This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

[PATCH, ARM] Don't unnecessarily clobber the flags for ADD Rd, Rd, Rm

From: Richard Earnshaw <rearnsha at arm dot com>
To: gcc-patches at gcc dot gnu dot org
Date: Fri, 17 Aug 2012 09:52:35 +0100
Subject: [PATCH, ARM] Don't unnecessarily clobber the flags for ADD Rd, Rd, Rm

Thumb2 add instructions of the form

	add	Rd, Rm

Are already 16-bit instructions, so turning them into

	adds	Rd, Rm

is pointless.

This patch adds support for this in the compiler and ensures that the
conversion to ADDS is skipped in this case.

The additional variant in arm.md is possibly redundant, but does mean
that we correctly calculate the length of this case and may even
encourage the compiler to try and reuse the source operation.

Tested on arm-eabi and applied to trunk.

R.

Attachment: short-add.patch
Description: Text document

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]