https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111303
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jiu Fu Guo <guoji...@gcc.gnu.org>: https://gcc.gnu.org/g:8d8bc560b6ab7f3153db23ffb37157528e5b2c9a commit r14-3913-g8d8bc560b6ab7f3153db23ffb37157528e5b2c9a Author: Jiufu Guo <guoji...@linux.ibm.com> Date: Wed Sep 6 21:38:11 2023 +0800 Checking undefined_p before using the vr For pattern "(X + C) / N": "div (plus@3 @0 INTEGER_CST@1) INTEGER_CST@2)", Even if "X" has value-range and "X + C" does not overflow, "@3" may still be undefined. Like below example: _3 = _2 + -5; if (0 != 0) goto <bb 3>; [34.00%] else goto <bb 4>; [66.00%] ;; succ: 3 ;; 4 ;; basic block 3, loop depth 0 ;; pred: 2 _5 = _3 / 5; ;; succ: 4 The whole pattern "(_2 + -5 ) / 5" is in "bb 3", but "bb 3" would be unreachable (because "if (0 != 0)" is always false). And "get_range_query (cfun)->range_of_expr (vr3, @3)" is checked in "bb 3", "range_of_expr" gets an "undefined vr3". Where "@3" is "_5". So, before using "vr3", it would be safe to check "!vr3.undefined_p ()". PR tree-optimization/111303 gcc/ChangeLog: * match.pd ((X - N * M) / N): Add undefined_p checking. ((X + N * M) / N): Likewise. ((X + C) div_rshift N): Likewise. gcc/testsuite/ChangeLog: * gcc.dg/pr111303.c: New test.
