1 -----------------------------------------------------------------------------
3 -- Building info tables.
5 -- (c) The University of Glasgow 2004
7 -----------------------------------------------------------------------------
10 emitClosureCodeAndInfoTable,
14 emitDirectReturnTarget, emitAlgReturnTarget,
15 emitDirectReturnInstr, emitVectoredReturnInstr,
19 mkFunGenInfoExtraBits,
20 entryCode, closureInfoPtr,
22 infoTable, infoTableClosureType,
23 infoTablePtrs, infoTableNonPtrs,
29 #include "HsVersions.h"
31 import ClosureInfo ( ClosureInfo, closureTypeDescr, closureName,
32 infoTableLabelFromCI, Liveness,
33 closureValDescr, closureSRT, closureSMRep,
34 closurePtrsSize, closureNonHdrSize, closureFunInfo,
35 C_SRT(..), needsSRT, isConstrClosure_maybe,
37 import SMRep ( StgHalfWord, hALF_WORD_SIZE_IN_BITS, hALF_WORD_SIZE,
39 smRepClosureTypeInt, tablesNextToCode,
40 rET_BIG, rET_SMALL, rET_VEC_BIG, rET_VEC_SMALL )
41 import CgBindery ( getLiveStackSlots )
42 import CgCallConv ( isBigLiveness, mkLivenessCLit, buildContLiveness,
43 argDescrType, getSequelAmode,
44 CtrlReturnConvention(..) )
45 import CgUtils ( mkStringCLit, packHalfWordsCLit, mkWordCLit,
46 cmmOffsetB, cmmOffsetExprW, cmmLabelOffW, cmmOffsetW,
47 emitDataLits, emitRODataLits, emitSwitch, cmmNegate,
51 import CmmUtils ( mkIntCLit, zeroCLit )
52 import Cmm ( CmmStmt(..), CmmExpr(..), CmmLit(..), LocalReg,
53 CmmBasicBlock, nodeReg )
54 import MachOp ( MachOp(..), wordRep, halfWordRep )
56 import StgSyn ( SRT(..) )
58 import DataCon ( DataCon, dataConTag, fIRST_TAG )
59 import Unique ( Uniquable(..) )
60 import CmdLineOpts ( opt_SccProfilingOn )
61 import ListSetOps ( assocDefault )
62 import Maybes ( isJust )
63 import Constants ( wORD_SIZE, sIZEOF_StgFunInfoExtraRev )
67 -------------------------------------------------------------------------
69 -- Generating the info table and code for a closure
71 -------------------------------------------------------------------------
73 -- Here we make a concrete info table, represented as a list of CmmAddr
74 -- (it can't be simply a list of Word, because the SRT field is
75 -- represented by a label+offset expression).
77 -- With tablesNextToCode, the layout is
78 -- <reversed variable part>
79 -- <normal forward StgInfoTable, but without
80 -- an entry point at the front>
83 -- Without tablesNextToCode, the layout of an info table is
85 -- <normal forward rest of StgInfoTable>
86 -- <forward variable part>
88 -- See includes/InfoTables.h
90 emitClosureCodeAndInfoTable :: ClosureInfo -> [LocalReg] -> CgStmts -> Code
91 emitClosureCodeAndInfoTable cl_info args body
92 = do { ty_descr_lit <-
94 then mkStringCLit (closureTypeDescr cl_info)
95 else return (mkIntCLit 0)
98 then mkStringCLit cl_descr_string
99 else return (mkIntCLit 0)
100 ; let std_info = mkStdInfoTable ty_descr_lit cl_descr_lit
101 cl_type srt_len layout_lit
103 ; blks <- cgStmtsToBlocks body
104 ; emitInfoTableAndCode info_lbl std_info extra_bits args blks }
106 info_lbl = infoTableLabelFromCI cl_info
108 cl_descr_string = closureValDescr cl_info
109 cl_type = smRepClosureTypeInt (closureSMRep cl_info)
111 srt = closureSRT cl_info
112 needs_srt = needsSRT srt
114 mb_con = isConstrClosure_maybe cl_info
115 is_con = isJust mb_con
119 Just con -> -- Constructors don't have an SRT
120 -- We keep the *zero-indexed* tag in the srt_len
121 -- field of the info table.
