On Tue, 8 Mar 2022, Jeff Law wrote: > > > On 3/8/2022 5:56 AM, Richard Biener via Gcc-patches wrote: > > This adds a --param to allow disabling of vectorization of > > floating point inductions. Ontop of -Ofast this should allow > > 549.fotonik3d_r to not miscompare. > > > > While I thought of a more elaborate way of disabling certain > > vectorization kinds (reductions also came to my mind) this > > for now simply uses a --param than some sophisticated -fvectorize-* > > scheme. > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu. I've > > verified that 549.fotonik3d_r miscompares with -Ofast -march=znver2 > > and passes when adding --param vect-induction-float=0 which > > should be valid at least for peak (but I guess also base for > > FOPTIMIZE for example). I did not benchmark against other > > workarounds (it has been said -fno-unsafe-math-optimizations > > or other similar things work as well). > Those other options do work well to throttle things back for fotonik. > Presumably the idea of having the param is to be more surgical about what > needs to be disabled to keep fotonik happy. Given the benchmark specific > nature of the option, I'm not opposed to it being a param (primarily for > developer use) vs a -f<blah> which are more geared to the user community.
Yes, my original idea was to provide more fine-grained control in a more user-friendly way but that requires quite a bit of bike-shedding that's not appropriate for this stage. > > > > OK for trunk? > > > > Thanks, > > Richard. > > > > 2022-03-08 Richard Biener <rguent...@suse.de> > > > > PR tree-optimization/84201 > > * params.opt (-param=vect-induction-float): Add. > > * doc/invoke.texi (vect-induction-float): Document. > > * tree-vect-loop.cc (vectorizable_induction): Honor > > param_vect_induction_float. > > > > * gcc.dg/vect/pr84201.c: New testcase. > LGTM. Thanks - pushed. Richard.
