On Thu, Feb 9, 2012 at 11:53 AM, Richard Guenther
<richard.guent...@gmail.com> wrote:
> On Thu, Feb 9, 2012 at 11:29 AM, Richard Guenther
> <richard.guent...@gmail.com> wrote:
>> On Wed, Feb 8, 2012 at 10:25 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
>>> 2012/1/11 Richard Guenther <richard.guent...@gmail.com>:
>>>>
>>>> count despite being declared volatile and only loaded once in the source
>>>> is loaded twice in gimple. If it were a HW register which destroys the
>>>> device after the 2nd load without an intervening store you'd wrecked
>>>> the device ;)
>>>>
>>>> Richard.
>>>
>>> Thanks for explaination. I tried to flip order for lhs/rhs in
>>> gimplify_modify_expr & co. Issue here is that for some cases we are
>>> relying here on lhs for gimplifying rhs (is_gimple_reg_rhs_or_call vs
>>> is_gimple_mem_rhs_or_call) and this doesn't work for cases in C++
>>> like:
>>>
>>> typedef const unsigned char _Jv_Utf8Const;
>>> typedef __SIZE_TYPE__ uaddr;
>>>
>>> void maybe_adjust_signature (_Jv_Utf8Const *&s, uaddr &special)
>>> {
>>> union {
>>> _Jv_Utf8Const *signature;
>>> uaddr signature_bits;
>>> };
>>> signature = s;
>>> special = signature_bits & 1;
>>> signature_bits -= special;
>>> s = signature;
>>> }
>>>
>>> So I modified gimplify_self_mod_expr for post-inc/dec so that we use
>>> following sequence
>>> and add it to pre_p for it:
>>>
>>> tmp = lhs;
>>> lvalue = tmp (+/-) rhs
>>> *expr_p = tmp;
>>
>> As I explained this is the wrong place to fix the PR. The issue is not
>> about self-modifying expressions but about evaluating call argument
>> side-effects before side-effects of the lhs.
>
> I am testing the attached instead.
Doesn't work. Btw, Kai, your patch surely breaks things if you put
the lvalue update into the pre queue.
Consider a simple
a[i++] = i;
you gimplify that to
i.0 = i;
D.1709 = i.0;
i = D.1709 + 1;
a[D.1709] = i;
which is wrong.
Seems we are lacking some basic pre-/post-modify testcases ...
Richard.
