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[Windows][Concurrency] Use the same clock as Dispatch. #76310

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Merged
merged 3 commits into from
Sep 7, 2024
Merged

[Windows][Concurrency] Use the same clock as Dispatch. #76310

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f5b146b
[Windows][Concurrency] Use the same clock as Dispatch.
al45tair Sep 6, 2024
86c643d
[Concurrency][Windows] Also update swift_get_clock_res().
al45tair Sep 6, 2024
8e91ae4
[Concurrency][Windows] Remove use of `GetProcAddress()`.
al45tair Sep 6, 2024
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5 changes: 4 additions & 1 deletion stdlib/public/Concurrency/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
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51 changes: 13 additions & 38 deletions stdlib/public/Concurrency/Clock.cpp
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Expand Up @@ -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
Expand All @@ -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
Expand Down Expand Up @@ -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
Expand Down