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Re: cant_combine_insn_p hard_reg->reg moves

From: Jan Hubicka <jh at suse dot cz>
To: Richard Henderson <rth at redhat dot com>, David Edelsohn <dje at watson dot ibm dot com>, Bernd Schmidt <bernds at redhat dot co dot uk>, Jan Hubicka <jh at suse dot cz>, gcc at gcc dot gnu dot org, degger at fhm dot edu
Date: Wed, 26 Dec 2001 13:10:56 +0100
Subject: Re: cant_combine_insn_p hard_reg->reg moves
References: <20011218125633.C322E6E18@Nicole.fhm.edu> <200112260202.VAA29248@makai.watson.ibm.com> <20011225231251.A6306@redhat.com>

> On Tue, Dec 25, 2001 at 09:02:42PM -0500, David Edelsohn wrote:
> > Could cant_combine_insn_p test for hard regs with either REG_EQUIV
> > involving computations of ARG_POINTER_REGNUM or FUNCTION_VALUE_REGNO_P?
> 
> No.  IIRC, this was introduced specifically to cure problems with
> argument registers.  x86 regparm is the biggest offender here.
> 
> The only solutions are a new register allocator, or post-reload
> cleanup optimizations such as -fcprop-registers.  Anything else
> risks keeping a hard register live too long.

BTW what is the situation of cprop-registers? Will it get enabled for 3.1
once the bugs are tracked down. Are the problems serisous.

Honza
> 
> 
> r~

Follow-Ups:
- Re: cant_combine_insn_p hard_reg->reg moves
  - From: Richard Henderson

References:
- Analysis try (was: Re: rs6000: Trivial code generation stupidity)
  - From: degger
- cant_combine_insn_p hard_reg->reg moves
  - From: David Edelsohn
- Re: cant_combine_insn_p hard_reg->reg moves
  - From: Richard Henderson

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