From: Antriksh Pany <antriksh.pany@gmail.com>
Date: Tue, 05 Apr 2011 23:55:24 GMT
Subject: Re: [PATCH 4/5] tree-walk: unroll get_mode since loop boundaries are well-known
Message-ID: <BANLkTin9P-OdTQhPTwcvgvpDoBg7E+va5Q@mail.gmail.com>
In-Reply-To: <BANLkTi==M=N+Z3qcsYk+tHap8A1Y41QfLw@mail.gmail.com>

On Mon, Apr 4, 2011 at 10:33 PM, Dan McGee <dpmcgee@gmail.com> wrote:
> ....
> Totally agree; I should have tried to do it this way in the first
> place. However, compiling the fixed-length 0 to 5 loop does not
> produce fully-unrolled assembly for me with CFLAGS="-march=native
> -mtune=native -O2 -pipe -g" on x86_64. I see two copies of the loop
> only, and even worse is the (lack of) performance (each is the mode of
> 3 runs). Compilers are stupid apparently.
> ....

Can you try -O3? Or an explicit '-funroll-loops'?
gcc I think does not do aggressive speed optimizations at the cost of
space when at O2.

Cheers
Antriksh