From: Jordan Rhee <jordanrh@microsoft.com>
Date: Wed, 19 Dec 2018 00:41:57 +0000 (-0800)
Subject: runtime: use QPC to implement cputicks() on windows/arm
X-Git-Tag: go1.12beta2~109
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=84066f1b0b68761a75ce9064f4c412f751ee2168;p=gostls13.git

runtime: use QPC to implement cputicks() on windows/arm

Tracing uses cputicks() to generate trace event timestamps. cputicks()
is expected to be a high resolution clock source. On Windows/ARM,
call QueryPerformanceCounter() which is the highest resolution clock
source available.

Updates #26148

Change-Id: I987fa556060b3d60c02f07b87b9e6320b9b026e2
Reviewed-on: https://go-review.googlesource.com/c/154762
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---

diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index 9b34589874..2e1ec58a0d 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -198,6 +198,13 @@ func loadOptionalSyscalls() {
 	}
 	_NtWaitForSingleObject = windowsFindfunc(n32, []byte("NtWaitForSingleObject\000"))
 
+	if GOARCH == "arm" {
+		_QueryPerformanceCounter = windowsFindfunc(k32, []byte("QueryPerformanceCounter\000"))
+		if _QueryPerformanceCounter == nil {
+			throw("could not find QPC syscalls")
+		}
+	}
+
 	if windowsFindfunc(n32, []byte("wine_get_version\000")) != nil {
 		// running on Wine
 		initWine(k32)
diff --git a/src/runtime/os_windows_arm.go b/src/runtime/os_windows_arm.go
index 3115f7241d..10aff75e31 100644
--- a/src/runtime/os_windows_arm.go
+++ b/src/runtime/os_windows_arm.go
@@ -4,9 +4,13 @@
 
 package runtime
 
+import "unsafe"
+
 //go:nosplit
 func cputicks() int64 {
-	return nanotime()
+	var counter int64
+	stdcall1(_QueryPerformanceCounter, uintptr(unsafe.Pointer(&counter)))
+	return counter
 }
 
 func checkgoarm() {