Now we're on MSVC 2015, try using std::chrono for timing again.

2015's std::chrono::high_resolution_clock should have a precision equal to our old custom code.

Tested this locally on Windows 10 and Mac (the two affected platforms).

Long term SkTime::GetNSecs() can probably be phased out for direct <chrono> use.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1950173002

Review-Url: https://codereview.chromium.org/1950173002

1 files changed, 6 insertions, 35 deletions

diff --git a/src/core/SkTime.cpp b/src/core/SkTime.cpp
index ba8fe3e3a3..e89d5b9b3a 100644
--- a/src/core/SkTime.cpp
+++ b/src/core/SkTime.cpp
@@ -5,10 +5,10 @@
  * found in the LICENSE file.
  */
 
-#include "SkOncePtr.h"
 #include "SkString.h"
 #include "SkTime.h"
 #include "SkTypes.h"
+#include <chrono>
 
 void SkTime::DateTime::toISO8601(SkString* dst) const {
     if (dst) {
@@ -65,37 +65,8 @@ void SkTime::GetDateTime(DateTime* dt) {
 }
 #endif // SK_BUILD_FOR_WIN32
 
-#if defined(_MSC_VER)
-    // TODO: try std::chrono again with MSVC 2015?
-    #include <intrin.h>
-    SK_DECLARE_STATIC_ONCE_PTR(double, ns_per_tick);
-    double SkTime::GetNSecs() {
-        uint64_t ticks = __rdtsc();
-        return ticks * *ns_per_tick.get([]{
-            LARGE_INTEGER khz;  // The docs say this returns Hz, but it returns KHz.
-            QueryPerformanceFrequency(&khz);
-            return new double(1e6 / khz.QuadPart);
-        });
-    }
-#elif defined(__MACH__)
-    // TODO: fold into std::chrono when available?
-    #include <mach/mach_time.h>
-    SK_DECLARE_STATIC_ONCE_PTR(double, ns_per_tick);
-    double SkTime::GetNSecs() {
-        uint64_t ticks = mach_absolute_time();
-        return ticks * *ns_per_tick.get([]{
-            mach_timebase_info_data_t timebase;
-            (void)mach_timebase_info(&timebase);
-            return new double(timebase.numer * 1.0 / timebase.denom);
-        });
-    }
-#else
-    // This std::chrono code looks great on Linux and Android,
-    // but MSVC 2013 returned mostly garbage (0ns times, etc).
-    #include <chrono>
-    double SkTime::GetNSecs() {
-        auto now = std::chrono::high_resolution_clock::now();
-        std::chrono::duration<double, std::nano> ns = now.time_since_epoch();
-        return ns.count();
-    }
-#endif
+double SkTime::GetNSecs() {
+    auto now = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double, std::nano> ns = now.time_since_epoch();
+    return ns.count();
+}