On Tue, May 7, 2024 at 1:45 PM Jeff Law <jeffreya...@gmail.com> wrote: > > > > On 4/30/24 9:21 PM, Andrew Pinski wrote: > > This adds a few more of what is currently done in phiopt's value_replacement > > to match. I noticed this when I was hooking up phiopt's value_replacement > > code to use match and disabling the old code. But this can be done > > independently from the hooking up phiopt's value_replacement as phiopt > > is already hooked up for simplified versions already. > > > > /* a != 0 ? a / b : 0 -> a / b iff b is nonzero. */ > > /* a != 0 ? a * b : 0 -> a * b */ > > /* a != 0 ? a & b : 0 -> a & b */ > > > > We prefer the `cond ? a : 0` forms to allow optimization of `a * cond` which > > uses that form. > > > > Bootstrapped and tested on x86_64-linux-gnu with no regressions. > > > > PR treee-optimization/114894 > > > > gcc/ChangeLog: > > > > * match.pd (`a != 0 ? a / b : 0`): New pattern. > > (`a != 0 ? a * b : 0`): New pattern. > > (`a != 0 ? a & b : 0`): New pattern. > > > > gcc/testsuite/ChangeLog: > > > > * gcc.dg/tree-ssa/phi-opt-value-5.c: New test. > Is there any need to also handle the reversed conditional with the arms > swapped? If not, this is fine as-is. If yes, then fine with the > obvious generalization.
The answer is yes and no. While the PHI-OPT pass will try both cases but the other (all?) passes does not. This is something I have been thinking about trying to solve in a generic way instead of adding many more patterns here. I will start working on that in the middle of June. Most of the time cond patterns in match are used is inside phiopt so having the revered conditional has not been on high on my priority but with VRP and scev and match (itself) producing more cond_expr, we should fix this once and for all for GCC 15. Thanks, Andrew Pinski > > jeff >
