On Thu, Aug 21, 2014 at 09:57:56AM +0100, Richard Biener wrote: > On Tue, Aug 19, 2014 at 10:39 PM, Steve Ellcey <sell...@mips.com> 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. > > > > So, OK to checkin? > > Without looking at the patch in detail what is the rationale for the > pass placement (looks quite early)? I would have guessed that > the pass could benefit from value-range analysis. > > Jeff, Steve is it possible to trigger the transform by simply > "manually forcing" the right "path" jump-threads from > inside VRP? That is, basically integrate the transform part > with the existing jump threading framework but do an > alternate discovery pass?
This seems like what I tried to do last year with: https://gcc.gnu.org/ml/gcc-patches/2013-06/msg01121.html It turns Jeff's jump-threading code in to a strange franken-pass of bits and pieces of detection and optimisation, and would need some substantial reworking to fit in with Jeff's changes last Autumn, but if it is more likely to be acceptable for trunk then perhaps we could look to revive it. It would be nice to reuse the path copy code Jeff added last year, but I don't have much intuition as to how feasible that is. Was this the sort of thing that you were imagining? Steve, Jeff? James > > Thanks, > Richard. > > > Steve Ellcey > > sell...@mips.com > > > > > > 2014-08-12 Steve Ellcey <sell...@mips.com> > > > > PR tree-opt/54742 > > * Makefile.in (OBJS): Add tree-switch-shortcut.o. > > * common.opt (ftree-switch-shortcut): New. > > * opts.c (default_options_table): Add OPT_ftree_switch_shortcut. > > * params.def (PARAM_MAX_SWITCH_INSNS): New. > > (PARAM_MAX_SWITCH_PATHS): New. > > * passes.def (pass_tree_switch_shortcut): New. > > * timevar.def (TV_TREE_SWITCH_SHORTCUT): New. > > * tree-pass.h (make_pass_tree_switch_shortcut): New. > > * tree-switch-shortcut.c: New. > > > > > > 2014-08-12 Steve Ellcey <sell...@mips.com> > > > > PR tree-opt/54742 > > * gcc.dg/pr54742.c: New test. > > >
