LLVM: Add in literal undefined value to binding

compiler/llvmGen/Llvm/Types.hs

@@ -101,6 +101,8 @@ data LlvmLit
   | LMFloatLit Double LlvmType
   -- | Literal NULL, only applicable to pointer types
   | LMNullLit LlvmType
+  -- | Undefined value, random bit pattern. Useful for optimisations.
+  | LMUndefLit LlvmType
   deriving (Eq)
 
 instance Show LlvmLit where
@@ -208,6 +210,7 @@ getLit (LMFloatLit r LMFloat ) = fToStr $ realToFrac r
 getLit (LMFloatLit r LMDouble) = dToStr r
 getLit f@(LMFloatLit _ _) = error $ "Can't print this float literal!" ++ show f
 getLit (LMNullLit _) = "null"
+getLit (LMUndefLit _) = "undef"
 
 -- | Return the 'LlvmType' of the 'LlvmVar'
 getVarType :: LlvmVar -> LlvmType
@@ -221,6 +224,7 @@ getLitType :: LlvmLit -> LlvmType
 getLitType (LMIntLit   _ t) = t
 getLitType (LMFloatLit _ t) = t
 getLitType (LMNullLit    t) = t
+getLitType (LMUndefLit   t) = t
 
 -- | Return the 'LlvmType' of the 'LlvmStatic'
 getStatType :: LlvmStatic -> LlvmType