crypto/fipsmodule/ec/asm/p256-armv8-asm.pl

#! /usr/bin/env perl
# Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


# ====================================================================
# Written by Andy Polyakov <appro@openssl.org> for the OpenSSL
# project.
# ====================================================================
#
# ECP_NISTZ256 module for ARMv8.
#
# February 2015.
#
# Original ECP_NISTZ256 submission targeting x86_64 is detailed in
# http://eprint.iacr.org/2013/816.
#
#			with/without -DECP_NISTZ256_ASM
# Apple A7		+190-360%
# Cortex-A53		+190-400%
# Cortex-A57		+190-350%
# Denver		+230-400%
#
# Ranges denote minimum and maximum improvement coefficients depending
# on benchmark. Lower coefficients are for ECDSA sign, server-side
# operation. Keep in mind that +400% means 5x improvement.

# The first two arguments should always be the flavour and output file path.
if ($#ARGV < 1) { die "Not enough arguments provided.
  Two arguments are necessary: the flavour and the output file path."; }

$flavour = shift;
$output = shift;

$0 =~ m/(.*[\/\\])[^\/\\]+$/; $dir=$1;
( $xlate="${dir}arm-xlate.pl" and -f $xlate ) or
( $xlate="${dir}../../../perlasm/arm-xlate.pl" and -f $xlate) or
die "can't locate arm-xlate.pl";

open OUT, "|-", $^X, $xlate, $flavour, $output;
*STDOUT=*OUT;

{
my ($rp,$ap,$bp,$bi,$a0,$a1,$a2,$a3,$t0,$t1,$t2,$t3,$poly1,$poly3,
    $acc0,$acc1,$acc2,$acc3,$acc4,$acc5) =
    map("x$_",(0..17,19,20));

my ($acc6,$acc7)=($ap,$bp);	# used in __ecp_nistz256_sqr_mont

$code.=<<___;
.section .rodata
.align	5
.Lpoly:
.quad	0xffffffffffffffff,0x00000000ffffffff,0x0000000000000000,0xffffffff00000001
.LRR:	// 2^512 mod P precomputed for NIST P256 polynomial
.quad	0x0000000000000003,0xfffffffbffffffff,0xfffffffffffffffe,0x00000004fffffffd
.Lone_mont:
.quad	0x0000000000000001,0xffffffff00000000,0xffffffffffffffff,0x00000000fffffffe
.Lone:
.quad	1,0,0,0
.Lord:
.quad	0xf3b9cac2fc632551,0xbce6faada7179e84,0xffffffffffffffff,0xffffffff00000000
.LordK:
.quad	0xccd1c8aaee00bc4f
.asciz	"ECP_NISTZ256 for ARMv8, CRYPTOGAMS by <appro\@openssl.org>"
.text

// void	ecp_nistz256_mul_mont(BN_ULONG x0[4],const BN_ULONG x1[4],
//					     const BN_ULONG x2[4]);
.globl	ecp_nistz256_mul_mont
.type	ecp_nistz256_mul_mont,%function
.align	4
ecp_nistz256_mul_mont:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-32]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]

	ldr	$bi,[$bp]		// bp[0]
	ldp	$a0,$a1,[$ap]
	ldp	$a2,$a3,[$ap,#16]
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]

	bl	__ecp_nistz256_mul_mont

	ldp	x19,x20,[sp,#16]
	ldp	x29,x30,[sp],#32
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_mul_mont,.-ecp_nistz256_mul_mont

// void	ecp_nistz256_sqr_mont(BN_ULONG x0[4],const BN_ULONG x1[4]);
.globl	ecp_nistz256_sqr_mont
.type	ecp_nistz256_sqr_mont,%function
.align	4
ecp_nistz256_sqr_mont:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-32]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]

	ldp	$a0,$a1,[$ap]
	ldp	$a2,$a3,[$ap,#16]
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]

	bl	__ecp_nistz256_sqr_mont

	ldp	x19,x20,[sp,#16]
	ldp	x29,x30,[sp],#32
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_sqr_mont,.-ecp_nistz256_sqr_mont

// void	ecp_nistz256_div_by_2(BN_ULONG x0[4],const BN_ULONG x1[4]);
.globl	ecp_nistz256_div_by_2
.type	ecp_nistz256_div_by_2,%function
.align	4
ecp_nistz256_div_by_2:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-16]!
	add	x29,sp,#0

	ldp	$acc0,$acc1,[$ap]
	ldp	$acc2,$acc3,[$ap,#16]
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]

	bl	__ecp_nistz256_div_by_2

	ldp	x29,x30,[sp],#16
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_div_by_2,.-ecp_nistz256_div_by_2

// void	ecp_nistz256_mul_by_2(BN_ULONG x0[4],const BN_ULONG x1[4]);
.globl	ecp_nistz256_mul_by_2
.type	ecp_nistz256_mul_by_2,%function
.align	4
ecp_nistz256_mul_by_2:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-16]!
	add	x29,sp,#0

	ldp	$acc0,$acc1,[$ap]
	ldp	$acc2,$acc3,[$ap,#16]
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]
	mov	$t0,$acc0
	mov	$t1,$acc1
	mov	$t2,$acc2
	mov	$t3,$acc3

	bl	__ecp_nistz256_add_to	// ret = a+a	// 2*a

	ldp	x29,x30,[sp],#16
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_mul_by_2,.-ecp_nistz256_mul_by_2

// void	ecp_nistz256_mul_by_3(BN_ULONG x0[4],const BN_ULONG x1[4]);
.globl	ecp_nistz256_mul_by_3
.type	ecp_nistz256_mul_by_3,%function
.align	4
ecp_nistz256_mul_by_3:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-16]!
	add	x29,sp,#0

	ldp	$acc0,$acc1,[$ap]
	ldp	$acc2,$acc3,[$ap,#16]
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]
	mov	$t0,$acc0
	mov	$t1,$acc1
	mov	$t2,$acc2
	mov	$t3,$acc3
	mov	$a0,$acc0
	mov	$a1,$acc1
	mov	$a2,$acc2
	mov	$a3,$acc3

	bl	__ecp_nistz256_add_to	// ret = a+a	// 2*a

	mov	$t0,$a0
	mov	$t1,$a1
	mov	$t2,$a2
	mov	$t3,$a3

	bl	__ecp_nistz256_add_to	// ret += a	// 2*a+a=3*a

	ldp	x29,x30,[sp],#16
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_mul_by_3,.-ecp_nistz256_mul_by_3

// void	ecp_nistz256_sub(BN_ULONG x0[4],const BN_ULONG x1[4],
//				        const BN_ULONG x2[4]);
.globl	ecp_nistz256_sub
.type	ecp_nistz256_sub,%function
.align	4
ecp_nistz256_sub:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-16]!
	add	x29,sp,#0

	ldp	$acc0,$acc1,[$ap]
	ldp	$acc2,$acc3,[$ap,#16]
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]

	bl	__ecp_nistz256_sub_from

	ldp	x29,x30,[sp],#16
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_sub,.-ecp_nistz256_sub

// void	ecp_nistz256_neg(BN_ULONG x0[4],const BN_ULONG x1[4]);
.globl	ecp_nistz256_neg
.type	ecp_nistz256_neg,%function
.align	4
ecp_nistz256_neg:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-16]!
	add	x29,sp,#0

	mov	$bp,$ap
	mov	$acc0,xzr		// a = 0
	mov	$acc1,xzr
	mov	$acc2,xzr
	mov	$acc3,xzr
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]

	bl	__ecp_nistz256_sub_from

	ldp	x29,x30,[sp],#16
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_neg,.-ecp_nistz256_neg

