[LLD] Remove global state in lldCommon

Move all variables at file-scope or function-static-scope into a hosting structure (lld::CommonLinkerContext) that lives at lldMain()-scope. Drivers will inherit from this structure and add their own global state, in the same way as for the existing COFFLinkerContext.

See discussion in https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html

Differential Revision: https://reviews.llvm.org/D108850

5 files changed, 96 insertions, 37 deletions

diff --git a/lld/Common/CMakeLists.txt b/lld/Common/CMakeLists.txt
index 9fdc67be7901..1ae7da1f5f7f 100644
--- a/lld/Common/CMakeLists.txt
+++ b/lld/Common/CMakeLists.txt
@@ -28,6 +28,7 @@ set_source_files_properties("${version_inc}"
 
 add_lld_library(lldCommon
   Args.cpp
+  CommonLinkerContext.cpp
   DWARF.cpp
   ErrorHandler.cpp
   Filesystem.cpp
diff --git a/lld/Common/CommonLinkerContext.cpp b/lld/Common/CommonLinkerContext.cpp
new file mode 100644
index 000000000000..75a58e84e03a
--- /dev/null
+++ b/lld/Common/CommonLinkerContext.cpp
@@ -0,0 +1,41 @@
+//===- CommonLinkerContext.cpp --------------------------------------------===//
+//
+// 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 "lld/Common/CommonLinkerContext.h"
+#include "lld/Common/ErrorHandler.h"
+#include "lld/Common/Memory.h"
+
+using namespace llvm;
+using namespace lld;
+
+// Reference to the current LLD instance.
+static CommonLinkerContext *lctx;
+
+CommonLinkerContext::CommonLinkerContext() { lctx = this; }
+
+CommonLinkerContext::~CommonLinkerContext() {
+  assert(lctx);
+  // Explicitly call the destructors since we created the objects with placement
+  // new in SpecificAlloc::create().
+  for (auto &it : instances)
+    it.second->~SpecificAllocBase();
+  lctx = nullptr;
+}
+
+CommonLinkerContext &lld::commonContext() {
+  assert(lctx);
+  return *lctx;
+}
+
+bool lld::hasContext() { return lctx != nullptr; }
+
+void CommonLinkerContext::destroy() {
+  if (lctx == nullptr)
+    return;
+  delete lctx;
+}
diff --git a/lld/Common/ErrorHandler.cpp b/lld/Common/ErrorHandler.cpp
index 399b6cac7547..15b3bd058ee9 100644
--- a/lld/Common/ErrorHandler.cpp
+++ b/lld/Common/ErrorHandler.cpp
@@ -10,6 +10,7 @@
 
 #include "llvm/Support/Parallel.h"
 
+#include "lld/Common/CommonLinkerContext.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
@@ -18,51 +19,69 @@
 #include "llvm/Support/Process.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
-#include <mutex>
 #include <regex>
 
 using namespace llvm;
 using namespace lld;
 
-// The functions defined in this file can be called from multiple threads,
-// but lld::outs() or lld::errs() are not thread-safe. We protect them using a
-// mutex.
-static std::mutex mu;
-
-// We want to separate multi-line messages with a newline. `sep` is "\n"
-// if the last messages was multi-line. Otherwise "".
-static StringRef sep;
-
 static StringRef getSeparator(const Twine &msg) {
   if (StringRef(msg.str()).contains('\n'))
     return "\n";
   return "";
 }
 
-raw_ostream *lld::stdoutOS;
-raw_ostream *lld::stderrOS;
+ErrorHandler::~ErrorHandler() {
+  if (cleanupCallback)
+    cleanupCallback();
+}
+
+void ErrorHandler::initialize(llvm::raw_ostream &stdoutOS,
+                              llvm::raw_ostream &stderrOS, bool exitEarly,
+                              bool disableOutput) {
+  this->stdoutOS = &stdoutOS;
+  this->stderrOS = &stderrOS;
+  stderrOS.enable_colors(stderrOS.has_colors());
+  this->exitEarly = exitEarly;
+  this->disableOutput = disableOutput;
+}
 
