On Wed, 12 Sep 2007, Tom Lane wrote:
> Jeremy Drake <pgsql@jdrake.com> writes:
> > I just saw that my buildfarm member (running ICC 9.0 on linux) failed
> > after the latest change to configure
>
> Argh! Can someone quote chapter and verse from the ICC manual about
> this? I was just following what Sergey said was the approved spelling
> of the switch ...
The docs are not particularly clear about these options, at least not in
9.0 (which is the version I have). I figured -ansi-alias- was what
-fno-strict-aliasing meant, that the gcc people decided to follow the ISO
C standard strictly unless you gave -fno-strict-aliasing, which could
result in additional optimization. This seems to match what the docs for
-ansi-alias, but with a different default.
The -fno-alias seems to go entirely the other way, saying you are not
going to be doing any aliasing, standard permitted or otherwise, so it can
optimize better accordingly.
Here are the docs for the two options.
======================================================================
ansi-alias, Qansi-alias
Enable use of ANSI aliasing rules in optimizations.
Syntax
Linux: -ansi-alias -ansi-alias-
Windows: /Qansi-alias /Qansi-alias-
Default
-ansi-alias- Disable use of ANSI aliasing rules in optimizations.
This option tells the compiler to assume that the program adheres to ISO C
Standard aliasability rules.
If your program adheres to these rules, then this option allows the
compiler to optimize more aggressively. If it doesn't adhere to these
rules, then it can cause the compiler to generate incorrect code.
======================================================================
falias
Specifies that aliasing should be assumed in the program.
Syntax
Linux: -falias -fno-alias
Windows: None
Default
-falias Aliasing is assumed in the program.
This option specifies that aliasing should be assumed in the program.
You must specify -fno-alias if you do not want aliasing to be assumed in
the program.
Alternate Options
Linux: None
Windows: /Oa
--
Remember: Silly is a state of Mind, Stupid is a way of Life. -- Dave Butler