// note that __ecp_nistz256_mul_mont expects a[0-3] input pre-loaded
// to $a0-$a3 and b[0] - to $bi
.type	__ecp_nistz256_mul_mont,%function
.align	4
__ecp_nistz256_mul_mont:
	mul	$acc0,$a0,$bi		// a[0]*b[0]
	umulh	$t0,$a0,$bi

	mul	$acc1,$a1,$bi		// a[1]*b[0]
	umulh	$t1,$a1,$bi

	mul	$acc2,$a2,$bi		// a[2]*b[0]
	umulh	$t2,$a2,$bi

	mul	$acc3,$a3,$bi		// a[3]*b[0]
	umulh	$t3,$a3,$bi
	ldr	$bi,[$bp,#8]		// b[1]

	adds	$acc1,$acc1,$t0		// accumulate high parts of multiplication
	 lsl	$t0,$acc0,#32
	adcs	$acc2,$acc2,$t1
	 lsr	$t1,$acc0,#32
	adcs	$acc3,$acc3,$t2
	adc	$acc4,xzr,$t3
	mov	$acc5,xzr
___
for($i=1;$i<4;$i++) {
        # Reduction iteration is normally performed by accumulating
        # result of multiplication of modulus by "magic" digit [and
        # omitting least significant word, which is guaranteed to
        # be 0], but thanks to special form of modulus and "magic"
        # digit being equal to least significant word, it can be
        # performed with additions and subtractions alone. Indeed:
        #
        #            ffff0001.00000000.0000ffff.ffffffff
        # *                                     abcdefgh
        # + xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx.abcdefgh
        #
        # Now observing that ff..ff*x = (2^n-1)*x = 2^n*x-x, we
        # rewrite above as:
        #
        #   xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx.abcdefgh
        # + abcdefgh.abcdefgh.0000abcd.efgh0000.00000000
        # - 0000abcd.efgh0000.00000000.00000000.abcdefgh
        #
        # or marking redundant operations:
        #
        #   xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx.--------
        # + abcdefgh.abcdefgh.0000abcd.efgh0000.--------
        # - 0000abcd.efgh0000.--------.--------.--------

$code.=<<___;
	subs	$t2,$acc0,$t0		// "*0xffff0001"
	sbc	$t3,$acc0,$t1
	adds	$acc0,$acc1,$t0		// +=acc[0]<<96 and omit acc[0]
	 mul	$t0,$a0,$bi		// lo(a[0]*b[i])
	adcs	$acc1,$acc2,$t1
	 mul	$t1,$a1,$bi		// lo(a[1]*b[i])
	adcs	$acc2,$acc3,$t2		// +=acc[0]*0xffff0001
	 mul	$t2,$a2,$bi		// lo(a[2]*b[i])
	adcs	$acc3,$acc4,$t3
	 mul	$t3,$a3,$bi		// lo(a[3]*b[i])
	adc	$acc4,$acc5,xzr

	adds	$acc0,$acc0,$t0		// accumulate low parts of multiplication
	 umulh	$t0,$a0,$bi		// hi(a[0]*b[i])
	adcs	$acc1,$acc1,$t1
	 umulh	$t1,$a1,$bi		// hi(a[1]*b[i])
	adcs	$acc2,$acc2,$t2
	 umulh	$t2,$a2,$bi		// hi(a[2]*b[i])
	adcs	$acc3,$acc3,$t3
	 umulh	$t3,$a3,$bi		// hi(a[3]*b[i])
	adc	$acc4,$acc4,xzr
___
$code.=<<___	if ($i<3);
	ldr	$bi,[$bp,#8*($i+1)]	// b[$i+1]
___
$code.=<<___;
	adds	$acc1,$acc1,$t0		// accumulate high parts of multiplication
	 lsl	$t0,$acc0,#32
	adcs	$acc2,$acc2,$t1
	 lsr	$t1,$acc0,#32
	adcs	$acc3,$acc3,$t2
	adcs	$acc4,$acc4,$t3
	adc	$acc5,xzr,xzr
___
}
$code.=<<___;
	// last reduction
	subs	$t2,$acc0,$t0		// "*0xffff0001"
	sbc	$t3,$acc0,$t1
	adds	$acc0,$acc1,$t0		// +=acc[0]<<96 and omit acc[0]
	adcs	$acc1,$acc2,$t1
	adcs	$acc2,$acc3,$t2		// +=acc[0]*0xffff0001
	adcs	$acc3,$acc4,$t3
	adc	$acc4,$acc5,xzr

	adds	$t0,$acc0,#1		// subs	$t0,$acc0,#-1 // tmp = ret-modulus
	sbcs	$t1,$acc1,$poly1
	sbcs	$t2,$acc2,xzr
	sbcs	$t3,$acc3,$poly3
	sbcs	xzr,$acc4,xzr		// did it borrow?

	csel	$acc0,$acc0,$t0,lo	// ret = borrow ? ret : ret-modulus
	csel	$acc1,$acc1,$t1,lo
	csel	$acc2,$acc2,$t2,lo
	stp	$acc0,$acc1,[$rp]
	csel	$acc3,$acc3,$t3,lo
	stp	$acc2,$acc3,[$rp,#16]

	ret
.size	__ecp_nistz256_mul_mont,.-__ecp_nistz256_mul_mont

// note that __ecp_nistz256_sqr_mont expects a[0-3] input pre-loaded
// to $a0-$a3
.type	__ecp_nistz256_sqr_mont,%function
.align	4
__ecp_nistz256_sqr_mont:
	//  |  |  |  |  |  |a1*a0|  |
	//  |  |  |  |  |a2*a0|  |  |
	//  |  |a3*a2|a3*a0|  |  |  |
	//  |  |  |  |a2*a1|  |  |  |
	//  |  |  |a3*a1|  |  |  |  |
	// *|  |  |  |  |  |  |  | 2|
	// +|a3*a3|a2*a2|a1*a1|a0*a0|
	//  |--+--+--+--+--+--+--+--|
	//  |A7|A6|A5|A4|A3|A2|A1|A0|, where Ax is $accx, i.e. follow $accx
	//
	//  "can't overflow" below mark carrying into high part of
	//  multiplication result, which can't overflow, because it
	//  can never be all ones.

	mul	$acc1,$a1,$a0		// a[1]*a[0]
	umulh	$t1,$a1,$a0
	mul	$acc2,$a2,$a0		// a[2]*a[0]
	umulh	$t2,$a2,$a0
	mul	$acc3,$a3,$a0		// a[3]*a[0]
	umulh	$acc4,$a3,$a0

	adds	$acc2,$acc2,$t1		// accumulate high parts of multiplication
	 mul	$t0,$a2,$a1		// a[2]*a[1]
	 umulh	$t1,$a2,$a1
	adcs	$acc3,$acc3,$t2
	 mul	$t2,$a3,$a1		// a[3]*a[1]
	 umulh	$t3,$a3,$a1
	adc	$acc4,$acc4,xzr		// can't overflow

	mul	$acc5,$a3,$a2		// a[3]*a[2]
	umulh	$acc6,$a3,$a2

	adds	$t1,$t1,$t2		// accumulate high parts of multiplication
	 mul	$acc0,$a0,$a0		// a[0]*a[0]
	adc	$t2,$t3,xzr		// can't overflow

	adds	$acc3,$acc3,$t0		// accumulate low parts of multiplication
	 umulh	$a0,$a0,$a0
	adcs	$acc4,$acc4,$t1
	 mul	$t1,$a1,$a1		// a[1]*a[1]
	adcs	$acc5,$acc5,$t2
	 umulh	$a1,$a1,$a1
	adc	$acc6,$acc6,xzr		// can't overflow

	adds	$acc1,$acc1,$acc1	// acc[1-6]*=2
	 mul	$t2,$a2,$a2		// a[2]*a[2]
	adcs	$acc2,$acc2,$acc2
	 umulh	$a2,$a2,$a2
	adcs	$acc3,$acc3,$acc3
	 mul	$t3,$a3,$a3		// a[3]*a[3]
	adcs	$acc4,$acc4,$acc4
	 umulh	$a3,$a3,$a3
	adcs	$acc5,$acc5,$acc5
	adcs	$acc6,$acc6,$acc6
	adc	$acc7,xzr,xzr

	adds	$acc1,$acc1,$a0		// +a[i]*a[i]
	adcs	$acc2,$acc2,$t1
	adcs	$acc3,$acc3,$a1
	adcs	$acc4,$acc4,$t2
	adcs	$acc5,$acc5,$a2
	 lsl	$t0,$acc0,#32
	adcs	$acc6,$acc6,$t3
	 lsr	$t1,$acc0,#32
	adc	$acc7,$acc7,$a3
___
for($i=0;$i<3;$i++) {			# reductions, see commentary in
					# multiplication for details
$code.=<<___;
	subs	$t2,$acc0,$t0		// "*0xffff0001"
	sbc	$t3,$acc0,$t1
	adds	$acc0,$acc1,$t0		// +=acc[0]<<96 and omit acc[0]
	adcs	$acc1,$acc2,$t1
	 lsl	$t0,$acc0,#32
	adcs	$acc2,$acc3,$t2		// +=acc[0]*0xffff0001
	 lsr	$t1,$acc0,#32
	adc	$acc3,$t3,xzr		// can't overflow
___
}
$code.=<<___;
	subs	$t2,$acc0,$t0		// "*0xffff0001"
	sbc	$t3,$acc0,$t1
	adds	$acc0,$acc1,$t0		// +=acc[0]<<96 and omit acc[0]
	adcs	$acc1,$acc2,$t1
	adcs	$acc2,$acc3,$t2		// +=acc[0]*0xffff0001
	adc	$acc3,$t3,xzr		// can't overflow

	adds	$acc0,$acc0,$acc4	// accumulate upper half
	adcs	$acc1,$acc1,$acc5
	adcs	$acc2,$acc2,$acc6
	adcs	$acc3,$acc3,$acc7
	adc	$acc4,xzr,xzr

	adds	$t0,$acc0,#1		// subs	$t0,$acc0,#-1 // tmp = ret-modulus
	sbcs	$t1,$acc1,$poly1
	sbcs	$t2,$acc2,xzr
	sbcs	$t3,$acc3,$poly3
	sbcs	xzr,$acc4,xzr		// did it borrow?

