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// Copyright ©2016 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
// Some of the loop unrolling code is copied from:
// http://golang.org/src/math/big/arith_amd64.s
// which is distributed under these terms:
//
// Copyright (c) 2012 The Go Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// +build !noasm,!gccgo,!safe
#include "textflag.h"
#define MOVDDUP_ALPHA LONG $0x44120FF2; WORD $0x2024 // @ MOVDDUP 32(SP), X0 /*XMM0, 32[RSP]*/
#define X_PTR SI
#define DST_PTR DI
#define IDX AX
#define LEN CX
#define TAIL BX
#define ALPHA X0
#define ALPHA_2 X1
// func ScalUnitaryTo(dst []float64, alpha float64, x []float64)
// This function assumes len(dst) >= len(x).
TEXT ·ScalUnitaryTo(SB), NOSPLIT, $0
MOVQ x_base+32(FP), X_PTR // X_PTR = &x
MOVQ dst_base+0(FP), DST_PTR // DST_PTR = &dst
MOVDDUP_ALPHA // ALPHA = { alpha, alpha }
MOVQ x_len+40(FP), LEN // LEN = len(x)
CMPQ LEN, $0
JE end // if LEN == 0 { return }
XORQ IDX, IDX // IDX = 0
MOVQ LEN, TAIL
ANDQ $7, TAIL // TAIL = LEN % 8
SHRQ $3, LEN // LEN = floor( LEN / 8 )
JZ tail_start // if LEN == 0 { goto tail_start }
MOVUPS ALPHA, ALPHA_2 // ALPHA_2 = ALPHA for pipelining
loop: // do { // dst[i] = alpha * x[i] unrolled 8x.
MOVUPS (X_PTR)(IDX*8), X2 // X_i = x[i]
MOVUPS 16(X_PTR)(IDX*8), X3
MOVUPS 32(X_PTR)(IDX*8), X4
MOVUPS 48(X_PTR)(IDX*8), X5
MULPD ALPHA, X2 // X_i *= ALPHA
MULPD ALPHA_2, X3
MULPD ALPHA, X4
MULPD ALPHA_2, X5
MOVUPS X2, (DST_PTR)(IDX*8) // dst[i] = X_i
MOVUPS X3, 16(DST_PTR)(IDX*8)
MOVUPS X4, 32(DST_PTR)(IDX*8)
MOVUPS X5, 48(DST_PTR)(IDX*8)
ADDQ $8, IDX // i += 8
DECQ LEN
JNZ loop // while --LEN > 0
CMPQ TAIL, $0
JE end // if TAIL == 0 { return }
tail_start: // Reset loop counters
MOVQ TAIL, LEN // Loop counter: LEN = TAIL
SHRQ $1, LEN // LEN = floor( TAIL / 2 )
JZ tail_one // if LEN == 0 { goto tail_one }
tail_two: // do {
MOVUPS (X_PTR)(IDX*8), X2 // X_i = x[i]
MULPD ALPHA, X2 // X_i *= ALPHA
MOVUPS X2, (DST_PTR)(IDX*8) // dst[i] = X_i
ADDQ $2, IDX // i += 2
DECQ LEN
JNZ tail_two // while --LEN > 0
ANDQ $1, TAIL
JZ end // if TAIL == 0 { return }
tail_one:
MOVSD (X_PTR)(IDX*8), X2 // X_i = x[i]
MULSD ALPHA, X2 // X_i *= ALPHA
MOVSD X2, (DST_PTR)(IDX*8) // dst[i] = X_i
end:
RET
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