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runtime: on windows, read nanotime with one instruction or issue barrier 

On 64-bit, this is more efficient, and on ARM64, this prevents the time
from moving backwards due to the weaker memory model. On ARM32 due to
the weaker memory model, we issue a memory barrier.

Updates #48072.

Change-Id: If4695716c3039d8af14e14808af217f5c99fc93a
Reviewed-on: https://go-review.googlesource.com/c/go/+/361057
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Jason A. Donenfeld 2021-11-03 18:19:04 +01:00
parent d4e0e8e4a4
commit cfd016df1f
7 changed files with 17 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/runtime/sys_windows_amd64.s
View File

@ -344,16 +344,9 @@ TEXT runtime·nanotime1(SB),NOSPLIT,$0-8
CMPB runtime·useQPCTime(SB), $0
JNE useQPC
MOVQ $_INTERRUPT_TIME, DI
loop:
MOVL time_hi1(DI), AX
MOVL time_lo(DI), BX
MOVL time_hi2(DI), CX
CMPL AX, CX
JNE loop
SHLQ $32, CX
ORQ BX, CX
IMULQ $100, CX
MOVQ CX, ret+0(FP)
MOVQ time_lo(DI), AX
IMULQ $100, AX
MOVQ AX, ret+0(FP)
RET
useQPC:
JMP runtime·nanotimeQPC(SB)

2
src/runtime/sys_windows_arm.s
View File

@ -350,7 +350,9 @@ TEXT runtime·nanotime1(SB),NOSPLIT|NOFRAME,$0-8
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

10
src/runtime/sys_windows_arm64.s
View File

@ -415,15 +415,7 @@ TEXT runtime·nanotime1(SB),NOSPLIT|NOFRAME,$0-8
CMP $0, R0
BNE useQPC
MOVD $_INTERRUPT_TIME, R3
loop:
MOVWU time_hi1(R3), R1
MOVWU time_lo(R3), R0
MOVWU time_hi2(R3), R2
CMP R1, R2
BNE loop
// wintime = R1:R0, multiply by 100
ORR R1<<32, R0
MOVD time_lo(R3), R0
MOVD $100, R1
MUL R1, R0
MOVD R0, ret+0(FP)

1
src/runtime/time_windows.h
View File

@ -9,6 +9,7 @@
// http://web.archive.org/web/20210411000829/https://wrkhpi.wordpress.com/2007/08/09/getting-os-information-the-kuser_shared_data-structure/
// Must read hi1, then lo, then hi2. The snapshot is valid if hi1 == hi2.
// Or, on 64-bit, just read lo:hi1 all at once atomically.
#define _INTERRUPT_TIME 0x7ffe0008
#define _SYSTEM_TIME 0x7ffe0014
#define time_lo 0

19
src/runtime/time_windows_amd64.s
View File

@ -12,27 +12,14 @@
TEXT time·now(SB),NOSPLIT,$0-24
CMPB runtime·useQPCTime(SB), $0
JNE useQPC
MOVQ $_INTERRUPT_TIME, DI
loop:
MOVL time_hi1(DI), AX
MOVL time_lo(DI), BX
MOVL time_hi2(DI), CX
CMPL AX, CX
JNE loop
SHLQ $32, AX
ORQ BX, AX
MOVQ time_lo(DI), AX
IMULQ $100, AX
MOVQ AX, mono+16(FP)
MOVQ $_SYSTEM_TIME, DI
wall:
MOVL time_hi1(DI), AX
MOVL time_lo(DI), BX
MOVL time_hi2(DI), CX
CMPL AX, CX
JNE wall
SHLQ $32, AX
ORQ BX, AX
MOVQ time_lo(DI), AX
MOVQ $116444736000000000, DI
SUBQ DI, AX
IMULQ $100, AX

4
src/runtime/time_windows_arm.s
View File

@ -17,7 +17,9 @@ TEXT time·now(SB),NOSPLIT|NOFRAME,$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
@ -34,7 +36,9 @@ loop:
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

22
src/runtime/time_windows_arm64.s
View File

@ -13,34 +13,18 @@ TEXT time·now(SB),NOSPLIT|NOFRAME,$0-24
MOVB runtime·useQPCTime(SB), R0
CMP $0, R0
BNE useQPC
MOVD $_INTERRUPT_TIME, R3
loop:
MOVWU time_hi1(R3), R1
MOVWU time_lo(R3), R0
MOVWU time_hi2(R3), R2
CMP R1, R2
BNE loop
// wintime = R1:R0, multiply by 100
ORR R1<<32, R0
MOVD $_INTERRUPT_TIME, R3
MOVD time_lo(R3), R0
MOVD $100, R1
MUL R1, R0
MOVD R0, mono+16(FP)
MOVD $_SYSTEM_TIME, R3
wall:
MOVWU time_hi1(R3), R1
MOVWU time_lo(R3), R0
MOVWU time_hi2(R3), R2
CMP R1, R2
BNE wall
// w = R1:R0 in 100ns units
MOVD time_lo(R3), R0
// convert to Unix epoch (but still 100ns units)
#define delta 116444736000000000
ORR R1<<32, R0
SUB $delta, R0
// Convert to nSec
MOVD $100, R1
MUL R1, R0