	csel	$acc0,$acc0,$t0,lo	// ret = borrow ? ret : ret-modulus
	csel	$acc1,$acc1,$t1,lo
	csel	$acc2,$acc2,$t2,lo
	stp	$acc0,$acc1,[$rp]
	csel	$acc3,$acc3,$t3,lo
	stp	$acc2,$acc3,[$rp,#16]

	ret
.size	__ecp_nistz256_sqr_mont,.-__ecp_nistz256_sqr_mont

// Note that __ecp_nistz256_add_to expects both input vectors pre-loaded to
// $a0-$a3 and $t0-$t3. This is done because it's used in multiple
// contexts, e.g. in multiplication by 2 and 3...
.type	__ecp_nistz256_add_to,%function
.align	4
__ecp_nistz256_add_to:
	adds	$acc0,$acc0,$t0		// ret = a+b
	adcs	$acc1,$acc1,$t1
	adcs	$acc2,$acc2,$t2
	adcs	$acc3,$acc3,$t3
	adc	$ap,xzr,xzr		// zap $ap

	adds	$t0,$acc0,#1		// subs	$t0,$a0,#-1 // tmp = ret-modulus
	sbcs	$t1,$acc1,$poly1
	sbcs	$t2,$acc2,xzr
	sbcs	$t3,$acc3,$poly3
	sbcs	xzr,$ap,xzr		// did subtraction borrow?

	csel	$acc0,$acc0,$t0,lo	// ret = borrow ? ret : ret-modulus
	csel	$acc1,$acc1,$t1,lo
	csel	$acc2,$acc2,$t2,lo
	stp	$acc0,$acc1,[$rp]
	csel	$acc3,$acc3,$t3,lo
	stp	$acc2,$acc3,[$rp,#16]

	ret
.size	__ecp_nistz256_add_to,.-__ecp_nistz256_add_to

.type	__ecp_nistz256_sub_from,%function
.align	4
__ecp_nistz256_sub_from:
	ldp	$t0,$t1,[$bp]
	ldp	$t2,$t3,[$bp,#16]
	subs	$acc0,$acc0,$t0		// ret = a-b
	sbcs	$acc1,$acc1,$t1
	sbcs	$acc2,$acc2,$t2
	sbcs	$acc3,$acc3,$t3
	sbc	$ap,xzr,xzr		// zap $ap

	subs	$t0,$acc0,#1		// adds	$t0,$a0,#-1 // tmp = ret+modulus
	adcs	$t1,$acc1,$poly1
	adcs	$t2,$acc2,xzr
	adc	$t3,$acc3,$poly3
	cmp	$ap,xzr			// did subtraction borrow?

	csel	$acc0,$acc0,$t0,eq	// ret = borrow ? ret+modulus : ret
	csel	$acc1,$acc1,$t1,eq
	csel	$acc2,$acc2,$t2,eq
	stp	$acc0,$acc1,[$rp]
	csel	$acc3,$acc3,$t3,eq
	stp	$acc2,$acc3,[$rp,#16]

	ret
.size	__ecp_nistz256_sub_from,.-__ecp_nistz256_sub_from

.type	__ecp_nistz256_sub_morf,%function
.align	4
__ecp_nistz256_sub_morf:
	ldp	$t0,$t1,[$bp]
	ldp	$t2,$t3,[$bp,#16]
	subs	$acc0,$t0,$acc0		// ret = b-a
	sbcs	$acc1,$t1,$acc1
	sbcs	$acc2,$t2,$acc2
	sbcs	$acc3,$t3,$acc3
	sbc	$ap,xzr,xzr		// zap $ap

	subs	$t0,$acc0,#1		// adds	$t0,$a0,#-1 // tmp = ret+modulus
	adcs	$t1,$acc1,$poly1
	adcs	$t2,$acc2,xzr
	adc	$t3,$acc3,$poly3
	cmp	$ap,xzr			// did subtraction borrow?

	csel	$acc0,$acc0,$t0,eq	// ret = borrow ? ret+modulus : ret
	csel	$acc1,$acc1,$t1,eq
	csel	$acc2,$acc2,$t2,eq
	stp	$acc0,$acc1,[$rp]
	csel	$acc3,$acc3,$t3,eq
	stp	$acc2,$acc3,[$rp,#16]

	ret
.size	__ecp_nistz256_sub_morf,.-__ecp_nistz256_sub_morf

.type	__ecp_nistz256_div_by_2,%function
.align	4
__ecp_nistz256_div_by_2:
	subs	$t0,$acc0,#1		// adds	$t0,$a0,#-1 // tmp = a+modulus
	adcs	$t1,$acc1,$poly1
	adcs	$t2,$acc2,xzr
	adcs	$t3,$acc3,$poly3
	adc	$ap,xzr,xzr		// zap $ap
	tst	$acc0,#1		// is a even?

	csel	$acc0,$acc0,$t0,eq	// ret = even ? a : a+modulus
	csel	$acc1,$acc1,$t1,eq
	csel	$acc2,$acc2,$t2,eq
	csel	$acc3,$acc3,$t3,eq
	csel	$ap,xzr,$ap,eq

	lsr	$acc0,$acc0,#1		// ret >>= 1
	orr	$acc0,$acc0,$acc1,lsl#63
	lsr	$acc1,$acc1,#1
	orr	$acc1,$acc1,$acc2,lsl#63
	lsr	$acc2,$acc2,#1
	orr	$acc2,$acc2,$acc3,lsl#63
	lsr	$acc3,$acc3,#1
	stp	$acc0,$acc1,[$rp]
	orr	$acc3,$acc3,$ap,lsl#63
	stp	$acc2,$acc3,[$rp,#16]

	ret
.size	__ecp_nistz256_div_by_2,.-__ecp_nistz256_div_by_2
___
########################################################################
# following subroutines are "literal" implementation of those found in
# ecp_nistz256.c
#
########################################################################
# void ecp_nistz256_point_double(P256_POINT *out,const P256_POINT *inp);
#
{
my ($S,$M,$Zsqr,$tmp0)=map(32*$_,(0..3));
# above map() describes stack layout with 4 temporary
# 256-bit vectors on top.
my ($rp_real,$ap_real) = map("x$_",(21,22));

$code.=<<___;
.globl	ecp_nistz256_point_double
.type	ecp_nistz256_point_double,%function
.align	5
ecp_nistz256_point_double:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-96]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]
	stp	x21,x22,[sp,#32]
	sub	sp,sp,#32*4

.Ldouble_shortcut:
	ldp	$acc0,$acc1,[$ap,#32]
	 mov	$rp_real,$rp
	ldp	$acc2,$acc3,[$ap,#48]
	 mov	$ap_real,$ap
	 adrp	$poly3,:pg_hi21:.Lpoly
	 add	$poly3,$poly3,:lo12:.Lpoly
	 ldr	$poly1,[$poly3,#8]
	mov	$t0,$acc0
	 ldr	$poly3,[$poly3,#24]
	mov	$t1,$acc1
	 ldp	$a0,$a1,[$ap_real,#64]	// forward load for p256_sqr_mont
	mov	$t2,$acc2
	mov	$t3,$acc3
	 ldp	$a2,$a3,[$ap_real,#64+16]
	add	$rp,sp,#$S
	bl	__ecp_nistz256_add_to	// p256_mul_by_2(S, in_y);

	add	$rp,sp,#$Zsqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Zsqr, in_z);

	ldp	$t0,$t1,[$ap_real]
	ldp	$t2,$t3,[$ap_real,#16]
	mov	$a0,$acc0		// put Zsqr aside for p256_sub
	mov	$a1,$acc1
	mov	$a2,$acc2
	mov	$a3,$acc3
	add	$rp,sp,#$M
	bl	__ecp_nistz256_add_to	// p256_add(M, Zsqr, in_x);

