[libc] remove redundant call_once

[nickdesaulniers]

Missed cleanup from https://reviews.llvm.org/D134716.

Fixes: #79220

[llvmbot]

@llvm/pr-subscribers-libc

Author: Nick Desaulniers (nickdesaulniers)

Changes

Missed cleanup from https://reviews.llvm.org/D134716.

Fixes: #79220

---

Full diff: https://github.com/llvm/llvm-project/pull/79226.diff

2 Files Affected:

• (removed) libc/src/threads/linux/call_once.cpp (-67)
• (removed) libc/src/threads/linux/thread_start_args.h.def (-11)

diff --git a/libc/src/threads/linux/call_once.cpp b/libc/src/threads/linux/call_once.cpp
deleted file mode 100644
index 5cdd8ebfd190ea..00000000000000
--- a/libc/src/threads/linux/call_once.cpp
+++ /dev/null
@@ -1,67 +0,0 @@
-//===-- Linux implementation of the call_once 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 "Futex.h"
-
-#include "src/__support/CPP/atomic.h"
-#include "src/__support/OSUtil/syscall.h" // For syscall functions.
-#include "src/__support/common.h"
-#include "src/threads/call_once.h"
-#include "src/threads/linux/Futex.h"
-
-#include <limits.h>
-#include <linux/futex.h>
-#include <sys/syscall.h> // For syscall numbers.
-#include <threads.h>     // For call_once related type definition.
-
-namespace LIBC_NAMESPACE {
-
-static constexpr FutexWordType START = 0x11;
-static constexpr FutexWordType WAITING = 0x22;
-static constexpr FutexWordType FINISH = 0x33;
-static constexpr once_flag ONCE_FLAG_INIT_VAL = ONCE_FLAG_INIT;
-
-LLVM_LIBC_FUNCTION(void, call_once,
-                   (once_flag * flag, __call_once_func_t func)) {
-  auto *futex_word = reinterpret_cast<cpp::Atomic<FutexWordType> *>(flag);
-  static_assert(sizeof(*futex_word) == sizeof(once_flag));
-
-  FutexWordType not_called = ONCE_FLAG_INIT_VAL.__word;
-
-  // The C standard wording says:
-  //
-  //     The completion of the function func synchronizes with all
-  //     previous or subsequent calls to call_once with the same
-  //     flag variable.
-  //
-  // What this means is that, the call_once call can return only after
-  // the called function |func| returns. So, we use futexes to synchronize
-  // calls with the same flag value.
-  if (futex_word->compare_exchange_strong(not_called, START)) {
-    func();
-    auto status = futex_word->exchange(FINISH);
-    if (status == WAITING) {
-      LIBC_NAMESPACE::syscall_impl(FUTEX_SYSCALL_ID, &futex_word->val,
-                                   FUTEX_WAKE_PRIVATE,
-                                   INT_MAX, // Wake all waiters.
-                                   0, 0, 0);
-    }
-    return;
-  }
-
-  FutexWordType status = START;
-  if (futex_word->compare_exchange_strong(status, WAITING) ||
-      status == WAITING) {
-    LIBC_NAMESPACE::syscall_impl(
-        FUTEX_SYSCALL_ID, &futex_word->val, FUTEX_WAIT_PRIVATE,
-        WAITING, // Block only if status is still |WAITING|.
-        0, 0, 0);
-  }
-}
-
-} // namespace LIBC_NAMESPACE
diff --git a/libc/src/threads/linux/thread_start_args.h.def b/libc/src/threads/linux/thread_start_args.h.def
deleted file mode 100644
index cc990a37548b6c..00000000000000
--- a/libc/src/threads/linux/thread_start_args.h.def
+++ /dev/null
@@ -1,11 +0,0 @@
-//===-- Implementation of the get_start_args_addr function ------*- C++ -*-===//
-//
-// 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 <stdint.h>
-
-%%include_file(${thread_start_args})