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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 X_PTR SI
#define LEN CX
#define TAIL BX
#define INC_X R8
#define INCx3_X R9
#define ALPHA X0
#define ALPHA_2 X1
// func ScalInc(alpha float64, x []float64, n, incX uintptr)
TEXT ·ScalInc(SB), NOSPLIT, $0
MOVSD alpha+0(FP), ALPHA // ALPHA = alpha
MOVQ x_base+8(FP), X_PTR // X_PTR = &x
MOVQ incX+40(FP), INC_X // INC_X = incX
SHLQ $3, INC_X // INC_X *= sizeof(float64)
MOVQ n+32(FP), LEN // LEN = n
CMPQ LEN, $0
JE end // if LEN == 0 { return }
MOVQ LEN, TAIL
ANDQ $3, TAIL // TAIL = LEN % 4
SHRQ $2, LEN // LEN = floor( LEN / 4 )
JZ tail_start // if LEN == 0 { goto tail_start }
MOVUPS ALPHA, ALPHA_2 // ALPHA_2 = ALPHA for pipelining
LEAQ (INC_X)(INC_X*2), INCx3_X // INCx3_X = INC_X * 3
loop: // do { // x[i] *= alpha unrolled 4x.
MOVSD (X_PTR), X2 // X_i = x[i]
MOVSD (X_PTR)(INC_X*1), X3
MOVSD (X_PTR)(INC_X*2), X4
MOVSD (X_PTR)(INCx3_X*1), X5
MULSD ALPHA, X2 // X_i *= a
MULSD ALPHA_2, X3
MULSD ALPHA, X4
MULSD ALPHA_2, X5
MOVSD X2, (X_PTR) // x[i] = X_i
MOVSD X3, (X_PTR)(INC_X*1)
MOVSD X4, (X_PTR)(INC_X*2)
MOVSD X5, (X_PTR)(INCx3_X*1)
LEAQ (X_PTR)(INC_X*4), X_PTR // X_PTR = &(X_PTR[incX*4])
DECQ LEN
JNZ loop // } while --LEN > 0
CMPQ TAIL, $0
JE end // if TAIL == 0 { return }
tail_start: // Reset loop registers
MOVQ TAIL, LEN // Loop counter: LEN = TAIL
SHRQ $1, LEN // LEN = floor( LEN / 2 )
JZ tail_one
tail_two: // do {
MOVSD (X_PTR), X2 // X_i = x[i]
MOVSD (X_PTR)(INC_X*1), X3
MULSD ALPHA, X2 // X_i *= a
MULSD ALPHA, X3
MOVSD X2, (X_PTR) // x[i] = X_i
MOVSD X3, (X_PTR)(INC_X*1)
LEAQ (X_PTR)(INC_X*2), X_PTR // X_PTR = &(X_PTR[incX*2])
ANDQ $1, TAIL
JZ end
tail_one:
MOVSD (X_PTR), X2 // X_i = x[i]
MULSD ALPHA, X2 // X_i *= ALPHA
MOVSD X2, (X_PTR) // x[i] = X_i
end:
RET
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