2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: AbsCSyn.lhs,v 1.46 2002/03/02 18:02:30 sof Exp $
6 \section[AbstractC]{Abstract C: the last stop before machine code}
8 This ``Abstract C'' data type describes the raw Spineless Tagless
9 machine model at a C-ish level; it is ``abstract'' in that it only
10 includes C-like structures that we happen to need. The conversion of
11 programs from @StgSyntax@ (basically a functional language) to
12 @AbstractC@ (basically imperative C) is the heart of code generation.
13 From @AbstractC@, one may convert to real C (for portability) or to
14 raw assembler/machine code.
25 mkAbstractCs, mkAbsCStmts, mkAlgAltsCSwitch,
34 MagicId(..), node, infoptr,
39 #include "HsVersions.h"
41 import {-# SOURCE #-} ClosureInfo ( ClosureInfo )
44 import Constants ( mAX_Vanilla_REG, mAX_Float_REG,
45 mAX_Double_REG, spRelToInt )
46 import CostCentre ( CostCentre, CostCentreStack )
47 import Literal ( mkMachInt, Literal(..) )
48 import ForeignCall ( CCallSpec )
49 import PrimRep ( PrimRep(..) )
50 import MachOp ( MachOp(..) )
51 import Unique ( Unique )
52 import StgSyn ( StgOp )
53 import TyCon ( TyCon )
54 import BitSet -- for liveness masks
60 @AbstractC@ is a list of Abstract~C statements, but the data structure
61 is tree-ish, for easier and more efficient putting-together.
67 | AbsCStmts AbstractC AbstractC
69 -- and the individual stmts...
72 A note on @CAssign@: In general, the type associated with an assignment
73 is the type of the lhs. However, when the lhs is a pointer to mixed
74 types (e.g. SpB relative), the type of the assignment is the type of
75 the rhs for float types, or the generic StgWord for all other types.
76 (In particular, a CharRep on the rhs is promoted to IntRep when
77 stored in a mixed type location.)
85 CAddrMode -- Put this in the program counter
86 -- eg `CJump (CReg (VanillaReg PtrRep 1))' puts Ret1 in PC
87 -- Enter can be done by:
88 -- CJump (CVal NodeRel zeroOff)
91 CAddrMode -- Fall through into this routine
92 -- (for the benefit of the native code generators)
93 -- Equivalent to CJump in C land
95 | CReturn -- Perform a return
96 CAddrMode -- Address of a RET_<blah> info table
97 ReturnInfo -- Whether it's a direct or vectored return
100 [(Literal, AbstractC)] -- alternatives
101 AbstractC -- default; if there is no real Abstract C in here
102 -- (e.g., all comments; see function "nonemptyAbsC"),
103 -- then that means the default _cannot_ occur.
104 -- If there is only one alternative & no default code,
105 -- then there is no need to check the tag.
107 -- CSwitch m [(tag,code)] AbsCNop == code
109 | CCodeBlock CLabel AbstractC
110 -- A labelled block of code; this "statement" is not
111 -- executed; rather, the labelled code will be hoisted
112 -- out to the top level (out of line) & it can be
115 | CInitHdr -- to initialise the header of a closure (both fixed/var parts)
117 CAddrMode -- address of the info ptr
118 !CAddrMode -- cost centre to place in closure
119 -- CReg CurCostCentre or CC_HDR(R1.p{-Node-})
120 Int -- size of closure, for profiling
122 -- NEW CASES FOR EXPANDED PRIMOPS
124 | CMachOpStmt -- Machine-level operation
127 [CAddrMode] -- Arguments
128 (Maybe [MagicId]) -- list of regs which need to be preserved
129 -- across the primop. This is allowed to be Nothing only if
130 -- machOpIsDefinitelyInline returns True. And that in turn may
131 -- only return True if we are absolutely sure that the mach op
132 -- can be done inline on all platforms.
134 | CSequential -- Do the nested AbstractCs sequentially.
135 [AbstractC] -- In particular, as far as the AbsCUtils.doSimultaneously
136 -- is concerned, these stmts are to be treated as atomic
137 -- and are not to be reordered.
139 -- end of NEW CASES FOR EXPANDED PRIMOPS
142 [CAddrMode] -- Results
144 [CAddrMode] -- Arguments
145 [MagicId] -- Potentially volatile/live registers
146 -- (to save/restore around the call/op)
148 -- INVARIANT: When a PrimOp which can cause GC is used, the
149 -- only live data is tidily on the STG stacks or in the STG
150 -- registers (the code generator ensures this).
152 -- Why this? Because if the arguments were arbitrary
153 -- addressing modes, they might be things like (Hp+6) which
154 -- will get utterly spongled by GC.
