Improve QElapsedTimer resolution on QNX

The standard POSIX clock functions are present on QNX, but only
return timing information with millisecond accuracy.  To get
accuracy beyond that, platform-specific functions must be used.

Change-Id: I54a0550f1865dbea3c60a86ecd8ad99df3fe42b4
Reviewed-by: Frank Osterfeld <frank.osterfeld@kdab.com>
Reviewed-by: Bernd Weimer <bweimer@blackberry.com>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>

src/corelib/tools/qelapsedtimer_unix.cpp

@@ -35,8 +35,12 @@
 #define _POSIX_C_SOURCE 200809L
 
 #include "qelapsedtimer.h"
-#ifdef Q_OS_VXWORKS
+#if defined(Q_OS_VXWORKS)
 #include "qfunctions_vxworks.h"
+#elif defined(Q_OS_QNX)
+#include <sys/neutrino.h>
+#include <sys/syspage.h>
+#include <inttypes.h>
 #else
 #include <sys/time.h>
 #include <time.h>
@@ -84,7 +88,18 @@ QT_BEGIN_NAMESPACE
  *  see http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html
  */
 
-#ifndef CLOCK_REALTIME
+#if defined(Q_OS_QNX)
+static inline void qt_clock_gettime(clockid_t clock, struct timespec *ts)
+{
+    // The standard POSIX clock calls only have 1ms accuracy on QNX.  To get
+    // higher accuracy, this platform-specific function must be used instead
+    quint64 cycles_per_sec = SYSPAGE_ENTRY(qtime)->cycles_per_sec;
+    quint64 cycles = ClockCycles();
+    ts->tv_sec = cycles / cycles_per_sec;
+    quint64 mod = cycles % cycles_per_sec;
+    ts->tv_nsec = mod * Q_INT64_C(1000000000) / cycles_per_sec;
+}
+#elif !defined(CLOCK_REALTIME)
 #  define CLOCK_REALTIME 0
 static inline void qt_clock_gettime(int, struct timespec *ts)
 {