On Wed, Aug 20, 2014 at 10:29 PM, Sebastian Pop <seb...@gmail.com> wrote: > James Greenhalgh wrote: >> On Tue, Aug 19, 2014 at 09:39:56PM +0100, Steve Ellcey wrote: >> > Here is an official submission for the switch optimization described in >> > PR 54742. I have addressed the formatting/comment issues that were raised >> > and also added a test case based on comment #27 from PR 54742 and I fixed a >> > bug I found while doing benchmarking with SPEC2006 (the perl benchmark was >> > generating an ICE in a routine with multiple switch statements). >> > >> > I ran the benchmarking to see if I could find any more tests that are >> > helped like coremark is and while I found a number of benchmarks in >> > SPEC 2006 and EEMBC where the optimization is triggered, this optimization >> > generally didn't affect the performance of those benchmarks. The biggest >> > impact I could find was on the perl benchmark in SPEC where I saw around >> > a 0.4% improvement on a MIPS 74k. Not huge, but not nothing. >> >> For what it is worth, I see a nice (~4%) improvement in Crafty from >> SPEC 2000. I haven't investigated too deeply, but at a first glance the >> number of branch mispredictions has dropped just over 1%, as you >> might hope from this optimisation. >> >> I can also attest to there being a number of places the optimisation is >> triggered (with high enough parameters; I was running with >> --param max-switch-paths=1000 --param max-switch-insns=10000), but like >> you I don't see much measurable change in execution time. > > Without change to the default params, I see the switch shortcut having a > performance impact on both png and jpeg, compress and decompress mode. > > I think that's enough to remove the "benchmarketing" label from the switch > shortcut transform.
Did you look at the actual code transformation the pass does to these? (what is 'png' and 'jpeg'?) What's the code size impact? Richard. > Sebastian
