The Tor Browser: security/nss/lib/freebl/arcfour-amd64-sun.s@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 / This Source Code Form is subject to the terms of the Mozilla Public

     2 / License, v. 2.0. If a copy of the MPL was not distributed with this

     3 / file, You can obtain one at http://mozilla.org/MPL/2.0/.

     5 / ** ARCFOUR implementation optimized for AMD64.

     6 / **

     7 / ** The throughput achieved by this code is about 320 MBytes/sec, on

     8 / ** a 1.8 GHz AMD Opteron (rev C0) processor.

    10 .text

    11 .align 16

    12 .globl ARCFOUR

    13 .type ARCFOUR,@function

    14 ARCFOUR:

    15 	pushq	%rbp

    16 	pushq	%rbx

    17 	movq	%rdi,		%rbp	/ key = ARG(key)

    18 	movq	%rsi,		%rbx	/ rbx = ARG(len)

    19 	movq	%rdx,		%rsi	/ in = ARG(in)

    20 	movq	%rcx,		%rdi	/ out = ARG(out)

    21 	movq	(%rbp),		%rcx	/ x = key->x

    22 	movq	8(%rbp),	%rdx	/ y = key->y

    23 	addq	$16,		%rbp	/ d = key->data

    24 	incq	%rcx			/ x++

    25 	andq	$255,		%rcx	/ x &= 0xff

    26 	leaq	-8(%rbx,%rsi),	%rbx	/ rbx = in+len-8

    27 	movq	%rbx,		%r9	/ tmp = in+len-8

    28 	movq	0(%rbp,%rcx,8),	%rax	/ tx = d[x]

    29 	cmpq	%rsi,		%rbx	/ cmp in with in+len-8

    30 	jl	.Lend			/ jump if (in+len-8 < in)

    32 .Lstart:

    33 	addq	$8,		%rsi		/ increment in

    34 	addq	$8,		%rdi		/ increment out

    36 	/ generate the next 8 bytes of the rc4 stream into %r8

    37 	movq	$8,		%r11		/ byte counter

    38 1:	addb	%al,		%dl		/ y += tx

    39 	movl	0(%rbp,%rdx,8),	%ebx		/ ty = d[y]

    40 	movl	%ebx,		0(%rbp,%rcx,8)	/ d[x] = ty

    41 	addb	%al,		%bl		/ val = ty + tx

    42 	movl	%eax,		0(%rbp,%rdx,8)	/ d[y] = tx

    43 	incb	%cl				/ x++		(NEXT ROUND)

    44 	movl	0(%rbp,%rcx,8),	%eax		/ tx = d[x]	(NEXT ROUND)

    45 	movb	0(%rbp,%rbx,8),	%r8b		/ val = d[val]

    46 	decb	%r11b

    47 	rorq	$8,		%r8		/ (ror does not change ZF)

    48 	jnz 	1b

    50 	/ xor 8 bytes

    51 	xorq	-8(%rsi),	%r8

    52 	cmpq	%r9,		%rsi		/ cmp in+len-8 with in

    53 	movq	%r8,		-8(%rdi)

    54 	jle	.Lstart				/ jump if (in <= in+len-8)

    56 .Lend:

    57 	addq	$8,		%r9		/ tmp = in+len

    59 	/ handle the last bytes, one by one

    60 1:	cmpq	%rsi,		%r9		/ cmp in with in+len

    61 	jle	.Lfinished			/ jump if (in+len <= in)

    62 	addb	%al,		%dl		/ y += tx

    63 	movl	0(%rbp,%rdx,8),	%ebx		/ ty = d[y]

    64 	movl	%ebx,		0(%rbp,%rcx,8)	/ d[x] = ty

    65 	addb	%al,		%bl		/ val = ty + tx

    66 	movl	%eax,		0(%rbp,%rdx,8)	/ d[y] = tx

    67 	incb	%cl				/ x++		(NEXT ROUND)

    68 	movl	0(%rbp,%rcx,8),	%eax		/ tx = d[x]	(NEXT ROUND)

    69 	movb	0(%rbp,%rbx,8),	%r8b		/ val = d[val]

    70 	xorb	(%rsi),		%r8b		/ xor 1 byte

    71 	movb	%r8b,		(%rdi)

    72 	incq	%rsi				/ in++

    73 	incq	%rdi				/ out++

    74 	jmp 1b

    76 .Lfinished:

    77 	decq	%rcx				/ x--

    78 	movb	%dl,		-8(%rbp)	/ key->y = y

    79 	movb	%cl,		-16(%rbp)	/ key->x = x

    80 	popq	%rbx

    81 	popq	%rbp

    82 	ret

    83 .L_ARCFOUR_end:

    84 .size ARCFOUR,.L_ARCFOUR_end-ARCFOUR

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