On Tue, Apr 16, 2024 at 04:00:59PM +0200, Richard Biener wrote:
> 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.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> OK for stage1?
>
> Thanks,
> Richard.
>
> 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.
LGTM.
Jakub
