Index: llvm/include/llvm/Support/TypeSize.h
===================================================================
--- llvm/include/llvm/Support/TypeSize.h
+++ llvm/include/llvm/Support/TypeSize.h
@@ -145,11 +145,10 @@
   }
 
   // Casts to a uint64_t if this is a fixed-width size.
-  //
-  // NOTE: This interface is obsolete and will be removed in a future version
+  // FIXME: This interface is obsolete and will be removed in a future version
   // of LLVM in favour of calling getFixedSize() directly.
   operator uint64_t() const {
-    return getFixedSize();
+    return isScalable() ? getKnownMinSize() : getFixedSize();
   }
 
   // Additional convenience operators needed to avoid ambiguous parses.