allwpilib/upstream_utils/llvm_patches/0004-Threading-updates.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: PJ Reiniger <pj.reiniger@gmail.com>
Date: Sat, 7 May 2022 22:17:19 -0400
Subject: [PATCH 04/35] Threading updates

- Remove guards for threads and exception
- Prefer scope gaurd over lock gaurd
---
 llvm/include/llvm/Support/Compiler.h |  6 -----
 llvm/lib/Support/ErrorHandling.cpp   | 39 +++++-----------------------
 llvm/lib/Support/ManagedStatic.cpp   | 10 +++----
 3 files changed, 11 insertions(+), 44 deletions(-)

diff --git a/llvm/include/llvm/Support/Compiler.h b/llvm/include/llvm/Support/Compiler.h
index 021d1d29368deb330418ff4e08fbf3931e4b7453..586242b53bbf4ceb9bad5c9c8b495f83cb088cda 100644
--- a/llvm/include/llvm/Support/Compiler.h
+++ b/llvm/include/llvm/Support/Compiler.h
@@ -648,7 +648,6 @@ void AnnotateIgnoreWritesEnd(const char *file, int line);
 /// initialize to some constant value. In almost all circumstances this is most
 /// appropriate for use with a pointer, integer, or small aggregation of
 /// pointers and integers.
-#if LLVM_ENABLE_THREADS
 #if __has_feature(cxx_thread_local) || defined(_MSC_VER)
 #define LLVM_THREAD_LOCAL thread_local
 #else
@@ -656,11 +655,6 @@ void AnnotateIgnoreWritesEnd(const char *file, int line);
 // we only need the restricted functionality that provides.
 #define LLVM_THREAD_LOCAL __thread
 #endif
-#else // !LLVM_ENABLE_THREADS
-// If threading is disabled entirely, this compiles to nothing and you get
-// a normal global variable.
-#define LLVM_THREAD_LOCAL
-#endif
 
 /// \macro LLVM_ENABLE_EXCEPTIONS
 /// Whether LLVM is built with exception support.
diff --git a/llvm/lib/Support/ErrorHandling.cpp b/llvm/lib/Support/ErrorHandling.cpp
index d4ca266f3c1f98337499fba4fd0675e49a7dcf18..4e1dca80a21881bfb8fa886a5921c780ca021bf2 100644
--- a/llvm/lib/Support/ErrorHandling.cpp
+++ b/llvm/lib/Support/ErrorHandling.cpp
@@ -15,7 +15,6 @@
 #include "llvm-c/ErrorHandling.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Config/config.h"
-#include "llvm/Config/llvm-config.h" // for LLVM_ENABLE_THREADS
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
@@ -45,7 +44,6 @@ static void *ErrorHandlerUserData = nullptr;
 static fatal_error_handler_t BadAllocErrorHandler = nullptr;
 static void *BadAllocErrorHandlerUserData = nullptr;
 
-#if LLVM_ENABLE_THREADS == 1
 // Mutexes to synchronize installing error handlers and calling error handlers.
 // Do not use ManagedStatic, or that may allocate memory while attempting to
 // report an OOM.
@@ -59,22 +57,17 @@ static void *BadAllocErrorHandlerUserData = nullptr;
 // builds. We can remove these ifdefs if that script goes away.
 static std::mutex ErrorHandlerMutex;
 static std::mutex BadAllocErrorHandlerMutex;
-#endif
 
 void llvm::install_fatal_error_handler(fatal_error_handler_t handler,
                                        void *user_data) {
-#if LLVM_ENABLE_THREADS == 1
-  std::lock_guard<std::mutex> Lock(ErrorHandlerMutex);
-#endif
+  std::scoped_lock Lock(ErrorHandlerMutex);
   assert(!ErrorHandler && "Error handler already registered!\n");
   ErrorHandler = handler;
   ErrorHandlerUserData = user_data;
 }
 
 void llvm::remove_fatal_error_handler() {
-#if LLVM_ENABLE_THREADS == 1
-  std::lock_guard<std::mutex> Lock(ErrorHandlerMutex);
-#endif
+  std::scoped_lock Lock(ErrorHandlerMutex);
   ErrorHandler = nullptr;
   ErrorHandlerUserData = nullptr;
 }
@@ -93,9 +86,7 @@ void llvm::report_fatal_error(std::string_view Reason, bool GenCrashDiag) {
   {
     // Only acquire the mutex while reading the handler, so as not to invoke a
     // user-supplied callback under a lock.
-#if LLVM_ENABLE_THREADS == 1
-    std::lock_guard<std::mutex> Lock(ErrorHandlerMutex);
-#endif
+    std::scoped_lock Lock(ErrorHandlerMutex);
     handler = ErrorHandler;
     handlerData = ErrorHandlerUserData;
   }
@@ -127,9 +118,7 @@ void llvm::report_fatal_error(std::string_view Reason, bool GenCrashDiag) {
 
