https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115863
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Uroš Bizjak from comment #6) > Please note that w/o .SAT_TRUNC the compiler is able to optimize hot loop in > compress2 to: > > <bb 5> [local count: 536870912]: > _18 = MIN_EXPR <left_8, 4294967295>; > iftmp.0_11 = (unsigned int) _18; > stream.avail_out = iftmp.0_11; > left_37 = left_8 - _18; > > while .SAT_TRUNC somehow interferes with this optimization to produce: > > <bb 5> [local count: 536870912]: > _45 = MIN_EXPR <left_8, 4294967295>; > iftmp.0_11 = .SAT_TRUNC (left_8); > stream.avail_out = iftmp.0_11; > left_37 = left_8 - _45; it looks like whatever recognizes .SAT_TRUNC doesn't pay attention that there are other uses of the MIN_EXPR and thus the MIN_EXPR stays live. IIRC :s on (match (...) is ignored (and that's good IMO) at the moment so the user of the match predicate has to check.
