m68k arch/cpu directives

[Vincent Rivière]

Hello.

I'm a bit puzzled about the various m68k arch/cpu directives in gas.

1) First, I don't really understand the difference between architecture 
and cpu. It seems that architecture is a general family, while a cpu is 
a precise model.

2) At the top of an assembly file, it seems that both .arch and .cpu are 
required to switch to a different CPU than the command line one. Is this 
really what is expected? I would have imagined that .cpu was enough, and 
that the architecture would have been automatically deduced...

3) Is it allowed to switch to different cpu instruction set at the 
middle of an assembly file? This is useful for example to autodetect 
special CPU features. It seems that doing so is only supported by the 
.chip directive, which is not documented, and present only for ancient 
MRI compatibility...

Any hint will be appreciated.

-- 
Vincent Rivière