#!/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 of '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...

# As was shown by Marc Bevand reordering of couple of load operations
# results in even higher performance gain of 3.3x:-) At least on
# Opteron... For reference, 1x in this case is RC4_CHAR C-code
# compiled with gcc 3.3.2, which performs at ~54MBps per 1GHz clock.
# Latter means that if you want to *estimate* what to expect from
# *your* Opteron, then multiply 54 by 3.3 and clock frequency in GHz.

# Intel P4 EM64T core was found to run the AMD64 code really slow...
# The only way to achieve comparable performance on P4 was to keep
# RC4_CHAR. Kind of ironic, huh? As it's apparently impossible to
# compose blended code, which would perform even within 30% marginal
# on either AMD and Intel platforms, I implement both cases. See
# rc4_skey.c for further details...

# P4 EM64T core appears to be "allergic" to 64-bit inc/dec. Replacing 
# those with add/sub results in 50% performance improvement of folded
# loop...

# As was shown by Zou Nanhai loop unrolling can improve Intel EM64T
# performance by >30% [unlike P4 32-bit case that is]. But this is
# provided that loads are reordered even more aggressively! Both code
# pathes, AMD64 and EM64T, reorder loads in essentially same manner
# as my IA-64 implementation. On Opteron this resulted in modest 5%
# improvement [I had to test it], while final Intel P4 performance
# achieves respectful 432MBps on 2.8GHz processor now. For reference.
# If executed on Xeon, current RC4_CHAR code-path is 2.7x faster than
# RC4_INT code-path. While if executed on Opteron, it's only 25%
# slower than the RC4_INT one [meaning that if CPU µ-arch detection
# is not implemented, then this final RC4_CHAR code-path should be
# preferred, as it provides better *all-round* performance].

$output=shift;
open STDOUT,"| $^X ../perlasm/x86_64-xlate.pl $output";

$dat="%rdi";	    # arg1
$len="%rsi";	    # arg2
$inp="%rdx";	    # arg3
$out="%rcx";	    # arg4

@XX=("%r8","%r10");
@TX=("%r9","%r11");
$YY="%r12";
$TY="%r13";

$code=<<___;
.text

.globl	RC4
.type	RC4,\@function,4
.align	16
RC4:	or	$len,$len
	jne	.Lentry
	ret
.Lentry:
	push	%r12
	push	%r13

	add	\$8,$dat
	movl	-8($dat),$XX[0]#d
	movl	-4($dat),$YY#d
	cmpl	\$-1,256($dat)
	je	.LRC4_CHAR
	inc	$XX[0]#b
	movl	($dat,$XX[0],4),$TX[0]#d
	test	\$-8,$len
	jz	.Lloop1
	jmp	.Lloop8
.align	16
.Lloop8:
___
for ($i=0;$i<8;$i++) {
$code.=<<___;
	add	$TX[0]#b,$YY#b
	mov	$XX[0],$XX[1]
	movl	($dat,$YY,4),$TY#d
	ror	\$8,%rax			# ror is redundant when $i=0
	inc	$XX[1]#b
	movl	($dat,$XX[1],4),$TX[1]#d
	cmp	$XX[1],$YY
	movl	$TX[0]#d,($dat,$YY,4)
	cmove	$TX[0],$TX[1]
	movl	$TY#d,($dat,$XX[0],4)
	add	$TX[0]#b,$TY#b
	movb	($dat,$TY,4),%al
___
push(@TX,shift(@TX)); push(@XX,shift(@XX));	# "rotate" registers
}
$code.=<<___;
	ror	\$8,%rax
	sub	\$8,$len

	xor	($inp),%rax
	add	\$8,$inp
	mov	%rax,($out)
	add	\$8,$out

	test	\$-8,$len
	jnz	.Lloop8
	cmp	\$0,$len
	jne	.Lloop1
___
$code.=<<___;
.Lexit:
	sub	\$1,$XX[0]#b
	movl	$XX[0]#d,-8($dat)
	movl	$YY#d,-4($dat)

