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Re: paradoxical subreg problem [ patch attached ]
- From: Richard Earnshaw <rearnsha at arm dot com>
- To: law at redhat dot com
- Cc: Jim Wilson <wilson at cygnus dot com>, gcc at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org, Richard dot Earnshaw at arm dot com
- Date: Tue, 29 Jan 2002 17:13:09 +0000
- Subject: Re: paradoxical subreg problem [ patch attached ]
- Organization: ARM Ltd.
- Reply-to: Richard dot Earnshaw at arm dot com
> 3. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is defined.
And doesn't return NIL for the mode of op0. The ARM port can do this for
HImode, since there are variants of the ARM (older ones) that don't extend
half-word memory fetches.
> In that
> case we know those bits are zeros or ones; however we do not know if
> they are the same as the upper bits of op1. It seems to me we should
> not make the simplification in this case.
R.