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diff --git a/src/runtime/time_windows_arm.s b/src/runtime/time_windows_arm.s
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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|NOFRAME,$0-20
+ MOVW $0, R0
+ MOVB runtime·useQPCTime(SB), R0
+ CMP $0, R0
+ BNE useQPC
+ 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
+useQPC:
+ B runtime·nowQPC(SB) // tail call
+