https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96697
--- Comment #5 from Andrew Macleod <amacleod at redhat dot com> --- (In reply to Andrew Macleod from comment #4) > (In reply to Jakub Jelinek from comment #2) > > Shall we do that as a specific matcher or e.g. in the ranger once it gets > > code for symbolic comparisons? I mean, for signed t = x % y note that t is > > in [-y + 1, y + 1] and on the division use that information to determine the > > division result range to be [0, 0] ? > > It could then handle even e.g. ((unsigned) x % y) / (y + 32) for signed y > > etc. > > IN theory the ranger should handle this when relations are available. > > <bb 2> : > _1 = x_2(D) % y_3(D); // Establish relation _1 < y_3 > _4 = _1 / y_3(D); > return _4; > > IT should recognize the relation _1 < y_3 from the first statement and when > we calculate _1 / y_3, it again ought to then apply the relation and > determine that _4 = [0,0] hum. but that'd only work for unsigned I guess? If y_3 is negative, then _1 > y_3 I believe. so if y_3 is VARYING, relations won't solve this issue :-P