	add	$bp,$ap_real,#0
	mov	$acc0,$a0		// restore Zsqr
	mov	$acc1,$a1
	 ldp	$a0,$a1,[sp,#$S]	// forward load for p256_sqr_mont
	mov	$acc2,$a2
	mov	$acc3,$a3
	 ldp	$a2,$a3,[sp,#$S+16]
	add	$rp,sp,#$Zsqr
	bl	__ecp_nistz256_sub_morf	// p256_sub(Zsqr, in_x, Zsqr);

	add	$rp,sp,#$S
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(S, S);

	ldr	$bi,[$ap_real,#32]
	ldp	$a0,$a1,[$ap_real,#64]
	ldp	$a2,$a3,[$ap_real,#64+16]
	add	$bp,$ap_real,#32
	add	$rp,sp,#$tmp0
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(tmp0, in_z, in_y);

	mov	$t0,$acc0
	mov	$t1,$acc1
	 ldp	$a0,$a1,[sp,#$S]	// forward load for p256_sqr_mont
	mov	$t2,$acc2
	mov	$t3,$acc3
	 ldp	$a2,$a3,[sp,#$S+16]
	add	$rp,$rp_real,#64
	bl	__ecp_nistz256_add_to	// p256_mul_by_2(res_z, tmp0);

	add	$rp,sp,#$tmp0
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(tmp0, S);

	 ldr	$bi,[sp,#$Zsqr]		// forward load for p256_mul_mont
	 ldp	$a0,$a1,[sp,#$M]
	 ldp	$a2,$a3,[sp,#$M+16]
	add	$rp,$rp_real,#32
	bl	__ecp_nistz256_div_by_2	// p256_div_by_2(res_y, tmp0);

	add	$bp,sp,#$Zsqr
	add	$rp,sp,#$M
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(M, M, Zsqr);

	mov	$t0,$acc0		// duplicate M
	mov	$t1,$acc1
	mov	$t2,$acc2
	mov	$t3,$acc3
	mov	$a0,$acc0		// put M aside
	mov	$a1,$acc1
	mov	$a2,$acc2
	mov	$a3,$acc3
	add	$rp,sp,#$M
	bl	__ecp_nistz256_add_to
	mov	$t0,$a0			// restore M
	mov	$t1,$a1
	 ldr	$bi,[$ap_real]		// forward load for p256_mul_mont
	mov	$t2,$a2
	 ldp	$a0,$a1,[sp,#$S]
	mov	$t3,$a3
	 ldp	$a2,$a3,[sp,#$S+16]
	bl	__ecp_nistz256_add_to	// p256_mul_by_3(M, M);

	add	$bp,$ap_real,#0
	add	$rp,sp,#$S
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S, S, in_x);

	mov	$t0,$acc0
	mov	$t1,$acc1
	 ldp	$a0,$a1,[sp,#$M]	// forward load for p256_sqr_mont
	mov	$t2,$acc2
	mov	$t3,$acc3
	 ldp	$a2,$a3,[sp,#$M+16]
	add	$rp,sp,#$tmp0
	bl	__ecp_nistz256_add_to	// p256_mul_by_2(tmp0, S);

	add	$rp,$rp_real,#0
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(res_x, M);

	add	$bp,sp,#$tmp0
	bl	__ecp_nistz256_sub_from	// p256_sub(res_x, res_x, tmp0);

	add	$bp,sp,#$S
	add	$rp,sp,#$S
	bl	__ecp_nistz256_sub_morf	// p256_sub(S, S, res_x);

	ldr	$bi,[sp,#$M]
	mov	$a0,$acc0		// copy S
	mov	$a1,$acc1
	mov	$a2,$acc2
	mov	$a3,$acc3
	add	$bp,sp,#$M
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S, S, M);

	add	$bp,$rp_real,#32
	add	$rp,$rp_real,#32
	bl	__ecp_nistz256_sub_from	// p256_sub(res_y, S, res_y);

	add	sp,x29,#0		// destroy frame
	ldp	x19,x20,[x29,#16]
	ldp	x21,x22,[x29,#32]
	ldp	x29,x30,[sp],#96
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_point_double,.-ecp_nistz256_point_double
___
}

########################################################################
# void ecp_nistz256_point_add(P256_POINT *out,const P256_POINT *in1,
#			      const P256_POINT *in2);
{
my ($res_x,$res_y,$res_z,
    $H,$Hsqr,$R,$Rsqr,$Hcub,
    $U1,$U2,$S1,$S2)=map(32*$_,(0..11));
my ($Z1sqr, $Z2sqr) = ($Hsqr, $Rsqr);
# above map() describes stack layout with 12 temporary
# 256-bit vectors on top.
my ($rp_real,$ap_real,$bp_real,$in1infty,$in2infty,$temp0,$temp1,$temp2)=map("x$_",(21..28));

$code.=<<___;
.globl	ecp_nistz256_point_add
.type	ecp_nistz256_point_add,%function
.align	5
ecp_nistz256_point_add:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-96]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]
	stp	x21,x22,[sp,#32]
	stp	x23,x24,[sp,#48]
	stp	x25,x26,[sp,#64]
	stp	x27,x28,[sp,#80]
	sub	sp,sp,#32*12

	ldp	$a0,$a1,[$bp,#64]	// in2_z
	ldp	$a2,$a3,[$bp,#64+16]
	 mov	$rp_real,$rp
	 mov	$ap_real,$ap
	 mov	$bp_real,$bp
	 adrp	$poly3,:pg_hi21:.Lpoly
	 add	$poly3,$poly3,:lo12:.Lpoly
	 ldr	$poly1,[$poly3,#8]
	 ldr	$poly3,[$poly3,#24]
	orr	$t0,$a0,$a1
	orr	$t2,$a2,$a3
	orr	$in2infty,$t0,$t2
	cmp	$in2infty,#0
	csetm	$in2infty,ne		// ~in2infty
	add	$rp,sp,#$Z2sqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Z2sqr, in2_z);

	ldp	$a0,$a1,[$ap_real,#64]	// in1_z
	ldp	$a2,$a3,[$ap_real,#64+16]
	orr	$t0,$a0,$a1
	orr	$t2,$a2,$a3
	orr	$in1infty,$t0,$t2
	cmp	$in1infty,#0
	csetm	$in1infty,ne		// ~in1infty
	add	$rp,sp,#$Z1sqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Z1sqr, in1_z);

	ldr	$bi,[$bp_real,#64]
	ldp	$a0,$a1,[sp,#$Z2sqr]
	ldp	$a2,$a3,[sp,#$Z2sqr+16]
	add	$bp,$bp_real,#64
	add	$rp,sp,#$S1
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S1, Z2sqr, in2_z);

	ldr	$bi,[$ap_real,#64]
	ldp	$a0,$a1,[sp,#$Z1sqr]
	ldp	$a2,$a3,[sp,#$Z1sqr+16]
	add	$bp,$ap_real,#64
	add	$rp,sp,#$S2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S2, Z1sqr, in1_z);

	ldr	$bi,[$ap_real,#32]
	ldp	$a0,$a1,[sp,#$S1]
	ldp	$a2,$a3,[sp,#$S1+16]
	add	$bp,$ap_real,#32
	add	$rp,sp,#$S1
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S1, S1, in1_y);

	ldr	$bi,[$bp_real,#32]
	ldp	$a0,$a1,[sp,#$S2]
	ldp	$a2,$a3,[sp,#$S2+16]
	add	$bp,$bp_real,#32
	add	$rp,sp,#$S2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S2, S2, in2_y);

	add	$bp,sp,#$S1
	 ldr	$bi,[sp,#$Z2sqr]	// forward load for p256_mul_mont
	 ldp	$a0,$a1,[$ap_real]
	 ldp	$a2,$a3,[$ap_real,#16]
	add	$rp,sp,#$R
	bl	__ecp_nistz256_sub_from	// p256_sub(R, S2, S1);

	orr	$acc0,$acc0,$acc1	// see if result is zero
	orr	$acc2,$acc2,$acc3
	orr	$temp0,$acc0,$acc2	// ~is_equal(S1,S2)

	add	$bp,sp,#$Z2sqr
	add	$rp,sp,#$U1
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(U1, in1_x, Z2sqr);

	ldr	$bi,[sp,#$Z1sqr]
	ldp	$a0,$a1,[$bp_real]
	ldp	$a2,$a3,[$bp_real,#16]
	add	$bp,sp,#$Z1sqr
	add	$rp,sp,#$U2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(U2, in2_x, Z1sqr);

	add	$bp,sp,#$U1
	 ldp	$a0,$a1,[sp,#$R]	// forward load for p256_sqr_mont
	 ldp	$a2,$a3,[sp,#$R+16]
	add	$rp,sp,#$H
	bl	__ecp_nistz256_sub_from	// p256_sub(H, U2, U1);

	orr	$acc0,$acc0,$acc1	// see if result is zero
	orr	$acc2,$acc2,$acc3
	orr	$acc0,$acc0,$acc2	// ~is_equal(U1,U2)

	mvn	$temp1,$in1infty	// -1/0 -> 0/-1
	mvn	$temp2,$in2infty	// -1/0 -> 0/-1
	orr	$acc0,$acc0,$temp1
	orr	$acc0,$acc0,$temp2
	orr	$acc0,$acc0,$temp0
	cbnz	$acc0,.Ladd_proceed	// if(~is_equal(U1,U2) | in1infty | in2infty | ~is_equal(S1,S2))

