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From: "Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@gmail.com>
To: grub-devel@gnu.org
Subject: Re: [RFT] Use pair of shifts instead of and in ARM code
Date: Wed, 13 Nov 2013 15:56:23 +0100	[thread overview]
Message-ID: <52839317.2050204@gmail.com> (raw)
In-Reply-To: <20131113141608.GT1557@rocoto.smurfnet.nu>

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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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      reply	other threads:[~2013-11-13 14:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
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 [this message]

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