Initial x86_64 implementation of ecc_25519_modp, 30% speedup.

ChangeLog

 2014-08-22  Niels Möller  <nisse@lysator.liu.se>
 
+	* x86_64/ecc-25519-modp.asm: New file. Initial assembly
+	implementation, 30% speedup of ecc_25519_modp.
+
 	* ecc-25519.c [HAVE_NATIVE_ecc_25519_modp]: Use assembly version
 	if available.
 

x86_64/ecc-25519-modp.asm

+C x86_64/ecc-25519-modp.asm
+
+ifelse(<
+   Copyright (C) 2014 Niels Möller
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle 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
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+>)
+
+	.file "ecc-25519-modp.asm"
+
+define(<RP>, <%rsi>)
+define(<U0>, <%rdi>) C Overlaps unused ecc input
+define(<U1>, <%rcx>)
+define(<U2>, <%r8>)
+define(<V1>, <%r9>)
+define(<V2>, <%r10>)
+define(<V3>, <%r11>)
+define(<M>, <%r12>)
+
+PROLOGUE(nettle_ecc_25519_modp)
+	W64_ENTRY(2, 0)
+	push	%r12
+	
+	mov	$38, M
+	mov	32(RP), %rax	
+	mul	M
+	mov	%rax, U0
+	mov	%rdx, V1
+
+	mov	40(RP), %rax
+	mul	M
+	mov	%rax, U1
+	mov	%rdx, V2
+	
+	mov	48(RP), %rax
+	mul	M
+	mov	%rax, U2
+	mov	%rdx, V3
+	
+	mov	56(RP), %rax
+	mul	M
+	
+	add	V1, U1
+	adc	V2, U2
+	adc	V3, %rax
+	adc	$0, %rdx
+
+	shr 	M
+	C FIXME: Load and add earlier?
+	add	(RP), U0
+	adc	8(RP), U1
+	adc	16(RP), U2
+	adc	24(RP), %rax
+	adc	$0, %rdx
+
+	add	%rax, %rax	C Copy high bit to carry
+	adc	%rdx, %rdx
+	shr	%rax		C Undo shift, clear high bit
+	imul	M, %rdx
+
+	add	%rdx, U0
+	mov	U0, (RP)
+	adc	$0, U1
+	mov	U1, 8(RP)
+	adc	$0, U2
+	mov	U2, 16(RP)
+	adc	$0, %rax
+	mov	%rax, 24(RP)
+
+	pop	%r12
+	W64_EXIT(2, 0)
+	ret
+EPILOGUE(nettle_ecc_25519_modp)