On Sun, May 20, 2018 at 9:45 PM Yuri Gribov <tetra2...@gmail.com> wrote:
> On Sun, May 20, 2018 at 1:01 PM, Alexander Monakov <amona...@ispras.ru> wrote: > > On Sun, 20 May 2018, Yuri Gribov wrote: > > > >> Hi all, > >> > >> This fixes PR 85822 by removing incorrect reversal of condition in VRP > >> assertion. Bootstrapped and regtested on x86_64. > >> > >> Ok for trunk? > > > > Please address the following issues: > > > > Use correct PR reference in Changelog. > Ah, right. > > Double-check the comment before the function, I think NE_EXPR and EQ_EXPR > > should be swapped there. > Thanks, fixed. > > Address Richard's request from the bug report: > > > >>> Ok, please make sure to say why not doing anything special for negative > >>> numbers is ok. > True, I didn't notice the "to say" part :/ > Comparison > (a & 11...100...0) == XX...X00..0 // RHS XX...X is covered by > 11...100...0 mask i.e. (RHS & MASK) == RHS > means that 'a' can have values > XX...X00...00 > XX...X00...01 > XX...X00...10 > ... > XX...X11...11 > Both for positive and negative, signed and unsigned RHSs the first > number is less than the last one so we can derive > XX...X00...00 <= a > a <= XX...X11...11 > in all cases. > > Note there are at least three special cases that are handled incorrectly either > > before or after the patch: > > > > - not two's complement integers > Commented by Richard. > > - mask being 0 > > - mask being ~0 > Done (AND with 0 or -1 is removed during Gimple generation so I didn't > bother to optimize this special case, just bail out). OK. Thanks, Richard. > -Y
