// 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.

//+build ignore

// gendaxpy creates the assembler code for the family of Daxpy functions.
package main

import (
	"fmt"
	"log"
	"os"
	"strings"
	"text/template"
)

var asm = template.Must(template.New("asm").Parse(`{{define "header"}}// Generated by running
//  go generate github.com/gonum/internal/asm
// DO NOT EDIT.

// 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

// TODO(fhs): use textflag.h after we drop Go 1.3 support
// #include "textflag.h"
// Don't insert stack check preamble.
#define NOSPLIT	4
{{end}}

{{define "unitary_preamble"}}
// func DaxpyUnitary(alpha float64, x, y []float64)
// This function assumes len(y) >= len(x).
TEXT ·DaxpyUnitary(SB), NOSPLIT, $0
	MOVHPD alpha+0(FP), X7
	MOVLPD alpha+0(FP), X7
	MOVQ   x+8(FP), R8
	MOVQ   x_len+16(FP), DI // n = len(x)
	MOVQ   y+32(FP), R9
{{end}}

{{define "unitaryto_preamble"}}
// func DaxpyUnitaryTo(dst []float64, alpha float64, x, y []float64)
// This function assumes len(y) >= len(x) and len(dst) >= len(x).
TEXT ·DaxpyUnitaryTo(SB), NOSPLIT, $0
	MOVQ   dst+0(FP), R10
	MOVHPD alpha+24(FP), X7
	MOVLPD alpha+24(FP), X7
	MOVQ   x+32(FP), R8
	MOVQ   x_len+40(FP), DI // n = len(x)
	MOVQ   y+56(FP), R9
{{end}}

{{define "unitary_body"}}
	MOVQ $0, SI // i = 0
	SUBQ $2, DI // n -= 2
	JL   tail   // if n < 0 goto tail

loop:
	MOVUPD 0(R8)(SI*8), X0
	MOVUPD 0(R9)(SI*8), X1
	MULPD  X7, X0
	ADDPD  X0, X1
	MOVUPD X1, 0({{if .To}}R10{{else}}R9{{end}})(SI*8)

	ADDQ $2, SI // i += 2
	SUBQ $2, DI // n -= 2
	JGE  loop   // if n >= 0 goto loop

tail:
	ADDQ $2, DI // n += 2
	JLE  end    // if n <= 0 goto end

	MOVSD 0(R8)(SI*8), X0
	MOVSD 0(R9)(SI*8), X1
	MULSD X7, X0
	ADDSD X0, X1
	MOVSD X1, 0({{if .To}}R10{{else}}R9{{end}})(SI*8)

end:
	RET
{{end}}`))

type Function struct {
	Name string
	To   bool

	template string
}

var funcs = []Function{
	{
		Name:     "DaxpyUnitary",
		To:       false,
		template: `{{template "header" .}}{{template "unitary_preamble" .}}{{template "unitary_body" .}}`,
	},
	{
		Name:     "DaxpyUnitaryTo",
		To:       true,
		template: `{{template "header" .}}{{template "unitaryto_preamble" .}}{{template "unitary_body" .}}`,
	},
}

func main() {
	for _, fn := range funcs {
		t, err := template.Must(asm.Clone()).Parse(fn.template)
		if err != nil {
			log.Fatalf("failed to parse template: %v", err)
		}

		file := strings.ToLower(fn.Name) + "_amd64.s"
		fmt.Println("Generating", file)
		f, err := os.Create(file)
		if err != nil {
			log.Fatalf("failed to create %q: %v", file, err)
		}
		err = t.Execute(f, fn)
		if err != nil {
			log.Fatalf("failed to execute template: %v", err)
		}
		f.Close()
	}
}