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%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
%
\section[CgUpdate]{Manipulating update frames}
\begin{code}
#include "HsVersions.h"
module CgUpdate ( pushUpdateFrame ) where
IMP_Ubiq(){-uitous-}
import CgMonad
import AbsCSyn
import Constants ( sTD_UF_SIZE, sCC_STD_UF_SIZE )
import CgStackery ( allocUpdateFrame )
import CmdLineOpts ( opt_SccProfilingOn )
import Util ( assertPanic )
\end{code}
%********************************************************
%* *
%* Setting up update frames *
%* *
%********************************************************
\subsection[setting-update-frames]{Setting up update frames}
@pushUpdateFrame@ $updatee$ pushes a general update frame which
points to $updatee$ as the thing to be updated. It is only used
when a thunk has just been entered, so the (real) stack pointers
are guaranteed to be nicely aligned with the top of stack.
@pushUpdateFrame@ adjusts the virtual and tail stack pointers
to reflect the frame pushed.
\begin{code}
pushUpdateFrame :: CAddrMode -> CAddrMode -> Code -> Code
pushUpdateFrame updatee vector code
= let
profiling_on = opt_SccProfilingOn
-- frame_size *includes* the return address
frame_size = if profiling_on
then sCC_STD_UF_SIZE
else sTD_UF_SIZE
in
getEndOfBlockInfo `thenFC` \ eob_info ->
ASSERT(case eob_info of { EndOfBlockInfo _ _ InRetReg -> True; _ -> False})
allocUpdateFrame frame_size vector (\ _ ->
-- Emit the push macro
absC (CMacroStmt PUSH_STD_UPD_FRAME [
updatee,
int_CLit0, -- Known to be zero because we have just
int_CLit0 -- entered a thunk
])
`thenC` code
)
int_CLit0 = mkIntCLit 0 -- out here to avoid pushUpdateFrame CAF (sigh)
{- ---------------------
What actually happens is something like this; but it got macro-ised
= pushOnBStack (CReg CurCostCentre) `thenFC` \ _ ->
pushOnBStack (CReg SuA) `thenFC` \ _ ->
pushOnBStack (CReg SuB) `thenFC` \ _ ->
pushOnBStack updatee `thenFC` \ _ ->
pushOnBStack (CLabel sTD_UPD_RET_VEC_LABEL CodePtrRep) `thenFC` \ _ ->
-- MAKE SuA, SuB POINT TO TOP OF A,B STACKS
-- Remember, SpB hasn't yet been incremented to account for the
-- 4-word update frame which has been pushed.
-- This code seems crude, but effective...
absC (AbsCStmts (CAssign (CReg SuA) (CReg SpA))
(CAssign (CReg SuB) (CAddr (SpBRel 0 4))))
-------------------------- -}
\end{code}
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