Revert "[flang] Add POSIX implementation for SYSTEM_CLOCK"

This reverts commit 2534d53.

Author: jeanPerier

flang/runtime/time-intrinsic.cpp

@@ -106,58 +106,6 @@ count_t GetSystemClockCountMax(fallback_implementation) {
   return std::min(std::numeric_limits<std::clock_t>::max(),
       std::numeric_limits<count_t>::max());
 }
-
-constexpr count_t NSECS_PER_SEC{1'000'000'000};
-
-// POSIX implementation using clock_gettime. This is only enabled if
-// clock_gettime is available.
-template <typename T = int, typename U = struct timespec>
-count_t GetSystemClockCount(preferred_implementation,
-    // We need some dummy parameters to pass to decltype(clock_gettime).
-    T ClockId = 0, U *Timespec = nullptr,
-    decltype(clock_gettime(ClockId, Timespec)) *Enabled = nullptr) {
-#if defined CLOCK_THREAD_CPUTIME_ID
-#define CLOCKID CLOCK_THREAD_CPUTIME_ID
-#elif defined CLOCK_PROCESS_CPUTIME_ID
-#define CLOCKID CLOCK_PROCESS_CPUTIME_ID
-#elif defined CLOCK_MONOTONIC
-#define CLOCKID CLOCK_MONOTONIC
-#else
-#define CLOCKID CLOCK_REALTIME
-#endif
-  struct timespec tspec;
-  if (clock_gettime(CLOCKID, &tspec) != 0) {
-    // Return -HUGE() to represent failure.
-    return -std::numeric_limits<count_t>::max();
-  }
-
-  // Wrap around to avoid overflows.
-  constexpr count_t max_secs{
-      std::numeric_limits<count_t>::max() / NSECS_PER_SEC};
-  count_t wrapped_secs{tspec.tv_sec % max_secs};
-
-  // At this point, wrapped_secs < max_secs, and max_secs has already been
-  // truncated by the division. Therefore, we should still have enough room to
-  // add tv_nsec, since it is < NSECS_PER_SEC.
-  return tspec.tv_nsec + wrapped_secs * NSECS_PER_SEC;
-}
-
-template <typename T = int, typename U = struct timespec>
-count_t GetSystemClockCountRate(preferred_implementation,
-    // We need some dummy parameters to pass to decltype(clock_gettime).
-    T ClockId = 0, U *Timespec = nullptr,
-    decltype(clock_gettime(ClockId, Timespec)) *Enabled = nullptr) {
-  return NSECS_PER_SEC;
-}
-
-template <typename T = int, typename U = struct timespec>
-count_t GetSystemClockCountMax(preferred_implementation,
-    // We need some dummy parameters to pass to decltype(clock_gettime).
-    T ClockId = 0, U *Timespec = nullptr,
-    decltype(clock_gettime(ClockId, Timespec)) *Enabled = nullptr) {
-  count_t max_secs{std::numeric_limits<count_t>::max() / NSECS_PER_SEC};
-  return max_secs * NSECS_PER_SEC - 1;
-}
 } // anonymous namespace
 
 namespace Fortran::runtime {