kmclaughlin abandoned this revision. kmclaughlin added a comment. I just wanted to give an update on this patch, which I'm abandoning for the time being:
@lebedev.ri raised some good questions about the approach taken and whether the additional compile time spent would be worth the additional opportunities for vectorisation. After posting the last update, I collected some benchmark results using Spec2017 to get a better understanding of the impact of these changes and found that several benchmarks showed performance regressions for fixed-width. The biggest outliers (in terms of percentage runtime change) were: 520.omnetpp_r: -3.00% 500.perlbench_r: -2.00% 502.gcc_r: -1.52% I also collected the results after adding in a threshold number of cases to be unswitched (set to 4), as was included in the first draft of this patch. This also showed some regressions in the benchmarks run and no significant improvements. Both sets of results showed increased compile times for many benchmarks. The same benchmarks as above, with the threshold of 4 set: 520.omnetpp_r: -3.46% 500.perlbench_r: -1.20% 502.gcc_r: -1.22% Results were collected on a Neoverse-N1 machine. Given that these results indicate this isn't the best approach to take, I'm abandoning the patch for now. When this is picked up in future, it will likely be better to follow either the suggestion to prevent canonicalisation of branches & compares into switch statements (under a given number of cases) in the first place, or to teach the loop vectoriser to recognise switches. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D108138/new/ https://reviews.llvm.org/D108138 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