156 | CSimultaneous -- Perform simultaneously all the statements
157 AbstractC -- in the nested AbstractC. They are only
158 -- allowed to be CAssigns, COpStmts and AbsCNops, so the
159 -- "simultaneous" part just concerns making
160 -- sure that permutations work.
161 -- For example { a := b, b := a }
162 -- needs to go via (at least one) temporary
164 | CCheck -- heap or stack checks, or both.
165 CCheckMacro -- These might include some code to fill in tags
166 [CAddrMode] -- on the stack, so we can't use CMacroStmt below.
169 | CRetDirect -- Direct return
170 !Unique -- for making labels
171 AbstractC -- return code
173 Liveness -- stack liveness at the return point
175 -- see the notes about these next few; they follow below...
176 | CMacroStmt CStmtMacro [CAddrMode]
177 | CCallProfCtrMacro FAST_STRING [CAddrMode]
178 | CCallProfCCMacro FAST_STRING [CAddrMode]
180 {- The presence of this constructor is a makeshift solution;
181 it being used to work around a gcc-related problem of
182 handling typedefs within statement blocks (or, rather,
183 the inability to do so.)
185 The AbstractC flattener takes care of lifting out these
186 typedefs if needs be (i.e., when generating .hc code and
187 compiling 'foreign import dynamic's)
189 | CCallTypedef Bool {- True => use "typedef"; False => use "extern"-}
190 CCallSpec Unique [CAddrMode] [CAddrMode]
192 -- *** the next three [or so...] are DATA (those above are CODE) ***
195 ClosureInfo -- Todo: maybe info_lbl & closure_lbl instead?
196 CAddrMode -- cost centre identifier to place in closure
197 [CAddrMode] -- free vars; ptrs, then non-ptrs.
199 | CSRT CLabel [CLabel] -- SRT declarations: basically an array of
200 -- pointers to static closures.
202 | CBitmap CLabel LivenessMask -- A bitmap to be emitted if and only if
203 -- it is larger than a target machine word.
205 | CClosureInfoAndCode
206 ClosureInfo -- Explains placement and layout of closure
207 AbstractC -- Slow entry point code
209 -- Fast entry point code, if any
210 String -- Closure description; NB we can't get this
211 -- from ClosureInfo, because the latter refers
212 -- to the *right* hand side of a defn, whereas
213 -- the "description" refers to *left* hand side
215 | CRetVector -- A labelled block of static data
219 Liveness -- stack liveness at the return point
221 | CClosureTbl -- table of constructors for enumerated types
222 TyCon -- which TyCon this table is for
224 | CModuleInitBlock -- module initialisation block
225 CLabel -- label for init block
226 AbstractC -- initialisation code
228 | CCostCentreDecl -- A cost centre *declaration*
229 Bool -- True <=> local => full declaration
230 -- False <=> extern; just say so
233 | CCostCentreStackDecl -- A cost centre stack *declaration*
234 CostCentreStack -- this is the declaration for a
235 -- pre-defined singleton CCS (see
238 | CSplitMarker -- Split into separate object modules here
240 -- C_SRT is what StgSyn.SRT gets translated to...
241 -- we add a label for the table, and expect only the 'offset/length' form
244 | C_SRT CLabel !Int{-offset-} !Int{-length-}
246 needsSRT :: C_SRT -> Bool
247 needsSRT NoC_SRT = False
248 needsSRT (C_SRT _ _ _) = True
251 About @CMacroStmt@, etc.: notionally, they all just call some
252 arbitrary C~macro or routine, passing the @CAddrModes@ as arguments.
253 However, we distinguish between various flavours of these things,
254 mostly just to keep things somewhat less wild and wooly.
258 Some {\em essential} bits of the STG execution model are done with C
259 macros. An example is @STK_CHK@, which checks for stack-space
260 overflow. This enumeration type lists all such macros:
263 = ARGS_CHK -- arg satisfaction check
264 | ARGS_CHK_LOAD_NODE -- arg check for top-level functions
265 | UPD_CAF -- update CAF closure with indirection
266 | UPD_BH_UPDATABLE -- eager backholing
267 | UPD_BH_SINGLE_ENTRY -- more eager blackholing
268 | PUSH_UPD_FRAME -- push update frame
269 | PUSH_SEQ_FRAME -- push seq frame
270 | UPDATE_SU_FROM_UPD_FRAME -- pull Su out of the update frame
271 | SET_TAG -- set TagReg if it exists
272 -- dataToTag# primop -- *only* used in unregisterised builds.
