> On May 19, 2014, at 2:39 AM, Richard Biener <richard.guent...@gmail.com>
> wrote:
>
>> On Mon, May 19, 2014 at 10:58 AM, Eric Botcazou <ebotca...@adacore.com>
>> wrote:
>> Hi,
>>
>> this fixes an over-optimization of the GIMPLE optimizer, whereby two
>> otherwise
>> identical calls to a pure function present in different EH regions are CSEd,
>> which changes the semantics of the program because the second EH handler is
>> not invoked:
>>
>> begin
>> I := F(0);
>> exception
>> when E => N := N + 1;
>> end;
>>
>> begin
>> I := F(0);
>> exception
>> when E => N := N +1;
>> end;
>>
>> Two passes (DOM and FRE) can optimize this construct and a test modelled on
>> stmt_can_throw_internal is used to coax them into not doing so.
>>
>> Tested on x86_64-suse-linux, OK for the mainline?
>
> Heh, interesting.
>
> Please keep the "redundant" test, it speeds up comparison on hash
> collisions. As you are on it I'd use size_int (lr).
>
> I think it's ok to CSE foo (0) for
>
> try {
> foo (0);
> } catch (...) { side-effect }
> foo (0);
>
> but not
>
> foo(0);
> try {
> foo (0);
> } catch (...) { side-effect }
>
> but I don't see a clever way to preserve one but not the other
> (at least in SCCVN). Do you think it's worth trying to preserve
> that?
>
> Otherwise the patch looks good to me. (bonus point for a C++
> testcase as Ada is not in our testing requirements and it would
> be nice to exercise this w/o Ada)
I thought we had decided a long time ago that pure and const functions could
not throw and that was the documented behavior.
Thanks,
Andrew
>
> Thanks,
> Richard.
>
>>
>> 2014-05-19 Eric Botcazou <ebotca...@adacore.com>
>>
>> * tree-ssa-dom.c (hashable_expr_equal_p) <EXPR_CALL>: Also compare the
>> EH region of calls to pure functions that can throw an exception.
>> * tree-ssa-sccvn.c (vn_reference_eq): Remove redundant test.
>> (copy_reference_ops_from_call): Also copy the EH region of the call if
>> it can throw an exception.
>>
>>
>> 2014-05-19 Eric Botcazou <ebotca...@adacore.com>
>>
>> * gnat.dg/opt35.adb: New test.
>> * gnat.dg/opt35_pkg.ad[sb]: New helper.
>>
>>
>> --
>> Eric Botcazou