.Ladd_double:
	mov	$ap,$ap_real
	mov	$rp,$rp_real
	ldp	x23,x24,[x29,#48]
	ldp	x25,x26,[x29,#64]
	ldp	x27,x28,[x29,#80]
	add	sp,sp,#256	// #256 is from #32*(12-4). difference in stack frames
	b	.Ldouble_shortcut

.align	4
.Ladd_proceed:
	add	$rp,sp,#$Rsqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Rsqr, R);

	ldr	$bi,[$ap_real,#64]
	ldp	$a0,$a1,[sp,#$H]
	ldp	$a2,$a3,[sp,#$H+16]
	add	$bp,$ap_real,#64
	add	$rp,sp,#$res_z
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(res_z, H, in1_z);

	ldp	$a0,$a1,[sp,#$H]
	ldp	$a2,$a3,[sp,#$H+16]
	add	$rp,sp,#$Hsqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Hsqr, H);

	ldr	$bi,[$bp_real,#64]
	ldp	$a0,$a1,[sp,#$res_z]
	ldp	$a2,$a3,[sp,#$res_z+16]
	add	$bp,$bp_real,#64
	add	$rp,sp,#$res_z
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(res_z, res_z, in2_z);

	ldr	$bi,[sp,#$H]
	ldp	$a0,$a1,[sp,#$Hsqr]
	ldp	$a2,$a3,[sp,#$Hsqr+16]
	add	$bp,sp,#$H
	add	$rp,sp,#$Hcub
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(Hcub, Hsqr, H);

	ldr	$bi,[sp,#$Hsqr]
	ldp	$a0,$a1,[sp,#$U1]
	ldp	$a2,$a3,[sp,#$U1+16]
	add	$bp,sp,#$Hsqr
	add	$rp,sp,#$U2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(U2, U1, Hsqr);

	mov	$t0,$acc0
	mov	$t1,$acc1
	mov	$t2,$acc2
	mov	$t3,$acc3
	add	$rp,sp,#$Hsqr
	bl	__ecp_nistz256_add_to	// p256_mul_by_2(Hsqr, U2);

	add	$bp,sp,#$Rsqr
	add	$rp,sp,#$res_x
	bl	__ecp_nistz256_sub_morf	// p256_sub(res_x, Rsqr, Hsqr);

	add	$bp,sp,#$Hcub
	bl	__ecp_nistz256_sub_from	//  p256_sub(res_x, res_x, Hcub);

	add	$bp,sp,#$U2
	 ldr	$bi,[sp,#$Hcub]		// forward load for p256_mul_mont
	 ldp	$a0,$a1,[sp,#$S1]
	 ldp	$a2,$a3,[sp,#$S1+16]
	add	$rp,sp,#$res_y
	bl	__ecp_nistz256_sub_morf	// p256_sub(res_y, U2, res_x);

	add	$bp,sp,#$Hcub
	add	$rp,sp,#$S2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S2, S1, Hcub);

	ldr	$bi,[sp,#$R]
	ldp	$a0,$a1,[sp,#$res_y]
	ldp	$a2,$a3,[sp,#$res_y+16]
	add	$bp,sp,#$R
	add	$rp,sp,#$res_y
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(res_y, res_y, R);

	add	$bp,sp,#$S2
	bl	__ecp_nistz256_sub_from	// p256_sub(res_y, res_y, S2);

	ldp	$a0,$a1,[sp,#$res_x]		// res
	ldp	$a2,$a3,[sp,#$res_x+16]
	ldp	$t0,$t1,[$bp_real]		// in2
	ldp	$t2,$t3,[$bp_real,#16]
___
for($i=0;$i<64;$i+=32) {		# conditional moves
$code.=<<___;
	ldp	$acc0,$acc1,[$ap_real,#$i]	// in1
	cmp	$in1infty,#0			// ~$in1intfy, remember?
	ldp	$acc2,$acc3,[$ap_real,#$i+16]
	csel	$t0,$a0,$t0,ne
	csel	$t1,$a1,$t1,ne
	ldp	$a0,$a1,[sp,#$res_x+$i+32]	// res
	csel	$t2,$a2,$t2,ne
	csel	$t3,$a3,$t3,ne
	cmp	$in2infty,#0			// ~$in2intfy, remember?
	ldp	$a2,$a3,[sp,#$res_x+$i+48]
	csel	$acc0,$t0,$acc0,ne
	csel	$acc1,$t1,$acc1,ne
	ldp	$t0,$t1,[$bp_real,#$i+32]	// in2
	csel	$acc2,$t2,$acc2,ne
	csel	$acc3,$t3,$acc3,ne
	ldp	$t2,$t3,[$bp_real,#$i+48]
	stp	$acc0,$acc1,[$rp_real,#$i]
	stp	$acc2,$acc3,[$rp_real,#$i+16]
___
}
$code.=<<___;
	ldp	$acc0,$acc1,[$ap_real,#$i]	// in1
	cmp	$in1infty,#0			// ~$in1intfy, remember?
	ldp	$acc2,$acc3,[$ap_real,#$i+16]
	csel	$t0,$a0,$t0,ne
	csel	$t1,$a1,$t1,ne
	csel	$t2,$a2,$t2,ne
	csel	$t3,$a3,$t3,ne
	cmp	$in2infty,#0			// ~$in2intfy, remember?
	csel	$acc0,$t0,$acc0,ne
	csel	$acc1,$t1,$acc1,ne
	csel	$acc2,$t2,$acc2,ne
	csel	$acc3,$t3,$acc3,ne
	stp	$acc0,$acc1,[$rp_real,#$i]
	stp	$acc2,$acc3,[$rp_real,#$i+16]

.Ladd_done:
	add	sp,x29,#0		// destroy frame
	ldp	x19,x20,[x29,#16]
	ldp	x21,x22,[x29,#32]
	ldp	x23,x24,[x29,#48]
	ldp	x25,x26,[x29,#64]
	ldp	x27,x28,[x29,#80]
	ldp	x29,x30,[sp],#96
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_point_add,.-ecp_nistz256_point_add
___
}

########################################################################
# void ecp_nistz256_point_add_affine(P256_POINT *out,const P256_POINT *in1,
#				     const P256_POINT_AFFINE *in2);
{
my ($res_x,$res_y,$res_z,
    $U2,$S2,$H,$R,$Hsqr,$Hcub,$Rsqr)=map(32*$_,(0..9));
my $Z1sqr = $S2;
# above map() describes stack layout with 10 temporary
# 256-bit vectors on top.
my ($rp_real,$ap_real,$bp_real,$in1infty,$in2infty,$temp)=map("x$_",(21..26));

$code.=<<___;
.globl	ecp_nistz256_point_add_affine
.type	ecp_nistz256_point_add_affine,%function
.align	5
ecp_nistz256_point_add_affine:
	AARCH64_SIGN_LINK_REGISTER
	stp	x29,x30,[sp,#-80]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]
	stp	x21,x22,[sp,#32]
	stp	x23,x24,[sp,#48]
	stp	x25,x26,[sp,#64]
	sub	sp,sp,#32*10

	mov	$rp_real,$rp
	mov	$ap_real,$ap
	mov	$bp_real,$bp
	adrp	$poly3,:pg_hi21:.Lpoly
	add	$poly3,$poly3,:lo12:.Lpoly
	ldr	$poly1,[$poly3,#8]
	ldr	$poly3,[$poly3,#24]

	ldp	$a0,$a1,[$ap,#64]	// in1_z
	ldp	$a2,$a3,[$ap,#64+16]
	orr	$t0,$a0,$a1
	orr	$t2,$a2,$a3
	orr	$in1infty,$t0,$t2
	cmp	$in1infty,#0
	csetm	$in1infty,ne		// ~in1infty

	ldp	$acc0,$acc1,[$bp]	// in2_x
	ldp	$acc2,$acc3,[$bp,#16]
	ldp	$t0,$t1,[$bp,#32]	// in2_y
	ldp	$t2,$t3,[$bp,#48]
	orr	$acc0,$acc0,$acc1
	orr	$acc2,$acc2,$acc3
	orr	$t0,$t0,$t1
	orr	$t2,$t2,$t3
	orr	$acc0,$acc0,$acc2
	orr	$t0,$t0,$t2
	orr	$in2infty,$acc0,$t0
	cmp	$in2infty,#0
	csetm	$in2infty,ne		// ~in2infty

