Index: lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
+++ lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
@@ -304,18 +304,18 @@
   // MaxStructCounterNameSize and append #NumFields and at least one
   // field type id.
   // Append #NumFields.
-  NameStr += "#";
+  NameStr += "_";
   Twine(StructTy->getNumElements()).toVector(NameStr);
   // Append struct field type ids in the reverse order.
   for (int i = StructTy->getNumElements() - 1; i >= 0; --i) {
-    NameStr += "#";
+    NameStr += "_";
     Twine(StructTy->getElementType(i)->getTypeID()).toVector(NameStr);
     if (NameStr.size() >= MaxStructCounterNameSize)
       break;
   }
   if (StructTy->isLiteral()) {
-    // End with # for literal struct.
-    NameStr += "#";
+    // End with _ for literal struct.
+    NameStr += "_";
   }
 }