-ErrorHandler &lld::errorHandler() {
-  static ErrorHandler handler;
-  return handler;
+void ErrorHandler::flushStreams() {
+  std::lock_guard<std::mutex> lock(mu);
+  outs().flush();
+  errs().flush();
 }
 
+ErrorHandler &lld::errorHandler() { return context().e; }
+
 raw_ostream &lld::outs() {
-  if (errorHandler().disableOutput)
+  ErrorHandler &e = errorHandler();
+  return e.outs();
+}
+
+raw_ostream &lld::errs() {
+  ErrorHandler &e = errorHandler();
+  return e.errs();
+}
+
+raw_ostream &ErrorHandler::outs() {
+  if (disableOutput)
     return llvm::nulls();
   return stdoutOS ? *stdoutOS : llvm::outs();
 }
 
-raw_ostream &lld::errs() {
-  if (errorHandler().disableOutput)
+raw_ostream &ErrorHandler::errs() {
+  if (disableOutput)
     return llvm::nulls();
   return stderrOS ? *stderrOS : llvm::errs();
 }
 
 void lld::exitLld(int val) {
-  // Delete any temporary file, while keeping the memory mapping open.
-  if (errorHandler().outputBuffer)
-    errorHandler().outputBuffer->discard();
+  if (hasContext()) {
+    ErrorHandler &e = errorHandler();
+    // Delete any temporary file, while keeping the memory mapping open.
+    if (e.outputBuffer)
+      e.outputBuffer->discard();
+  }
 
   // Re-throw a possible signal or exception once/if it was catched by
   // safeLldMain().
@@ -75,11 +94,9 @@ void lld::exitLld(int val) {
   if (!CrashRecoveryContext::GetCurrent())
     llvm_shutdown();
 
-  {
-    std::lock_guard<std::mutex> lock(mu);
-    lld::outs().flush();
-    lld::errs().flush();
-  }
+  if (hasContext())
+    lld::errorHandler().flushStreams();
+
   // When running inside safeLldMain(), restore the control flow back to the
   // CrashRecoveryContext. Otherwise simply use _exit(), meanning no cleanup,
   // since we want to avoid further crashes on shutdown.
diff --git a/lld/Common/Memory.cpp b/lld/Common/Memory.cpp
index c53e1d3e6cfc..7c90ff1d799c 100644
--- a/lld/Common/Memory.cpp
+++ b/lld/Common/Memory.cpp
@@ -7,16 +7,19 @@
 //===----------------------------------------------------------------------===//
 
 #include "lld/Common/Memory.h"
+#include "lld/Common/CommonLinkerContext.h"
 
 using namespace llvm;
 using namespace lld;
 
-BumpPtrAllocator lld::bAlloc;
-StringSaver lld::saver{bAlloc};
-std::vector<SpecificAllocBase *> lld::SpecificAllocBase::instances;
-
-void lld::freeArena() {
-  for (SpecificAllocBase *alloc : SpecificAllocBase::instances)
-    alloc->reset();
-  bAlloc.Reset();
+SpecificAllocBase *
+lld::SpecificAllocBase::getOrCreate(void *tag, size_t size, size_t align,
+                                    SpecificAllocBase *(&creator)(void *)) {
+  auto &instances = context().instances;
+  auto &instance = instances[tag];
+  if (instance == nullptr) {
+    void *storage = context().bAlloc.Allocate(size, align);
+    instance = creator(storage);
+  }
+  return instance;
 }
diff --git a/lld/Common/TargetOptionsCommandFlags.cpp b/lld/Common/TargetOptionsCommandFlags.cpp
index d39477ed89ad..b7749c4a2032 100644
--- a/lld/Common/TargetOptionsCommandFlags.cpp
+++ b/lld/Common/TargetOptionsCommandFlags.cpp
@@ -7,12 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "lld/Common/TargetOptionsCommandFlags.h"
-
 #include "llvm/CodeGen/CommandFlags.h"
 #include "llvm/Target/TargetOptions.h"
 
-static llvm::codegen::RegisterCodeGenFlags CGF;
-
 llvm::TargetOptions lld::initTargetOptionsFromCodeGenFlags() {
   return llvm::codegen::InitTargetOptionsFromCodeGenFlags(llvm::Triple());
 }