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Re: Your change of September 11, 1998
- To: Richard Henderson <rth at redhat dot com>
- Subject: Re: Your change of September 11, 1998
- From: Bernd Schmidt <bernds at redhat dot com>
- Date: Tue, 16 Jan 2001 13:33:12 +0000 (GMT)
- Cc: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>, <gcc at gcc dot gnu dot org>
On Tue, 16 Jan 2001, Richard Henderson wrote:
> On Tue, Jan 16, 2001 at 07:26:19AM -0500, Richard Kenner wrote:
> > Useful, yes. Essential? Maybe yes, maybe no, depending on reorg.
> >
> > And flow.
>
> No, I understand how flow works and it doesn't care.
>
> We scan backwards from the end of a block. If we see a register used,
> and it had been dead, it becomes live. If a register is either set or
> clobbered -- we do not care which -- it becomes dead.
But other passes care about the clobber/set distinction; or more precisely
about seeing side effects explicitly in rtl. For example, build_insn_chain
in global.c (and other code in that file) relies on it.
Bernd