diff --git a/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp b/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
--- a/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64RegisterBankInfo.cpp
@@ -38,12 +38,14 @@
 
 AArch64RegisterBankInfo::AArch64RegisterBankInfo(const TargetRegisterInfo &TRI)
     : AArch64GenRegisterBankInfo() {
+  static std::mutex RegisterBankInitLock;
   static bool AlreadyInit = false;
   // We have only one set of register banks, whatever the subtarget
   // is. Therefore, the initialization of the RegBanks table should be
   // done only once. Indeed the table of all register banks
   // (AArch64::RegBanks) is unique in the compiler. At some point, it
   // will get tablegen'ed and the whole constructor becomes empty.
+  std::lock_guard<std::mutex> Guard(RegisterBankInitLock);
   if (AlreadyInit)
     return;
   AlreadyInit = true;