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//===-- Baremetal implementation of the clock function --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "src/time/clock.h"
#include "hdr/time_macros.h"
#include "hdr/types/struct_timespec.h"
#include "src/__support/CPP/limits.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/__support/time/units.h"
namespace LIBC_NAMESPACE_DECL {
extern "C" bool __llvm_libc_timespec_get_active(struct timespec *ts);
LLVM_LIBC_FUNCTION(clock_t, clock, ()) {
using namespace time_units;
struct timespec ts;
if (!__llvm_libc_timespec_get_active(&ts))
return clock_t(-1);
// The above call gets the CPU time in seconds plus nanoseconds.
// The standard requires that we return clock_t(-1) if we cannot represent
// clocks as a clock_t value.
constexpr clock_t CLOCK_SECS_MAX =
cpp::numeric_limits<clock_t>::max() / CLOCKS_PER_SEC;
if (ts.tv_sec > CLOCK_SECS_MAX)
return clock_t(-1);
if (ts.tv_nsec / 1_s_ns > CLOCK_SECS_MAX - ts.tv_sec)
return clock_t(-1);
// For the integer computation converting tv_nsec to clocks to work
// correctly, we want CLOCKS_PER_SEC to be less than 1000000000.
static_assert(1_s_ns > CLOCKS_PER_SEC,
"Expected CLOCKS_PER_SEC to be less than 1'000'000'000.");
return clock_t(ts.tv_sec * CLOCKS_PER_SEC +
ts.tv_nsec / (1_s_ns / CLOCKS_PER_SEC));
}
} // namespace LIBC_NAMESPACE_DECL
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