Eliminate sign-comparison warnings in APInt

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140158 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index d7291a1..931c885 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -54,12 +54,14 @@
       return r;
 
     r = cdigit - 'A';
-    if (r <= radix - 11U)
+    if (r <= unsigned(radix - 11U))
       return r + 10;
 
     r = cdigit - 'a';
-    if (r <= radix - 11U)
+    if (r <= unsigned(radix - 11U))
       return r + 10;
+    
+    radix = 10;
   }
 
   r = cdigit - '0';