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Re: [dataflow] partial register handling
- From: Rask Ingemann Lambertsen <rask at sygehus dot dk>
- To: Roman Zippel <zippel at linux-m68k dot org>
- Cc: gcc at gcc dot gnu dot org, zadeck at naturalbridge dot com, dberlin at dberlin dot org
- Date: Fri, 11 May 2007 14:33:41 +0200
- Subject: Re: [dataflow] partial register handling
- References: <Pine.LNX.4.64.0705101940450.2958@scrub.home>
On Thu, May 10, 2007 at 07:43:19PM +0200, Roman Zippel wrote:
> Looking closer at this I don't think strict_low_part should be required
> as splitting DI registers produces a lot of (subreg:SI (reg:DI)) even as
> destination, but they only set strictly part of the register. If I look
> through i386/m68k I don't see a single (strict_low_part (subreg:SI)).
That's because with UNITS_PER_WORD == 4, (subreg:SI (reg:DI) n) is
implicitly a strict low part for n == 0 or n == 4. When used as destination,
such a subreg is defined as not clobbering anything outside the subreg.
--
Rask Ingemann Lambertsen