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[PATCH] ARM/Thumb Avoid use of LR in Thumb code

From: Richard Earnshaw <rearnsha at arm dot com>
To: gcc-patches at gcc dot gnu dot org
Cc: Richard dot Earnshaw at arm dot com
Date: Fri, 31 Oct 2003 21:47:58 +0000
Subject: [PATCH] ARM/Thumb Avoid use of LR in Thumb code
Organization: ARM Ltd.
Reply-to: Richard dot Earnshaw at arm dot com

This is really a work-around for a bug rather than a solution in itself.

In thumb code a branch of a very long distance has to be done using a BL 
instruction, but this has the nasty side-effect of clobbering the link 
register.  Since the branch instruction doesn't describe this side effect 
the compile can occasionally allocate r14 for use across such a branch 
(with disastrous consequences).  This patch is the brute-force solution to 
the problem:  Don't use R14 at all in Thumb code.

2003-10-31  Richard Earnshaw  <rearnsha@arm.com>

	PR target/7513
	* arm.h (CONDITIONAL_REGISTER_USAGE): Disable use of LR in Thumb
	code.

Attachment: thumb-lr.patch
Description: thumb-lr.patch

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