1 /* -----------------------------------------------------------------------------
2 * $Id: Updates.hc,v 1.25 2000/01/13 14:34:05 hwloidl Exp $
4 * (c) The GHC Team, 1998-1999
6 * Code to perform updates.
8 * ---------------------------------------------------------------------------*/
13 #include "HeapStackCheck.h"
16 #if defined(GRAN) || defined(PAR)
21 The update frame return address must be *polymorphic*, that means
22 we have to cope with both vectored and non-vectored returns. This
23 is done by putting the return vector right before the info table, and
24 having a standard direct return address after the info table (pointed
25 to by the return address itself, as usual).
27 Each entry in the vector table points to a specialised entry code fragment
28 that knows how to return after doing the update. It would be possible to
29 use a single generic piece of code that simply entered the return value
30 to return, but it's quicker this way. The direct return code of course
31 just does another direct return when it's finished.
33 Why is there necessarily an activation underneath us on the stack?
34 Because if we're returning, that means we've got a constructor in
35 our hands. If there were any arguments to be applied to it, that
36 would be a type error. We don't ever return a PAP to an update frame,
37 the update is handled manually by stg_update_PAP.
40 /* on entry to the update code
41 (1) R1 points to the closure being returned
42 (2) R2 contains the tag (if we returned directly, non-vectored)
43 (3) Sp points to the update frame
46 /* Why updatee is placed in a temporary variable here: this helps
47 gcc's aliasing by indicating that the location of the updatee
48 doesn't change across assignments. Saves one instruction in the
53 #define UPD_FRAME_ENTRY_TEMPLATE(label,ret) \
59 Su = (StgUpdateFrame *)((StgUpdateFrame *)Sp)->updatee; \
61 /* Tick - it must be a con, all the paps are handled \
62 * in stg_upd_PAP and PAP_entry below \
64 TICK_UPD_CON_IN_NEW(sizeW_fromITBL(get_itbl(Su))); \
68 /* reset Su to the next update frame */ \
69 Su = ((StgUpdateFrame *)Sp)->link; \
71 /* remove the update frame from the stack */ \
72 Sp += sizeofW(StgUpdateFrame); \
79 #define UPD_FRAME_ENTRY_TEMPLATE(label,ret) \
83 StgClosure *updatee; \
86 updatee = ((StgUpdateFrame *)Sp)->updatee; \
88 /* Tick - it must be a con, all the paps are handled \
89 * in stg_upd_PAP and PAP_entry below \
91 TICK_UPD_CON_IN_NEW(sizeW_fromITBL(get_itbl(updatee))); \
93 UPD_IND(updatee, R1.cl); \
95 /* reset Su to the next update frame */ \
96 Su = ((StgUpdateFrame *)Sp)->link; \
98 /* remove the update frame from the stack */ \
99 Sp += sizeofW(StgUpdateFrame); \
106 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_entry,ENTRY_CODE(Sp[0]));
107 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_0_entry,RET_VEC(Sp[0],0));
108 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_1_entry,RET_VEC(Sp[0],1));
109 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_2_entry,RET_VEC(Sp[0],2));
110 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_3_entry,RET_VEC(Sp[0],3));
111 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_4_entry,RET_VEC(Sp[0],4));
112 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_5_entry,RET_VEC(Sp[0],5));
113 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_6_entry,RET_VEC(Sp[0],6));
114 UPD_FRAME_ENTRY_TEMPLATE(Upd_frame_7_entry,RET_VEC(Sp[0],7));
117 Make sure this table is big enough to handle the maximum vectored
122 #define UPD_FRAME_BITMAP 3
124 #define UPD_FRAME_BITMAP 1
127 /* this bitmap indicates that the first word of an update frame is a
128 * non-pointer - this is the update frame link. (for profiling,
129 * there's a cost-centre-stack in there too).
132 VEC_POLY_INFO_TABLE(Upd_frame,UPD_FRAME_BITMAP, NULL/*srt*/, 0/*srt_off*/, 0/*srt_len*/, UPDATE_FRAME,, EF_);
134 /* -----------------------------------------------------------------------------
135 Entry Code for a PAP.
137 The idea is to copy the chunk of stack from the PAP object and then
138 re-enter the function closure that failed it's args check in the
141 In fact, we do a little optimisation too, by performing the updates
142 for any update frames sitting on top of the stack. (ToDo: is this
143 really an optimisation? --SDM)
144 -------------------------------------------------------------------------- */
146 INFO_TABLE(PAP_info,PAP_entry,/*special layout*/0,0,PAP,,EF_,0,0);
156 pap = (StgPAP *) R1.p;
159 * remove any update frames on the top of the stack, by just
160 * performing the update here.
