From cfd016df1fba2a2a104f4cca705aa4357777986b Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 3 Nov 2021 18:19:04 +0100 Subject: 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 Run-TryBot: Jason A. Donenfeld TryBot-Result: Go Bot Reviewed-by: Austin Clements --- src/runtime/time_windows_arm64.s | 22 +++------------------- 1 file changed, 3 insertions(+), 19 deletions(-) (limited to 'src/runtime/time_windows_arm64.s') diff --git a/src/runtime/time_windows_arm64.s b/src/runtime/time_windows_arm64.s index ef52ce4c99..e8a0eb2f93 100644 --- a/src/runtime/time_windows_arm64.s +++ b/src/runtime/time_windows_arm64.s @@ -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 -- cgit v1.3