through a function pointer right?
> The acquired data has uses in optimization of indirect function call
> heavy applications. Our initial findings show that using the profile data
> in optimizations would help improve the performance of some of the spec
> benchmarks notably. We have a proof of concept implementation,  which we
> plan to put it up for review. However, I’d like to inquire prior if there
> are any plans or ongoing work done in the community to enable indirect
> call target profiling support or not. Please inform if cfe-dev is a better
> candidate for posting PGO related emails.
I'll be interested in seeing your work.  I'm interested in techniques 
for guarded devirtualization, but the profiling infrastructure should be 
fairly common.  If we could arrange the instrumentation in such a way to 
enable both use cases, we could share infrastructure.

> Thanks,
> -Betul Buyukkurt
> Employee of the Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
> Foundation Collaborative Project
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