Patch by Dan Liew for ConstantExpr::isTrue() and ConstantExpr::isFalse():

http://keeda.stanford.edu/pipermail/klee-dev/2012-August/000892.html

git-svn-id: https://llvm.org/svn/llvm-project/klee/trunk@163606 91177308-0d34-0410-b5e6-96231b3b80d8

include/klee/Expr.h

@@ -473,12 +473,12 @@ public:
   
   /// isTrue - Is this the true expression.
   bool isTrue() const { 
-    return getZExtValue(1) == 1;
+    return (getWidth() == Expr::Bool && value.getBoolValue()==true);
   }
 
   /// isFalse - Is this the false expression.
   bool isFalse() const {
-    return getZExtValue(1) == 0;
+    return (getWidth() == Expr::Bool && value.getBoolValue()==false);
   }
 
   /// isAllOnes - Is this constant all ones.