2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgMonad.lhs,v 1.21 1999/06/08 15:56:47 simonmar Exp $
6 \section[CgMonad]{The code generation monad}
8 See the beginning of the top-level @CodeGen@ module, to see how this
9 monadic stuff fits into the Big Picture.
16 initC, thenC, thenFC, listCs, listFCs, mapCs, mapFCs,
17 returnFC, fixC, absC, nopC, getAbsC,
19 forkClosureBody, forkStatics, forkAlts, forkEval,
20 forkEvalHelp, forkAbsC,
23 addBindC, addBindsC, modifyBindC, lookupBindC,
26 setEndOfBlockInfo, getEndOfBlockInfo,
28 setSRTLabel, getSRTLabel,
30 StackUsage, Slot(..), HeapUsage,
34 costCentresC, moduleName,
36 Sequel(..), -- ToDo: unabstract?
39 -- out of general friendliness, we also export ...
40 CgInfoDownwards(..), CgState(..), -- non-abstract
44 #include "HsVersions.h"
46 import {-# SOURCE #-} CgBindery ( CgIdInfo(..), CgBindings, maybeStkLoc, nukeVolatileBinds )
47 import {-# SOURCE #-} CgUsages ( getSpRelOffset )
50 import AbsCUtils ( mkAbsCStmts )
51 import CmdLineOpts ( opt_SccProfilingOn, opt_DoTickyProfiling )
52 import CLabel ( CLabel, mkUpdInfoLabel, pprCLabel )
53 import Module ( Module )
54 import DataCon ( ConTag )
57 import PrimRep ( PrimRep(..) )
58 import StgSyn ( StgLiveVars )
61 infixr 9 `thenC` -- Right-associative!
65 %************************************************************************
67 \subsection[CgMonad-environment]{Stuff for manipulating environments}
69 %************************************************************************
71 This monadery has some information that it only passes {\em
72 downwards}, as well as some ``state'' which is modified as we go
76 data CgInfoDownwards -- information only passed *downwards* by the monad
78 CompilationInfo -- COMPLETELY STATIC info about this compilation
79 -- (e.g., what flags were passed to the compiler)
81 CgBindings -- [Id -> info] : static environment
83 CLabel -- label of the current SRT
85 EndOfBlockInfo -- Info for stuff to do at end of basic block:
90 Module -- the module name
94 AbstractC -- code accumulated so far
95 CgBindings -- [Id -> info] : *local* bindings environment
96 -- Bindings for top-level things are given in the info-down part
100 @EndOfBlockInfo@ tells what to do at the end of this block of code or,
101 if the expression is a @case@, what to do at the end of each
107 VirtualSpOffset -- Args Sp: trim the stack to this point at a
108 -- return; push arguments starting just
109 -- above this point on a tail call.
111 -- This is therefore the stk ptr as seen
112 -- by a case alternative.
115 initEobInfo = EndOfBlockInfo 0 (OnStack 0)
118 Any addressing modes inside @Sequel@ must be ``robust,'' in the sense
119 that it must survive stack pointer adjustments at the end of the
125 VirtualSpOffset -- Continuation is on the stack, at the
126 -- specified location
131 CAddrMode -- Jump to this; if the continuation is for a vectored
132 -- case this might be the label of a return
133 -- vector Guaranteed to be a non-volatile
134 -- addressing mode (I think)
137 | SeqFrame -- like CaseAlts but push a seq frame too.
141 type SemiTaggingStuff
142 = Maybe -- Maybe[1] we don't have any semi-tagging stuff...
143 ([(ConTag, JoinDetails)], -- Alternatives
144 Maybe (Maybe Id, JoinDetails) -- Default (but Maybe[2] we don't have one)
145 -- Maybe[3] the default is a
146 -- bind-default (Just b); that is,
147 -- it expects a ptr to the thing
148 -- in Node, bound to b
152 = (AbstractC, CLabel) -- Code to load regs from heap object + profiling macros,
153 -- and join point label
155 -- The abstract C is executed only from a successful semitagging
156 -- venture, when a case has looked at a variable, found that it's
157 -- evaluated, and wants to load up the contents and go to the join
161 -- The OnStack case of sequelToAmode delivers an Amode which is only
162 -- valid just before the final control transfer, because it assumes
163 -- that Sp is pointing to the top word of the return address. This
164 -- seems unclean but there you go.
