time_windows_arm.s

Documentation: runtime

     1// Copyright 2018 The Go Authors. All rights reserved.
     2// Use of this source code is governed by a BSD-style
     3// license that can be found in the LICENSE file.
     4
     5//go:build !faketime
     6
     7#include "go_asm.h"
     8#include "textflag.h"
     9#include "time_windows.h"
    10
    11TEXT time·now(SB),NOSPLIT,$0-20
    12	MOVW	$_INTERRUPT_TIME, R3
    13loop:
    14	MOVW	time_hi1(R3), R1
    15	DMB	MB_ISH
    16	MOVW	time_lo(R3), R0
    17	DMB	MB_ISH
    18	MOVW	time_hi2(R3), R2
    19	CMP	R1, R2
    20	BNE	loop
    21
    22	// wintime = R1:R0, multiply by 100
    23	MOVW	$100, R2
    24	MULLU	R0, R2, (R4, R3)    // R4:R3 = R1:R0 * R2
    25	MULA	R1, R2, R4, R4
    26
    27	// wintime*100 = R4:R3
    28	MOVW	R3, mono+12(FP)
    29	MOVW	R4, mono+16(FP)
    30
    31	MOVW	$_SYSTEM_TIME, R3
    32wall:
    33	MOVW	time_hi1(R3), R1
    34	DMB	MB_ISH
    35	MOVW	time_lo(R3), R0
    36	DMB	MB_ISH
    37	MOVW	time_hi2(R3), R2
    38	CMP	R1, R2
    39	BNE	wall
    40
    41	// w = R1:R0 in 100ns untis
    42	// convert to Unix epoch (but still 100ns units)
    43	#define delta 116444736000000000
    44	SUB.S   $(delta & 0xFFFFFFFF), R0
    45	SBC     $(delta >> 32), R1
    46
    47	// Convert to nSec
    48	MOVW    $100, R2
    49	MULLU   R0, R2, (R4, R3)    // R4:R3 = R1:R0 * R2
    50	MULA    R1, R2, R4, R4
    51	// w = R2:R1 in nSec
    52	MOVW    R3, R1	      // R4:R3 -> R2:R1
    53	MOVW    R4, R2
    54
    55	// multiply nanoseconds by reciprocal of 10**9 (scaled by 2**61)
    56	// to get seconds (96 bit scaled result)
    57	MOVW	$0x89705f41, R3		// 2**61 * 10**-9
    58	MULLU	R1,R3,(R6,R5)		// R7:R6:R5 = R2:R1 * R3
    59	MOVW	$0,R7
    60	MULALU	R2,R3,(R7,R6)
    61
    62	// unscale by discarding low 32 bits, shifting the rest by 29
    63	MOVW	R6>>29,R6		// R7:R6 = (R7:R6:R5 >> 61)
    64	ORR	R7<<3,R6
    65	MOVW	R7>>29,R7
    66
    67	// subtract (10**9 * sec) from nsec to get nanosecond remainder
    68	MOVW	$1000000000, R5	// 10**9
    69	MULLU	R6,R5,(R9,R8)   // R9:R8 = R7:R6 * R5
    70	MULA	R7,R5,R9,R9
    71	SUB.S	R8,R1		// R2:R1 -= R9:R8
    72	SBC	R9,R2
    73
    74	// because reciprocal was a truncated repeating fraction, quotient
    75	// may be slightly too small -- adjust to make remainder < 10**9
    76	CMP	R5,R1	// if remainder > 10**9
    77	SUB.HS	R5,R1   //    remainder -= 10**9
    78	ADD.HS	$1,R6	//    sec += 1
    79
    80	MOVW	R6,sec_lo+0(FP)
    81	MOVW	R7,sec_hi+4(FP)
    82	MOVW	R1,nsec+8(FP)
    83	RET
    84
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