[LLVMdev] Autotuning parameters/heuristics within LLVM (original) (raw)

John Criswell jtcriswel at gmail.com
Fri Oct 3 06:15:45 PDT 2014

Dear Jonas,

Very cool.

I've added a link to your paper on the LLVM publications page. Please feel free to email the list about other papers you or your group at EPFL publish that use LLVM; we love adding to the links on the Publications page.

Regards,

John Criswell

On 10/3/14, 4:00 AM, Jonas Wagner wrote:

Dear Robert, a while ago, we had this idea of using compiler optimizations to increase the performance of /verifying/ an app, instead of the performance of /executing/ it. We found that there were a number of settings that had an effect on verification performance: * The amount of loop unswitching |-loop-unswitch-threshold=...| * The amount of loop unrolling |-unroll-threshold=...| * The amount of function inlining |-inline-threshold=...| * The amount of jump threading |-jump-threading-threshold=...| * Whether to favor branches or select instructions |-phi-node-folding-threshold=... -max-phi-to-fold-per-bb=...| The effect that these had on verification (in our case, exhaustive symbolic testing) was quite drastic, with speedups of 95x in some cases. The core idea behind the work is that compilers use /cost models/ that tell them how expensive an operation is. For verification, the costs are different. I'm writing you because these settings also have an impact en execution performance. If you find other parameters that have large effects, I'd be thrilled to hear about it. Cheers, Jonas PS: more details on our experiments: http://infoscience.epfl.ch/record/186012?ln=en <http://infoscience.epfl.ch/record/186012?ln=en%3F>

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-- John Criswell Assistant Professor Department of Computer Science, University of Rochester http://www.cs.rochester.edu/u/criswell

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