166 -- sequelToAmode returns an amode which refers to an info table. The info
167 -- table will always be of the RET(_VEC)?_(BIG|SMALL) kind. We're careful
168 -- not to handle real code pointers, just in case we're compiling for
169 -- an unregisterised/untailcallish architecture, where info pointers and
170 -- code pointers aren't the same.
172 sequelToAmode :: Sequel -> FCode CAddrMode
174 sequelToAmode (OnStack virt_sp_offset)
175 = getSpRelOffset virt_sp_offset `thenFC` \ sp_rel ->
176 returnFC (CVal sp_rel RetRep)
178 sequelToAmode UpdateCode = returnFC (CLbl mkUpdInfoLabel RetRep)
179 sequelToAmode (CaseAlts amode _) = returnFC amode
180 sequelToAmode (SeqFrame _ _) = cgPanic (text "sequelToAmode: SeqFrame")
182 type CgStksAndHeapUsage -- stacks and heap usage information
183 = (StackUsage, HeapUsage)
185 data Slot = Free | NonPointer deriving (Eq,Show)
188 (Int, -- virtSp: Virtual offset of topmost allocated slot
189 [(Int,Slot)], -- free: List of free slots, in increasing order
190 Int, -- realSp: Virtual offset of real stack pointer
191 Int) -- hwSp: Highest value ever taken by virtSp
194 (HeapOffset, -- virtHp: Virtual offset of highest-allocated word
195 HeapOffset) -- realHp: Virtual offset of real heap ptr
198 NB: absolutely every one of the above Ints is really
199 a VirtualOffset of some description (the code generator
200 works entirely in terms of VirtualOffsets).
205 initialStateC = MkCgState AbsCNop emptyVarEnv initUsage
207 initUsage :: CgStksAndHeapUsage
208 initUsage = ((0,[],0,0), (0,0))
211 "envInitForAlternatives" initialises the environment for a case alternative,
212 assuming that the alternative is entered after an evaluation.
215 - zapping any volatile bindings, which aren't valid.
217 - zapping the heap usage. It should be restored by a heap check.
219 - setting the virtual AND real stack pointer fields to the given
220 virtual stack offsets. this doesn't represent any {\em code}; it is a
221 prediction of where the real stack pointer will be when we come back
222 from the case analysis.
224 - BUT LEAVING the rest of the stack-usage info because it is all
225 valid. In particular, we leave the tail stack pointers unchanged,
226 becuase the alternative has to de-allocate the original @case@
227 expression's stack. \end{itemize}
229 @stateIncUsage@$~e_1~e_2$ incorporates in $e_1$ the stack and heap high water
230 marks found in $e_2$.
233 stateIncUsage :: CgState -> CgState -> CgState
235 stateIncUsage (MkCgState abs_c bs ((v,f,r,h1),(vH1,rH1)))
236 (MkCgState _ _ ((_,_,_,h2),(vH2, _)))
239 ((v,f,r,h1 `max` h2),
240 (vH1 `max` vH2, rH1))
243 %************************************************************************
245 \subsection[CgMonad-basics]{Basic code-generation monad magic}
247 %************************************************************************
250 type FCode a = CgInfoDownwards -> CgState -> (a, CgState)
