On Thu, Jul 21, 2011 at 1:17 PM, Uros Bizjak <ubiz...@gmail.com> wrote:
> On Thu, Jul 21, 2011 at 10:00 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>
>>> /* Represents viewing something of one type as being of a second type.
>>> This corresponds to an "Unchecked Conversion" in Ada and roughly to
>>> the idiom *(type2 *)&X in C. The only operand is the value to be
>>> viewed as being of another type. **It is undefined if the type of the
>>> input and of the expression have different sizes.**
>>>
>>> ...
>>> DEFTREECODE (VIEW_CONVERT_EXPR, "view_convert_expr", tcc_reference, 1)
>>>
>>> We have:
>>>
>>> <bb 2>:
>>> D.2709_8 = VIEW_CONVERT_EXPR<double>(&xxxx);
>>> D.2702_1 = u.d;
>>> D.2704_3 = D.2702_1 == D.2709_8;
>>> D.2701_4 = (int) D.2704_3;
>>> return D.2701_4;
>>>
>>> Where
>>>
>>> sizeof (double) = 64
>>> sizeof (ptr_type) = 32.
>>>
>>
>> Are you sure that you used -mx32? I couldn't reproduce it.
>> It looks like an x86 backend bug to me.
>
> Hm, can't reproduce it anymore... x32 -O2 looks OK:
>
> <bb 2>:
> v = {};
> v.m = &xxxx;
> D.2702_1 = u.d;
> D.2703_2 = v.d;
> D.2704_3 = D.2702_1 == D.2703_2;
> D.2701_4 = (int) D.2704_3;
> return D.2701_4;
>
> }
>
> Expand generates:
>
> (insn 8 6 9 (set (reg:SI 68)
> (symbol_ref:SI ("xxxx") [flags 0x40] <var_decl 0x7fccc360b140 xxxx>))
> p
> r49798.c:12 -1
> (nil))
>
> (insn 9 8 10 (set (reg:DI 67)
> (zero_extend:DI (reg:SI 68))) pr49798.c:12 -1
> (nil))
>
> I don't know if this is OK to be transformed to DImode load.
>
I believe it is valid.
--
H.J.