162 while ((W_)Su - (W_)Sp == 0) {
164 switch (get_itbl(Su)->type) {
167 /* We're sitting on top of an update frame, so let's do the business */
168 UPD_IND(Su->updatee, pap);
170 #if defined(PROFILING)
172 * Restore the Cost Centre too (if required); again see Sansom
173 * thesis p 183. Take the CC out of the update frame if a
177 CCCS = Su->header.prof.ccs;
178 #endif /* PROFILING */
181 Sp += sizeofW(StgUpdateFrame);
185 /* Just pop the seq frame and return to the activation record
186 * underneath us - R1 already contains the address of the PAP.
188 Su = ((StgSeqFrame *)Su)->link;
189 Sp += sizeofW(StgSeqFrame);
190 JMP_(ENTRY_CODE(*Sp));
193 /* can't happen, see stg_update_PAP */
194 barf("PAP_entry: CATCH_FRAME");
197 barf("PAP_entry: strange activation record");
205 * Check for stack overflow.
207 STK_CHK_NP(Words,1,);
212 /* Enter PAP cost centre -- lexical scoping only */
213 ENTER_CCS_PAP_CL(pap);
216 p = (P_)(pap->payload);
218 /* Reload the stack */
219 for (i=0; i<Words; i++) Sp[i] = (W_) *p++;
223 JMP_(GET_ENTRY(R1.cl));
227 /* -----------------------------------------------------------------------------
228 stg_update_PAP: Update the current closure with a partial application.
230 This function is called whenever an argument satisfaction check fails.
231 -------------------------------------------------------------------------- */
233 EXTFUN(stg_update_PAP)
237 CostCentreStack *CCS_pap;
240 StgClosure *Fun, *Updatee;
246 /* Save the pointer to the function closure that just failed the
247 * argument satisfaction check
251 /* Just copy the whole block of stack between the stack pointer
252 * and the update frame pointer.
254 Words = (P_)Su - (P_)Sp;
255 ASSERT((int)Words >= 0);
257 #if defined(PROFILING)
258 /* pretend we just entered the function closure */
266 * No arguments, only Node. Skip building the PAP and
267 * just plan to update with an indirection.
270 PapClosure = (StgPAP *)Fun;
275 PapSize = Words + sizeofW(StgPAP);
278 * First we need to do a heap check, which involves saving
279 * everything on the stack. We only have one live pointer:
280 * Fun, the function closure that was passed to us. If the
281 * heap check fails, we push the function closure on the stack
282 * and instruct the scheduler to try entering it again when
283 * the garbage collector has run.
285 * It's done this way because there's a possibility that the
286 * garbage collector might have messed around with the stack,
287 * such as removing the update frame.
289 if ((Hp += PapSize) > HpLim) {
292 JMP_(stg_gc_entertop);
295 TICK_ALLOC_UPD_PAP(1/*fun*/ + Words, 0);
297 CCS_ALLOC(CCS_pap, PapSize);
300 PapClosure = (StgPAP *)(Hp + 1 - PapSize); /* The new PapClosure */
302 SET_HDR(PapClosure,&PAP_info,CCS_pap);
303 PapClosure->n_args = Words;
304 PapClosure->fun = Fun;
306 /* Now fill in the closure fields */
309 for (i = Words-1; i >= 0; i--) {
315 * Finished constructing PAP closure; now update the updatee.
318 /* ToDo: we'd like to just jump to the code for PAP_entry here,
319 * which deals with a stack of update frames in one go. What to
320 * do about the special ticky and profiling stuff here?
323 switch (get_itbl(Su)->type) {
326 /* Set Sp to just above the SEQ frame (should be an activation rec.)*/
327 Sp = (P_)Su + sizeofW(StgSeqFrame);
330 Su = ((StgSeqFrame *)Su)->link;
332 /* return to the activation record, with the address of the PAP in R1 */
333 R1.p = (P_)PapClosure;
334 JMP_(ENTRY_CODE(*Sp));
337 /* Set Sp to just above the CATCH frame (should be an activation rec.)*/
338 Sp = (P_)Su + sizeofW(StgCatchFrame);
341 Su = ((StgCatchFrame *)Su)->link;
343 /* restart by entering the PAP */
344 R1.p = (P_)PapClosure;
345 JMP_(GET_ENTRY(R1.cl));
349 * Now we have a standard update frame, so we update the updatee with
350 * either the new PAP or Node.
353 Updatee = Su->updatee;
355 #if defined(PROFILING)
357 UPD_IND(Updatee,PapClosure);
358 TICK_UPD_PAP_IN_NEW(Words+1);
360 /* Lexical scoping requires a *permanent* indirection, and we
361 * also have to set the cost centre for the indirection.
