On Wed, Apr 26, 2017 at 6:02 PM, Tamar Christina <tamar.christ...@arm.com> wrote: > Hi all, > > r245676 (PR/79665) introduced a change to calculate the costs of signed > and unsigned div operations independently and when both are possible to > allow you to specify a preference via cost mode. > > From the cover letter https://gcc.gnu.org/ml/gcc-patches/2017-02/msg01408.html > this was also supposed to apply to modulo but it only changed division. > This adds the changes to modulo as well. > > I believe this to be a regression from GCC7 since now modulo generates worse > code > and blocks CSE when e.g. div and mod are used together. > > Bootstrapped on aarch64-none-linux-gnu and x86_64-linux > and reg-tested on aarch64-none-linux-gnu with no regressions. > > OK for trunk and back-port to GCC7?
The only non-obvious part is that now fixed-point modulo go to binop (might have been a bug before). It's less obvious why mod now generates worse code -- the mod path didn't change. Yes, I see how it may block CSE so it qualifies as a regression. Ok for trunk. Ok for branch after 7.1 is out. Thanks, Richard. > Thanks, > Tamar > > > gcc/ > 2017-04-26 Tamar Christina <tamar.christ...@arm.com> > > PR middle-end/79665 > * expr.c (expand_expr_real_2): Move TRUNC_MOD_EXPR, FLOOR_MOD_EXPR, > CEIL_MOD_EXPR, ROUND_MOD_EXPR cases.
