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[libc] implement clock_gettime using vDSO #108458

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Merged
merged 2 commits into from
Sep 13, 2024
Merged

[libc] implement clock_gettime using vDSO #108458

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8d41997
[libc] implement clock_gettime using vDSO
SchrodingerZhu Sep 12, 2024
043dae5
fix
SchrodingerZhu Sep 13, 2024
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7 changes: 4 additions & 3 deletions libc/src/__support/macros/optimization.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_MACROS_OPTIMIZATION_H
#define LLVM_LIBC_SRC___SUPPORT_MACROS_OPTIMIZATION_H

#include "src/__support/macros/attributes.h" // LIBC_INLINE
#include "src/__support/macros/attributes.h" // LIBC_INLINE
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/compiler.h" // LIBC_COMPILER_IS_CLANG

Expand All @@ -24,9 +24,10 @@ LIBC_INLINE constexpr bool expects_bool_condition(T value, T expected) {
}
} // namespace details
} // namespace LIBC_NAMESPACE_DECL
#define LIBC_LIKELY(x) LIBC_NAMESPACE::details::expects_bool_condition(x, true)
#define LIBC_LIKELY(x) \
LIBC_NAMESPACE::details::expects_bool_condition(!!(x), true)
#define LIBC_UNLIKELY(x) \
LIBC_NAMESPACE::details::expects_bool_condition(x, false)
LIBC_NAMESPACE::details::expects_bool_condition(!!(x), false)

#if defined(LIBC_COMPILER_IS_CLANG)
#define LIBC_LOOP_NOUNROLL _Pragma("nounroll")
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1 change: 1 addition & 0 deletions libc/src/__support/time/linux/CMakeLists.txt
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Expand Up @@ -9,6 +9,7 @@ add_header_library(
libc.src.__support.common
libc.src.__support.error_or
libc.src.__support.OSUtil.osutil
libc.src.__support.OSUtil.vdso
)

add_header_library(
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9 changes: 9 additions & 0 deletions libc/src/__support/time/linux/clock_gettime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@

#include "hdr/types/clockid_t.h"
#include "hdr/types/struct_timespec.h"
#include "src/__support/OSUtil/linux/vdso.h"
#include "src/__support/OSUtil/linux/x86_64/vdso.h"
#include "src/__support/OSUtil/syscall.h"
#include "src/__support/common.h"
#include "src/__support/error_or.h"
Expand All @@ -20,11 +22,18 @@
namespace LIBC_NAMESPACE_DECL {
namespace internal {
LIBC_INLINE ErrorOr<int> clock_gettime(clockid_t clockid, timespec *ts) {
using namespace vdso;
#if SYS_clock_gettime
TypedSymbol<VDSOSym::ClockGetTime> clock_gettime;
if (LIBC_LIKELY(clock_gettime))
return clock_gettime(clockid, ts);
int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime,
static_cast<long>(clockid),
reinterpret_cast<long>(ts));
#elif defined(SYS_clock_gettime64)
TypedSymbol<VDSOSym::ClockGetTime64> clock_gettime64;
if (LIBC_LIKELY(clock_gettime64))
return clock_gettime64(clockid, ts);
static_assert(
sizeof(time_t) == sizeof(int64_t),
"SYS_clock_gettime64 requires struct timespec with 64-bit members.");
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