	add	$rp,sp,#$Z1sqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Z1sqr, in1_z);

	mov	$a0,$acc0
	mov	$a1,$acc1
	mov	$a2,$acc2
	mov	$a3,$acc3
	ldr	$bi,[$bp_real]
	add	$bp,$bp_real,#0
	add	$rp,sp,#$U2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(U2, Z1sqr, in2_x);

	add	$bp,$ap_real,#0
	 ldr	$bi,[$ap_real,#64]	// forward load for p256_mul_mont
	 ldp	$a0,$a1,[sp,#$Z1sqr]
	 ldp	$a2,$a3,[sp,#$Z1sqr+16]
	add	$rp,sp,#$H
	bl	__ecp_nistz256_sub_from	// p256_sub(H, U2, in1_x);

	add	$bp,$ap_real,#64
	add	$rp,sp,#$S2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S2, Z1sqr, in1_z);

	ldr	$bi,[$ap_real,#64]
	ldp	$a0,$a1,[sp,#$H]
	ldp	$a2,$a3,[sp,#$H+16]
	add	$bp,$ap_real,#64
	add	$rp,sp,#$res_z
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(res_z, H, in1_z);

	ldr	$bi,[$bp_real,#32]
	ldp	$a0,$a1,[sp,#$S2]
	ldp	$a2,$a3,[sp,#$S2+16]
	add	$bp,$bp_real,#32
	add	$rp,sp,#$S2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S2, S2, in2_y);

	add	$bp,$ap_real,#32
	 ldp	$a0,$a1,[sp,#$H]	// forward load for p256_sqr_mont
	 ldp	$a2,$a3,[sp,#$H+16]
	add	$rp,sp,#$R
	bl	__ecp_nistz256_sub_from	// p256_sub(R, S2, in1_y);

	add	$rp,sp,#$Hsqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Hsqr, H);

	ldp	$a0,$a1,[sp,#$R]
	ldp	$a2,$a3,[sp,#$R+16]
	add	$rp,sp,#$Rsqr
	bl	__ecp_nistz256_sqr_mont	// p256_sqr_mont(Rsqr, R);

	ldr	$bi,[sp,#$H]
	ldp	$a0,$a1,[sp,#$Hsqr]
	ldp	$a2,$a3,[sp,#$Hsqr+16]
	add	$bp,sp,#$H
	add	$rp,sp,#$Hcub
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(Hcub, Hsqr, H);

	ldr	$bi,[$ap_real]
	ldp	$a0,$a1,[sp,#$Hsqr]
	ldp	$a2,$a3,[sp,#$Hsqr+16]
	add	$bp,$ap_real,#0
	add	$rp,sp,#$U2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(U2, in1_x, Hsqr);

	mov	$t0,$acc0
	mov	$t1,$acc1
	mov	$t2,$acc2
	mov	$t3,$acc3
	add	$rp,sp,#$Hsqr
	bl	__ecp_nistz256_add_to	// p256_mul_by_2(Hsqr, U2);

	add	$bp,sp,#$Rsqr
	add	$rp,sp,#$res_x
	bl	__ecp_nistz256_sub_morf	// p256_sub(res_x, Rsqr, Hsqr);

	add	$bp,sp,#$Hcub
	bl	__ecp_nistz256_sub_from	//  p256_sub(res_x, res_x, Hcub);

	add	$bp,sp,#$U2
	 ldr	$bi,[$ap_real,#32]	// forward load for p256_mul_mont
	 ldp	$a0,$a1,[sp,#$Hcub]
	 ldp	$a2,$a3,[sp,#$Hcub+16]
	add	$rp,sp,#$res_y
	bl	__ecp_nistz256_sub_morf	// p256_sub(res_y, U2, res_x);

	add	$bp,$ap_real,#32
	add	$rp,sp,#$S2
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(S2, in1_y, Hcub);

	ldr	$bi,[sp,#$R]
	ldp	$a0,$a1,[sp,#$res_y]
	ldp	$a2,$a3,[sp,#$res_y+16]
	add	$bp,sp,#$R
	add	$rp,sp,#$res_y
	bl	__ecp_nistz256_mul_mont	// p256_mul_mont(res_y, res_y, R);

	add	$bp,sp,#$S2
	bl	__ecp_nistz256_sub_from	// p256_sub(res_y, res_y, S2);

	ldp	$a0,$a1,[sp,#$res_x]		// res
	ldp	$a2,$a3,[sp,#$res_x+16]
	ldp	$t0,$t1,[$bp_real]		// in2
	ldp	$t2,$t3,[$bp_real,#16]
___
for($i=0;$i<64;$i+=32) {		# conditional moves
$code.=<<___;
	ldp	$acc0,$acc1,[$ap_real,#$i]	// in1
	cmp	$in1infty,#0			// ~$in1intfy, remember?
	ldp	$acc2,$acc3,[$ap_real,#$i+16]
	csel	$t0,$a0,$t0,ne
	csel	$t1,$a1,$t1,ne
	ldp	$a0,$a1,[sp,#$res_x+$i+32]	// res
	csel	$t2,$a2,$t2,ne
	csel	$t3,$a3,$t3,ne
	cmp	$in2infty,#0			// ~$in2intfy, remember?
	ldp	$a2,$a3,[sp,#$res_x+$i+48]
	csel	$acc0,$t0,$acc0,ne
	csel	$acc1,$t1,$acc1,ne
	ldp	$t0,$t1,[$bp_real,#$i+32]	// in2
	csel	$acc2,$t2,$acc2,ne
	csel	$acc3,$t3,$acc3,ne
	ldp	$t2,$t3,[$bp_real,#$i+48]
	stp	$acc0,$acc1,[$rp_real,#$i]
	stp	$acc2,$acc3,[$rp_real,#$i+16]
___
$code.=<<___	if ($i == 0);
	adrp	$bp_real,:pg_hi21:.Lone_mont-64
	add	$bp_real,$bp_real,:lo12:.Lone_mont-64
___
}
$code.=<<___;
	ldp	$acc0,$acc1,[$ap_real,#$i]	// in1
	cmp	$in1infty,#0			// ~$in1intfy, remember?
	ldp	$acc2,$acc3,[$ap_real,#$i+16]
	csel	$t0,$a0,$t0,ne
	csel	$t1,$a1,$t1,ne
	csel	$t2,$a2,$t2,ne
	csel	$t3,$a3,$t3,ne
	cmp	$in2infty,#0			// ~$in2intfy, remember?
	csel	$acc0,$t0,$acc0,ne
	csel	$acc1,$t1,$acc1,ne
	csel	$acc2,$t2,$acc2,ne
	csel	$acc3,$t3,$acc3,ne
	stp	$acc0,$acc1,[$rp_real,#$i]
	stp	$acc2,$acc3,[$rp_real,#$i+16]

	add	sp,x29,#0		// destroy frame
	ldp	x19,x20,[x29,#16]
	ldp	x21,x22,[x29,#32]
	ldp	x23,x24,[x29,#48]
	ldp	x25,x26,[x29,#64]
	ldp	x29,x30,[sp],#80
	AARCH64_VALIDATE_LINK_REGISTER
	ret
.size	ecp_nistz256_point_add_affine,.-ecp_nistz256_point_add_affine
___
}
if (1) {
my ($ord0,$ord1) = ($poly1,$poly3);
my ($ord2,$ord3,$ordk,$t4) = map("x$_",(21..24));
my $acc7 = $bi;