251 type Code = CgInfoDownwards -> CgState -> CgState
254 {-# INLINE thenFC #-}
255 {-# INLINE returnFC #-}
257 The Abstract~C is not in the environment so as to improve strictness.
260 initC :: CompilationInfo -> Code -> AbstractC
263 = case (code (MkCgInfoDown
265 (error "initC: statics")
269 MkCgState abc _ _ -> abc
271 returnFC :: a -> FCode a
273 returnFC val info_down state = (val, state)
278 -> (CgInfoDownwards -> CgState -> a)
279 -> CgInfoDownwards -> CgState -> a
281 -- thenC has both of the following types:
282 -- thenC :: Code -> Code -> Code
283 -- thenC :: Code -> FCode a -> FCode a
285 thenC m k info_down state
286 = k info_down new_state
288 new_state = m info_down state
290 listCs :: [Code] -> Code
292 listCs [] info_down state = state
293 listCs (c:cs) info_down state = stateN
295 state1 = c info_down state
296 stateN = listCs cs info_down state1
298 mapCs :: (a -> Code) -> [a] -> Code
300 mapCs f [] info_down state = state
301 mapCs f (c:cs) info_down state = stateN
303 state1 = (f c) info_down state
304 stateN = mapCs f cs info_down state1
309 -> (a -> CgInfoDownwards -> CgState -> c)
310 -> CgInfoDownwards -> CgState -> c
312 -- thenFC :: FCode a -> (a -> FCode b) -> FCode b
313 -- thenFC :: FCode a -> (a -> Code) -> Code
315 thenFC m k info_down state
316 = k m_result info_down new_state
318 (m_result, new_state) = m info_down state
320 listFCs :: [FCode a] -> FCode [a]
322 listFCs [] info_down state = ([], state)
323 listFCs (fc:fcs) info_down state = (thing : things, stateN)
325 (thing, state1) = fc info_down state
326 (things, stateN) = listFCs fcs info_down state1
328 mapFCs :: (a -> FCode b) -> [a] -> FCode [b]
330 mapFCs f [] info_down state = ([], state)
331 mapFCs f (fc:fcs) info_down state = (thing : things, stateN)
333 (thing, state1) = (f fc) info_down state
334 (things, stateN) = mapFCs f fcs info_down state1
337 And the knot-tying combinator:
339 fixC :: (a -> FCode a) -> FCode a
340 fixC fcode info_down state = result
342 result@(v, _) = fcode v info_down state
346 @forkClosureBody@ takes a code, $c$, and compiles it in a completely
347 fresh environment, except that:
348 - compilation info and statics are passed in unchanged.
349 The current environment is passed on completely unaltered, except that
350 abstract C from the fork is incorporated.
352 @forkAbsC@ takes a code and compiles it in the current environment,
353 returning the abstract C thus constructed. The current environment
354 is passed on completely unchanged. It is pretty similar to @getAbsC@,
355 except that the latter does affect the environment. ToDo: combine?
357 @forkStatics@ $fc$ compiles $fc$ in an environment whose statics come
358 from the current bindings, but which is otherwise freshly initialised.
359 The Abstract~C returned is attached to the current state, but the
360 bindings and usage information is otherwise unchanged.
363 forkClosureBody :: Code -> Code
366 (MkCgInfoDown cg_info statics srt _)
367 (MkCgState absC_in binds un_usage)
368 = MkCgState (AbsCStmts absC_in absC_fork) binds un_usage
370 fork_state = code body_info_down initialStateC
371 MkCgState absC_fork _ _ = fork_state
372 body_info_down = MkCgInfoDown cg_info statics srt initEobInfo
374 forkStatics :: FCode a -> FCode a
376 forkStatics fcode (MkCgInfoDown cg_info _ srt _)
377 (MkCgState absC_in statics un_usage)
378 = (result, MkCgState (AbsCStmts absC_in absC_fork) statics un_usage)
380 (result, state) = fcode rhs_info_down initialStateC
381 MkCgState absC_fork _ _ = state -- Don't merge these this line with the one
382 -- above or it becomes too strict!
383 rhs_info_down = MkCgInfoDown cg_info statics srt initEobInfo
385 forkAbsC :: Code -> FCode AbstractC
386 forkAbsC code info_down (MkCgState absC1 bs usage)
389 MkCgState absC2 _ ((_, _, _,h2), _) =
390 code info_down (MkCgState AbsCNop bs usage)
391 ((v, f, r, h1), heap_usage) = usage
393 new_usage = ((v, f, r, h1 `max` h2), heap_usage)
394 new_state = MkCgState absC1 bs new_usage
397 @forkAlts@ $bs~d$ takes fcodes $bs$ for the branches of a @case@, and
398 an fcode for the default case $d$, and compiles each in the current
399 environment. The current environment is passed on unmodified, except
401 - the worst stack high-water mark is incorporated
402 - the virtual Hp is moved on to the worst virtual Hp for the branches
405 forkAlts :: [FCode a] -> FCode b -> FCode ([a],b)
407 forkAlts branch_fcodes deflt_fcode info_down in_state
408 = ((branch_results , deflt_result), out_state)
410 compile fc = fc info_down in_state
412 (branch_results, branch_out_states) = unzip (map compile branch_fcodes)
414 (deflt_result, deflt_out_state) = deflt_fcode info_down in_state
416 out_state = foldl stateIncUsage in_state (deflt_out_state:branch_out_states)
417 -- NB foldl. in_state is the *left* argument to stateIncUsage
420 @forkEval@ takes two blocks of code.
