1 /* -----------------------------------------------------------------------------
2 * $Id: HeapStackCheck.hc,v 1.3 1999/02/05 16:02:43 simonm Exp $
4 * (c) The GHC Team, 1998-1999
6 * Canned Heap-Check and Stack-Check sequences.
8 * ---------------------------------------------------------------------------*/
11 #include "Storage.h" /* for CurrentTSO */
12 #include "StgRun.h" /* for StgReturn and register saving */
13 #include "Schedule.h" /* for context_switch */
14 #include "HeapStackCheck.h"
16 /* Stack/Heap Check Failure
17 * ------------------------
19 * On discovering that a stack or heap check has failed, we do the following:
21 * - If the context_switch flag is set, indicating that there are more
22 * threads waiting to run, we yield to the scheduler
23 * (return ThreadYeilding).
25 * - If Hp > HpLim, we've had a heap check failure. This means we've
26 * come to the end of the current heap block, so we try to chain
27 * another block on with ExtendNursery().
29 * - If this succeeds, we carry on without returning to the
32 * - If it fails, we return to the scheduler claiming HeapOverflow
33 * so that a garbage collection can be performed.
35 * - If Hp <= HpLim, it must have been a stack check that failed. In
36 * which case, we return to the scheduler claiming StackOverflow, the
37 * scheduler will either increase the size of our stack, or flag
38 * an error if the stack is already too big.
40 * The effect of checking for context switch only in the heap/stack check
41 * failure code is that we'll switch threads after the current thread has
42 * reached the end of its heap block. If a thread isn't allocating
43 * at all, it won't yield. Hopefully this won't be a problem in practice.
46 /* Remember that the return address is *removed* when returning to a
47 * ThreadRunGHC thread.
53 if (ExtendNursery(Hp,HpLim)) { \
54 if (context_switch) { \
55 R1.i = ThreadYielding; \
58 JMP_(ENTRY_CODE(Sp[-1])); \
61 R1.i = HeapOverflow; \
64 R1.i = StackOverflow; \
67 CurrentTSO->whatNext = ThreadRunGHC; \
72 if (ExtendNursery(Hp,HpLim)) { \
73 if (context_switch) { \
74 R1.i = ThreadYielding; \
78 JMP_(ENTRY_CODE(*R1.p)); \
81 R1.i = HeapOverflow; \
84 R1.i = StackOverflow; \
87 CurrentTSO->whatNext = ThreadEnterGHC; \
92 CurrentTSO->whatNext = ThreadRunGHC; \
93 R1.i = HeapOverflow; \
98 CurrentTSO->whatNext = ThreadRunGHC; \
99 R1.i = StackOverflow; \
102 #define YIELD_GENERIC \
104 CurrentTSO->whatNext = ThreadRunGHC; \
105 R1.i = ThreadYielding; \
108 #define YIELD_TO_HUGS \
110 CurrentTSO->whatNext = ThreadEnterHugs; \
111 R1.i = ThreadYielding; \
114 #define BLOCK_GENERIC \
116 CurrentTSO->whatNext = ThreadRunGHC; \
117 R1.i = ThreadBlocked; \
120 #define BLOCK_ENTER \
122 CurrentTSO->whatNext = ThreadEnterGHC;\
123 R1.i = ThreadBlocked; \
126 /* -----------------------------------------------------------------------------
128 -------------------------------------------------------------------------- */
131 * This one is used when we want to *enter* the top thing on the stack
132 * when we return, instead of the just returning to an address. See
133 * UpdatePAP for an example.
136 EXTFUN(stg_gc_entertop)
143 /* -----------------------------------------------------------------------------
144 Heap checks in non-top-level thunks/functions.
146 In these cases, node always points to the function closure. This gives
147 us an easy way to return to the function: just leave R1 on the top of
148 the stack, and have the scheduler enter it to return.
150 There are canned sequences for 'n' pointer values in registers.
151 -------------------------------------------------------------------------- */
153 EXTFUN(stg_gc_enter_1)
162 /*- 2 Regs--------------------------------------------------------------------*/
164 EXTFUN(stg_gc_enter_2)
174 /*- 3 Regs -------------------------------------------------------------------*/
176 EXTFUN(stg_gc_enter_3)
187 /*- 4 Regs -------------------------------------------------------------------*/
189 EXTFUN(stg_gc_enter_4)
201 /*- 5 Regs -------------------------------------------------------------------*/
203 EXTFUN(stg_gc_enter_5)
216 /*- 6 Regs -------------------------------------------------------------------*/
218 EXTFUN(stg_gc_enter_6)
232 /*- 7 Regs -------------------------------------------------------------------*/
234 EXTFUN(stg_gc_enter_7)
249 /*- 8 Regs -------------------------------------------------------------------*/
251 EXTFUN(stg_gc_enter_8)
267 /* -----------------------------------------------------------------------------
268 For a case expression on a polymorphic or function-typed object, if
269 the default branch (there can only be one branch) of the case fails
270 a heap-check, instead of using stg_gc_enter_1 as normal, we must
271 push a new SEQ frame on the stack, followed by the object returned.
