fold_const.c/tree_swap_operands_p change from Oct 11 breaks m68k

[Roger Sayle]

On Sat, 25 Oct 2003, Richard Henderson wrote:
> On Sat, Oct 25, 2003 at 01:35:54PM -0600, Roger Sayle wrote:
> > I'm not really a back-end expert.  Here is the relevant define_insn
> > from line 196 of m68k.md.  Can anyone see an obvious mistake?
>
> Let me introduce you to NOTICE_UPDATE_CC.

Many thanks.


> Incidentally, it's not your bug.

Indeed, but my responsibility to atleast analyse the true source of
the latent bug that I unwittingly exposed.


> Indeed, the bug appears to be that
>
>       case ASHIFT: case ASHIFTRT: case LSHIFTRT:
>       case ROTATE: case ROTATERT:
>
> are not special-cased at all.

These have been "#if 0"'d inside m68k.c's notice_update_cc since the
start of current CVS.  Is there a way of finding out why the special
casing of these RTX codes was originally disabled?

Many thanks for your help.  I guess the m68k maintainers can take it
from here, as I'd be unable to test the impact of tweaking m68k.c's
notice_update_cc.

Roger
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