Merge pull request #76310 from al45tair/eng/PR-135413803

[Windows][Concurrency] Use the same clock as Dispatch.

Author: al45tair

stdlib/public/Concurrency/CMakeLists.txt

@@ -15,7 +15,10 @@ set(SWIFT_RUNTIME_CONCURRENCY_SWIFT_FLAGS -I${CMAKE_CURRENT_SOURCE_DIR}/Internal
 
 set(swift_concurrency_private_link_libraries)
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
-  list(APPEND swift_concurrency_private_link_libraries Synchronization)
+  list(APPEND swift_concurrency_private_link_libraries
+    Synchronization
+    mincore.lib # For QueryInterruptTime()
+  )
 endif()
 
 set(swift_concurrency_incorporate_object_libraries_so swiftThreading)

stdlib/public/Concurrency/Clock.cpp

@@ -41,19 +41,15 @@ void swift_get_time(
 #elif (defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__wasi__))
       clock_gettime(CLOCK_MONOTONIC, &continuous);
 #elif defined(_WIN32)
-      LARGE_INTEGER freq;
-      QueryPerformanceFrequency(&freq);
-      LARGE_INTEGER count;
-      QueryPerformanceCounter(&count);
-      // Divide count (number of ticks) by frequency (number of ticks per
-      // second) to get the counter in seconds. We also need to multiply the
-      // count by 1,000,000,000 to get nanosecond resolution. By multiplying
-      // first, we maintain high precision. The resulting value is the tick
-      // count in nanoseconds. Use 128-bit math to avoid overflowing.
-      auto quadPart = static_cast<unsigned _BitInt(128)>(count.QuadPart);
-      auto ns = (quadPart * 1'000'000'000) / freq.QuadPart;
-      continuous.tv_sec = ns / 1'000'000'000;
-      continuous.tv_nsec = ns % 1'000'000'000;
+      // This needs to match what swift-corelibs-libdispatch does
+
+      // QueryInterruptTimePrecise() outputs a value measured in 100ns
+      // units. We must divide the output by 10,000,000 to get a value in
+      // seconds and multiply the remainder by 100 to get nanoseconds.
+      ULONGLONG interruptTime;
+      (void)QueryInterruptTimePrecise(&interruptTime);
+      continuous.tv_sec = interruptTime / 10'000'000;
+      continuous.tv_nsec = (interruptTime % 10'000'000) * 100;
 #else
 #error Missing platform continuous time definition
 #endif
@@ -72,32 +68,13 @@ void swift_get_time(
 #elif (defined(__OpenBSD__) || defined(__FreeBSD__))
       clock_gettime(CLOCK_UPTIME, &suspending);
 #elif defined(_WIN32)
-      // QueryUnbiasedInterruptTimePrecise() was added in Windows 10 and is, as
-      // the name suggests, more precise than QueryUnbiasedInterruptTime().
-      // Unfortunately, the symbol is not listed in any .lib file in the SDK and
-      // must be looked up dynamically at runtime even if our minimum deployment
-      // target is Windows 10.
-      typedef decltype(QueryUnbiasedInterruptTimePrecise) *QueryUITP_FP;
-      static QueryUITP_FP queryUITP = nullptr;
-      static swift::once_t onceToken;
-      swift::once(onceToken, [] {
-        if (HMODULE hKernelBase = GetModuleHandleW(L"KernelBase.dll")) {
-          queryUITP = reinterpret_cast<QueryUITP_FP>(
-            GetProcAddress(hKernelBase, "QueryUnbiasedInterruptTimePrecise")
-          );
-        }
-      });
+      // This needs to match what swift-corelibs-libdispatch does
 
-      // Call whichever API is available. Both output a value measured in 100ns
+      // QueryUnbiasedInterruptTimePrecise() outputs a value measured in 100ns
       // units. We must divide the output by 10,000,000 to get a value in
       // seconds and multiply the remainder by 100 to get nanoseconds.
       ULONGLONG unbiasedTime;
-      if (queryUITP) {
-        (* queryUITP)(&unbiasedTime);
-      } else {
-        // Fall back to the older, less precise API.
-        (void)QueryUnbiasedInterruptTime(&unbiasedTime);
-      }
+      (void)QueryUnbiasedInterruptTimePrecise(&unbiasedTime);
       suspending.tv_sec = unbiasedTime / 10'000'000;
       suspending.tv_nsec = (unbiasedTime % 10'000'000) * 100;
 #else
@@ -128,10 +105,8 @@ switch (clock_id) {
 #elif (defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__wasi__))
       clock_getres(CLOCK_MONOTONIC, &continuous);
 #elif defined(_WIN32)
-      LARGE_INTEGER freq;
-      QueryPerformanceFrequency(&freq);
       continuous.tv_sec = 0;
-      continuous.tv_nsec = 1'000'000'000 / freq.QuadPart;
+      continuous.tv_nsec = 100;
 #else
 #error Missing platform continuous time definition
 #endif