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Re: .def files for insn and reg notes
- From: Graham Stott <graham dot stott at btinternet dot com>
- To: Eric Botcazou <ebotcazou at libertysurf dot fr>
- Cc: Zack Weinberg <zack at codesourcery dot com>, gcc-patches at gcc dot gnu dot org
- Date: Mon, 20 Sep 2004 10:32:10 +0100
- Subject: Re: .def files for insn and reg notes
- References: <87d61onkqk.fsf@codesourcery.com> <200409201015.11171.ebotcazou@libertysurf.fr>
All,
Eric Botcazou wrote:
There appears to have been no good reason why the reg_note enumeration
began at 1.
GCC code is somewhat lax in how it uses the mode field within EXPR_LIST
and INSN_LIST.
reg notes definately can't start a zero as it will conflict with the use of
VOIDmode for true data dependence! ANTI and OUTPUT dependence use proper
reg notes.
Besides REG_NOTES themselves we also store 0, VOIDmode, SImode, and DImode, and perhaps
a few others I've yet to notice.
Graham
ps. I've been working on a patch to add a proper REG_DEP_TRUE note to replace the
use of VOIDmode for true data dependence. It's proving tricky to find all the
relevant 0 and VOIDmode uses in the middle and backends.