On Thu, Jul 28, 2011 at 11:34 PM, Paolo Bonzini <bonz...@gnu.org> wrote:
> Ok, you removed ignore_address_wrap_around, so we're almost there.
>
> On 07/28/2011 07:59 PM, H.J. Lu wrote:
>>
>> @@ -712,7 +715,16 @@ convert_modes (enum machine_mode mode, enum
>> machine_mode oldmode, rtx x, int uns
>> if (GET_CODE (x) == SUBREG&& SUBREG_PROMOTED_VAR_P (x)
>> && GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))>= GET_MODE_SIZE
>> (mode)
>> && SUBREG_PROMOTED_UNSIGNED_P (x) == unsignedp)
>> - x = gen_lowpart (mode, x);
>> + {
>> + temp = rtl_hooks.gen_lowpart_no_emit (mode, x);
>> + if (temp)
>> + x = temp;
>> + else
>> + {
>> + gcc_assert (!no_emit);
>> + x = gen_lowpart (mode, x);
>> + }
>> + }
>
> + {
> + /* gen_lowpart_no_emit should always succeed here. */
> + x = rtl_hooks.gen_lowpart_no_emit (mode, x);
> + }
>
>>
>> if (GET_MODE (x) != VOIDmode)
>> oldmode = GET_MODE (x);
>> @@ -776,6 +788,10 @@ convert_modes (enum machine_mode mode, enum
>> machine_mode oldmode, rtx x, int uns
>> return gen_int_mode (val, mode);
>> }
>>
>> + temp = rtl_hooks.gen_lowpart_no_emit (mode, x);
>> + if (temp)
>> + return temp;
>> + gcc_assert (!no_emit);
>> return gen_lowpart (mode, x);
>
> Right now, gen_lowpart_no_emit will never return NULL, so these tests in
> convert_modes are dead. Instead, please include in your patch mine at
> http://permalink.gmane.org/gmane.comp.gcc.patches/242085 and adjust as
> follows.
>
> + temp = rtl_hooks.gen_lowpart_no_emit (mode, x);
> + if (no_emit)
> + return rtl_hooks.gen_lowpart_no_emit (mode, x);
> + else
> + return gen_lowpart (mode, x);
>
>> }
>
> If it does not work, PLEASE say why instead of posting another "updated
> patch".
The whole approach doesn't work. The testcase at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49721#c1
shows GCC depends on transforming:
(zero_extend:DI (plus:SI (FOO:SI) (const_int Y)))
to
(plus:DI (zero_extend:DI (FOO:SI)) (const_int Y))
Otherwise we either get compiler crash or wrong codes.
--
H.J.
