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Re: Optimizing GCC
- From: "Gareth Pearce" <tilps at hotmail dot com>
- To: <cheapisp at sensewave dot com>,<pop at gauvain dot u-strasbg dot fr>,"Robert Dewar" <dewar at gnat dot com>
- Cc: <gcc at gcc dot gnu dot org>
- Date: Wed, 5 Mar 2003 07:41:58 +1100
- Subject: Re: Optimizing GCC
- References: <20030304202950.EFC1DF2E07@nile.gnat.com>
----- Original Message -----
From: "Robert Dewar" <dewar at gnat dot com>
To: <cheapisp at sensewave dot com>; <pop at gauvain dot u-strasbg dot fr>
Cc: <gcc at gcc dot gnu dot org>
Sent: Wednesday, March 05, 2003 7:29 AM
Subject: Re: Optimizing GCC
> > In part this is false: it depends only on whether the optimization flag
> > you add to build gcc is safe or not.
> >
> > If the optimization doesn't introduce junks, in other words if the
> > optimization is valid, then the optimized GCC is semantically equivalent
> > to the non-optimized GCC. Thus you'll get the same output for the same
> > input on both versions of GCC.
> >
> > Otherwise it is an error in the optimization you used to optimize GCC.
>
> Or there is a bug in the GCC code which only shows up in the optimized
context ...
>
such as relying on undefined behviour.
Gareth