Name threadpool threads.

[Benoit]

Summary

This gives our worker threads some names that allow easily identifying them in tools such as profilers and debuggers.

[Benoit]

shorter

[Benoit]

rebased, retrigger CI for suspected x64 debian flake.

[Benoit]

rebased, retrigger CI (fuzzer tests were still red on CI)

llvm/lib/Support/ThreadPool.cpp

 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/ThreadPool.h"
 
 #include "llvm/Config/llvm-config.h"
 
 #if LLVM_ENABLE_THREADS
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Threading.h"
 #else
 #include "llvm/Support/raw_ostream.h"
 #endif
 
 using namespace llvm;
 
 #if LLVM_ENABLE_THREADS

 void ThreadPool::grow(int requested) {
   llvm::sys::ScopedWriter LockGuard(ThreadsLock);
   if (Threads.size() >= MaxThreadCount)
     return; // Already hit the max thread pool size.
   int newThreadCount = std::min<int>(requested, MaxThreadCount);
   while (static_cast<int>(Threads.size()) < newThreadCount) {
     int ThreadID = Threads.size();
     Threads.emplace_back([this, ThreadID] {
+      set_thread_name(formatv("llvm::ThreadPool worker {0}", ThreadID));
       Strategy.apply_thread_strategy(ThreadID);
       processTasks(nullptr);
     });
   }
 }
 
 #ifndef NDEBUG
 // The group of the tasks run by the current thread.