122 (mkIntCLit 0, fromIntegral (dataConTagZ con))
124 Nothing -> -- Not a constructor
125 srtLabelAndLength srt info_lbl
127 ptrs = closurePtrsSize cl_info
129 size = closureNonHdrSize cl_info
130 layout_lit = packHalfWordsCLit ptrs nptrs
133 | is_fun = fun_extra_bits
135 | needs_srt = [srt_label]
138 maybe_fun_stuff = closureFunInfo cl_info
139 is_fun = isJust maybe_fun_stuff
140 (Just (arity, arg_descr)) = maybe_fun_stuff
143 | ArgGen liveness <- arg_descr
146 makeRelativeRefTo info_lbl $ mkLivenessCLit liveness,
148 | needs_srt = [fun_amode, srt_label]
149 | otherwise = [fun_amode]
151 slow_entry = makeRelativeRefTo info_lbl (CmmLabel slow_entry_label)
152 slow_entry_label = mkSlowEntryLabel (closureName cl_info)
154 fun_amode = packHalfWordsCLit fun_type arity
155 fun_type = argDescrType arg_descr
157 -- We keep the *zero-indexed* tag in the srt_len field of the info
158 -- table of a data constructor.
159 dataConTagZ :: DataCon -> ConTagZ
160 dataConTagZ con = dataConTag con - fIRST_TAG
162 -- A low-level way to generate the variable part of a fun-style info table.
163 -- (must match fun_extra_bits above). Used by the C-- parser.
164 mkFunGenInfoExtraBits :: Int -> Int -> CmmLit -> CmmLit -> CmmLit -> [CmmLit]
165 mkFunGenInfoExtraBits fun_type arity srt_label liveness slow_entry
166 = [ packHalfWordsCLit fun_type arity,
171 -------------------------------------------------------------------------
173 -- Generating the info table and code for a return point
175 -------------------------------------------------------------------------
177 -- Here's the layout of a return-point info table
179 -- Tables next to code:
181 -- <reversed vector table>
183 -- <standard info table>
184 -- ret-addr --> <entry code (if any)>
186 -- Not tables-next-to-code:
188 -- ret-addr --> <ptr to entry code>
189 -- <standard info table>
191 -- <forward vector table>
193 -- * The vector table is only present for vectored returns
195 -- * The SRT slot is only there if either
196 -- (a) there is SRT info to record, OR
197 -- (b) if the return is vectored
198 -- The latter (b) is necessary so that the vector is in a
201 vectorSlot :: CmmExpr -> CmmExpr -> CmmExpr
202 -- Get the vector slot from the info pointer
203 vectorSlot info_amode zero_indexed_tag
205 = cmmOffsetExprW (cmmOffsetW info_amode (- (stdInfoTableSizeW + 2)))
206 (cmmNegate zero_indexed_tag)
207 -- The "2" is one for the SRT slot, and one more
208 -- to get to the first word of the vector
211 = cmmOffsetExprW (cmmOffsetW info_amode (stdInfoTableSizeW + 2))
213 -- The "2" is one for the entry-code slot and one for the SRT slot
215 retVec :: CmmExpr -> CmmExpr -> CmmExpr
216 -- Get a return vector from the info pointer
217 retVec info_amode zero_indexed_tag
218 = let slot = vectorSlot info_amode zero_indexed_tag
219 tableEntry = CmmLoad slot wordRep
220 in if tablesNextToCode
221 then CmmMachOp (MO_Add wordRep) [tableEntry, info_amode]
226 -> CgStmts -- The direct-return code (if any)
227 -- (empty for vectored returns)
228 -> [CmmLit] -- Vector of return points
229 -- (empty for non-vectored returns)
232 emitReturnTarget name stmts vector srt
233 = do { live_slots <- getLiveStackSlots
234 ; liveness <- buildContLiveness name live_slots
235 ; srt_info <- getSRTInfo name srt
238 cl_type = case (null vector, isBigLiveness liveness) of
239 (True, True) -> rET_BIG
240 (True, False) -> rET_SMALL
241 (False, True) -> rET_VEC_BIG
242 (False, False) -> rET_VEC_SMALL
244 (std_info, extra_bits) =
245 mkRetInfoTable info_lbl liveness srt_info cl_type vector
247 ; blks <- cgStmtsToBlocks stmts
248 ; emitInfoTableAndCode info_lbl std_info extra_bits args blks
251 args = trace "emitReturnTarget: missing args" []
252 uniq = getUnique name
253 info_lbl = mkReturnInfoLabel uniq
