[llvm-commits] [llvm] r103834 - /llvm/trunk/include/llvm/Constants.h

[Dan Gohman]

Author: djg
Date: Fri May 14 18:01:02 2010
New Revision: 103834

URL: http://llvm.org/viewvc/llvm-project?rev=103834&view=rev
Log:
Add some comments about undef.

Modified:
    llvm/trunk/include/llvm/Constants.h

Modified: llvm/trunk/include/llvm/Constants.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Constants.h?rev=103834&r1=103833&r2=103834&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Constants.h (original)
+++ llvm/trunk/include/llvm/Constants.h Fri May 14 18:01:02 2010
@@ -923,7 +923,11 @@
 /// UndefValue - 'undef' values are things that do not have specified contents.
 /// These are used for a variety of purposes, including global variable
 /// initializers and operands to instructions.  'undef' values can occur with
-/// any type.
+/// any first-class type.
+///
+/// Undef values aren't exactly constants; if they have multiple uses, they
+/// can appear to have different bit patterns at each use. See
+/// LangRef.html#undefvalues for details.
 ///
 class UndefValue : public Constant {
   friend struct ConstantCreator<UndefValue, Type, char>;
@@ -954,6 +958,7 @@
     return V->getValueID() == UndefValueVal;
   }
 };
+
 } // End llvm namespace
 
 #endif