[PATCH] Add divide by zero side effect.

[Richard Biener]

On Tue, May 17, 2022 at 8:40 PM Andrew MacLeod via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> I haven't checked this patch in yet.  This implements a side effect that
> the divisor cannot be 0 after a divide executes. This allows us to fold
> the divide away:
>
> a = b / c;
> if (c == 0)
>    dead();
>
> This bootstraps on x86_64-pc-linux-gnu with no regressions, but I first
> wanted to check to see if there are some flags or conditions that should
> e checked in order NOT to do this optimization.  I am guessing there is
> probably something :-)    Anyway, this is how we straightforwardly add
> side effects now.
>
> Does the patch conditions need tweaking to apply the side effect?

What does "after the stmt" mean?  If the stmt throws internally then on
the EH edge the divisor can be zero.

How do you fold away the divide in your above example?

Richard.

>
> Andrew
>