Avoid creating a redundant zero APInt.

llvm-svn: 52602
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index e13011f..38b3790 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -2048,7 +2048,7 @@
     result = "-";
     insert_at = 1;
   }
-  if (tmp == APInt(tmp.getBitWidth(), 0))
+  if (tmp == zero)
     result = "0";
   else while (tmp.ne(zero)) {
     APInt APdigit(1,0);