$code.=<<___;
////////////////////////////////////////////////////////////////////////
// void ecp_nistz256_ord_mul_mont(uint64_t res[4], uint64_t a[4],
//                                uint64_t b[4]);
.globl	ecp_nistz256_ord_mul_mont
.type	ecp_nistz256_ord_mul_mont,%function
.align	4
ecp_nistz256_ord_mul_mont:
	AARCH64_VALID_CALL_TARGET
	// Armv8.3-A PAuth: even though x30 is pushed to stack it is not popped later.
	stp	x29,x30,[sp,#-64]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]
	stp	x21,x22,[sp,#32]
	stp	x23,x24,[sp,#48]

	adrp	$ordk,:pg_hi21:.Lord
	add	$ordk,$ordk,:lo12:.Lord
	ldr	$bi,[$bp]		// bp[0]
	ldp	$a0,$a1,[$ap]
	ldp	$a2,$a3,[$ap,#16]

	ldp	$ord0,$ord1,[$ordk,#0]
	ldp	$ord2,$ord3,[$ordk,#16]
	ldr	$ordk,[$ordk,#32]

	mul	$acc0,$a0,$bi		// a[0]*b[0]
	umulh	$t0,$a0,$bi

	mul	$acc1,$a1,$bi		// a[1]*b[0]
	umulh	$t1,$a1,$bi

	mul	$acc2,$a2,$bi		// a[2]*b[0]
	umulh	$t2,$a2,$bi

	mul	$acc3,$a3,$bi		// a[3]*b[0]
	umulh	$acc4,$a3,$bi

	mul	$t4,$acc0,$ordk

	adds	$acc1,$acc1,$t0		// accumulate high parts of multiplication
	adcs	$acc2,$acc2,$t1
	adcs	$acc3,$acc3,$t2
	adc	$acc4,$acc4,xzr
	mov	$acc5,xzr
___
for ($i=1;$i<4;$i++) {
	################################################################
	#            ffff0000.ffffffff.yyyyyyyy.zzzzzzzz
	# *                                     abcdefgh
	# + xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx
	#
	# Now observing that ff..ff*x = (2^n-1)*x = 2^n*x-x, we
	# rewrite above as:
	#
	#   xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx
	# - 0000abcd.efgh0000.abcdefgh.00000000.00000000
	# + abcdefgh.abcdefgh.yzayzbyz.cyzdyzey.zfyzgyzh
$code.=<<___;
	ldr	$bi,[$bp,#8*$i]		// b[i]

	lsl	$t0,$t4,#32
	subs	$acc2,$acc2,$t4
	lsr	$t1,$t4,#32
	sbcs	$acc3,$acc3,$t0
	sbcs	$acc4,$acc4,$t1
	sbc	$acc5,$acc5,xzr

	subs	xzr,$acc0,#1
	umulh	$t1,$ord0,$t4
	mul	$t2,$ord1,$t4
	umulh	$t3,$ord1,$t4

	adcs	$t2,$t2,$t1
	 mul	$t0,$a0,$bi
	adc	$t3,$t3,xzr
	 mul	$t1,$a1,$bi

	adds	$acc0,$acc1,$t2
	 mul	$t2,$a2,$bi
	adcs	$acc1,$acc2,$t3
	 mul	$t3,$a3,$bi
	adcs	$acc2,$acc3,$t4
	adcs	$acc3,$acc4,$t4
	adc	$acc4,$acc5,xzr

	adds	$acc0,$acc0,$t0		// accumulate low parts
	umulh	$t0,$a0,$bi
	adcs	$acc1,$acc1,$t1
	umulh	$t1,$a1,$bi
	adcs	$acc2,$acc2,$t2
	umulh	$t2,$a2,$bi
	adcs	$acc3,$acc3,$t3
	umulh	$t3,$a3,$bi
	adc	$acc4,$acc4,xzr
	mul	$t4,$acc0,$ordk
	adds	$acc1,$acc1,$t0		// accumulate high parts
	adcs	$acc2,$acc2,$t1
	adcs	$acc3,$acc3,$t2
	adcs	$acc4,$acc4,$t3
	adc	$acc5,xzr,xzr
___
}
$code.=<<___;
	lsl	$t0,$t4,#32		// last reduction
	subs	$acc2,$acc2,$t4
	lsr	$t1,$t4,#32
	sbcs	$acc3,$acc3,$t0
	sbcs	$acc4,$acc4,$t1
	sbc	$acc5,$acc5,xzr

	subs	xzr,$acc0,#1
	umulh	$t1,$ord0,$t4
	mul	$t2,$ord1,$t4
	umulh	$t3,$ord1,$t4

	adcs	$t2,$t2,$t1
	adc	$t3,$t3,xzr

	adds	$acc0,$acc1,$t2
	adcs	$acc1,$acc2,$t3
	adcs	$acc2,$acc3,$t4
	adcs	$acc3,$acc4,$t4
	adc	$acc4,$acc5,xzr

	subs	$t0,$acc0,$ord0		// ret -= modulus
	sbcs	$t1,$acc1,$ord1
	sbcs	$t2,$acc2,$ord2
	sbcs	$t3,$acc3,$ord3
	sbcs	xzr,$acc4,xzr

	csel	$acc0,$acc0,$t0,lo	// ret = borrow ? ret : ret-modulus
	csel	$acc1,$acc1,$t1,lo
	csel	$acc2,$acc2,$t2,lo
	stp	$acc0,$acc1,[$rp]
	csel	$acc3,$acc3,$t3,lo
	stp	$acc2,$acc3,[$rp,#16]

	ldp	x19,x20,[sp,#16]
	ldp	x21,x22,[sp,#32]
	ldp	x23,x24,[sp,#48]
	ldr	x29,[sp],#64
	ret
.size	ecp_nistz256_ord_mul_mont,.-ecp_nistz256_ord_mul_mont

////////////////////////////////////////////////////////////////////////
// void ecp_nistz256_ord_sqr_mont(uint64_t res[4], uint64_t a[4],
//                                uint64_t rep);
.globl	ecp_nistz256_ord_sqr_mont
.type	ecp_nistz256_ord_sqr_mont,%function
.align	4
ecp_nistz256_ord_sqr_mont:
	AARCH64_VALID_CALL_TARGET
	// Armv8.3-A PAuth: even though x30 is pushed to stack it is not popped later.
	stp	x29,x30,[sp,#-64]!
	add	x29,sp,#0
	stp	x19,x20,[sp,#16]
	stp	x21,x22,[sp,#32]
	stp	x23,x24,[sp,#48]

	adrp	$ordk,:pg_hi21:.Lord
	add	$ordk,$ordk,:lo12:.Lord
	ldp	$a0,$a1,[$ap]
	ldp	$a2,$a3,[$ap,#16]

	ldp	$ord0,$ord1,[$ordk,#0]
	ldp	$ord2,$ord3,[$ordk,#16]
	ldr	$ordk,[$ordk,#32]
	b	.Loop_ord_sqr

.align	4
.Loop_ord_sqr:
	sub	$bp,$bp,#1
	////////////////////////////////////////////////////////////////
	//  |  |  |  |  |  |a1*a0|  |
	//  |  |  |  |  |a2*a0|  |  |
	//  |  |a3*a2|a3*a0|  |  |  |
	//  |  |  |  |a2*a1|  |  |  |
	//  |  |  |a3*a1|  |  |  |  |
	// *|  |  |  |  |  |  |  | 2|
	// +|a3*a3|a2*a2|a1*a1|a0*a0|
	//  |--+--+--+--+--+--+--+--|
	//  |A7|A6|A5|A4|A3|A2|A1|A0|, where Ax is $accx, i.e. follow $accx
	//
	//  "can't overflow" below mark carrying into high part of
	//  multiplication result, which can't overflow, because it
	//  can never be all ones.

	mul	$acc1,$a1,$a0		// a[1]*a[0]
	umulh	$t1,$a1,$a0
	mul	$acc2,$a2,$a0		// a[2]*a[0]
	umulh	$t2,$a2,$a0
	mul	$acc3,$a3,$a0		// a[3]*a[0]
	umulh	$acc4,$a3,$a0

	adds	$acc2,$acc2,$t1		// accumulate high parts of multiplication
	 mul	$t0,$a2,$a1		// a[2]*a[1]
	 umulh	$t1,$a2,$a1
	adcs	$acc3,$acc3,$t2
	 mul	$t2,$a3,$a1		// a[3]*a[1]
	 umulh	$t3,$a3,$a1
	adc	$acc4,$acc4,xzr		// can't overflow

	mul	$acc5,$a3,$a2		// a[3]*a[2]
	umulh	$acc6,$a3,$a2

	adds	$t1,$t1,$t2		// accumulate high parts of multiplication
	 mul	$acc0,$a0,$a0		// a[0]*a[0]
	adc	$t2,$t3,xzr		// can't overflow

	adds	$acc3,$acc3,$t0		// accumulate low parts of multiplication
	 umulh	$a0,$a0,$a0
	adcs	$acc4,$acc4,$t1
	 mul	$t1,$a1,$a1		// a[1]*a[1]
	adcs	$acc5,$acc5,$t2
	 umulh	$a1,$a1,$a1
	adc	$acc6,$acc6,xzr		// can't overflow

	adds	$acc1,$acc1,$acc1	// acc[1-6]*=2
	 mul	$t2,$a2,$a2		// a[2]*a[2]
	adcs	$acc2,$acc2,$acc2
	 umulh	$a2,$a2,$a2
	adcs	$acc3,$acc3,$acc3
	 mul	$t3,$a3,$a3		// a[3]*a[3]
	adcs	$acc4,$acc4,$acc4
	 umulh	$a3,$a3,$a3
	adcs	$acc5,$acc5,$acc5
	adcs	$acc6,$acc6,$acc6
	adc	$acc7,xzr,xzr

