From 62c70559bc70aae463204ea05afb242b9baaaeb8 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Fri, 14 May 2010 23:01:02 +0000 Subject: [PATCH] Add some comments about undef. llvm-svn: 103834 --- llvm/include/llvm/Constants.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/llvm/include/llvm/Constants.h b/llvm/include/llvm/Constants.h index ba0ace3f7a1b..9ca845ec9d72 100644 --- a/llvm/include/llvm/Constants.h +++ b/llvm/include/llvm/Constants.h @@ -923,7 +923,11 @@ DEFINE_TRANSPARENT_CASTED_OPERAND_ACCESSORS(ConstantExpr, Constant) /// 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; @@ -954,6 +958,7 @@ public: return V->getValueID() == UndefValueVal; } }; + } // End llvm namespace #endif