[LLVMdev] Profiling support in LLVM

[John Criswell]

Dear Najem,

You might want to read the llvm-prof documentation if you haven't 
already: http://llvm.org/cmds/llvm-prof.html.  The documentation 
mentions a script in the utils directory that automates some of the 
profiling tasks for you.

I suspect the way that llvm-prof works is to compile your whole program 
to a single LLVM bitcode file, run a transform on it, and then generate 
native code, link in the LLVM profiling run-time library, and then run 
the program.  You then use llvm-prof to analyze the original bitcode 
file and the output from running the program to get the report.  That's 
just a guess, though; I've never used llvm-prof myself.

I bet looking at the script in the utils directory will shed light on 
how to use llvm-prof.

-- John T.


On 3/21/11 4:46 PM, Andrew Trick wrote:
> Hi Najem,
>
> On Mar 21, 2011, at 9:47 AM, NaJeM ErMeLeH wrote:
>> I'm assisting my doctor who is doing a research and he wants to use 
>> the llvm compiler, my job is to profile build the benchmarks using 
>> llvm-prof.
>>
>> What i want to know is the following
>>
>> 1- does llvm support profile feedback optimizations!?
>
> Not yet. Please see Bob's proposal:
> http://article.gmane.org/gmane.comp.compilers.llvm.devel/37107/match=profile
>
>> 2- when i've used the llvm-prof it's input is an object file (not 
>> binary as other compilers) my question is how could I profile a whole 
>> benchmark program using the llvm-prof ?
>
> I haven't done it, but I think the correct answer is to use llvm-ld to 
> generate a single bitcode file, then run llvm-prof.
>
>> 3- is there a way to print the spill code information (e.g. spill 
>> code count in a single function or basic block) ?
>
> -stats give you aggregate counts. Unfortunately, I don't know a way to 
> do per-function reporting without using llvm-extract.
>
> You might be able to scrape -debug-only=spiller output for block info.
>
> -Andy
>
>> your help is appreciated.
>>
>> regards,
>> ~Najem
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