	pop	%r13
	pop	%r12
	ret
.align	16
.Lloop1:
	add	$TX[0]#b,$YY#b
	movl	($dat,$YY,4),$TY#d
	movl	$TX[0]#d,($dat,$YY,4)
	movl	$TY#d,($dat,$XX[0],4)
	add	$TY#b,$TX[0]#b
	inc	$XX[0]#b
	movl	($dat,$TX[0],4),$TY#d
	movl	($dat,$XX[0],4),$TX[0]#d
	xorb	($inp),$TY#b
	inc	$inp
	movb	$TY#b,($out)
	inc	$out
	dec	$len
	jnz	.Lloop1
	jmp	.Lexit

.align	16
.LRC4_CHAR:
	add	\$1,$XX[0]#b
	movzb	($dat,$XX[0]),$TX[0]#d
	test	\$-8,$len
	jz	.Lcloop1
	push	%rbx
	jmp	.Lcloop8
.align	16
.Lcloop8:
	mov	($inp),%eax
	mov	4($inp),%ebx
___
# unroll 2x4-wise, because 64-bit rotates kill Intel P4...
for ($i=0;$i<4;$i++) {
$code.=<<___;
	add	$TX[0]#b,$YY#b
	lea	1($XX[0]),$XX[1]
	movzb	($dat,$YY),$TY#d
	movzb	$XX[1]#b,$XX[1]#d
	movzb	($dat,$XX[1]),$TX[1]#d
	movb	$TX[0]#b,($dat,$YY)
	cmp	$XX[1],$YY
	movb	$TY#b,($dat,$XX[0])
	jne	.Lcmov$i			# Intel cmov is sloooow...
	mov	$TX[0],$TX[1]
.Lcmov$i:
	add	$TX[0]#b,$TY#b
	xor	($dat,$TY),%al
	ror	\$8,%eax
___
push(@TX,shift(@TX)); push(@XX,shift(@XX));	# "rotate" registers
}
for ($i=4;$i<8;$i++) {
$code.=<<___;
	add	$TX[0]#b,$YY#b
	lea	1($XX[0]),$XX[1]
	movzb	($dat,$YY),$TY#d
	movzb	$XX[1]#b,$XX[1]#d
	movzb	($dat,$XX[1]),$TX[1]#d
	movb	$TX[0]#b,($dat,$YY)
	cmp	$XX[1],$YY
	movb	$TY#b,($dat,$XX[0])
	jne	.Lcmov$i			# Intel cmov is sloooow...
	mov	$TX[0],$TX[1]
.Lcmov$i:
	add	$TX[0]#b,$TY#b
	xor	($dat,$TY),%bl
	ror	\$8,%ebx
___
push(@TX,shift(@TX)); push(@XX,shift(@XX));	# "rotate" registers
}
$code.=<<___;
	lea	-8($len),$len
	mov	%eax,($out)
	lea	8($inp),$inp
	mov	%ebx,4($out)
	lea	8($out),$out

	test	\$-8,$len
	jnz	.Lcloop8
	pop	%rbx
	cmp	\$0,$len
	jne	.Lcloop1
	jmp	.Lexit
___
$code.=<<___;
.align	16
.Lcloop1:
	add	$TX[0]#b,$YY#b
	movzb	($dat,$YY),$TY#d
	movb	$TX[0]#b,($dat,$YY)
	movb	$TY#b,($dat,$XX[0])
	add	$TX[0]#b,$TY#b
	add	\$1,$XX[0]#b
	movzb	($dat,$TY),$TY#d
	movzb	($dat,$XX[0]),$TX[0]#d
	xorb	($inp),$TY#b
	lea	1($inp),$inp
	movb	$TY#b,($out)
	lea	1($out),$out
	sub	\$1,$len
	jnz	.Lcloop1
	jmp	.Lexit
.size	RC4,.-RC4
___

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

print $code;

close STDOUT;
