Re: [PATCH] ARM: Fix strcmp() for Thumb-1

[nick clifton <nickc at redhat dot com>]

Hi Sebastian,

> The GCC multilib for ARMv4T is broken with the current strcmp()
> implementation.  GCC will pass no architecture flag to AS in case it
> builds a multilib for -mthumb with no further architecture options.  The
> default architecture is ARMv4T in GCC.  The usage of ".syntax unified"
> instructs AS to produce output for the ARMv6T2 architecture.  Thus we
> have (readelf -A):
>
> File: ./arm-rtems4.11/thumb/newlib/libc/machine/arm/lib_a-strcmp.o
> Attribute Section: aeabi
> File Attributes
>    Tag_CPU_arch: v6T2
>    Tag_THUMB_ISA_use: Thumb-2

This appears to be correct.  It seems however that there is a similar 
problem for the memchr function as well:

% readelf -A arm-rtems4.11/thumb/newlib/libc/machine/arm/lib_a-memchr.o
Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "7-A"
  Tag_CPU_arch: v7
  Tag_CPU_arch_profile: Application
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-2


> newlib/ChangeLog
> 2013-05-26  Sebastian Huber <sebastian.huber@embedded-brains.de>
>
> 	libc/machine/arm/strcmp.S: Fix Thumb-1 version.

The patch works, although given the mail from Chenq I think that adding 
a comment would be helpful.  As in:

> +/* Do not use unified syntax for thumb1 multilibs - it results
> +   in the assembler marking the object as requiring a thumb2 ISA.  */
> +#if !(defined (__thumb__) && !defined (__thumb2__))
>   .syntax         unified
> +#endif


Cheers
  Nick