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Re: AIX regression due to DFA scheduler merge
- From: law at redhat dot com
- To: David Edelsohn <dje at watson dot ibm dot com>
- Cc: "Vladimir N. Makarov" <vmakarov at redhat dot com>, gcc-patches at gcc dot gnu dot org, Mark Mitchell <mark at codesourcery dot com>
- Date: Mon, 03 Jun 2002 09:00:46 -0600
- Subject: Re: AIX regression due to DFA scheduler merge
- Reply-to: law at redhat dot com
In message <200206030220.WAA28130@makai.watson.ibm.com>, David Edelsohn
writes:
> Yes, I was looking at forward dependencies as well. Without the
> libcall patch, the relevant dependencies look like the following. insn
> 2954 is the troublesome instruction.
[ ... ]
Look at this code in compute_forward_dependencies:
for (link = LOG_LINKS (insn); link; link = XEXP (link, 1))
{
rtx x = group_leader (XEXP (link, 0));
rtx new_link;
if (x != XEXP (link, 0))
continue;
INSN is the current insn and we're going to take its backwards dataflow
dependencies and turn them into forward dataflow dependencies. So let's
assume INSN has a dependency on something in a libcall block. We call
group_leader and get the tail of the libcall block, then we "continue"
and thus effectively drop the dependency.
Jeff