363 UPD_PERM_IND(Updatee,PapClosure);
364 TICK_UPD_PAP_IN_PLACE();
365 Updatee->header.prof.ccs = CCS_pap;
368 UPD_IND(Updatee,PapClosure);
370 TICK_UPD_PAP_IN_NEW(Words+1);
372 TICK_UPD_PAP_IN_PLACE();
376 #if defined(PROFILING)
377 CCCS = Su->header.prof.ccs;
378 ENTER_CCS_PAP(CCS_pap);
379 #endif /* PROFILING */
385 * Squeeze out update frame from stack.
387 for (i = Words-1; i >= 0; i--) {
388 Sp[i+(sizeofW(StgUpdateFrame))] = Sp[i];
390 Sp += sizeofW(StgUpdateFrame);
394 barf("stg_update_PAP: strange activation record");
398 * All done! Restart by re-entering Node
399 * Don't count this entry for ticky-ticky profiling.
401 JMP_(GET_ENTRY(R1.cl));
406 /* -----------------------------------------------------------------------------
407 Entry Code for an AP_UPD.
409 The idea is to copy the chunk of stack from the AP object and then
410 enter the function closure.
412 (This code is a simplified copy of the PAP code - with all the
413 update frame code stripped out.)
414 -------------------------------------------------------------------------- */
417 INFO_TABLE(AP_UPD_info,AP_UPD_entry,/*special layout*/0,0,AP_UPD,,EF_,0,0);
427 ap = (StgAP_UPD *) R1.p;
432 * Check for stack overflow.
434 STK_CHK(Words+sizeofW(StgUpdateFrame),AP_UPD_entry,R2.p,1,);
436 PUSH_UPD_FRAME(R1.p, 0);
437 Sp -= sizeofW(StgUpdateFrame) + Words;
441 /* Enter PAP cost centre -- lexical scoping only */
442 ENTER_CCS_PAP_CL(ap); /* ToDo: ENTER_CC_AP_UPD_CL */
445 p = (P_)(ap->payload);
447 /* Reload the stack */
448 for (i=0; i<Words; i++) Sp[i] = (W_) *p++;
452 JMP_(GET_ENTRY(R1.cl));
457 /*-----------------------------------------------------------------------------
460 We don't have a primitive seq# operator: it is just a 'case'
461 expression whose scrutinee has either a polymorphic or function type
462 (constructor types can be handled by normal 'case' expressions).
464 To handle a polymorphic/function typed seq, we push a SEQ_FRAME on
465 the stack. This is a polymorphic activation record that just pops
466 itself and returns when entered. The purpose of the SEQ_FRAME is to
467 act as a barrier in case the scrutinee is a partial application - in
468 this way it is just like an update frame, except that it doesn't
470 -------------------------------------------------------------------------- */
472 #define SEQ_FRAME_ENTRY_TEMPLATE(label,ret) \
476 Su = ((StgSeqFrame *)Sp)->link; \
477 Sp += sizeofW(StgSeqFrame); \
482 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_entry, ENTRY_CODE(Sp[0]));
483 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_0_entry,ENTRY_CODE(Sp[0]));
484 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_1_entry,ENTRY_CODE(Sp[0]));
485 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_2_entry,ENTRY_CODE(Sp[0]));
486 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_3_entry,ENTRY_CODE(Sp[0]));
487 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_4_entry,ENTRY_CODE(Sp[0]));
488 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_5_entry,ENTRY_CODE(Sp[0]));
489 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_6_entry,ENTRY_CODE(Sp[0]));
490 SEQ_FRAME_ENTRY_TEMPLATE(seq_frame_7_entry,ENTRY_CODE(Sp[0]));
492 VEC_POLY_INFO_TABLE(seq_frame, UPD_FRAME_BITMAP, NULL/*srt*/, 0/*srt_off*/, 0/*srt_len*/, SEQ_FRAME,, EF_);
494 /* -----------------------------------------------------------------------------
497 * This closure takes one argument, which it evaluates and returns the
498 * result with a direct return (never a vectored return!) in R1. It
499 * does this by pushing a SEQ_FRAME on the stack and
500 * entering its argument.
502 * It is used in deleteThread when reverting blackholes.
503 * -------------------------------------------------------------------------- */
505 INFO_TABLE(seq_info,seq_entry,1,0,FUN,,EF_,0,0);
509 STK_CHK_GEN(sizeofW(StgSeqFrame), NO_PTRS, seq_entry, );
510 Sp -= sizeofW(StgSeqFrame);
512 R1.cl = R1.cl->payload[0];
513 JMP_(ENTRY_CODE(*R1.p));