257 :: CLabel -- info label
258 -> Liveness -- liveness
260 -> Int -- type (eg. rET_SMALL)
261 -> [CmmLit] -- vector
262 -> ([CmmLit],[CmmLit])
263 mkRetInfoTable info_lbl liveness srt_info cl_type vector
264 = (std_info, extra_bits)
266 (srt_label, srt_len) = srtLabelAndLength srt_info info_lbl
268 srt_slot | need_srt = [srt_label]
271 need_srt = needsSRT srt_info || not (null vector)
272 -- If there's a vector table then we must allocate
273 -- an SRT slot, so that the vector table is at a
274 -- known offset from the info pointer
276 liveness_lit = makeRelativeRefTo info_lbl $ mkLivenessCLit liveness
277 std_info = mkStdInfoTable zeroCLit zeroCLit cl_type srt_len liveness_lit
278 extra_bits = srt_slot ++ map (makeRelativeRefTo info_lbl) vector
281 emitDirectReturnTarget
283 -> CgStmts -- The direct-return code
286 emitDirectReturnTarget name code srt
287 = emitReturnTarget name code [] srt
290 :: Name -- Just for its unique
291 -> [(ConTagZ, CgStmts)] -- Tagged branches
292 -> Maybe CgStmts -- Default branch (if any)
293 -> SRT -- Continuation's SRT
294 -> CtrlReturnConvention
295 -> FCode (CLabel, SemiTaggingStuff)
297 emitAlgReturnTarget name branches mb_deflt srt ret_conv
299 UnvectoredReturn fam_sz -> do
300 { blks <- getCgStmts $
301 emitSwitch tag_expr branches mb_deflt 0 (fam_sz - 1)
302 -- NB: tag_expr is zero-based
303 ; lbl <- emitDirectReturnTarget name blks srt
304 ; return (lbl, Nothing) }
305 -- Nothing: the internal branches in the switch don't have
306 -- global labels, so we can't use them at the 'call site'
308 VectoredReturn fam_sz -> do
309 { let tagged_lbls = zip (map fst branches) $
310 map (CmmLabel . mkAltLabel uniq . fst) branches
311 deflt_lbl | isJust mb_deflt = CmmLabel $ mkDefaultLabel uniq
312 | otherwise = mkIntCLit 0
313 ; let vector = [ assocDefault deflt_lbl tagged_lbls i
314 | i <- [0..fam_sz-1]]
315 ; lbl <- emitReturnTarget name noCgStmts vector srt
316 ; mapFCs emit_alt branches
317 ; emit_deflt mb_deflt
318 ; return (lbl, Just (tagged_lbls, deflt_lbl)) }
320 uniq = getUnique name
321 tag_expr = getConstrTag (CmmReg nodeReg)
323 emit_alt :: (Int, CgStmts) -> FCode (Int, CmmLit)
324 -- Emit the code for the alternative as a top-level
325 -- code block returning a label for it
326 emit_alt (tag, stmts) = do { let lbl = mkAltLabel uniq tag
327 ; blks <- cgStmtsToBlocks stmts
328 ; emitProc [] lbl [] blks
329 ; return (tag, CmmLabel lbl) }
331 emit_deflt (Just stmts) = do { let lbl = mkDefaultLabel uniq
332 ; blks <- cgStmtsToBlocks stmts
333 ; emitProc [] lbl [] blks
334 ; return (CmmLabel lbl) }
335 emit_deflt Nothing = return (mkIntCLit 0)
336 -- Nothing case: the simplifier might have eliminated a case
337 -- so we may have e.g. case xs of
339 -- In that situation the default should never be taken,
340 -- so we just use a NULL pointer
342 --------------------------------
343 emitDirectReturnInstr :: Code
344 emitDirectReturnInstr
345 = do { info_amode <- getSequelAmode
346 ; stmtC (CmmJump (entryCode info_amode) []) }
348 emitVectoredReturnInstr :: CmmExpr -- *Zero-indexed* constructor tag
350 emitVectoredReturnInstr zero_indexed_tag
351 = do { info_amode <- getSequelAmode
352 -- HACK! assign info_amode to a temp, because retVec
353 -- uses it twice and the NCG doesn't have any CSE yet.
354 ; x <- newTemp wordRep
355 ; stmtC (CmmAssign x info_amode)
356 ; let target = retVec (CmmReg x) zero_indexed_tag
357 ; stmtC (CmmJump target []) }
360 -------------------------------------------------------------------------
362 -- Generating a standard info table
364 -------------------------------------------------------------------------
366 -- The standard bits of an info table. This part of the info table
367 -- corresponds to the StgInfoTable type defined in InfoTables.h.
