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Re: Question on insn scheduling and SP
- From: Richard Henderson <rth at redhat dot com>
- To: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>
- Cc: dalej at apple dot com, gcc at gcc dot gnu dot org
- Date: Tue, 22 Oct 2002 09:53:41 -0700
- Subject: Re: Question on insn scheduling and SP
- References: <10210221036.AA22890@vlsi1.ultra.nyu.edu>
On Tue, Oct 22, 2002 at 06:36:51AM -0400, Richard Kenner wrote:
> I did, but some things aren't clear, at least in the comments that
> were added. What was added is a (clobber (mem)). It's true that the
> address was stack_pointer_rtx, but nothing in the comments suggest
> that the form of the address is relevant. Instead, they imply that
> it was the mere addition of the CLOBBER that was sufficient.
>
> Am I missing something?
*Two* clobbers are necessary.
(clobber (mem:BLK (scratch)))
(clobber (mem:BLK stack_pointer_rtx))
The first has the magic form that conflicts with all memory,
the second contains a reference to the stack pointer. Thus
the stack pointer adjustment depends on the second clobber,
the second clobber depends on the first clobber, and the
first clobber depends on all memory references.
r~