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Re: gfortran: the good news and the good news

From: Tim Prince <n8tm at aol dot com>
To: Hans Horn <hannes at 2horns dot com>
Cc: fortran at gcc dot gnu dot org
Date: Thu, 05 Nov 2009 12:10:56 -0800
Subject: Re: gfortran: the good news and the good news
References: <hcv2vo$djn$1@ger.gmane.org>
Reply-to: tprince at computer dot org

Hans Horn wrote:

These are the optimization flags I used for fortran (basically carried over from g77):

-O3
-fno-strict-aliasing
-Winline
-fexpensive-optimizations
-finline-functions
-finline-limit=100000
-fstrength-reduce
-fgcse
-fgcse-lm
-fgcse-sm
-funroll-loops
-fforce-addr
-fomit-frame-pointer
-malign-double

Are there any I should NOT be using?
Did I omit any important one?

Depending on your CPU model and application, -funroll-loops may have become excessively aggressive. For Core i7, I limit unrolling to 4, as well as avoiding flags whose effect I'm not sure of. -fno-strict-aliasing tells the compiler not to assume that your code is standard compliant as to overlapping function arguments.

References:
- gfortran: the good news and the good news
  - From: Hans Horn

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