[libcxx] Support for using timespec_get (#117362)

clock_gettime is a POSIX API that may not be available on platforms like
baremetal; timespec_get is the C11 equivalent. This change adds support
for using timespec_get instead of clock_gettime to improve compatibility
with non-POSIX platforms. For now, this is only enabled with LLVM libc
which implemented timespec_get in #116102, but in the future this can be
expanded to other platforms.

Related to #84879.

2 files changed, 32 insertions, 0 deletions

diff --git a/libcxx/src/chrono.cpp b/libcxx/src/chrono.cpp
index 3510569..dbc0f61 100644
--- a/libcxx/src/chrono.cpp
+++ b/libcxx/src/chrono.cpp
@@ -31,6 +31,10 @@
 #  include <sys/time.h> // for gettimeofday and timeval
 #endif
 
+#if defined(__LLVM_LIBC__)
+#  define _LIBCPP_HAS_TIMESPEC_GET
+#endif
+
 // OpenBSD and GPU do not have a fully conformant suite of POSIX timers, but
 // it does have clock_gettime and CLOCK_MONOTONIC which is all we need.
 #if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__OpenBSD__) || defined(__AMDGPU__) ||                      \
@@ -115,6 +119,15 @@ static system_clock::time_point __libcpp_system_clock_now() {
   return system_clock::time_point(duration_cast<system_clock::duration>(d - nt_to_unix_epoch));
 }
 
+#elif defined(_LIBCPP_HAS_TIMESPEC_GET)
+
+static system_clock::time_point __libcpp_system_clock_now() {
+  struct timespec ts;
+  if (timespec_get(&ts, TIME_UTC) != TIME_UTC)
+    __throw_system_error(errno, "timespec_get(TIME_UTC) failed");
+  return system_clock::time_point(seconds(ts.tv_sec) + microseconds(ts.tv_nsec / 1000));
+}
+
 #elif defined(_LIBCPP_HAS_CLOCK_GETTIME)
 
 static system_clock::time_point __libcpp_system_clock_now() {
@@ -216,6 +229,15 @@ static steady_clock::time_point __libcpp_steady_clock_now() noexcept {
   return steady_clock::time_point(nanoseconds(_zx_clock_get_monotonic()));
 }
 
+#  elif defined(_LIBCPP_HAS_TIMESPEC_GET)
+
+static steady_clock::time_point __libcpp_steady_clock_now() {
+  struct timespec ts;
+  if (timespec_get(&ts, TIME_MONOTONIC) != TIME_MONOTONIC)
+    __throw_system_error(errno, "timespec_get(TIME_MONOTONIC) failed");
+  return steady_clock::time_point(seconds(ts.tv_sec) + microseconds(ts.tv_nsec / 1000));
+}
+
 #  elif defined(_LIBCPP_HAS_CLOCK_GETTIME)
 
 static steady_clock::time_point __libcpp_steady_clock_now() {
diff --git a/libcxx/src/filesystem/filesystem_clock.cpp b/libcxx/src/filesystem/filesystem_clock.cpp
index d174ecd..e1f8870 100644
--- a/libcxx/src/filesystem/filesystem_clock.cpp
+++ b/libcxx/src/filesystem/filesystem_clock.cpp
@@ -30,6 +30,10 @@
 #  include <sys/time.h> // for gettimeofday and timeval
 #endif
 
+#if defined(__LLVM_LIBC__)
+#  define _LIBCPP_HAS_TIMESPEC_GET
+#endif
+
 #if defined(__APPLE__) || defined(__gnu_hurd__) || defined(__AMDGPU__) || defined(__NVPTX__) ||                        \
     (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
 #  define _LIBCPP_HAS_CLOCK_GETTIME
@@ -50,6 +54,12 @@ _FilesystemClock::time_point _FilesystemClock::now() noexcept {
   GetSystemTimeAsFileTime(&time);
   detail::TimeSpec tp = detail::filetime_to_timespec(time);
   return time_point(__secs(tp.tv_sec) + chrono::duration_cast<duration>(__nsecs(tp.tv_nsec)));
+#elif defined(_LIBCPP_HAS_TIMESPEC_GET)
+  typedef chrono::duration<rep, nano> __nsecs;
+  struct timespec ts;
+  if (timespec_get(&ts, TIME_UTC) != TIME_UTC)
+    __throw_system_error(errno, "timespec_get(TIME_UTC) failed");
+  return time_point(__secs(ts.tv_sec) + chrono::duration_cast<duration>(__nsecs(ts.tv_nsec)));
 #elif defined(_LIBCPP_HAS_CLOCK_GETTIME)
   typedef chrono::duration<rep, nano> __nsecs;
   struct timespec tp;