SkTime::GetNSecs()

   - Move high-precision wall timers from tools/timer to SkTime.
   - Implement SkTime::GetMSecs() in terms of SkTime::GetNSecs().
   - Delete unused tools/timer code.

I have no idea what's going on there in src/animator.
I don't intend to investigate.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/70084cbc16ee8162649f2601377feb6e49de0217

CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Debug-CrOS_Link-Trybot

Committed: https://skia.googlesource.com/skia/+/a1840d50e29fd95e4df2d1168fe54c34c2a5c30c

Committed: https://skia.googlesource.com/skia/+/38a88e4c0c28a7be981aac7bb4a198ad95a62a63

Review URL: https://codereview.chromium.org/1422513003

1 files changed, 36 insertions, 0 deletions

diff --git a/src/core/SkTime.cpp b/src/core/SkTime.cpp
index fa6c04447d..86a0685c70 100644
--- a/src/core/SkTime.cpp
+++ b/src/core/SkTime.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "SkOncePtr.h"
 #include "SkString.h"
 #include "SkTime.h"
 
@@ -22,3 +23,38 @@ void SkTime::DateTime::toISO8601(SkString* dst) const {
                     timeZoneMinutes);
     }
 }
+
+#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