Integrate LLVM at llvm/llvm-project@644de6ad1c75

Updates LLVM usage to match
[644de6ad1c75](llvm/llvm-project@644de6ad1c75)

PiperOrigin-RevId: 713739019

bazel/import_llvm.bzl

@@ -7,7 +7,7 @@ load(
 
 def import_llvm(name):
     """Imports LLVM."""
-    LLVM_COMMIT = "faa3f752896903c2d09d389970d3d0ebf50a1073"
+    LLVM_COMMIT = "644de6ad1c758d3bf754d7d50b98c555df5231b1"
 
     new_git_repository(
         name = name,

patches/llvm.patch

@@ -1 +1,17 @@
 Auto generated patch. Do not edit or delete it, even if empty.
+diff -ruN --strip-trailing-cr a/llvm/lib/Support/Timer.cpp b/llvm/lib/Support/Timer.cpp
+--- a/llvm/lib/Support/Timer.cpp
++++ b/llvm/lib/Support/Timer.cpp
+@@ -507,11 +507,11 @@
+   // Order of these members and initialization below is important. For example
+   // the DefaultTimerGroup uses the TimerLock. Most of these also depend on the
+   // options above.
++  std::once_flag InitDeferredFlag;
+   std::unique_ptr<SignpostEmitter> SignpostsPtr;
+   std::unique_ptr<sys::SmartMutex<true>> TimerLockPtr;
+   std::unique_ptr<TimerGroup> DefaultTimerGroupPtr;
+   std::unique_ptr<Name2PairMap> NamedGroupedTimersPtr;
+-  std::once_flag InitDeferredFlag;
+   TimerGlobals &initDeferred() {
+     std::call_once(InitDeferredFlag, [this]() {
+       SignpostsPtr = std::make_unique<SignpostEmitter>();