Index: include/llvm/Support/Error.h
===================================================================
--- include/llvm/Support/Error.h
+++ include/llvm/Support/Error.h
@@ -280,6 +280,12 @@
                 (reinterpret_cast<uintptr_t>(EI) &
                  ~static_cast<uintptr_t>(0x1)) |
                 (reinterpret_cast<uintptr_t>(Payload) & 0x1));
+
+# if !defined(NDEBUG)
+    if (BreakOnError && EI != nullptr) {
+      LLVM_BUILTIN_DEBUGTRAP;
+    }
+# endif
 #else
     Payload = EI;
 #endif
@@ -316,6 +322,11 @@
   }
 
   ErrorInfoBase *Payload = nullptr;
+
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS && !defined(NDEBUG)
+  // Set to true in debug sessions to immediately break when an error occcurs.
+  static bool BreakOnError;
+#endif
 };
 
 /// Subclass of Error for the sole purpose of identifying the success path in
Index: lib/Support/Error.cpp
===================================================================
--- lib/Support/Error.cpp
+++ lib/Support/Error.cpp
@@ -54,6 +54,10 @@
 char ECError::ID = 0;
 char StringError::ID = 0;
 
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS && !defined(NDEBUG)
+bool Error::BreakOnError = false;
+#endif
+
 void logAllUnhandledErrors(Error E, raw_ostream &OS, Twine ErrorBanner) {
   if (!E)
     return;