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* [RFT] Use pair of shifts instead of and in ARM code
@ 2013-11-13  0:00 Vladimir 'φ-coder/phcoder' Serbinenko
  2013-11-13 14:16 ` Leif Lindholm
  0 siblings, 1 reply; 3+ messages in thread
From: Vladimir 'φ-coder/phcoder' Serbinenko @ 2013-11-13  0:00 UTC (permalink / raw)
  To: The development of GRUB 2

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1ff and 3fff can't be easily loaded on ARM. This patch replaces load+and
with pair of shift to keep only wanted bits.

diff --git a/grub-core/kern/arm/cache_armv7.S
b/grub-core/kern/arm/cache_armv7.S
index 0c16b10..454bad3 100644
--- a/grub-core/kern/arm/cache_armv7.S
+++ b/grub-core/kern/arm/cache_armv7.S
@@ -58,11 +64,17 @@ clean_invalidate_dcache:
        @ read current cache information
        mrc     p15, 1, r8, c0, c0, 0   @ Read CCSIDR
        lsr     r3, r8, #13             @ Number of sets -1
-       ldr     r9, =0x3fff
-       and     r3, r3, r9
+
+       @ Keep only 14 bits of r3
+       lsl     r3, r3, #18
+       lsr     r3, r3, #18
+
        lsr     r4, r8, #3              @ Number of ways -1
-       ldr     r9, =0x1ff
-       and     r4, r4, r9
+
+       @ Keep only 9  bits of r4
+       lsl     r4, r4, #23
+       lsr     r4, r4, #23
+
        and     r7, r8, #7              @ log2(line size in words) - 2
        add     r7, r7, #2              @  adjust
        mov     r8, #1


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^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [RFT] Use pair of shifts instead of and in ARM code
  2013-11-13  0:00 [RFT] Use pair of shifts instead of and in ARM code Vladimir 'φ-coder/phcoder' Serbinenko
@ 2013-11-13 14:16 ` Leif Lindholm
  2013-11-13 14:56   ` Vladimir 'φ-coder/phcoder' Serbinenko
  0 siblings, 1 reply; 3+ messages in thread
From: Leif Lindholm @ 2013-11-13 14:16 UTC (permalink / raw)
  To: The development of GNU GRUB

On Wed, Nov 13, 2013 at 01:00:17AM +0100, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> 1ff and 3fff can't be easily loaded on ARM. This patch replaces load+and
> with pair of shift to keep only wanted bits.
 
Actually, on ARMv7 we could just use MOVW instead:

> diff --git a/grub-core/kern/arm/cache_armv7.S
> b/grub-core/kern/arm/cache_armv7.S
> index 0c16b10..454bad3 100644
> --- a/grub-core/kern/arm/cache_armv7.S
> +++ b/grub-core/kern/arm/cache_armv7.S
> @@ -58,11 +64,17 @@ clean_invalidate_dcache:
>         @ read current cache information
>         mrc     p15, 1, r8, c0, c0, 0   @ Read CCSIDR
>         lsr     r3, r8, #13             @ Number of sets -1
> -       ldr     r9, =0x3fff
	movw	r9, #0x3fff
> -       and     r3, r3, r9
> +
> +       @ Keep only 14 bits of r3
> +       lsl     r3, r3, #18
> +       lsr     r3, r3, #18
> +
>         lsr     r4, r8, #3              @ Number of ways -1
> -       ldr     r9, =0x1ff
	movw	r9, #0x1ff
> -       and     r4, r4, r9
> +
> +       @ Keep only 9  bits of r4
> +       lsl     r4, r4, #23
> +       lsr     r4, r4, #23
> +
>         and     r7, r8, #7              @ log2(line size in words) - 2
>         add     r7, r7, #2              @  adjust
>         mov     r8, #1
> 

/
    Leif


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [RFT] Use pair of shifts instead of and in ARM code
  2013-11-13 14:16 ` Leif Lindholm
@ 2013-11-13 14:56   ` Vladimir 'φ-coder/phcoder' Serbinenko
  0 siblings, 0 replies; 3+ messages in thread
From: Vladimir 'φ-coder/phcoder' Serbinenko @ 2013-11-13 14:56 UTC (permalink / raw)
  To: grub-devel

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On 13.11.2013 15:16, Leif Lindholm wrote:
> On Wed, Nov 13, 2013 at 01:00:17AM +0100, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>> 1ff and 3fff can't be easily loaded on ARM. This patch replaces load+and
>> with pair of shift to keep only wanted bits.
>  
> Actually, on ARMv7 we could just use MOVW instead:
> 
Another goal of this patch was to make this code compilable with clang
(just a silly experiment) which lacks many useful ARM facilities
including architecture switching in file (other than thumb<->arm). This
was one of culprits. The other one was that I had to manually assemble
barrier instructions.
>> diff --git a/grub-core/kern/arm/cache_armv7.S
>> b/grub-core/kern/arm/cache_armv7.S
>> index 0c16b10..454bad3 100644
>> --- a/grub-core/kern/arm/cache_armv7.S
>> +++ b/grub-core/kern/arm/cache_armv7.S
>> @@ -58,11 +64,17 @@ clean_invalidate_dcache:
>>         @ read current cache information
>>         mrc     p15, 1, r8, c0, c0, 0   @ Read CCSIDR
>>         lsr     r3, r8, #13             @ Number of sets -1
>> -       ldr     r9, =0x3fff
> 	movw	r9, #0x3fff
>> -       and     r3, r3, r9
>> +
>> +       @ Keep only 14 bits of r3
>> +       lsl     r3, r3, #18
>> +       lsr     r3, r3, #18
>> +
>>         lsr     r4, r8, #3              @ Number of ways -1
>> -       ldr     r9, =0x1ff
> 	movw	r9, #0x1ff
>> -       and     r4, r4, r9
>> +
>> +       @ Keep only 9  bits of r4
>> +       lsl     r4, r4, #23
>> +       lsr     r4, r4, #23
>> +
>>         and     r7, r8, #7              @ log2(line size in words) - 2
>>         add     r7, r7, #2              @  adjust
>>         mov     r8, #1
>>
> 
> /
>     Leif
> 
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://lists.gnu.org/mailman/listinfo/grub-devel
> 



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2013-11-13  0:00 [RFT] Use pair of shifts instead of and in ARM code Vladimir 'φ-coder/phcoder' Serbinenko
2013-11-13 14:16 ` Leif Lindholm
2013-11-13 14:56   ` Vladimir 'φ-coder/phcoder' Serbinenko

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