369 -- Its shape varies with ticky/profiling/tables next to code etc
370 -- so we can't use constant offsets from Constants
373 :: CmmLit -- closure type descr (profiling)
374 -> CmmLit -- closure descr (profiling)
375 -> Int -- closure type
376 -> StgHalfWord -- SRT length
377 -> CmmLit -- layout field
380 mkStdInfoTable type_descr closure_descr cl_type srt_len layout_lit
381 = -- Parallel revertible-black hole field
383 -- Ticky info (none at present)
384 -- Debug info (none at present)
385 ++ [layout_lit, type_lit]
389 | opt_SccProfilingOn = [closure_descr, type_descr]
392 type_lit = packHalfWordsCLit cl_type srt_len
394 stdInfoTableSizeW :: WordOff
395 -- The size of a standard info table varies with profiling/ticky etc,
396 -- so we can't get it from Constants
397 -- It must vary in sync with mkStdInfoTable
399 = size_fixed + size_prof
401 size_fixed = 2 -- layout, type
402 size_prof | opt_SccProfilingOn = 2
405 stdInfoTableSizeB = stdInfoTableSizeW * wORD_SIZE :: ByteOff
407 stdSrtBitmapOffset :: ByteOff
408 -- Byte offset of the SRT bitmap half-word which is
409 -- in the *higher-addressed* part of the type_lit
410 stdSrtBitmapOffset = stdInfoTableSizeB - hALF_WORD_SIZE
412 stdClosureTypeOffset :: ByteOff
413 -- Byte offset of the closure type half-word
414 stdClosureTypeOffset = stdInfoTableSizeB - wORD_SIZE
416 stdPtrsOffset, stdNonPtrsOffset :: ByteOff
417 stdPtrsOffset = stdInfoTableSizeB - 2*wORD_SIZE
418 stdNonPtrsOffset = stdInfoTableSizeB - 2*wORD_SIZE + hALF_WORD_SIZE
420 -------------------------------------------------------------------------
422 -- Accessing fields of an info table
424 -------------------------------------------------------------------------
426 closureInfoPtr :: CmmExpr -> CmmExpr
427 -- Takes a closure pointer and returns the info table pointer
428 closureInfoPtr e = CmmLoad e wordRep
430 entryCode :: CmmExpr -> CmmExpr
431 -- Takes an info pointer (the first word of a closure)
432 -- and returns its entry code
433 entryCode e | tablesNextToCode = e
434 | otherwise = CmmLoad e wordRep
436 getConstrTag :: CmmExpr -> CmmExpr
437 -- Takes a closure pointer, and return the *zero-indexed*
438 -- constructor tag obtained from the info table
439 -- This lives in the SRT field of the info table
440 -- (constructors don't need SRTs).
441 getConstrTag closure_ptr
442 = CmmMachOp (MO_U_Conv halfWordRep wordRep) [infoTableConstrTag info_table]
444 info_table = infoTable (closureInfoPtr closure_ptr)
446 infoTable :: CmmExpr -> CmmExpr
447 -- Takes an info pointer (the first word of a closure)
448 -- and returns a pointer to the first word of the standard-form
449 -- info table, excluding the entry-code word (if present)
451 | tablesNextToCode = cmmOffsetB info_ptr (- stdInfoTableSizeB)
452 | otherwise = cmmOffsetW info_ptr 1 -- Past the entry code pointer
454 infoTableConstrTag :: CmmExpr -> CmmExpr
455 -- Takes an info table pointer (from infoTable) and returns the constr tag
456 -- field of the info table (same as the srt_bitmap field)
457 infoTableConstrTag = infoTableSrtBitmap
459 infoTableSrtBitmap :: CmmExpr -> CmmExpr
460 -- Takes an info table pointer (from infoTable) and returns the srt_bitmap
461 -- field of the info table
462 infoTableSrtBitmap info_tbl
463 = CmmLoad (cmmOffsetB info_tbl stdSrtBitmapOffset) halfWordRep
465 infoTableClosureType :: CmmExpr -> CmmExpr
466 -- Takes an info table pointer (from infoTable) and returns the closure type
467 -- field of the info table.
