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// Copyright 2018 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.
//go:build !faketime
#include "go_asm.h"
#include "textflag.h"
#include "time_windows.h"
TEXT time·now(SB),NOSPLIT,$0-20
MOVW $_INTERRUPT_TIME, R3
loop:
MOVW time_hi1(R3), R1
DMB MB_ISH
MOVW time_lo(R3), R0
DMB MB_ISH
MOVW time_hi2(R3), R2
CMP R1, R2
BNE loop
// wintime = R1:R0, multiply by 100
MOVW $100, R2
MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
MULA R1, R2, R4, R4
// wintime*100 = R4:R3
MOVW R3, mono+12(FP)
MOVW R4, mono+16(FP)
MOVW $_SYSTEM_TIME, R3
wall:
MOVW time_hi1(R3), R1
DMB MB_ISH
MOVW time_lo(R3), R0
DMB MB_ISH
MOVW time_hi2(R3), R2
CMP R1, R2
BNE wall
// w = R1:R0 in 100ns untis
// convert to Unix epoch (but still 100ns units)
#define delta 116444736000000000
SUB.S $(delta & 0xFFFFFFFF), R0
SBC $(delta >> 32), R1
// Convert to nSec
MOVW $100, R2
MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
MULA R1, R2, R4, R4
// w = R2:R1 in nSec
MOVW R3, R1 // R4:R3 -> R2:R1
MOVW R4, R2
// multiply nanoseconds by reciprocal of 10**9 (scaled by 2**61)
// to get seconds (96 bit scaled result)
MOVW $0x89705f41, R3 // 2**61 * 10**-9
MULLU R1,R3,(R6,R5) // R7:R6:R5 = R2:R1 * R3
MOVW $0,R7
MULALU R2,R3,(R7,R6)
// unscale by discarding low 32 bits, shifting the rest by 29
MOVW R6>>29,R6 // R7:R6 = (R7:R6:R5 >> 61)
ORR R7<<3,R6
MOVW R7>>29,R7
// subtract (10**9 * sec) from nsec to get nanosecond remainder
MOVW $1000000000, R5 // 10**9
MULLU R6,R5,(R9,R8) // R9:R8 = R7:R6 * R5
MULA R7,R5,R9,R9
SUB.S R8,R1 // R2:R1 -= R9:R8
SBC R9,R2
// because reciprocal was a truncated repeating fraction, quotient
// may be slightly too small -- adjust to make remainder < 10**9
CMP R5,R1 // if remainder > 10**9
SUB.HS R5,R1 // remainder -= 10**9
ADD.HS $1,R6 // sec += 1
MOVW R6,sec_lo+0(FP)
MOVW R7,sec_hi+4(FP)
MOVW R1,nsec+8(FP)
RET
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