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Re: cant_combine_insn_p hard_reg->reg moves
- From: Richard Henderson <rth at redhat dot com>
- To: David Edelsohn <dje at watson dot ibm dot com>
- Cc: 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: Tue, 25 Dec 2001 23:12:51 -0800
- Subject: Re: cant_combine_insn_p hard_reg->reg moves
- References: <20011218125633.C322E6E18@Nicole.fhm.edu> <200112260202.VAA29248@makai.watson.ibm.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.
r~