422 - The first meddles with the environment to set it up as expected by
423 the alternatives of a @case@ which does an eval (or gc-possible primop).
424 - The second block is the code for the alternatives.
425 (plus info for semi-tagging purposes)
427 @forkEval@ picks up the virtual stack pointer and returns a suitable
428 @EndOfBlockInfo@ for the caller to use, together with whatever value
429 is returned by the second block.
431 It uses @initEnvForAlternatives@ to initialise the environment, and
432 @stateIncUsageAlt@ to incorporate usage; the latter ignores the heap
436 forkEval :: EndOfBlockInfo -- For the body
437 -> Code -- Code to set environment
438 -> FCode Sequel -- Semi-tagging info to store
439 -> FCode EndOfBlockInfo -- The new end of block info
441 forkEval body_eob_info env_code body_code
442 = forkEvalHelp body_eob_info env_code body_code `thenFC` \ (v, sequel) ->
443 returnFC (EndOfBlockInfo v sequel)
445 forkEvalHelp :: EndOfBlockInfo -- For the body
446 -> Code -- Code to set environment
447 -> FCode a -- The code to do after the eval
449 a) -- Result of the FCode
451 forkEvalHelp body_eob_info env_code body_code
452 info_down@(MkCgInfoDown cg_info statics srt _) state
453 = ((v,value_returned), state `stateIncUsageEval` state_at_end_return)
455 info_down_for_body = MkCgInfoDown cg_info statics srt body_eob_info
457 (MkCgState _ binds ((v,f,_,_), _)) = env_code info_down_for_body state
458 -- These v and f things are now set up as the body code expects them
460 (value_returned, state_at_end_return)
461 = body_code info_down_for_body state_for_body
463 state_for_body = MkCgState AbsCNop
464 (nukeVolatileBinds binds)
468 stateIncUsageEval :: CgState -> CgState -> CgState
469 stateIncUsageEval (MkCgState absC1 bs ((v,f,r,h1),heap_usage))
470 (MkCgState absC2 _ ((_,_,_,h2), _))
471 = MkCgState (absC1 `AbsCStmts` absC2)
472 -- The AbsC coming back should consist only of nested declarations,
473 -- notably of the return vector!
475 ((v,f,r,h1 `max` h2), heap_usage)
476 -- We don't max the heap high-watermark because stateIncUsageEval is
477 -- used only in forkEval, which in turn is only used for blocks of code
478 -- which do their own heap-check.
481 %************************************************************************
483 \subsection[CgMonad-spitting-AbstractC]{Spitting out @AbstractC@}
485 %************************************************************************
487 @nopC@ is the no-op for the @Code@ monad; it adds no Abstract~C to the
488 environment; @absC@ glues @ab_C@ onto the Abstract~C collected so far.
491 nopC info_down state = state
493 absC :: AbstractC -> Code
494 absC more_absC info_down state@(MkCgState absC binds usage)
495 = MkCgState (mkAbsCStmts absC more_absC) binds usage
498 These two are just like @absC@, except they examine the compilation
499 info (whether SCC profiling or profiling-ctrs going) and possibly emit
503 costCentresC :: FAST_STRING -> [CAddrMode] -> Code
505 costCentresC macro args _ state@(MkCgState absC binds usage)
506 = if opt_SccProfilingOn
507 then MkCgState (mkAbsCStmts absC (CCallProfCCMacro macro args)) binds usage
510 profCtrC :: FAST_STRING -> [CAddrMode] -> Code
512 profCtrC macro args _ state@(MkCgState absC binds usage)
513 = if not opt_DoTickyProfiling
515 else MkCgState (mkAbsCStmts absC (CCallProfCtrMacro macro args)) binds usage
517 {- Try to avoid adding too many special compilation strategies here.
