https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94589
--- Comment #21 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:f5f1838435400b837c8677c53a611e2dc6d56442 commit r12-733-gf5f1838435400b837c8677c53a611e2dc6d56442 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed May 12 09:46:03 2021 +0200 match.pd: Optimize (x & y) == x into (x & ~y) == 0 [PR94589] > Somewhere in RTL (_M_value&1)==_M_value is turned into (_M_value&-2)==0, > that could be worth doing already in GIMPLE. Apparently it is /* Simplify eq/ne (and/ior x y) x/y) for targets with a BICS instruction or constant folding if x/y is a constant. */ if ((code == EQ || code == NE) && (op0code == AND || op0code == IOR) && !side_effects_p (op1) && op1 != CONST0_RTX (cmp_mode)) { /* Both (eq/ne (and x y) x) and (eq/ne (ior x y) y) simplify to (eq/ne (and (not y) x) 0). */ ... /* Both (eq/ne (and x y) y) and (eq/ne (ior x y) x) simplify to (eq/ne (and (not x) y) 0). */ Yes, doing that on GIMPLE for the case where the not argument is constant would simplify the phiopt follow-up (it would be single imm use then). On Thu, May 06, 2021 at 09:42:41PM +0200, Marc Glisse wrote: > We can probably do it in 2 steps, first something like > > (for cmp (eq ne) > (simplify > (cmp (bit_and:c @0 @1) @0) > (cmp (@0 (bit_not! @1)) { build_zero_cst (TREE_TYPE (@0)); }))) > > to get rid of the double use, and then simplify X&C==0 to X<=~C if C is a > mask 111...000 (I thought we already had a function to detect such masks, or > the 000...111, but I can't find them anymore). Ok, here is the first step then. 2021-05-12 Jakub Jelinek <ja...@redhat.com> Marc Glisse <marc.gli...@inria.fr> PR tree-optimization/94589 * match.pd ((X & Y) == X -> (X & ~Y) == 0, (X | Y) == Y -> (X & ~Y) == 0): New GIMPLE simplifications. * gcc.dg/tree-ssa/pr94589-1.c: New test.
