[clang] [llvm] [LLVM] Add GNU make jobserver support (PR #145131)

[Artem Belevich via llvm-commits]

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@@ -0,0 +1,257 @@
+//===- llvm/Support/Jobserver.cpp - Jobserver Client Implementation -------===//
+//
+// 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 "llvm/Support/Jobserver.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <atomic>
+#include <memory>
+#include <mutex>
+#include <new>
+
+#define DEBUG_TYPE "jobserver"
+
+using namespace llvm;
+
+namespace {
+struct JobserverConfig {
+  enum Mode {
+    None,
+    PosixFifo,
+    PosixPipe,
+    Win32Semaphore,
+  };
+  Mode TheMode = None;
+  std::string Path;
+  int ReadFD = -1;
+  int WriteFD = -1;
+};
+
+/// A helper function that checks if `Input` starts with `Prefix`.
+/// If it does, it removes the prefix from `Input`, assigns the remainder to
+/// `Value`, and returns true. Otherwise, it returns false.
+bool getPrefixedValue(StringRef Input, StringRef Prefix, StringRef &Value) {
+  if (Input.consume_front(Prefix)) {
+    Value = Input;
+    return true;
+  }
+  return false;
+}
+
+/// A helper function to parse a string in the format "R,W" where R and W are
+/// non-negative integers representing file descriptors. It populates the
+/// `ReadFD` and `WriteFD` output parameters. Returns true on success.
+bool getFileDescriptorPair(StringRef Input, int &ReadFD, int &WriteFD) {
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Artem-B wrote:

Returning `optional<pair<int, int>>` might work well here.

https://github.com/llvm/llvm-project/pull/145131