Index: llvm/include/llvm/Support/Error.h
===================================================================
--- llvm/include/llvm/Support/Error.h
+++ llvm/include/llvm/Support/Error.h
@@ -246,20 +246,31 @@
   }
 
 private:
-  void assertIsChecked() {
 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
-    if (!getChecked() || getPtr()) {
-      dbgs() << "Program aborted due to an unhandled Error:\n";
-      if (getPtr())
-        getPtr()->log(dbgs());
-      else
-        dbgs()
-            << "Error value was Success. (Note: Success values must still be "
-               "checked prior to being destroyed).\n";
-      abort();
-    }
-#endif
+  // assertIsChecked() happens very frequently, but under normal circumstances
+  // is supposed to be a no-op.  So we want it to be inlined, but having a bunch
+  // of debug prints can cause the function to be too large for inlining.  So
+  // we hint the compiler by making sure the unlikely path doesn't get inlined,
+  // which should guarantee that the fast path does get inlined.
+  LLVM_ATTRIBUTE_NOINLINE
+  void fatalUncheckedError() const {
+    dbgs() << "Program aborted due to an unhandled Error:\n";
+    if (getPtr())
+      getPtr()->log(dbgs());
+    else
+      dbgs() << "Error value was Success. (Note: Success values must still be "
+                "checked prior to being destroyed).\n";
+    abort();
+  }
+
+  void assertIsChecked() {
+    if (LLVM_UNLIKELY(!getChecked() || getPtr()))
+      fatalUncheckedError();
+  }
+#else
+  void assertIsChecked() {
   }
+#endif
 
   ErrorInfoBase *getPtr() const {
     return reinterpret_cast<ErrorInfoBase*>(