[PATCH 2/3] ARM: entry: Remove unnecessary masking when decoding Thumb-2 instructions

[Nicolas Pitre]

On Tue, 16 Aug 2011, Dave Martin wrote:

> When testing whether a Thumb-2 instruction is 32 bits long or not,
> the masking done in order to test bits 11-15 of the first
> instruction halfword won't affect the result of the comparison, so
> remove it.
> 
> Signed-off-by: Dave Martin <dave.martin at linaro.org>

Acked-by: Nicolas Pitre <nicolas.pitre at linaro.org>


> ---
>  arch/arm/kernel/entry-armv.S |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
> index a87cbf8..b7236d4 100644
> --- a/arch/arm/kernel/entry-armv.S
> +++ b/arch/arm/kernel/entry-armv.S
> @@ -262,8 +262,7 @@ __und_svc:
>  	ldr	r0, [r4, #-4]
>  #else
>  	ldrh	r0, [r4, #-2]			@ Thumb instruction at LR - 2
> -	and	r9, r0, #0xf800
> -	cmp	r9, #0xe800			@ 32-bit instruction if xx >= 0
> +	cmp	r0, #0xe800			@ 32-bit instruction if xx >= 0
>  	ldrhhs	r9, [r4]			@ bottom 16 bits
>  	orrhs	r0, r9, r0, lsl #16
>  #endif
> @@ -445,8 +444,7 @@ __und_usr:
>   ARM(	ldrht	r5, [r4], #2	)
>   THUMB(	ldrht	r5, [r4]	)
>   THUMB(	add	r4, r4, #2	)
> -	and	r0, r5, #0xf800			@ mask bits 111x x... .... ....
> -	cmp	r0, #0xe800			@ 32bit instruction if xx != 0
> +	cmp	r5, #0xe800			@ 32bit instruction if xx != 0
>  	blo	__und_usr_unknown
>  3:	ldrht	r0, [r4]
>  	add	r2, r2, #2			@ r2 is PC + 2, make it PC + 4
> -- 
> 1.7.4.1
>