273 -- (see AbsCUtils.dsCOpStmt)
276 | REGISTER_FOREIGN_EXPORT -- register a foreign exported fun
277 | REGISTER_IMPORT -- register an imported module
278 | REGISTER_DIMPORT -- register an imported module from
281 | GRAN_FETCH -- for GrAnSim only -- HWL
282 | GRAN_RESCHEDULE -- for GrAnSim only -- HWL
283 | GRAN_FETCH_AND_RESCHEDULE -- for GrAnSim only -- HWL
284 | THREAD_CONTEXT_SWITCH -- for GrAnSim only -- HWL
285 | GRAN_YIELD -- for GrAnSim only -- HWL
288 Heap/Stack checks. There are far too many of these.
293 = HP_CHK_NP -- heap/stack checks when
294 | STK_CHK_NP -- node points to the closure
296 | HP_CHK_SEQ_NP -- for 'seq' style case alternatives
298 | HP_CHK -- heap/stack checks when
299 | STK_CHK -- node doesn't point
301 -- case alternative heap checks:
303 | HP_CHK_NOREGS -- no registers live
304 | HP_CHK_UNPT_R1 -- R1 is boxed/unlifted
305 | HP_CHK_UNBX_R1 -- R1 is unboxed
306 | HP_CHK_F1 -- FloatReg1 (only) is live
307 | HP_CHK_D1 -- DblReg1 (only) is live
308 | HP_CHK_L1 -- LngReg1 (only) is live
309 | HP_CHK_UT_ALT -- unboxed tuple return.
311 | HP_CHK_GEN -- generic heap check
314 \item[@CCallProfCtrMacro@:]
315 The @String@ names a macro that, if \tr{#define}d, will bump one/some
316 of the STG-event profiling counters.
318 \item[@CCallProfCCMacro@:]
319 The @String@ names a macro that, if \tr{#define}d, will perform some
320 cost-centre-profiling-related action.
323 %************************************************************************
325 \subsection[CAddrMode]{C addressing modes}
327 %************************************************************************
331 = CVal RegRelative PrimRep
332 -- On RHS of assign: Contents of Magic[n]
333 -- On LHS of assign: location Magic[n]
334 -- (ie at addr Magic+n)
337 -- On RHS of assign: Address of Magic[n]; ie Magic+n
338 -- n=0 gets the Magic location itself
339 -- (NB: n=0 case superceded by CReg)
340 -- On LHS of assign: only sensible if n=0,
341 -- which gives the magic location itself
342 -- (NB: superceded by CReg)
344 -- JRS 2002-02-05: CAddr is really scummy and should be fixed.
345 -- The effect is that the semantics of CAddr depend on what the
346 -- contained RegRelative is; it is decidely non-orthogonal.
348 | CReg MagicId -- To replace (CAddr MagicId 0)
350 | CTemp !Unique !PrimRep -- Temporary locations
351 -- ``Temporaries'' correspond to local variables in C, and registers in
354 | CLbl CLabel -- Labels in the runtime system, etc.
355 PrimRep -- the kind is so we can generate accurate C decls
357 | CCharLike CAddrMode -- The address of a static char-like closure for
358 -- the specified character. It is guaranteed to be in
359 -- the range mIN_CHARLIKE..mAX_CHARLIKE
361 | CIntLike CAddrMode -- The address of a static int-like closure for the
362 -- specified small integer. It is guaranteed to be in
363 -- the range mIN_INTLIKE..mAX_INTLIKE
367 | CJoinPoint -- This is used as the amode of a let-no-escape-bound
369 VirtualSpOffset -- Sp value after any volatile free vars
370 -- of the rhs have been saved on stack.
371 -- Just before the code for the thing is jumped to,
372 -- Sp will be set to this value,
373 -- and then any stack-passed args pushed,
374 -- then the code for this thing will be entered
376 !PrimRep -- the kind of the result
377 CExprMacro -- the macro to generate a value
378 [CAddrMode] -- and its arguments
380 | CBytesPerWord -- Word size, in bytes, on this platform
381 -- required for: half-word loads (used in fishing tags
382 -- out of info tables), and sizeofByteArray#.
