/// -*- mode: asm; asm-comment-char: ?/ -*-
///
/// Fancy SIMD implementation of ChaCha
///
/// (c) 2015 Straylight/Edgeware
///

///----- Licensing notice ---------------------------------------------------
///
/// This file is part of Catacomb.
///
/// Catacomb is free software; you can redistribute it and/or modify
/// it under the terms of the GNU Library General Public License as
/// published by the Free Software Foundation; either version 2 of the
/// License, or (at your option) any later version.
///
/// Catacomb is distributed in the hope that it will be useful,
/// but WITHOUT ANY WARRANTY; without even the implied warranty of
/// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
/// GNU Library General Public License for more details.
///
/// You should have received a copy of the GNU Library General Public
/// License along with Catacomb; if not, write to the Free
/// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
/// MA 02111-1307, USA.

///--------------------------------------------------------------------------
/// Preliminaries.

#include "config.h"
#include "asm-common.h"

	.text

///--------------------------------------------------------------------------
/// Main code.

FUNC(chacha_core_x86ish_avx)
	.arch	.avx
	vzeroupper
  endprologue
	// drop through...
ENDFUNC

	.arch	pentium4

FUNC(chacha_core_x86ish_sse2)

	// Initial setup.

#if CPUFAM_X86
	// Arguments come in on the stack, and will need to be collected.  We
	// can get away with just the scratch registers for integer work, but
	// we'll run out of XMM registers and will need some properly aligned
	// space which we'll steal from the stack.  I don't trust the stack
	// pointer's alignment, so I'll have to mask the stack pointer, which
	// in turn means I'll need to keep track of the old value.  Hence I'm
	// making a full i386-style stack frame here.
	//
	// The Windows and SysV ABIs are sufficiently similar that we don't
	// need to worry about the differences here.

#  define NR ecx
#  define IN eax
#  define OUT edx
#  define SAVE0 xmm5
#  define SAVE1 xmm6
#  define SAVE2 xmm7
#  define SAVE3 [SP]

	pushreg	BP
	setfp
	stalloc	16
	mov	IN, [BP + 12]
	mov	OUT, [BP + 16]
	and	SP, ~15
	mov	NR, [BP + 8]
#endif

#if CPUFAM_AMD64 && ABI_SYSV
	// This is nice.  We have plenty of XMM registers, and the arguments
	// are in useful places.  There's no need to spill anything and we
	// can just get on with the code.

#  define NR edi
#  define IN rsi
#  define OUT rdx
#  define SAVE0 xmm5
#  define SAVE1 xmm6
#  define SAVE2 xmm7
#  define SAVE3 xmm8
#endif

#if CPUFAM_AMD64 && ABI_WIN
	// Arguments come in registers, but they're different between Windows
	// and everyone else (and everyone else is saner).
	//
	// The Windows ABI insists that we preserve some of the XMM
	// registers, but we want more than we can use as scratch space.  We
	// only need to save a copy of the input for the feedforward at the
	// end, so we might as well use memory rather than spill extra
	// registers.  (We need an extra 8 bytes to align the stack.)

#  define NR ecx
#  define IN rdx
#  define OUT r8
#  define SAVE0 xmm5
#  define SAVE1 [SP +  0]
#  define SAVE2 [SP + 16]
#  define SAVE3 [SP + 32]

	stalloc	48 + 8
#endif

  endprologue

	// First job is to slurp the matrix into XMM registers.  Be careful:
	// the input matrix isn't likely to be properly aligned.
	//
	//	[ 0  1  2  3] (a, xmm0)
	//	[ 4  5  6  7] (b, xmm1)
	//	[ 8  9 10 11] (c, xmm2)
	//	[12 13 14 15] (d, xmm3)
	movdqu	xmm0, [IN +  0]
	movdqu	xmm1, [IN + 16]
	movdqu	xmm2, [IN + 32]
	movdqu	xmm3, [IN + 48]

	// Take a copy for later.  This one is aligned properly, by
	// construction.
	movdqa	SAVE0, xmm0
	movdqa	SAVE1, xmm1
	movdqa	SAVE2, xmm2
	movdqa	SAVE3, xmm3

0:
	// Apply a column quarterround to each of the columns simultaneously.
	// Alas, there doesn't seem to be a packed doubleword rotate, so we
	// have to synthesize it.

