[Bug tree-optimization/104356] [12 Regression] divide by zero trap is being removed now when it should not be in some cases

[ebotcazou at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104356

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-02-03
                 CC|                            |ebotcazou at gcc dot gnu.org

--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Hmm, but doesn't ada enable -fdelete-dead-exceptions?  That is, I'm not sure
> we make division by zero well-defined with -fnon-call-exceptions - the
> transform assumes the exception cannot happen (because undefinedness) and
> removes the exceptional path.

Yes, the division by zero can be optimized away in Ada if the result of the
operation is not used later, so we would need to add a pragma Volatile to the
gnat.dg/div_zero.adb testcase:

  D : Integer := Zero;
  pragma Volatile (D);

for strict semantics, but this usually does not matter at -O0 when the result
is assigned to a user variable:

  D := 1 / D;