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Re: Switching to and from ARM/Thumb

From: Daniel Jacobowitz <drow at false dot org>
To: Shaun Jackman <sjackman at gmail dot com>
Cc: Paul Brook <paul at codesourcery dot com>, binutils at sources dot redhat dot com
Date: Mon, 17 Jan 2005 20:45:16 -0500
Subject: Re: Switching to and from ARM/Thumb
References: <7f45d9390501171142ffea371@mail.gmail.com> <200501172255.25997.paul@codesourcery.com> <7f45d939050117171859504aa2@mail.gmail.com>

On Mon, Jan 17, 2005 at 05:18:06PM -0800, Shaun Jackman wrote:
> Does gas insert zero bytes for alignment? and is this a reasonable nop
> instruction? gas compiles 'nop' to 46c0 nop (mov r8, r8).

I believe it will align with nops.

> > .code32
> > arm_to_thumb:
> > #ifdef __ARMv4T__
> >  add ip, pc, #1
> >  bx ip
> > #else
> >  sub pc, pc, #1
> > #endif
> > thumb_code:
> 
> If this is used in inline assembler, does gcc need to be informed of
> ip being trashed?

Definitely.  I admit I've never seen the arm-to-thumb sequence done
quite that way before... I knew loads interworked and mov didn't so I
would have assumed that sub didn't either.

-- 
Daniel Jacobowitz

Follow-Ups:
- Re: Switching to and from ARM/Thumb
  - From: Paul Brook

References:
- Switching to and from ARM/Thumb
  - From: Shaun Jackman
- Re: Switching to and from ARM/Thumb
  - From: Paul Brook
- Re: Switching to and from ARM/Thumb
  - From: Shaun Jackman

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