https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110134
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- r6-1814-g66e1cacf608045 caused GCC 6 to stop doing both. Because they were considered redundant with the patterns added by: r6-1113-g534bd33b61d08e Which was mostly true. I think forwprop was working again with r8-2194-g4f450a2b102212 for f2 (I am not 100% sure). So to summarize r6-1814-g66e1cacf608045 removed the unsigned/wrapping case for NE/EQ since it was originally thought as redundant. My patch adds support back for those 2. case EQ_EXPR: case NE_EXPR: ... - /* Similarly for a NEGATE_EXPR. */ - if (TREE_CODE (arg0) == NEGATE_EXPR - && TREE_CODE (arg1) == INTEGER_CST - && 0 != (tem = negate_expr (fold_convert_loc (loc, TREE_TYPE (arg0), - arg1))) - && TREE_CODE (tem) == INTEGER_CST - && !TREE_OVERFLOW (tem)) - return fold_build2_loc (loc, code, type, TREE_OPERAND (arg0, 0), tem); ... - /* Fold -X op -Y as X op Y, where op is eq/ne. */ - if (TREE_CODE (arg0) == NEGATE_EXPR - && TREE_CODE (arg1) == NEGATE_EXPR) - return fold_build2_loc (loc, code, type, - TREE_OPERAND (arg0, 0), - fold_convert_loc (loc, TREE_TYPE (arg0), - TREE_OPERAND (arg1, 0))); Since these 2 did cases didn't test TYPE_OVERFLOW_UNDEFINED, we should handle EQ/NE also in match.pd the same way.
