On Wed, Jun 5, 2019 at 12:56 PM Martin Liška <mli...@suse.cz> wrote: > > Hi. > > I'm suggesting one multiplication simplification pattern. > > Patch can bootstrap on x86_64-linux-gnu and survives regression tests. > > Ready to be installed?
+ (if (INTEGRAL_TYPE_P (type) + && wi::eq_p (get_nonzero_bits (@1), wi::one (TYPE_PRECISION (type))) + && wi::eq_p (get_nonzero_bits (@2), wi::one (TYPE_PRECISION (type)))) && wi::eq_p (wi::bit_or (get_nonzero_bits (@1), get_nonzero_bits (@2)), 1)) (I think literal 1 still works)? How does it behave for singed/unsigned 1-bit bitfields? A gimple testcase maybe necessary to see. Does this mean we want to turn plus into bit_ior when get_nonzero_bits() & get_nonzero_bits() is zero? X * [0, 1] -> X & sign-extend-from-bit-1 also works I guess, but multiplication looks more canonical. Thanks, Richard. > Thanks, > Martin > > gcc/ChangeLog: > > 2019-06-05 Martin Liska <mli...@suse.cz> > > PR tree-optimization/87954 > * match.pd: Simplify mult where both arguments are 0 or 1. > > gcc/testsuite/ChangeLog: > > 2019-06-05 Martin Liska <mli...@suse.cz> > > PR tree-optimization/87954 > * gcc.dg/pr87954.c: New test. > --- > gcc/match.pd | 8 ++++++++ > gcc/testsuite/gcc.dg/pr87954.c | 21 +++++++++++++++++++++ > 2 files changed, 29 insertions(+) > create mode 100644 gcc/testsuite/gcc.dg/pr87954.c > >
