> Simple question, but I'm not entirely clear from reading the documentation
>
> If I have a gcc configured for i686-* target system and I use that compiler to
> build a package without any -m submodel options , is the generated code
> 1) only suitable for i686 and better, or
> 2) tuned for i686 and better but still OK for i386
>From gcc manual:
While picking a specific cpu-type will schedule things appropriately
for that particular chip, the compiler will not generate any code that
does not run on the i386 without the -march=cpu-type option being
used.
It means even if you make -march=pentium-4 and run this code on 386 it
will run (maybe you'll have problems with SSE (but i think gcc inserts
code to bypass sse if you do not have it)).
> What about 32bit code generated with x86_64 targeted gcc (with -m32)?
>From the same gcc manual:
These -m switches are supported in addition to the above on AMD x86-64
processors in 64-bit environments.
-m32
-m64
Generate code for a 32-bit or 64-bit environment. The 32-bit
environment sets int, long and pointer to 32 bits and generates code
that runs on any i386 system. The 64-bit environment sets int to 32
bits and long and pointer to 64 bits and generates code for AMD's
x86-64 architecture.
Arturas Moskvinas
P.S.: for more specific i386 optimization and options read:
http://gcc.gnu.org/onlinedocs/gcc-3.4.3/gcc/i386-and-x86_002d64-Options.html
