\begin{code} primCode [res] IsHNF [arg] = let res' = amodeToStix res arg' = amodeToStix arg arg_info = StInd PtrRep arg' word_32 = StInd WordRep (StIndex PtrRep arg_info (StInt (-1))) masked_le32 = StPrim SrlOp [word_32, StInt 16] masked_be32 = StPrim AndOp [word_32, StInt 65535] #ifdef WORDS_BIGENDIAN ty_info = masked_le32 #else ty_info = masked_be32 #endif not_a_thunk = StPrim IntEqOp [ StPrim AndOp [ty_info, StInt 0x10] , StInt 0x0 ] -- ToDo: don't hardwire the value of _THUNK from InfoTables.h assign = StAssign IntRep res' not_a_thunk in returnUs (\ xs -> assign : xs) \end{code}

This code looks bogus - it is checking a bit in the info table, which would have been correct when we used to store flags in the info table, but that changed a while back. closure_THUNK() works by getting the type field (i.e. get_itbl(c)->type), and using that to index into the table of closure flags (see ghc/rts/ClosureFlags.c), and checking the "THU" flag. This is the portable way to do it. The hacky way to do it would be to compare against the closure types directly - fortunately you can use the names rather than the constants, see ghc/compiler/codeGen/SMRep.lhs. Cheers, Simon