RC4 tune-up for AMD64. Performance improvement of 2.22x is measured for

#!/usr/bin/env perl

#

# ====================================================================

# Written by Andy Polyakov <appro@fy.chalmers.se> for the OpenSSL

# project. Rights for redistribution and usage in source and binary

# forms are granted according to the OpenSSL license.

# ====================================================================

#

# 2.22x RC4 tune-up:-) It should be noted though that my hand [as in

# "hand-coded assembler"] doesn't stand for the whole improvement

# coefficient. It turned out that eliminating RC4_CHAR from config

# line results in ~40% improvement (yes, even for C implementation).

# Presumably it has everything to do with AMD cache architecture and

# RAW or whatever penalties. Once again! The module *requires* config

# line *without* RC4_CHAR! As for coding "secret," I bet on partial

# register arithmetics. For example instead 'inc %r8; and $255,%r8'

# I simply 'inc %r8b'. Even though optimization manual discourages

# to operate on partial registers, it turned out to be the best bet.

# At least for AMD... How IA32E would perform remains to be seen...

$output=shift;

$win64=1 if ($output =~ /win64.[s|asm]/);

open STDOUT,">$output" || die "can't open $output: $!";

if (defined($win64)) {

    $dat="%rcx";	# arg1

    $len="%rdx";	# arg2

    $inp="%rsi";	# r8, arg3 moves here

    $out="%rdi";	# r9, arg4 moves here

} else {

    $dat="%rdi";	# arg1

    $len="%rsi";	# arg2

    $inp="%rdx";	# arg3

    $out="%rcx";	# arg4

}

$XX="%r10";

$TX="%r8";

$YY="%r11";

$TY="%r9";

sub PTR() {

    my $ret=shift;

    if (defined($win64)) {

	$ret =~ s/\[([\S]+)\+([\S]+)\]/[$2+$1]/g; # [%rN+%rM*4]->[%rM*4+%rN]

    } else {

	$ret =~ s/[\+\*]/,/g;		# [%rN+%rM*4]->[%rN,%rM,4]

	$ret =~ s/\[([^\]]+)\]/($1)/g;	# [%rN]->(%rN)

    }

    $ret;

}

$code=<<___ if (!defined($win64));

.text

.globl	RC4

.type	RC4,\@function

.align	16

RC4:	or	$len,$len

	jne	.Lentry

	.byte	0xF3,0xC3	# repz ret, 2-byte ret

.Lentry:

___

$code=<<___ if (defined($win64));

TEXT	SEGMENT

PUBLIC	RC4

ALIGN	16

RC4	PROC NEAR

	or	$len,$len

	jne	.Lentry

	DB	F3h,C3h		; repz ret, 2-byte ret

.Lentry:

	push	%edi

	push	%esi

	sub	\$40,%esp

	mov	%r8,$inp

	mov	%r9,$out

___

$code.=<<___;

	add	\$8,$dat

	movl	`&PTR("DWORD-8[$dat]")`,$XX#d

	movl	`&PTR("DWORD-4[$dat]")`,$YY#d

	test	\$-8,$len

	jz	.Lloop1

.align	16

.Lloop8:

	movq	`&PTR("QWORD[$inp]")`,%rax

	inc	$XX#b

	movl	`&PTR("DWORD[$dat+$XX*4]")`,$TX#d

	add	$TX#b,$YY#b

	movl	`&PTR("DWORD[$dat+$YY*4]")`,$TY#d

	movl	$TX#d,`&PTR("DWORD[$dat+$YY*4]")`

	movl	$TY#d,`&PTR("DWORD[$dat+$XX*4]")`

	add	$TY#b,$TX#b

	inc	$XX#b

	movl	`&PTR("DWORD[$dat+$TX*4]")`,$TY#d

	xor	$TY,%rax

___

for ($i=1;$i<=6;$i++) {

$code.=<<___;

	movl	`&PTR("DWORD[$dat+$XX*4]")`,$TX#d

	add	$TX#b,$YY#b

	movl	`&PTR("DWORD[$dat+$YY*4]")`,$TY#d

	movl	$TX#d,`&PTR("DWORD[$dat+$YY*4]")`

	movl	$TY#d,`&PTR("DWORD[$dat+$XX*4]")`

	add	$TY#b,$TX#b

	movl	`&PTR("DWORD[$dat+$TX*4]")`,$TY#d

	shl	\$`8*$i`,$TY

	inc	$XX#b

	xor	$TY,%rax

___

}

$code.=<<___;

	movl	`&PTR("DWORD[$dat+$XX*4]")`,$TX#d

	add	$TX#b,$YY#b

	movl	`&PTR("DWORD[$dat+$YY*4]")`,$TY#d

	movl	$TX#d,`&PTR("DWORD[$dat+$YY*4]")`

	movl	$TY#d,`&PTR("DWORD[$dat+$XX*4]")`

	sub	\$8,$len

	add	$TY#b,$TX#b

	add	\$8,$out

	movl	`&PTR("DWORD[$dat+$TX*4]")`,$TY#d

	shl	\$56,$TY

	add	\$8,$inp

	xor	$TY,%rax

	mov	%rax,`&PTR("QWORD-8[$out]")`

	test	\$-8,$len

	jnz	.Lloop8

	cmp	\$0,$len

	jne	.Lloop1

.Lexit:

	movl	$XX#d,`&PTR("DWORD-8[$dat]")`

	movl	$YY#d,`&PTR("DWORD-4[$dat]")`

___

$code.=<<___ if (defined($win64));

	add	\$40,%esp

	pop	%esi

	pop	%edi

	DB	F3h,C3h		; retz ret, 2-byte ret

___

$code.=<<___ if (!defined($win64));

	.byte	0xF3,0xC3	# repz ret, 2-byte ret

___

$code.=<<___;

.align	16

.Lloop1:

	movzb	`&PTR("BYTE[$inp]")`,%rax

	inc	$XX#b

	nop

	movl	`&PTR("DWORD[$dat+$XX*4]")`,$TX#d

	add	$TX#b,$YY#b

	movl	`&PTR("DWORD[$dat+$YY*4]")`,$TY#d

	movl	$TX#d,`&PTR("DWORD[$dat+$YY*4]")`

	movl	$TY#d,`&PTR("DWORD[$dat+$XX*4]")`

	add	$TY#b,$TX#b

	movl	`&PTR("DWORD[$dat+$TX*4]")`,$TY#d

	xor	$TY,%rax

	inc	$inp

	movb	%al,`&PTR("BYTE[$out]")`

	inc	$out

	dec	$len

	jnz	.Lloop1

	jmp	.Lexit

___

if (defined($win64)) {

    $code.="RC4	ENDP\n";

} else {

    $code.=".size	RC4,.-RC4\n"

}

$code =~ s/#([bwd])/$1/gm;

$code =~ s/\`([^\`]*)\`/eval $1/gem;

if (defined($win64)) {

    $code =~ s/\.align/ALIGN/gm;

    $code =~ s/[\$%]//gm;

    $code =~ s/\.L/\$L/gm;

    $code =~ s/([\w]+)([\s]+)([\S]+),([\S]+)/$1$2$4,$3/gm;

    $code =~ s/([QD]*WORD|BYTE)/$1 PTR /gm;

    $code =~ s/(mov[z]*)[bwlq]/$1/gm;

} else {

    $code =~ s/[QD]*WORD|BYTE//gm;

}

print $code;