QElapsedTimer/Darwin: merge with the Unix implementation

Old versions of the Apple operating systems did not implement the POSIX
realtime monotonic clock, so we used the Mach absolute timer. The LLVM
libc++ implementation[1] unconditionally uses CLOCK_MONOTONIC_RAW on
these OSes:
 * macOS >= 10.12
 * iPhoneOS >= 10.0
 * tvOS >= 10.0
 * watchOS >= 3.0

Qt 6 doesn't support the latter two and the former two are much older
than what we require, so we can use this functionality too.

[1] https://github.com/llvm/llvm-project/blob/main/libcxx/src/chrono.cpp

Change-Id: Ieec322d73c1e40ad95c8fffd174641c723b81be2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

src/corelib/CMakeLists.txt

@@ -573,7 +573,6 @@ qt_internal_extend_target(Core CONDITION APPLE
         kernel/qcore_foundation.mm
         kernel/qcore_mac.mm kernel/qcore_mac_p.h
         kernel/qcoreapplication_mac.cpp
-        kernel/qelapsedtimer_mac.cpp
         kernel/qeventdispatcher_cf.mm kernel/qeventdispatcher_cf_p.h
     LIBRARIES
         ${FWCoreFoundation}
@@ -973,7 +972,7 @@ qt_internal_extend_target(Core CONDITION APPLE AND NOT MACOS
         ${FWMobileCoreServices}
 )
 
-qt_internal_extend_target(Core CONDITION UNIX AND NOT APPLE
+qt_internal_extend_target(Core CONDITION UNIX
     SOURCES
         kernel/qelapsedtimer_unix.cpp
 )

src/corelib/kernel/qdeadlinetimer.cpp

@@ -107,7 +107,7 @@ bool TimeReference::sign(qint64 secs, qint64 nsecs)
     return nsecs > 0;
 }
 
-#if defined(Q_OS_UNIX) && !defined(Q_OS_DARWIN)
+#if defined(Q_OS_UNIX)
 inline bool TimeReference::addNanoseconds(qint64 arg)
 {
     return addSecsAndNSecs(arg / giga, arg % giga);

src/corelib/kernel/qdeadlinetimer_p.h

@@ -20,7 +20,7 @@
 QT_BEGIN_NAMESPACE
 
 enum {
-#if defined(Q_OS_UNIX) && !defined(Q_OS_DARWIN)
+#if defined(Q_OS_UNIX)
     // t1 contains seconds and t2 contains nanoseconds
     QDeadlineTimerNanosecondsInT2 = 1
 #else

src/corelib/kernel/qelapsedtimer_mac.cpp

@@ -1,130 +0,0 @@
-// Copyright (C) 2016 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
-
-// ask for the latest POSIX, just in case
-#define _POSIX_C_SOURCE 200809L
-
-#include "qelapsedtimer.h"
-#include "qdeadlinetimer.h"
-#include "qdeadlinetimer_p.h"
-#include <sys/time.h>
-#include <time.h>
-#include <unistd.h>
-
-#include <mach/mach_time.h>
-#include <private/qcore_unix_p.h>
-
-QT_BEGIN_NAMESPACE
-
-#ifdef __LP64__
-typedef __int128_t LargeInt;
-#else
-typedef qint64 LargeInt;
-#endif
-
-QElapsedTimer::ClockType QElapsedTimer::clockType() noexcept
-{
-    return MachAbsoluteTime;
-}
-
-bool QElapsedTimer::isMonotonic() noexcept
-{
-    return true;
-}
-
-static mach_timebase_info_data_t info = { 0, 0 };
-static qint64 absoluteToNSecs(qint64 cpuTime)
-{
-    if (info.denom == 0)
-        mach_timebase_info(&info);
-
-    // don't do multiplication & division if those are equal
-    // (mathematically it would be the same, but it's computationally expensive)
-    if (info.numer == info.denom)
-        return cpuTime;
-    qint64 nsecs = LargeInt(cpuTime) * info.numer / info.denom;
-    return nsecs;
-}
-
-static qint64 absoluteToMSecs(qint64 cpuTime)
-{
-    return absoluteToNSecs(cpuTime) / 1000000;
-}
-
-timespec qt_gettime() noexcept
-{
-    timespec tv;
-
-    uint64_t cpu_time = mach_absolute_time();
-    uint64_t nsecs = absoluteToNSecs(cpu_time);
-    tv.tv_sec = nsecs / 1000000000ull;
-    tv.tv_nsec = nsecs - (tv.tv_sec * 1000000000ull);
-    return tv;
-}
-
-void qt_nanosleep(timespec amount)
-{
-    // Mac doesn't have clock_nanosleep, but it does have nanosleep.
-    // nanosleep is POSIX.1-1993
-
-    int r;
-    EINTR_LOOP(r, nanosleep(&amount, &amount));
-}
-
-void QElapsedTimer::start() noexcept
-{
-    t1 = mach_absolute_time();
-    t2 = 0;
-}
-
-qint64 QElapsedTimer::restart() noexcept
-{
-    qint64 old = t1;
-    t1 = mach_absolute_time();
-    t2 = 0;
-
-    return absoluteToMSecs(t1 - old);
-}
-
-qint64 QElapsedTimer::nsecsElapsed() const noexcept
-{
-    uint64_t cpu_time = mach_absolute_time();
-    return absoluteToNSecs(cpu_time - t1);
-}
-
-qint64 QElapsedTimer::elapsed() const noexcept
-{
-    uint64_t cpu_time = mach_absolute_time();
-    return absoluteToMSecs(cpu_time - t1);
-}
-
-qint64 QElapsedTimer::msecsSinceReference() const noexcept
-{
-    return absoluteToMSecs(t1);
-}
-
-qint64 QElapsedTimer::msecsTo(const QElapsedTimer &other) const noexcept
-{
-    return absoluteToMSecs(other.t1 - t1);
-}
-
-qint64 QElapsedTimer::secsTo(const QElapsedTimer &other) const noexcept
-{
-    return msecsTo(other) / 1000;
-}
-
-bool operator<(const QElapsedTimer &v1, const QElapsedTimer &v2) noexcept
-{
-    return v1.t1 < v2.t1;
-}
-
-QDeadlineTimer QDeadlineTimer::current(Qt::TimerType timerType) noexcept
-{
-    static_assert(!QDeadlineTimerNanosecondsInT2);
-    QDeadlineTimer result;
-    result.type = timerType;
-    result.t1 = absoluteToNSecs(mach_absolute_time());
-    return result;
-}
-
-QT_END_NAMESPACE

src/corelib/thread/qwaitcondition_unix.cpp

@@ -60,9 +60,8 @@ void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where)
 void qt_abstime_for_timeout(timespec *ts, QDeadlineTimer deadline)
 {
 #ifdef Q_OS_DARWIN
-    // on Mac, qt_gettime() (on qelapsedtimer_mac.cpp) returns ticks related to the Mach absolute time
-    // that doesn't work with pthread
-    // Mac also doesn't have clock_gettime
+    // on Mac, we don't have pthread_condattr_setclock(), so we need to
+    // calculate the CLOCK_REALTIME deadline
     struct timeval tv;
     qint64 nsec = deadline.remainingTimeNSecs();
     gettimeofday(&tv, 0);