	adds	$acc1,$acc1,$a0		// +a[i]*a[i]
	 mul	$t4,$acc0,$ordk
	adcs	$acc2,$acc2,$t1
	adcs	$acc3,$acc3,$a1
	adcs	$acc4,$acc4,$t2
	adcs	$acc5,$acc5,$a2
	adcs	$acc6,$acc6,$t3
	adc	$acc7,$acc7,$a3
___
for($i=0; $i<4; $i++) {			# reductions
$code.=<<___;
	subs	xzr,$acc0,#1
	umulh	$t1,$ord0,$t4
	mul	$t2,$ord1,$t4
	umulh	$t3,$ord1,$t4

	adcs	$t2,$t2,$t1
	adc	$t3,$t3,xzr

	adds	$acc0,$acc1,$t2
	adcs	$acc1,$acc2,$t3
	adcs	$acc2,$acc3,$t4
	adc	$acc3,xzr,$t4		// can't overflow
___
$code.=<<___	if ($i<3);
	mul	$t3,$acc0,$ordk
___
$code.=<<___;
	lsl	$t0,$t4,#32
	subs	$acc1,$acc1,$t4
	lsr	$t1,$t4,#32
	sbcs	$acc2,$acc2,$t0
	sbc	$acc3,$acc3,$t1		// can't borrow
___
	($t3,$t4) = ($t4,$t3);
}
$code.=<<___;
	adds	$acc0,$acc0,$acc4	// accumulate upper half
	adcs	$acc1,$acc1,$acc5
	adcs	$acc2,$acc2,$acc6
	adcs	$acc3,$acc3,$acc7
	adc	$acc4,xzr,xzr

	subs	$t0,$acc0,$ord0		// ret -= modulus
	sbcs	$t1,$acc1,$ord1
	sbcs	$t2,$acc2,$ord2
	sbcs	$t3,$acc3,$ord3
	sbcs	xzr,$acc4,xzr

	csel	$a0,$acc0,$t0,lo	// ret = borrow ? ret : ret-modulus
	csel	$a1,$acc1,$t1,lo
	csel	$a2,$acc2,$t2,lo
	csel	$a3,$acc3,$t3,lo

	cbnz	$bp,.Loop_ord_sqr

	stp	$a0,$a1,[$rp]
	stp	$a2,$a3,[$rp,#16]

	ldp	x19,x20,[sp,#16]
	ldp	x21,x22,[sp,#32]
	ldp	x23,x24,[sp,#48]
	ldr	x29,[sp],#64
	ret
.size	ecp_nistz256_ord_sqr_mont,.-ecp_nistz256_ord_sqr_mont
___
}	}

########################################################################
# select subroutines
# These select functions are similar to those in p256-x86_64-asm.pl
# They load all points in the lookup table
# keeping in the output only the one corresponding to the input index.
{
my ($val,$in_t)=map("x$_",(0..1));
my ($index)=("w2");
my ($Idx_ctr,$Val_in, $Mask_64)=("w9", "x10", "x11");
my ($Mask)=("v3");
my ($Ra,$Rb,$Rc,$Rd,$Re,$Rf)=map("v$_",(16..21));
my ($T0a,$T0b,$T0c,$T0d,$T0e,$T0f)=map("v$_",(22..27));
$code.=<<___;
////////////////////////////////////////////////////////////////////////
// void ecp_nistz256_select_w5(uint64_t *val, uint64_t *in_t, int index);
.globl	ecp_nistz256_select_w5
.type	ecp_nistz256_select_w5,%function
.align	4
ecp_nistz256_select_w5:
    AARCH64_VALID_CALL_TARGET

    // $Val_in := $val
    // $Idx_ctr := 0; loop counter and incremented internal index
    mov     $Val_in, $val
    mov     $Idx_ctr, #0

    // [$Ra-$Rf] := 0
    movi    $Ra.16b, #0
    movi    $Rb.16b, #0
    movi    $Rc.16b, #0
    movi    $Rd.16b, #0
    movi    $Re.16b, #0
    movi    $Rf.16b, #0

.Lselect_w5_loop:
    // Loop 16 times.

    // Increment index (loop counter); tested at the end of the loop
    add $Idx_ctr, $Idx_ctr, #1

    // [$T0a-$T0f] := Load a (3*256-bit = 6*128-bit) table entry starting at $in_t
    //  and advance $in_t to point to the next entry
    ld1     {$T0a.2d, $T0b.2d, $T0c.2d, $T0d.2d}, [$in_t],#64

    // $Mask_64 := ($Idx_ctr == $index)? All 1s : All 0s
    cmp     $Idx_ctr, $index
    csetm   $Mask_64, eq

    // continue loading ...
    ld1     {$T0e.2d, $T0f.2d}, [$in_t],#32

    // duplicate mask_64 into Mask (all 0s or all 1s)
    dup     $Mask.2d, $Mask_64

    // [$Ra-$Rd] := (Mask == all 1s)? [$T0a-$T0d] : [$Ra-$Rd]
    // i.e., values in output registers will remain the same if $Idx_ctr != $index
    bit     $Ra.16b, $T0a.16b, $Mask.16b
    bit     $Rb.16b, $T0b.16b, $Mask.16b

    bit     $Rc.16b, $T0c.16b, $Mask.16b
    bit     $Rd.16b, $T0d.16b, $Mask.16b

    bit     $Re.16b, $T0e.16b, $Mask.16b
    bit     $Rf.16b, $T0f.16b, $Mask.16b

    // If bit #4 is not 0 (i.e. idx_ctr < 16) loop back
    tbz    $Idx_ctr, #4, .Lselect_w5_loop

    // Write [$Ra-$Rf] to memory at the output pointer
    st1     {$Ra.2d, $Rb.2d, $Rc.2d, $Rd.2d}, [$Val_in],#64
    st1     {$Re.2d, $Rf.2d}, [$Val_in]

	ret
.size	ecp_nistz256_select_w5,.-ecp_nistz256_select_w5


////////////////////////////////////////////////////////////////////////
// void ecp_nistz256_select_w7(uint64_t *val, uint64_t *in_t, int index);
.globl	ecp_nistz256_select_w7
.type	ecp_nistz256_select_w7,%function
.align	4
ecp_nistz256_select_w7:
    AARCH64_VALID_CALL_TARGET

    // $Idx_ctr := 0; loop counter and incremented internal index
    mov     $Idx_ctr, #0

    // [$Ra-$Rf] := 0
    movi    $Ra.16b, #0
    movi    $Rb.16b, #0
    movi    $Rc.16b, #0
    movi    $Rd.16b, #0

.Lselect_w7_loop:
    // Loop 64 times.

    // Increment index (loop counter); tested at the end of the loop
    add $Idx_ctr, $Idx_ctr, #1

    // [$T0a-$T0d] := Load a (2*256-bit = 4*128-bit) table entry starting at $in_t
    //  and advance $in_t to point to the next entry
    ld1     {$T0a.2d, $T0b.2d, $T0c.2d, $T0d.2d}, [$in_t],#64

    // $Mask_64 := ($Idx_ctr == $index)? All 1s : All 0s
    cmp     $Idx_ctr, $index
    csetm   $Mask_64, eq

    // duplicate mask_64 into Mask (all 0s or all 1s)
    dup     $Mask.2d, $Mask_64

    // [$Ra-$Rd] := (Mask == all 1s)? [$T0a-$T0d] : [$Ra-$Rd]
    // i.e., values in output registers will remain the same if $Idx_ctr != $index
    bit     $Ra.16b, $T0a.16b, $Mask.16b
    bit     $Rb.16b, $T0b.16b, $Mask.16b

    bit     $Rc.16b, $T0c.16b, $Mask.16b
    bit     $Rd.16b, $T0d.16b, $Mask.16b

    // If bit #6 is not 0 (i.e. idx_ctr < 64) loop back
    tbz    $Idx_ctr, #6, .Lselect_w7_loop

    // Write [$Ra-$Rd] to memory at the output pointer
    st1     {$Ra.2d, $Rb.2d, $Rc.2d, $Rd.2d}, [$val]

	ret
.size	ecp_nistz256_select_w7,.-ecp_nistz256_select_w7
___
}

foreach (split("\n",$code)) {
	s/\`([^\`]*)\`/eval $1/ge;

	print $_,"\n";
}
close STDOUT or die "error closing STDOUT: $!";	# enforce flush