Re: Use-and-clobber insns and REG_DEAD notes (fwd)

[Richard Henderson <rth at redhat dot com>]

On Wed, Jul 16, 2003 at 03:20:06AM +0200, Michael Matz wrote:
> > I think that the death note SHOULD exist in the clobber case.
> 
> In this particular case, right?

Um?

> flow added a REG_UNUSED for the clobber, which I think is wrong.

Yes, in this case, because as I recall the register *was* used
in the insn.

> Adding a REG_DEAD for a clobber doesn't make sense IMO.

Not because of the clobber per-se, but because that's
where the register dies.

The problem is sure to be bad interaction with other code
that correctly tries to prevent a REG_DEAD note for a register
that is both used and SET (not clobbered) in the same insn.


r~