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// Copyright ©2015 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,!appengine
#include "textflag.h"
#define X_PTR SI
#define Y_PTR DI
#define DST_PTR DI
#define IDX AX
#define LEN CX
#define TAIL BX
#define ALPHA X0
#define ALPHA_2 X1
// func AxpyUnitary(alpha float64, x, y []float64)
TEXT ·AxpyUnitary(SB), NOSPLIT, $0
MOVQ x_base+8(FP), X_PTR // X_PTR := &x
MOVQ y_base+32(FP), Y_PTR // Y_PTR := &y
MOVQ x_len+16(FP), LEN // LEN = min( len(x), len(y) )
CMPQ y_len+40(FP), LEN
CMOVQLE y_len+40(FP), LEN
CMPQ LEN, $0 // if LEN == 0 { return }
JE end
XORQ IDX, IDX
MOVSD alpha+0(FP), ALPHA // ALPHA := { alpha, alpha }
SHUFPD $0, ALPHA, ALPHA
MOVUPS ALPHA, ALPHA_2 // ALPHA_2 := ALPHA for pipelining
MOVQ Y_PTR, TAIL // Check memory alignment
ANDQ $15, TAIL // TAIL = &y % 16
JZ no_trim // if TAIL == 0 { goto no_trim }
// Align on 16-byte boundary
MOVSD (X_PTR), X2 // X2 := x[0]
MULSD ALPHA, X2 // X2 *= a
ADDSD (Y_PTR), X2 // X2 += y[0]
MOVSD X2, (DST_PTR) // y[0] = X2
INCQ IDX // i++
DECQ LEN // LEN--
JZ end // if LEN == 0 { return }
no_trim:
MOVQ LEN, TAIL
ANDQ $7, TAIL // TAIL := n % 8
SHRQ $3, LEN // LEN = floor( n / 8 )
JZ tail_start // if LEN == 0 { goto tail2_start }
loop: // do {
// y[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 *= a
MULPD ALPHA_2, X3
MULPD ALPHA, X4
MULPD ALPHA_2, X5
ADDPD (Y_PTR)(IDX*8), X2 // X_i += y[i]
ADDPD 16(Y_PTR)(IDX*8), X3
ADDPD 32(Y_PTR)(IDX*8), X4
ADDPD 48(Y_PTR)(IDX*8), X5
MOVUPS X2, (DST_PTR)(IDX*8) // y[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 // if TAIL == 0 { return }
JE end
tail_start: // Reset loop registers
MOVQ TAIL, LEN // Loop counter: LEN = TAIL
SHRQ $1, LEN // LEN = floor( TAIL / 2 )
JZ tail_one // if TAIL == 0 { goto tail }
tail_two: // do {
MOVUPS (X_PTR)(IDX*8), X2 // X2 = x[i]
MULPD ALPHA, X2 // X2 *= a
ADDPD (Y_PTR)(IDX*8), X2 // X2 += y[i]
MOVUPS X2, (DST_PTR)(IDX*8) // y[i] = X2
ADDQ $2, IDX // i += 2
DECQ LEN
JNZ tail_two // } while --LEN > 0
ANDQ $1, TAIL
JZ end // if TAIL == 0 { goto end }
tail_one:
MOVSD (X_PTR)(IDX*8), X2 // X2 = x[i]
MULSD ALPHA, X2 // X2 *= a
ADDSD (Y_PTR)(IDX*8), X2 // X2 += y[i]
MOVSD X2, (DST_PTR)(IDX*8) // y[i] = X2
end:
RET