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Re: [PATCH] Enhance reload_cse_move2add


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


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