518 It's better to modify the header files as necessary for particular
519 targets, so that we can get away with as few variants of .hc files
524 @getAbsC@ compiles the code in the current environment, and returns
525 the abstract C thus constructed (leaving the abstract C being carried
526 around in the state untouched). @getAbsC@ does not generate any
527 in-line Abstract~C itself, but the environment it returns is that
528 obtained from the compilation.
531 getAbsC :: Code -> FCode AbstractC
533 getAbsC code info_down (MkCgState absC binds usage)
534 = (absC2, MkCgState absC binds2 usage2)
536 (MkCgState absC2 binds2 usage2)
537 = code info_down (MkCgState AbsCNop binds usage)
542 moduleName :: FCode Module
543 moduleName (MkCgInfoDown (MkCompInfo mod_name) _ _ _) state
549 setEndOfBlockInfo :: EndOfBlockInfo -> Code -> Code
550 setEndOfBlockInfo eob_info code (MkCgInfoDown c_info statics srt _) state
551 = code (MkCgInfoDown c_info statics srt eob_info) state
553 getEndOfBlockInfo :: FCode EndOfBlockInfo
554 getEndOfBlockInfo (MkCgInfoDown c_info statics _ eob_info) state
559 getSRTLabel :: FCode CLabel
560 getSRTLabel (MkCgInfoDown _ _ srt _) state
563 setSRTLabel :: CLabel -> Code -> Code
564 setSRTLabel srt code (MkCgInfoDown c_info statics _ eob_info) state
565 = code (MkCgInfoDown c_info statics srt eob_info) state
568 %************************************************************************
570 \subsection[CgMonad-bindery]{Monad things for fiddling with @CgBindings@}
572 %************************************************************************
574 There are three basic routines, for adding (@addBindC@), modifying
575 (@modifyBindC@) and looking up (@lookupBindC@) bindings.
577 A @Id@ is bound to a @(VolatileLoc, StableLoc)@ triple.
578 The name should not already be bound. (nice ASSERT, eh?)
581 addBindC :: Id -> CgIdInfo -> Code
582 addBindC name stuff_to_bind info_down (MkCgState absC binds usage)
583 = MkCgState absC (extendVarEnv binds name stuff_to_bind) usage
585 addBindsC :: [(Id, CgIdInfo)] -> Code
586 addBindsC new_bindings info_down (MkCgState absC binds usage)
587 = MkCgState absC new_binds usage
589 new_binds = foldl (\ binds (name,info) -> extendVarEnv binds name info)
593 modifyBindC :: Id -> (CgIdInfo -> CgIdInfo) -> Code
594 modifyBindC name mangle_fn info_down (MkCgState absC binds usage)
595 = MkCgState absC (modifyVarEnv mangle_fn binds name) usage
597 lookupBindC :: Id -> FCode CgIdInfo
598 lookupBindC name info_down@(MkCgInfoDown _ static_binds srt _)
599 state@(MkCgState absC local_binds usage)
602 val = case (lookupVarEnv local_binds name) of
603 Nothing -> try_static
607 case (lookupVarEnv static_binds name) of
610 -> cgPanic (text "lookupBindC: no info for" <+> ppr name) info_down state
612 cgPanic :: SDoc -> CgInfoDownwards -> CgState -> a
613 cgPanic doc info_down@(MkCgInfoDown _ static_binds srt _)
614 state@(MkCgState absC local_binds usage)
617 ptext SLIT("static binds for:"),
618 vcat [ ppr i | (MkCgIdInfo i _ _ _) <- rngVarEnv static_binds ],
619 ptext SLIT("local binds for:"),
620 vcat [ ppr i | (MkCgIdInfo i _ _ _) <- rngVarEnv local_binds ],
621 ptext SLIT("SRT label") <+> pprCLabel srt