https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116024
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Artemiy Volkov from comment #5) > Hi Andrew, thank you for the breakdown. For i1() (the case applicable to > the initial bug report) something like this seems to fix the issue: > > diff --git a/gcc/match.pd b/gcc/match.pd > index cf359b0ec0f..8ab6d47e278 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -8773,2 +8773,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > > +/* Transform comparisons of the form C1 - X CMP C2 to X - C1 CMP -C2. */ > +(for cmp (lt le gt ge eq ne) > + rcmp (gt ge lt le eq ne) > + (simplify > + (cmp (minus INTEGER_CST@0 @1) INTEGER_CST@2) > + (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@1))) > + (rcmp (minus @1 @0) (negate @2))))) > + > /* Canonicalizations of BIT_FIELD_REFs. */ > > Would it make sense for this ticket to be assigned to me so I could refine > and post the above patch as well as tackle i2() and i3() (should those be > extracted to a separate PR or is it fine to fix all three under this PR)? I don't think this is correct for types with undefined behavior on overflow because you can't negate INT_MIN.
