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Re: PATCH: PR target/50603: [x32] Unnecessary lea
On Tue, Oct 4, 2011 at 1:19 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Tue, Oct 4, 2011 at 10:06 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
>>>> This patch improves address combine for x32 by forcing the memory memory
>>>> operand of PLUS operation into register. ?Tested on Linux/x86-64 with
>>>> -mx32. ?OK for trunk?
>>>
>>> Does the patch fix
>>>
>>> FAIL: gcc.target/i386/pr45670.c scan-assembler-not lea[lq]
>>>
>>> on x32 ?
>>
>> It does.
>>
>> Following patch is the same, but takes into account that non-matching
>> memory can only be in src2, so it avoids a bunch of unnecessary
>> checks. Can you please check the effects of the patch with some
>> codesize benchmark?
>
> OTOH, x86_64 and i686 targets can also benefit from this change. If
> combine can't create more complex address (covered by lea), then it
> will simply propagate memory operand back into the add insn. It looks
> to me that we can't loose here, so:
>
> ?/* Improve address combine. ?*/
> ?if (code == PLUS && MEM_P (src2))
> ? ?src2 = force_reg (mode, src2);
>
> Any opinions?
>
It doesn't work with 64bit libstdc++:
/export/gnu/import/git/gcc/libstdc++-v3/src/strstream.cc: In member
function ‘void std::strstream::_ZTv0_n24_NSt9strstreamD1Ev()’:
/export/gnu/import/git/gcc/libstdc++-v3/src/strstream.cc:418:1: error:
insn does not satisfy its constraints:
(insn 3 2 4 (set (reg:DI 59)
(mem:DI (plus:DI (reg:DI 39 r10)
(const_int -24 [0xffffffffffffffe8])) [0 S8 A8])) 62
{*movdi_internal_rex64}
(nil))
/export/gnu/import/git/gcc/libstdc++-v3/src/strstream.cc:418:1:
internal compiler error: in final_scan_insn, at final.c:2648
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
make[7]: *** [strstream.lo] Error 1
make[7]: *** Waiting for unfinished jobs....
--
H.J.