> \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
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