[PATCH] Enhance reload_cse_move2add

[Jie Zhang]

On 07/10/2010 08:06 AM, Bernd Schmidt wrote:
> On 07/09/2010 06:58 PM, Jie Zhang wrote:
>> I just tested idctrn01 on my pentium-m laptop. My patch does not change
>> the performance of idctrn01 on i386. I did some investigation. It's
>> because i386 can directly use "symbol_ref + offset" as the address in
>> load instructions. So there is no optimization opportunity that my patch
>> can utilize. That's the difference between RISC and CISC.
> [...]
>> I collected the code size data from SPEC2000 on AMD64. My patch does not
>> change code size for any test whether -O2 or -O3, except
>>
>> Code Size
>> =========
>> Test  -O2        Before    After    Change
>> ----------------------------------------------
>> 172.mgrid        14962    14976        14
>>
>> Code Size
>> Test  -O3        Before    After    Change
>> ----------------------------------------------
>> 171.swim        19231    19247        16
>
> So what kinds of changes are there that would explain a 1.48% drop on
> 179.art?  If you can verify that the code is in fact identical, and the
> performance change is noise, the patch is ok.
>
I checked the disassemblies of all SPEC2000 tests. My patch generates 
different code only for 171.swim, 172.mgrid and 173.applu whether with 
-O2 or -O3. It seems the noise can be as large as 1.48%.


-- 
Jie Zhang
CodeSourcery