Subzero: Fix the name mangling code's base-36 increment.

src/IceGlobalContext.cpp

Index: src/IceGlobalContext.cpp
diff --git a/src/IceGlobalContext.cpp b/src/IceGlobalContext.cpp
index 50ac5bd80adde1c3c0ae726b20a483bc8de0d13f..a7b1b64c2951f8780f7ad8304129539109f136e4 100644
--- a/src/IceGlobalContext.cpp
+++ b/src/IceGlobalContext.cpp
@@ -166,9 +166,10 @@ void GlobalContext::incrementSubstitutions(ManglerVector &OldName) const {
         assert(OldName[OldPos - 1] == 'S');
         assert(OldName[OldPos + Length] == '_');
         if (AllZs) {
-          // Replace N 'Z' characters with N+1 '0' characters.  (This
-          // is also true for N=0, i.e. S_ ==> S0_ .)
-          for (size_t i = 0; i < Length + 1; ++i) {
+          // Replace N 'Z' characters with a '0' (if N=0) or '1' (if
+          // N>0) followed by N '0' characters.
+          NewName[NewPos++] = (Length ? '1' : '0');
+          for (size_t i = 0; i < Length; ++i) {
             NewName[NewPos++] = '0';
           }
         } else {