[LLVMdev] Counting instructions in MCJIT

[Verena Beckham]

Hi there,

I wondered whether anyone could give me any advice about counting 
assembly instructions when using MCJIT?
For performance regression testing I would like to be able to count the 
number of instructions generated during the jit compilation of a given 
module.

The Statistic class, as far as I understand, cannot collect this data 
per-module (per-ExecutionEngine/per-MCJIT), and there is no way of 
extracting a single statistic without doing string manipulation. I'm 
also doing several code gens in parallel, so even if the class is 
thread-safe, I cannot find the values for the single modules.

In JIT you can add a JITListener, which can count the 
MachineInstructions, with the assumption that there is a (more or less) 
1-2-1 mapping between machine and assembly instructions. Is there 
something equivalent for MCJIT?

I can write a MachineFunctionPass to do the same, but I can find no way 
of inserting that into the PassManager that MCJIT uses. This means I'm 
replicating the passes and doing code gen twice, basically.

Any advice would be much appreciated!
Thank you very much,

-- 
Verena Beckham

Vice President Engineering

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