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Re: 100x perfomance regression between gcc 3.4.5 and gcc 4.X


On 3/12/06, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
>
> It is valid.  We should understand why this behavior has changed so drastically.
>

I've attached assembler output from different compiler versions:

3.4.5-athlon-xp: gcc-3.4.5 -O3 -march=athlon-xp
3.4.5-pentium4: gcc-3.4.5 -O3 -march=pentium4
4.1.0-athlon-xp: gcc-4.1.0 -O3 -march=athlon-xp

As you can see, gcc-3.4.5 generates fastest code for
"-march=athlon-xp". This code should also run faster on any pentium
machine.

gcc-4.1.0 generates "same" slow code for "pentium" and "athlon" arch.

--
Nickolay

Attachment: test_cmd-3.4.5-athlon-xp.s
Description: Binary data

Attachment: test_cmd-3.4.5-pentium4.s
Description: Binary data

Attachment: test_cmd-4.1.0-athlon-xp.s
Description: Binary data


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