Bug#288721: gcc-3.3: gcc produces wrong code with -O1 or -O2 for very simple C program (included)

[Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>]

Manuel Bilderbeek wrote:
> Package: gcc-3.3
> Version: 1:3.3.5-5
> Severity: important
> 
> 
> When compiling the included program with the mentioned versions of gcc,
> wrong code is generated when using -O1 or -O2. See the comments in the
> program, which I saved as test.c:
> 
> ---------------------- CUT HERE -----------------------
> 
> /* This small program shows a bug in the optimizer of gcc.
>  * It occurs at least in these versions: 
>  * - gcc (GCC) 3.3.4 (Debian 1:3.3.4-13)
>  * - gcc (GCC) 3.3.5 (Debian 1:3.3.5-5)
>  * It does not occur when the body of f is put directly in main.
>  * It does not occur when the "if" is split into two "if"s.
>  * It does not occur when -O0 or -O3 (or higher) is used. 
>  * It only occurs if -O1 or -O2 are used.

I couldn't reproduce it on mips with gcc 3.3.5-5, so it seems also to
be arch-specific. On i386 I see the problem as well.


Thiemo