	// a += b; d ^= a; d <<<= 16
	paddd	xmm0, xmm1
	pxor	xmm3, xmm0
	movdqa	xmm4, xmm3
	pslld	xmm3, 16
	psrld	xmm4, 16
	por	xmm3, xmm4

	// c += d; b ^= c; b <<<= 12
	paddd	xmm2, xmm3
	pxor	xmm1, xmm2
	movdqa	xmm4, xmm1
	pslld	xmm1, 12
	psrld	xmm4, 20
	por	xmm1, xmm4

	// a += b; d ^= a; d <<<=  8
	paddd	xmm0, xmm1
	pxor	xmm3, xmm0
	movdqa	xmm4, xmm3
	pslld	xmm3, 8
	psrld	xmm4, 24
	por	xmm3, xmm4

	// c += d; b ^= c; b <<<=  7
	paddd	xmm2, xmm3
	 pshufd	xmm3, xmm3, SHUF(2, 1, 0, 3)
	pxor	xmm1, xmm2
	 pshufd	xmm2, xmm2, SHUF(1, 0, 3, 2)
	movdqa	xmm4, xmm1
	pslld	xmm1, 7
	psrld	xmm4, 25
	por	xmm1, xmm4

	// The not-quite-transpose conveniently only involves reordering
	// elements of individual rows, which can be done quite easily.  It
	// doesn't involve any movement of elements between rows, or even
	// renaming of the rows.
	//
	//	[ 0  1  2  3]		[ 0  1  2  3] (a, xmm0)
	//	[ 4  5  6  7]    -->	[ 5  6  7  4] (b, xmm1)
	//	[ 8  9 10 11]		[10 11  8  9] (c, xmm2)
	//	[12 13 14 15]		[15 12 13 14] (d, xmm3)
	//
	// The shuffles have quite high latency, so they've mostly been
	// pushed upwards.  The remaining one can't be moved, though.
	pshufd	xmm1, xmm1, SHUF(0, 3, 2, 1)

	// Apply the diagonal quarterround to each of the columns
	// simultaneously.

	// a += b; d ^= a; d <<<= 16
	paddd	xmm0, xmm1
	pxor	xmm3, xmm0
	movdqa	xmm4, xmm3
	pslld	xmm3, 16
	psrld	xmm4, 16
	por	xmm3, xmm4

	// c += d; b ^= c; b <<<= 12
	paddd	xmm2, xmm3
	pxor	xmm1, xmm2
	movdqa	xmm4, xmm1
	pslld	xmm1, 12
	psrld	xmm4, 20
	por	xmm1, xmm4

	// a += b; d ^= a; d <<<=  8
	paddd	xmm0, xmm1
	pxor	xmm3, xmm0
	movdqa	xmm4, xmm3
	pslld	xmm3, 8
	psrld	xmm4, 24
	por	xmm3, xmm4

	// c += d; b ^= c; b <<<=  7
	paddd	xmm2, xmm3
	 pshufd	xmm3, xmm3, SHUF(0, 3, 2, 1)
	pxor	xmm1, xmm2
	 pshufd	xmm2, xmm2, SHUF(1, 0, 3, 2)
	movdqa	xmm4, xmm1
	pslld	xmm1, 7
	psrld	xmm4, 25
	por	xmm1, xmm4

	// Finally, finish off undoing the transpose, and we're done for this
	// doubleround.  Again, most of this was done above so we don't have
	// to wait for the shuffles.
	pshufd	xmm1, xmm1, SHUF(2, 1, 0, 3)

	// Decrement the loop counter and see if we should go round again.
	sub	NR, 2
	ja	0b

	// Almost there.  Firstly, the feedforward addition.
	paddd	xmm0, SAVE0
	paddd	xmm1, SAVE1
	paddd	xmm2, SAVE2
	paddd	xmm3, SAVE3

	// And now we write out the result.  This one won't be aligned
	// either.
	movdqu	[OUT +  0], xmm0
	movdqu	[OUT + 16], xmm1
	movdqu	[OUT + 32], xmm2
	movdqu	[OUT + 48], xmm3

	// Tidy things up.
#if CPUFAM_X86
	dropfp
	popreg	BP
#endif
#if CPUFAM_AMD64 && ABI_WIN
	stfree	48 + 8
#endif

	// And with that, we're done.
	ret

ENDFUNC

///----- That's all, folks --------------------------------------------------