Projects for beginners

[Michael Matz]

Hi,

On Wed, 31 Jan 2001, Hans-Peter Nilsson wrote:
> > This is where I admit that I have never been able to understand any of
> > the multiple different ways of handling condition codes in GCC.
> > There's the pure cc0 approach, the every-insn's-a-parallel approach
> > taken by the x86 back end, the cbranch stuff which I totally agree
> > needs more documentation, and the pure flag registers approach which
> > apparently only works on machines where that is the hardware.
> 
> You could change cc0-ports to the flags-register approach (as
> was done with x86), but your .md would be cluttered with
> clobbers for insns that affect cc0 on your machine.  This is
> somewhat seen in the x86 back-end, though "luckily" it seems
> it's mostly arithmetic insns that set its cc0 (now expressed as
> (reg:CC 17)).

A very unfortunate side-effect of this PARALLEL wrapping of insns is, that
GCSE doesn't look into stuff in parallel's at all.


Ciao,
Michael.