On Thu, 2020-05-07 at 16:27 +0200, Jakub Jelinek via Gcc-patches wrote: > On Thu, May 07, 2020 at 09:59:57AM +0200, Richard Biener wrote: > > Maybe write A - B + -1 >= A to actually match what you match below > ... > > on the plus :c is not needed, canonicalization will put the constant > > literal second > > > > The previous pattern has a single_use check on the minus, since > > the result is always "simple" (a single stmt) the :s have no > > effect (hmm, I guess a genmatch warning for this case might be nice). > > > > And yes, if the TYPE_OVERFLOW_WRAPS checks are unnecessary remove > > them please, we'll hopefully resist all attempts to ubsan > > unsigned overflow ... > > So like this if it passes bootstrap/regtest? > > 2020-05-07 Jakub Jelinek <ja...@redhat.com> > > PR tree-optimization/94913 > * match.pd (A - B + -1 >= A to B >= A): New simplification. > (A - B > A to A < B): Don't test TYPE_OVERFLOW_WRAPS which is always > true for TYPE_UNSIGNED integral types. > > * gcc.dg/tree-ssa/pr94913.c: New test. I wouldn't be surprised if this trips issues with -Wuninitialized and the C++ runtime. I like the change, but the VRP bits which detect overflow tests and extract ranges are fragile -- though it's also possible your change would eliminate the need for those bits.
jeff >
