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Date: Sun, 18 Jun 2017 15:14:51 +0300 (MSK)
From: Alexander Monakov <amonakov@...ras.ru>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] fix arm run-time abi string functions
Sorry for a bit of extreme nit-picking, but
On Tue, 21 Feb 2017, Szabolcs Nagy wrote:
> +__aeabi_memmove8:
> +__aeabi_memmove4:
> +__aeabi_memmove:
> + cmp r0, r1
> + bls 2f
> + cmp r2, #0
> + bxeq lr
> + add r0, r0, r2
> + add r2, r1, r2
> +1: ldrb r3, [r2, #-1]!
> + cmp r1, r2
> + strb r3, [r0, #-1]!
> + bne 1b
> + bx lr
> +__aeabi_memcpy8:
> +__aeabi_memcpy4:
> +__aeabi_memcpy:
> +2: cmp r2, #0
> + bxeq lr
> + sub r0, r0, #1
> + add r2, r1, r2
> +1: ldrb r3, [r1], #1
> + cmp r1, r2
> + strb r3, [r0, #1]!
> + bne 1b
> + bx lr
here it's possible to hoist and deduplicate 'cmp r2, #0; bxeq lr' by placing it
prior to the direction check.
> +__aeabi_memclr8:
> +__aeabi_memclr4:
> +__aeabi_memclr:
> + mov r2, #0
> +__aeabi_memset8:
> +__aeabi_memset4:
> +__aeabi_memset:
> + cmp r1, #0
> + bxeq lr
> + and r2, r2, #255
here I don't see why the 'and' is useful, I don't think the following strb
needs high bits cleared?
> + add r1, r0, r1
> +1: strb r2, [r0], #1
> + cmp r1, r0
> + bne 1b
> + bx lr
Alexander
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