468 infoTableClosureType info_tbl
469 = CmmLoad (cmmOffsetB info_tbl stdClosureTypeOffset) halfWordRep
471 infoTablePtrs :: CmmExpr -> CmmExpr
472 infoTablePtrs info_tbl
473 = CmmLoad (cmmOffsetB info_tbl stdPtrsOffset) halfWordRep
475 infoTableNonPtrs :: CmmExpr -> CmmExpr
476 infoTableNonPtrs info_tbl
477 = CmmLoad (cmmOffsetB info_tbl stdNonPtrsOffset) halfWordRep
479 funInfoTable :: CmmExpr -> CmmExpr
480 -- Takes the info pointer of a function,
481 -- and returns a pointer to the first word of the StgFunInfoExtra struct
482 -- in the info table.
483 funInfoTable info_ptr
485 = cmmOffsetB info_ptr (- stdInfoTableSizeB - sIZEOF_StgFunInfoExtraRev)
487 = cmmOffsetW info_ptr (1 + stdInfoTableSizeW)
488 -- Past the entry code pointer
490 -------------------------------------------------------------------------
492 -- Emit the code for a closure (or return address)
493 -- and its associated info table
495 -------------------------------------------------------------------------
497 -- The complication here concerns whether or not we can
498 -- put the info table next to the code
501 :: CLabel -- Label of info table
502 -> [CmmLit] -- ...its invariant part
503 -> [CmmLit] -- ...and its variant part
504 -> [LocalReg] -- ...args
505 -> [CmmBasicBlock] -- ...and body
508 emitInfoTableAndCode info_lbl std_info extra_bits args blocks
509 | tablesNextToCode -- Reverse the extra_bits; and emit the top-level proc
510 = emitProc (reverse extra_bits ++ std_info)
511 entry_lbl args blocks
512 -- NB: the info_lbl is discarded
514 | null blocks -- No actual code; only the info table is significant
515 = -- Use a zero place-holder in place of the
516 -- entry-label in the info table
517 emitRODataLits info_lbl (zeroCLit : std_info ++ extra_bits)
519 | otherwise -- Separately emit info table (with the function entry
520 = -- point as first entry) and the entry code
521 do { emitDataLits info_lbl (CmmLabel entry_lbl : std_info ++ extra_bits)
522 ; emitProc [] entry_lbl args blocks }
525 entry_lbl = infoLblToEntryLbl info_lbl
527 -------------------------------------------------------------------------
529 -- Static reference tables
531 -------------------------------------------------------------------------
533 -- There is just one SRT for each top level binding; all the nested
534 -- bindings use sub-sections of this SRT. The label is passed down to
535 -- the nested bindings via the monad.
537 getSRTInfo :: Name -> SRT -> FCode C_SRT
538 getSRTInfo id NoSRT = return NoC_SRT
539 getSRTInfo id (SRT off len bmp)
540 | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
541 = do { srt_lbl <- getSRTLabel
542 ; let srt_desc_lbl = mkSRTDescLabel id
543 ; emitRODataLits srt_desc_lbl
544 ( cmmLabelOffW srt_lbl off
545 : mkWordCLit (fromIntegral len)
546 : map mkWordCLit bmp)
547 ; return (C_SRT srt_desc_lbl 0 srt_escape) }
550 = do { srt_lbl <- getSRTLabel
551 ; return (C_SRT srt_lbl off (fromIntegral (head bmp))) }
552 -- The fromIntegral converts to StgHalfWord
554 srt_escape = (-1) :: StgHalfWord
556 srtLabelAndLength :: C_SRT -> CLabel -> (CmmLit, StgHalfWord)
557 srtLabelAndLength NoC_SRT _
559 srtLabelAndLength (C_SRT lbl off bitmap) info_lbl
560 = (makeRelativeRefTo info_lbl $ cmmLabelOffW lbl off, bitmap)
562 -------------------------------------------------------------------------
564 -- Position independent code
566 -------------------------------------------------------------------------
567 -- In order to support position independent code, we mustn't put absolute
568 -- references into read-only space. Info tables in the tablesNextToCode
569 -- case must be in .text, which is read-only, so we doctor the CmmLits
570 -- to use relative offsets instead.
572 -- Note that this is done even when the -fPIC flag is not specified,
573 -- as we want to keep binary compatibility between PIC and non-PIC.
575 makeRelativeRefTo :: CLabel -> CmmLit -> CmmLit
577 makeRelativeRefTo info_lbl (CmmLabel lbl)
579 = CmmLabelDiffOff lbl info_lbl 0
580 makeRelativeRefTo info_lbl (CmmLabelOff lbl off)
582 = CmmLabelDiffOff lbl info_lbl off
583 makeRelativeRefTo _ lit = lit