libcxx/include/__support/ibm/gettod_zos.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___SUPPORT_IBM_GETTOD_ZOS_H
  11 #define _LIBCPP___SUPPORT_IBM_GETTOD_ZOS_H
  12
  13 #include <time.h>
  14
  15 inline _LIBCPP_HIDE_FROM_ABI int gettimeofdayMonotonic(struct timespec64* Output) {
  16   // The POSIX gettimeofday() function is not available on z/OS. Therefore,
  17   // we will call stcke and other hardware instructions in implement equivalent.
  18   // Note that nanoseconds alone will overflow when reaching new epoch in 2042.
  19
  20   struct _t {
  21     uint64_t Hi;
  22     uint64_t Lo;
  23   };
  24   struct _t Value = {0, 0};
  25   uint64_t CC     = 0;
  26   asm(" stcke %0\n"
  27       " ipm %1\n"
  28       " srlg %1,%1,28\n"
  29       : "=m"(Value), "+r"(CC)::);
  30
  31   if (CC != 0) {
  32     errno = EMVSTODNOTSET;
  33     return CC;
  34   }
  35   uint64_t us = (Value.Hi >> 4);
  36   uint64_t ns = ((Value.Hi & 0x0F) << 8) + (Value.Lo >> 56);
  37   ns          = (ns * 1000) >> 12;
  38   us          = us - 2208988800000000;
  39
  40   register uint64_t DivPair0 asm("r0"); // dividend (upper half), remainder
  41   DivPair0 = 0;
  42   register uint64_t DivPair1 asm("r1"); // dividend (lower half), quotient
  43   DivPair1         = us;
  44   uint64_t Divisor = 1000000;
  45   asm(" dlgr %0,%2" : "+r"(DivPair0), "+r"(DivPair1) : "r"(Divisor) :);
  46
  47   Output->tv_sec  = DivPair1;
  48   Output->tv_nsec = DivPair0 * 1000 + ns;
  49   return 0;
  50 }
  51
  52 #endif // _LIBCPP___SUPPORT_IBM_GETTOD_ZOS_H