From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Lehmann To: gcc@gcc.gnu.org Subject: Re: type based aliasing again Date: Thu, 30 Sep 1999 18:02:00 -0000 Message-ID: <19990915020836.M3983@cerebro.laendle> References: <199909141102.NAA18232@quatramaran.ens.fr> X-SW-Source: 1999-09n/msg00570.html Message-ID: <19990930180200.Kky-VdyjLlKSSe-RdvE3xNzLrHiF4QHKZnZ-EjDvqnE@z> On Tue, Sep 14, 1999 at 01:02:51PM +0200, Marc Espie wrote: > I'm not too fond of pgcc idea of -O4 -> -O9 turning on `unsafe' optimizations. Thats not pgcc's idea. "Unsafe" optimizations are off at all optimization levels. The distinction between -O2 and higher is that its easy to test ("experimental compiler"), since bugs with -O2 are most probably gcc bugs. > Therefore, I don't believe moving -fstrict-aliasing to -O3 or -O4 is a > good idea. It's an issue of whether we consider this optimization as > `safe' or `unsafe'. No, it's an issue wether we define C as ISO C or (some variant). But putting it at an higher optimization level makes it more special than it is. Maybe the _real_ issue is what will break at all? The asm checks "broke" much more programs (glibc, linux-kernel, other kernels, drivers) then the aliasing stuff. At least I believe this until somebody gives me more than the two examples (linux and openbsd) I have heard of yet. -- -----==- | ----==-- _ | ---==---(_)__ __ ____ __ Marc Lehmann +-- --==---/ / _ \/ // /\ \/ / pcg@goof.com |e| -=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+ The choice of a GNU generation | |