https://gcc.gnu.org/g:667c19de86b33648f5f4599f589a5e02adbb35cb
commit r15-67-g667c19de86b33648f5f4599f589a5e02adbb35cb Author: Richard Biener <rguent...@suse.de> Date: Tue Apr 16 14:05:35 2024 +0200 middle-end/13421 - -ftrapv vs. POINTER_DIFF_EXPR Currently we expand POINTER_DIFF_EXPR using subv_optab when -ftrapv (but -fsanitize=undefined does nothing). That's not consistent with the behavior of POINTER_PLUS_EXPR which never uses addv_optab with -ftrapv. Both are because of the way we select whether to use the trapping or the non-trapping optab - we look at the result type of the expression and check trapv = INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_TRAPS (type); the bugreport correctly complains that -ftrapv affects pointer subtraction (there's no -ftrapv-pointer). Now that we have POINTER_DIFF_EXPR we can honor that appropriately. The patch moves both POINTER_DIFF_EXPR and POINTER_PLUS_EXPR handling so they will never consider trapping (or saturating) optabs. PR middle-end/13421 * optabs-tree.cc (optab_for_tree_code): Do not consider {add,sub}v or {us,ss}{add,sub} optabs for POINTER_DIFF_EXPR or POINTER_PLUS_EXPR. Diff: --- gcc/optabs-tree.cc | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/gcc/optabs-tree.cc b/gcc/optabs-tree.cc index e7bd0d10892..b69a5bc3676 100644 --- a/gcc/optabs-tree.cc +++ b/gcc/optabs-tree.cc @@ -135,6 +135,12 @@ optab_for_tree_code (enum tree_code code, const_tree type, case MIN_EXPR: return TYPE_UNSIGNED (type) ? umin_optab : smin_optab; + case POINTER_PLUS_EXPR: + return add_optab; + + case POINTER_DIFF_EXPR: + return sub_optab; + case REALIGN_LOAD_EXPR: return vec_realign_load_optab; @@ -249,13 +255,11 @@ optab_for_tree_code (enum tree_code code, const_tree type, trapv = INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_TRAPS (type); switch (code) { - case POINTER_PLUS_EXPR: case PLUS_EXPR: if (TYPE_SATURATING (type)) return TYPE_UNSIGNED (type) ? usadd_optab : ssadd_optab; return trapv ? addv_optab : add_optab; - case POINTER_DIFF_EXPR: case MINUS_EXPR: if (TYPE_SATURATING (type)) return TYPE_UNSIGNED (type) ? ussub_optab : sssub_optab;