Adding FreeBSD support

This commit adds required conditional compilation blocks to enable bulding on
FreeBSD (tested on x86_64 FreeBSD 14.1-RELEASE-p6). Also implements FreeBSD
synchronization shims using `_umtx_op(2)`

stdlib/public/Platform/Platform.swift

@@ -338,12 +338,12 @@ public var SIG_DFL: sig_t? { return nil }
 public var SIG_IGN: sig_t { return unsafeBitCast(1, to: sig_t.self) }
 public var SIG_ERR: sig_t { return unsafeBitCast(-1, to: sig_t.self) }
 public var SIG_HOLD: sig_t { return unsafeBitCast(5, to: sig_t.self) }
-#elseif os(OpenBSD)
+#elseif os(OpenBSD) || os(FreeBSD)
 public var SIG_DFL: sig_t? { return nil }
 public var SIG_IGN: sig_t { return unsafeBitCast(1, to: sig_t.self) }
 public var SIG_ERR: sig_t { return unsafeBitCast(-1, to: sig_t.self) }
 public var SIG_HOLD: sig_t { return unsafeBitCast(3, to: sig_t.self) }
-#elseif os(Linux) || os(FreeBSD) || os(PS4) || os(Android) || os(Haiku)
+#elseif os(Linux) || os(PS4) || os(Android) || os(Haiku)
 #if !canImport(SwiftMusl)
 public typealias sighandler_t = __sighandler_t
 #endif
@@ -495,3 +495,7 @@ public var environ: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?> {
 }
 #endif
 #endif // SWIFT_STDLIB_HAS_ENVIRON
+
+#if os(FreeBSD)
+public let inet_pton = __inet_pton
+#endif

stdlib/public/Platform/SwiftGlibc.h.gyb

@@ -65,6 +65,7 @@ headers = [
   'spawn.h',
   'strings.h',
   'sys/event.h',
+  'sys/extattr.h',
   'sys/file.h',
   'sys/inotify.h',
   'sys/ioctl.h',
@@ -84,6 +85,7 @@ headers = [
   'sys/times.h',
   'sys/types.h',
   'sys/uio.h',
+  'sys/umtx.h',
   'sys/un.h',
   'sys/user.h',
   'sys/utsname.h',

stdlib/public/Platform/glibc.modulemap.gyb

@@ -19,7 +19,7 @@
 /// It's not named just Glibc so that it doesn't conflict in the event of a
 /// future official glibc modulemap.
 module SwiftGlibc [system] {
-% if CMAKE_SDK in ["LINUX", "OPENBSD"]:
+% if CMAKE_SDK in ["LINUX", "OPENBSD", "FREEBSD"]:
       link "m"
 % end
 % if CMAKE_SDK in ["LINUX", "FREEBSD", "OPENBSD", "CYGWIN"]:

stdlib/public/SwiftShims/swift/shims/_SynchronizationShims.h

@@ -66,4 +66,9 @@ static inline __swift_uint32_t _swift_stdlib_futex_unlock(__swift_uint32_t *lock
 
 #endif // defined(__linux__)
 
+#if defined(__FreeBSD__)
+#include <sys/types.h>
+#include <sys/umtx.h>
+#endif
+
 #endif // SWIFT_STDLIB_SYNCHRONIZATION_SHIMS_H

stdlib/public/Synchronization/CMakeLists.txt

@@ -54,6 +54,13 @@ set(SWIFT_SYNCHRONIZATION_LINUX_SOURCES
   Mutex/SpinLoopHint.swift
 )
 
+# FreeBSD sources
+
+set(SWIFT_SYNCHRONIZATION_FREEBSD_SOURCES
+  Mutex/FreeBSDImpl.swift
+  Mutex/Mutex.swift
+)
+
 # Wasm sources
 
 set(SWIFT_SYNCHRONIZATION_WASM_SOURCES
@@ -101,6 +108,8 @@ add_swift_target_library(swiftSynchronization ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES
     ${SWIFT_SYNCHRONIZATION_WASM_SOURCES}
   SWIFT_SOURCES_DEPENDS_WINDOWS
     ${SWIFT_SYNCHRONIZATION_WINDOWS_SOURCES}
+  SWIFT_SOURCES_DEPENDS_FREEBSD
+    ${SWIFT_SYNCHRONIZATION_FREEBSD_SOURCES}
   SWIFT_SOURCES_DEPENDS_FREESTANDING
     Mutex/MutexUnavailable.swift
 
@@ -124,6 +133,8 @@ add_swift_target_library(swiftSynchronization ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES
     Android
   SWIFT_MODULE_DEPENDS_WINDOWS
     WinSDK
+  SWIFT_MODULE_DEPENDS_FREEBSD
+    Glibc
 
   SWIFT_COMPILE_FLAGS
     ${SWIFT_SYNCHRNOIZATION_SWIFT_FLAGS}

stdlib/public/Synchronization/Mutex/FreeBSDImpl.swift

@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Atomics open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Glibc
+
+@available(SwiftStdlib 6.0, *)
+@frozen
+@_staticExclusiveOnly
+public struct _MutexHandle: ~Copyable {
+  @usableFromInline
+  let value: _Cell<umutex>
+
+  @available(SwiftStdlib 6.0, *)
+  @_alwaysEmitIntoClient
+  @_transparent
+  public init() {
+    value = _Cell(umutex())
+  }
+
+  @available(SwiftStdlib 6.0, *)
+  @_alwaysEmitIntoClient
+  @_transparent
+  internal borrowing func _lock() {
+    _umtx_op(value._address, UMTX_OP_MUTEX_LOCK, 0, nil, nil)
+  }
+
+  @available(SwiftStdlib 6.0, *)
+  @_alwaysEmitIntoClient
+  @_transparent
+  internal borrowing func _tryLock() -> Bool {
+    _umtx_op(value._address, UMTX_OP_MUTEX_TRYLOCK, 0, nil, nil) != -1
+  }
+
+  @available(SwiftStdlib 6.0, *)
+  @_alwaysEmitIntoClient
+  @_transparent
+  internal borrowing func _unlock() {
+    _umtx_op(value._address, UMTX_OP_MUTEX_UNLOCK, 0, nil, nil)
+  }
+}