On Sun, Jan 19, 2014 at 3:30 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>>>> For LEA operation with SImode_address_operand, which zero-extends SImode
>>>>> to DImode, ix86_split_lea_for_addr turns
>>>>>
>>>>> (set (reg:DI) ...)
>>>>>
>>>>> into
>>>>>
>>>>> (set (reg:SI) ...)
>>>>>
>>>>> We need to do
>>>>>
>>>>> (set (reg:DI) (zero_extend:DI (reg:SI)))
>>>>>
>>>>> at the end. If the LEA operation is
>>>>>
>>>>> (set (reg:DI) (zero_extend:DI (reg:SI)))
>>>>
>>>> ree pass should remove these. However, we can just emit zero-extend
>>>> insn at the end of sequence, and ree (which is located after
>>>> post-reload split) should handle it:
>>>>
>>>> --cut here--
>>>> Index: config/i386/i386.md
>>>> ===================================================================
>>>> --- config/i386/i386.md (revision 206753)
>>>> +++ config/i386/i386.md (working copy)
>>>> @@ -5428,12 +5428,17 @@
>>>> operands[0] = SET_DEST (pat);
>>>> operands[1] = SET_SRC (pat);
>>>>
>>>> - /* Emit all operations in SImode for zero-extended addresses. Recall
>>>> - that x86_64 inheretly zero-extends SImode operations to DImode. */
>>>> + /* Emit all operations in SImode for zero-extended addresses. */
>>>> if (SImode_address_operand (operands[1], VOIDmode))
>>>> mode = SImode;
>>>>
>>>> ix86_split_lea_for_addr (curr_insn, operands, mode);
>>>> +
>>>> + /* Zero-extend return register to DImode for zero-extended addresses.
>>>> */
>>>> + if (mode != <MODE>mode)
>>>> + emit_insn (gen_zero_extendsidi2
>>>> + (operands[0], gen_lowpart ((mode), operands[0])));
>>>> +
>>>> DONE;
>>>> }
>>>> [(set_attr "type" "lea")
>>>> --cut here--
>>>>
>>>> The patch was tested with a testcase from Comment #9 of the PR using
>>>> "-O --march=corei7 -mtune=slm", and resulting binary runs without
>>>> problems.
>>>>
>>>
>>> Yes, the resulting GCC works correctly. However, we generate
>>> extra
>>>
>>> (set (reg:DI) (zero_extend:DI (reg:SI)))
>>>
>>> It is because we generate
>>>
>>> (set (reg:SI) (reg:SI)
>>> (set (reg:DI) (zero_extend:DI (reg:SI)))
>>>
>>> REE pass doesn't know
>>>
>>> (set (reg:SI) (reg:SI)
>>>
>>> has an implicit ZERO_EXTEND. Here is a testcase:
>>
>> This is the correct sequence,and REE pass should be improved to handle
>> this situation.
>>
>> Note, that the problem was that we assumed SImode operations
>> (including move) have implicit DImode zero-extend, but in fact we
>> haven't communicate this to the compiler in a proper way.
>>
>> So, I propose we go with my patch and file an enhancement PR for the REE
>> pass.
>>
>
> That is fine with me. Please install it on all affected branches
> and close the PR. I will open a new PR for REE pass.
Installed with following ChangeLog:
2014-01-18 Uros Bizjak <ubiz...@gmail.com>
H.J. Lu <hongjiu...@intel.com>
PR target/59379
* config/i386/i386.md (*lea<mode>): Zero-extend return register
to DImode for zero-extended addresses.
Bootstrapped and regression tested on x86_64-pc-linux-gnu, will
backport in a couple of days.
Uros.