385 Various C macros for values which are dependent on the back-end layout.
391 | ARG_TAG -- stack argument tagging
392 | GET_TAG -- get current constructor tag
398 Convenience functions:
401 mkIntCLit :: Int -> CAddrMode
402 mkIntCLit i = CLit (mkMachInt (toInteger i))
404 mkCString :: FAST_STRING -> CAddrMode
405 mkCString s = CLit (MachStr s)
407 mkCCostCentre :: CostCentre -> CAddrMode
408 mkCCostCentre cc = CLbl (mkCC_Label cc) DataPtrRep
410 mkCCostCentreStack :: CostCentreStack -> CAddrMode
411 mkCCostCentreStack ccs = CLbl (mkCCS_Label ccs) DataPtrRep
414 %************************************************************************
416 \subsection[RegRelative]{@RegRelatives@: ???}
418 %************************************************************************
423 | SpRel FastInt -- }- offsets in StgWords
424 | NodeRel FastInt -- }
425 | CIndex CAddrMode CAddrMode PrimRep -- pointer arithmetic :-)
426 -- CIndex a b k === (k*)a[b]
429 = DirectReturn -- Jump directly, if possible
430 | StaticVectoredReturn Int -- Fixed tag, starting at zero
431 | DynamicVectoredReturn CAddrMode -- Dynamic tag given by amode, starting at zero
433 hpRel :: VirtualHeapOffset -- virtual offset of Hp
434 -> VirtualHeapOffset -- virtual offset of The Thing
435 -> RegRelative -- integer offset
436 hpRel hp off = HpRel (iUnbox (hp - off))
438 spRel :: VirtualSpOffset -- virtual offset of Sp
439 -> VirtualSpOffset -- virtual offset of The Thing
440 -> RegRelative -- integer offset
441 spRel sp off = SpRel (iUnbox (spRelToInt sp off))
443 nodeRel :: VirtualHeapOffset
445 nodeRel off = NodeRel (iUnbox off)
449 %************************************************************************
451 \subsection[Liveness]{Liveness Masks}
453 %************************************************************************
455 We represent liveness bitmaps as a BitSet (whose internal
456 representation really is a bitmap). These are pinned onto case return
457 vectors to indicate the state of the stack for the garbage collector.
459 In the compiled program, liveness bitmaps that fit inside a single
460 word (StgWord) are stored as a single word, while larger bitmaps are
461 stored as a pointer to an array of words. When we compile via C
462 (especially when we bootstrap via HC files), we generate identical C
463 code regardless of whether words are 32- or 64-bit on the target
464 machine, by postponing the decision of how to store each liveness
465 bitmap to C compilation time (or rather, C preprocessing time).
468 type LivenessMask = [BitSet]
470 data Liveness = Liveness CLabel LivenessMask
473 %************************************************************************
475 \subsection[HeapOffset]{@Heap Offsets@}
477 %************************************************************************
479 This used to be a grotesquely complicated datatype in an attempt to
480 hide the details of header sizes from the compiler itself. Now these
481 constants are imported from the RTS, and we deal in real Ints.
484 type HeapOffset = Int -- ToDo: remove
486 type VirtualHeapOffset = HeapOffset
487 type VirtualSpOffset = Int
489 type HpRelOffset = HeapOffset
490 type SpRelOffset = Int
493 %************************************************************************
495 \subsection[MagicId]{@MagicIds@: registers and such}
497 %************************************************************************
501 = BaseReg -- mentioned only in nativeGen
503 -- Argument and return registers
504 | VanillaReg -- pointers, unboxed ints and chars
506 FastInt -- its number (1 .. mAX_Vanilla_REG)
508 | FloatReg -- single-precision floating-point registers
509 FastInt -- its number (1 .. mAX_Float_REG)
511 | DoubleReg -- double-precision floating-point registers
512 FastInt -- its number (1 .. mAX_Double_REG)
515 | Sp -- Stack ptr; points to last occupied stack location.
516 | Su -- Stack update frame pointer
517 | SpLim -- Stack limit
518 | Hp -- Heap ptr; points to last occupied heap location.
519 | HpLim -- Heap limit register
520 | CurCostCentre -- current cost centre register.
521 | VoidReg -- see "VoidPrim" type; just a placeholder;
522 -- no actual register
523 | LongReg -- long int registers (64-bit, really)
524 PrimRep -- Int64Rep or Word64Rep
525 FastInt -- its number (1 .. mAX_Long_REG)
527 | CurrentTSO -- pointer to current thread's TSO
528 | CurrentNursery -- pointer to allocation area
529 | HpAlloc -- allocation count for heap check failure
532 node = VanillaReg PtrRep (_ILIT 1) -- A convenient alias for Node
533 tagreg = VanillaReg WordRep (_ILIT 2) -- A convenient alias for TagReg
538 We need magical @Eq@ because @VanillaReg@s come in multiple flavors.
541 instance Eq MagicId where
542 reg1 == reg2 = tag reg1 ==# tag reg2
544 tag BaseReg = (_ILIT(0) :: FastInt)
550 tag CurCostCentre = _ILIT(6)
551 tag VoidReg = _ILIT(7)
553 tag (VanillaReg _ i) = _ILIT(8) +# i
555 tag (FloatReg i) = _ILIT(8) +# maxv +# i
556 tag (DoubleReg i) = _ILIT(8) +# maxv +# maxf +# i
557 tag (LongReg _ i) = _ILIT(8) +# maxv +# maxf +# maxd +# i
559 maxv = iUnbox mAX_Vanilla_REG
560 maxf = iUnbox mAX_Float_REG
561 maxd = iUnbox mAX_Double_REG
564 Returns True for any register that {\em potentially} dies across
565 C calls (or anything near equivalent). We just say @True@ and
566 let the (machine-specific) registering macros sort things out...
569 isVolatileReg :: MagicId -> Bool
570 isVolatileReg any = True