[LLVMdev] [Polly] GSoC Proposal: Reducing LLVM-Polly Compiling overhead

Tobias Grosser tobias at grosser.es
Thu May 2 02:38:22 PDT 2013

On 04/30/2013 04:13 PM, Star Tan wrote:
> Hi all,
> How could I find out where the time is spent on between two adjacent Polly passes? Can anyone give me some advice?

Hi Star Tan,

I propose to do the performance analysis using the 'opt' tool and 
optimizing LLVM-IR, instead of running it from within clang. For the 
'opt' tool there are two commands that should help you:

1) -debug-pass=Structure or -debug-pass=Details

This should give you the list of passes that is executed. You can 
compare the list to see at which point additional passes are scheduled.

2) -time-passes

This gives you the time spent in the different passes.

These two commands may remove the need for a Polly specific profiling 
infrastructure. Also, if you talk about performance issues you see, it 
would be great if you could attach the .ll file you use as well as the 
exact command line you profile.


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