// Copyright 2016 The Go 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 !appengine
// +build gc
// +build !noasm

#include "textflag.h"

// fl is short for floating point math. fx is short for fixed point math.

DATA flAlmost65536<>+0x00(SB)/8, $0x477fffff477fffff
DATA flAlmost65536<>+0x08(SB)/8, $0x477fffff477fffff
DATA flOne<>+0x00(SB)/8, $0x3f8000003f800000
DATA flOne<>+0x08(SB)/8, $0x3f8000003f800000
DATA flSignMask<>+0x00(SB)/8, $0x7fffffff7fffffff
DATA flSignMask<>+0x08(SB)/8, $0x7fffffff7fffffff

// scatterAndMulBy0x101 is a PSHUFB mask that brings the low four bytes of an
// XMM register to the low byte of that register's four uint32 values. It
// duplicates those bytes, effectively multiplying each uint32 by 0x101.
//
// It transforms a little-endian 16-byte XMM value from
//	ijkl????????????
// to
//	ii00jj00kk00ll00
DATA scatterAndMulBy0x101<>+0x00(SB)/8, $0x8080010180800000
DATA scatterAndMulBy0x101<>+0x08(SB)/8, $0x8080030380800202

// gather is a PSHUFB mask that brings the second-lowest byte of the XMM
// register's four uint32 values to the low four bytes of that register.
//
// It transforms a little-endian 16-byte XMM value from
//	?i???j???k???l??
// to
//	ijkl000000000000
DATA gather<>+0x00(SB)/8, $0x808080800d090501
DATA gather<>+0x08(SB)/8, $0x8080808080808080

DATA fxAlmost65536<>+0x00(SB)/8, $0x0000ffff0000ffff
DATA fxAlmost65536<>+0x08(SB)/8, $0x0000ffff0000ffff
DATA inverseFFFF<>+0x00(SB)/8, $0x8000800180008001
DATA inverseFFFF<>+0x08(SB)/8, $0x8000800180008001

GLOBL flAlmost65536<>(SB), (NOPTR+RODATA), $16
GLOBL flOne<>(SB), (NOPTR+RODATA), $16
GLOBL flSignMask<>(SB), (NOPTR+RODATA), $16
GLOBL scatterAndMulBy0x101<>(SB), (NOPTR+RODATA), $16
GLOBL gather<>(SB), (NOPTR+RODATA), $16
GLOBL fxAlmost65536<>(SB), (NOPTR+RODATA), $16
GLOBL inverseFFFF<>(SB), (NOPTR+RODATA), $16

// func haveSSE4_1() bool
TEXT ·haveSSE4_1(SB), NOSPLIT, $0
	MOVQ $1, AX
	CPUID
	SHRQ $19, CX
	ANDQ $1, CX
	MOVB CX, ret+0(FP)
	RET

// ----------------------------------------------------------------------------

// func {{.LongName}}SIMD({{.Args}})
//
// XMM registers. Variable names are per
// https://github.com/google/font-rs/blob/master/src/accumulate.c
//
//	xmm0	scratch
//	xmm1	x
//	xmm2	y, z
//	xmm3	{{.XMM3}}
//	xmm4	{{.XMM4}}
//	xmm5	{{.XMM5}}
//	xmm6	{{.XMM6}}
//	xmm7	offset
//	xmm8	{{.XMM8}}
//	xmm9	{{.XMM9}}
//	xmm10	{{.XMM10}}
TEXT ·{{.LongName}}SIMD(SB), NOSPLIT, ${{.FrameSize}}-{{.ArgsSize}}
	{{.LoadArgs}}

	// R10 = len(src) &^ 3
	// R11 = len(src)
	MOVQ R10, R11
	ANDQ $-4, R10

	{{.Setup}}

	{{.LoadXMMRegs}}

	// offset := XMM(0x00000000 repeated four times) // Cumulative sum.
	XORPS X7, X7

	// i := 0
	MOVQ $0, R9

{{.ShortName}}Loop4:
	// for i < (len(src) &^ 3)
	CMPQ R9, R10
	JAE  {{.ShortName}}Loop1

	// x = XMM(s0, s1, s2, s3)
	//
	// Where s0 is src[i+0], s1 is src[i+1], etc.
	MOVOU (SI), X1

	// scratch = XMM(0, s0, s1, s2)
	// x += scratch                                  // yields x == XMM(s0, s0+s1, s1+s2, s2+s3)
	MOVOU    X1, X0
	PSLLO    $4, X0
	{{.Add}} X0, X1

	// scratch = XMM(0, 0, 0, 0)
	// scratch = XMM(scratch@0, scratch@0, x@0, x@1) // yields scratch == XMM(0, 0, s0, s0+s1)
	// x += scratch                                  // yields x == XMM(s0, s0+s1, s0+s1+s2, s0+s1+s2+s3)
	XORPS    X0, X0
	SHUFPS   $0x40, X1, X0
	{{.Add}} X0, X1

	// x += offset
	{{.Add}} X7, X1

	{{.ClampAndScale}}

	{{.ConvertToInt32}}

	{{.Store4}}

	// offset = XMM(x@3, x@3, x@3, x@3)
	MOVOU  X1, X7
	SHUFPS $0xff, X1, X7

	// i += 4
	// dst = dst[4:]
	// src = src[4:]
	ADDQ $4, R9
	ADDQ ${{.DstElemSize4}}, DI
	ADDQ $16, SI
	JMP  {{.ShortName}}Loop4

{{.ShortName}}Loop1:
	// for i < len(src)
	CMPQ R9, R11
	JAE  {{.ShortName}}End

	// x = src[i] + offset
	MOVL     (SI), X1
	{{.Add}} X7, X1

	{{.ClampAndScale}}

	{{.ConvertToInt32}}

	{{.Store1}}

	// offset = x
	MOVOU X1, X7

	// i += 1
	// dst = dst[1:]
	// src = src[1:]
	ADDQ $1, R9
	ADDQ ${{.DstElemSize1}}, DI
	ADDQ $4, SI
	JMP  {{.ShortName}}Loop1

{{.ShortName}}End:
	RET