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// Copyright ©2017 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.
// +build !noasm,!appengine,!safe
#include "textflag.h"
#define X_PTR SI
#define Y_PTR DI
#define LEN CX
#define TAIL BX
#define INC_X R8
#define INCx3_X R10
#define INC_Y R9
#define INCx3_Y R11
#define SUM X0
#define P_SUM X1
// func DotInc(x, y []float32, n, incX, incY, ix, iy uintptr) (sum float32)
TEXT ·DotInc(SB), NOSPLIT, $0
MOVQ x_base+0(FP), X_PTR // X_PTR = &x
MOVQ y_base+24(FP), Y_PTR // Y_PTR = &y
PXOR SUM, SUM // SUM = 0
MOVQ n+48(FP), LEN // LEN = n
CMPQ LEN, $0
JE dot_end
MOVQ ix+72(FP), INC_X // INC_X = ix
MOVQ iy+80(FP), INC_Y // INC_Y = iy
LEAQ (X_PTR)(INC_X*4), X_PTR // X_PTR = &(x[ix])
LEAQ (Y_PTR)(INC_Y*4), Y_PTR // Y_PTR = &(y[iy])
MOVQ incX+56(FP), INC_X // INC_X := incX * sizeof(float32)
SHLQ $2, INC_X
MOVQ incY+64(FP), INC_Y // INC_Y := incY * sizeof(float32)
SHLQ $2, INC_Y
MOVQ LEN, TAIL
ANDQ $0x3, TAIL // TAIL = LEN % 4
SHRQ $2, LEN // LEN = floor( LEN / 4 )
JZ dot_tail // if LEN == 0 { goto dot_tail }
PXOR P_SUM, P_SUM // P_SUM = 0 for pipelining
LEAQ (INC_X)(INC_X*2), INCx3_X // INCx3_X = INC_X * 3
LEAQ (INC_Y)(INC_Y*2), INCx3_Y // INCx3_Y = INC_Y * 3
dot_loop: // Loop unrolled 4x do {
MOVSS (X_PTR), X2 // X_i = x[i:i+1]
MOVSS (X_PTR)(INC_X*1), X3
MOVSS (X_PTR)(INC_X*2), X4
MOVSS (X_PTR)(INCx3_X*1), X5
MULSS (Y_PTR), X2 // X_i *= y[i:i+1]
MULSS (Y_PTR)(INC_Y*1), X3
MULSS (Y_PTR)(INC_Y*2), X4
MULSS (Y_PTR)(INCx3_Y*1), X5
ADDSS X2, SUM // SUM += X_i
ADDSS X3, P_SUM
ADDSS X4, SUM
ADDSS X5, P_SUM
LEAQ (X_PTR)(INC_X*4), X_PTR // X_PTR = &(X_PTR[INC_X * 4])
LEAQ (Y_PTR)(INC_Y*4), Y_PTR // Y_PTR = &(Y_PTR[INC_Y * 4])
DECQ LEN
JNZ dot_loop // } while --LEN > 0
ADDSS P_SUM, SUM // P_SUM += SUM
CMPQ TAIL, $0 // if TAIL == 0 { return }
JE dot_end
dot_tail: // do {
MOVSS (X_PTR), X2 // X2 = x[i]
MULSS (Y_PTR), X2 // X2 *= y[i]
ADDSS X2, SUM // SUM += X2
ADDQ INC_X, X_PTR // X_PTR += INC_X
ADDQ INC_Y, Y_PTR // Y_PTR += INC_Y
DECQ TAIL
JNZ dot_tail // } while --TAIL > 0
dot_end:
MOVSS SUM, sum+88(FP) // return SUM
RET