 void llvm::install_bad_alloc_error_handler(fatal_error_handler_t handler,
                                            void *user_data) {
-#if LLVM_ENABLE_THREADS == 1
-  std::lock_guard<std::mutex> Lock(BadAllocErrorHandlerMutex);
-#endif
+  std::scoped_lock Lock(BadAllocErrorHandlerMutex);
   assert(!BadAllocErrorHandler &&
          "Bad alloc error handler already registered!\n");
   BadAllocErrorHandler = handler;
@@ -137,9 +126,7 @@ void llvm::install_bad_alloc_error_handler(fatal_error_handler_t handler,
 }
 
 void llvm::remove_bad_alloc_error_handler() {
-#if LLVM_ENABLE_THREADS == 1
-  std::lock_guard<std::mutex> Lock(BadAllocErrorHandlerMutex);
-#endif
+  std::scoped_lock Lock(BadAllocErrorHandlerMutex);
   BadAllocErrorHandler = nullptr;
   BadAllocErrorHandlerUserData = nullptr;
 }
@@ -150,9 +137,7 @@ void llvm::report_bad_alloc_error(const char *Reason, bool GenCrashDiag) {
   {
     // Only acquire the mutex while reading the handler, so as not to invoke a
     // user-supplied callback under a lock.
-#if LLVM_ENABLE_THREADS == 1
-    std::lock_guard<std::mutex> Lock(BadAllocErrorHandlerMutex);
-#endif
+    std::scoped_lock Lock(BadAllocErrorHandlerMutex);
     Handler = BadAllocErrorHandler;
     HandlerData = BadAllocErrorHandlerUserData;
   }
@@ -162,10 +147,6 @@ void llvm::report_bad_alloc_error(const char *Reason, bool GenCrashDiag) {
     llvm_unreachable("bad alloc handler should not return");
   }
 
-#ifdef LLVM_ENABLE_EXCEPTIONS
-  // If exceptions are enabled, make OOM in malloc look like OOM in new.
-  throw std::bad_alloc();
-#else
   // Don't call the normal error handler. It may allocate memory. Directly write
   // an OOM to stderr and abort.
   const char *OOMMessage = "LLVM ERROR: out of memory\n";
@@ -174,15 +155,8 @@ void llvm::report_bad_alloc_error(const char *Reason, bool GenCrashDiag) {
   (void)!::write(2, Reason, strlen(Reason));
   (void)!::write(2, Newline, strlen(Newline));
   abort();
-#endif
 }
 
-#ifdef LLVM_ENABLE_EXCEPTIONS
-// Do not set custom new handler if exceptions are enabled. In this case OOM
-// errors are handled by throwing 'std::bad_alloc'.
-void llvm::install_out_of_memory_new_handler() {
-}
-#else
 // Causes crash on allocation failure. It is called prior to the handler set by
 // 'install_bad_alloc_error_handler'.
 static void out_of_memory_new_handler() {
@@ -197,7 +171,6 @@ void llvm::install_out_of_memory_new_handler() {
   assert((old == nullptr || old == out_of_memory_new_handler) &&
          "new-handler already installed");
 }
-#endif
 
 void llvm::llvm_unreachable_internal(const char *msg, const char *file,
                                      unsigned line) {
diff --git a/llvm/lib/Support/ManagedStatic.cpp b/llvm/lib/Support/ManagedStatic.cpp
index a6ae67066ea0423334e8ee52106f220cd456e25e..fc798b7ec1b788e232c7374b9968dc71d4f506f0 100644
--- a/llvm/lib/Support/ManagedStatic.cpp
+++ b/llvm/lib/Support/ManagedStatic.cpp
@@ -12,23 +12,23 @@
 
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Config/config.h"
-#include "llvm/Support/Threading.h"
+#include "llvm/Support/mutex.h"
 #include <cassert>
 #include <mutex>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = nullptr;
 
-static std::recursive_mutex *getManagedStaticMutex() {
-  static std::recursive_mutex m;
+static llvm::mutex *getManagedStaticMutex() {
+  static llvm::mutex m;
   return &m;
 }
 
 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
   assert(Creator);
-  if (llvm_is_multithreaded()) {
-    std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
+  if (1) {
+    std::scoped_lock Lock(*getManagedStaticMutex());
 
     if (!Ptr.load(std::memory_order_relaxed)) {
       void *Tmp = Creator();