Index: lib/Support/APInt.cpp
===================================================================
--- lib/Support/APInt.cpp
+++ lib/Support/APInt.cpp
@@ -2159,6 +2159,16 @@
     return;
   }
 
+  // Second, check for a one bit value and just short circuit the logic below.
+  if (*this == 1 && getBitWidth() == 1) {
+    while (*Prefix) {
+      Str.push_back(*Prefix);
+      ++Prefix;
+    };
+    Str.push_back('1');
+    return;
+  }
+
   static const char Digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
   if (isSingleWord()) {
Index: test/CodeGen/Generic/signed-one-bit-int.ll
===================================================================
--- test/CodeGen/Generic/signed-one-bit-int.ll
+++ test/CodeGen/Generic/signed-one-bit-int.ll
@@ -0,0 +1,16 @@
+; RUN: llc -debug %s -o /dev/null 2>&1 | FileCheck %s
+
+define i32 @main() #0 {
+entry:
+  %cmp = icmp eq i32 0, 1
+; CHECK: ch = EntryToken
+; CHECK-NOT: i1 = Constant<-1>
+; CHECK: ch = BasicBlock<if.end
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then: 
+  ret i32 1
+
+if.end:  
+  ret i32 0
+}