273 Otherwise, if the object is a function, it won't return to the
274 correct activation record on returning from garbage collection. It will
275 assume it has some arguments and apply itself.
276 -------------------------------------------------------------------------- */
281 Sp -= 1 + sizeofW(StgSeqFrame);
282 PUSH_SEQ_FRAME(Sp+1);
288 /* -----------------------------------------------------------------------------
289 Heap checks in Primitive case alternatives
291 A primitive case alternative is entered with a value either in
292 R1, FloatReg1 or D1 depending on the return convention. All the
293 cases are covered below.
294 -------------------------------------------------------------------------- */
296 /*-- No regsiters live, return address already on the stack: ---------------- */
298 EXTFUN(stg_gc_noregs)
305 /*-- R1 is boxed/unpointed -------------------------------------------------- */
307 INFO_TABLE_SRT_BITMAP(stg_gc_unpt_r1_info, stg_gc_unpt_r1_entry, 0/*BITMAP*/,
308 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
309 RET_SMALL, const, EF_, 0, 0);
311 EXTFUN(stg_gc_unpt_r1_entry)
316 JMP_(ENTRY_CODE(Sp[0]));
320 EXTFUN(stg_gc_unpt_r1)
325 Sp[0] = (W_)&stg_gc_unpt_r1_info;
330 /*-- R1 is unboxed -------------------------------------------------- */
332 INFO_TABLE_SRT_BITMAP(stg_gc_unbx_r1_info, stg_gc_unbx_r1_entry, 1/*BITMAP*/,
333 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
334 RET_SMALL, const, EF_, 0, 0);
335 /* the 1 is a bitmap - i.e. 1 non-pointer word on the stack. */
337 EXTFUN(stg_gc_unbx_r1_entry)
342 JMP_(ENTRY_CODE(Sp[0]));
346 EXTFUN(stg_gc_unbx_r1)
351 Sp[0] = (W_)&stg_gc_unbx_r1_info;
356 /*-- F1 contains a float ------------------------------------------------- */
358 INFO_TABLE_SRT_BITMAP(stg_gc_f1_info, stg_gc_f1_entry, 1/*BITMAP*/,
359 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
360 RET_SMALL, const, EF_, 0, 0);
362 EXTFUN(stg_gc_f1_entry)
367 JMP_(ENTRY_CODE(Sp[0]));
375 ASSIGN_FLT(Sp+1, F1);
376 Sp[0] = (W_)&stg_gc_f1_info;
381 /*-- D1 contains a double ------------------------------------------------- */
383 /* we support doubles of either 1 or 2 words in size */
385 #if SIZEOF_DOUBLE == SIZEOF_VOID_P
386 # define DBL_BITMAP 1
388 # define DBL_BITMAP 3
391 INFO_TABLE_SRT_BITMAP(stg_gc_d1_info, stg_gc_d1_entry, DBL_BITMAP,
392 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
393 RET_SMALL, const, EF_, 0, 0);
395 EXTFUN(stg_gc_d1_entry)
399 Sp += sizeofW(StgDouble);
400 JMP_(ENTRY_CODE(Sp[0]));
407 Sp -= 1 + sizeofW(StgDouble);
409 Sp[0] = (W_)&stg_gc_d1_info;
414 /* -----------------------------------------------------------------------------
415 Heap checks for unboxed tuple case alternatives
419 - for an unboxed tuple with n components, we rearrange the components
420 with pointers first followed by non-pointers. (NB: not done yet)
422 - The first k components are allocated registers, where k is the
423 number of components that will fit in real registers.
425 - The rest are placed on the stack, with space left for tagging
426 of the non-pointer block if necessary.
428 - On failure of a heap check:
429 - the tag is filled in if necessary,
430 - we load Ri with the address of the continuation,
431 where i is the lowest unused vanilla register.
432 - jump to 'stg_gc_ut_x_y' where x is the number of pointer
433 registers and y the number of non-pointers.
434 - if the required canned sequence isn't available, it will
435 have to be generated at compile-time by the code
436 generator (this will probably happen if there are
437 floating-point values, for instance).
439 For now, just deal with R1, hence R2 contains the sequel address.
440 -------------------------------------------------------------------------- */
442 /*---- R1 contains a pointer: ------ */
444 INFO_TABLE_SRT_BITMAP(stg_gc_ut_1_0_info, stg_gc_ut_1_0_entry, 1/*BITMAP*/,
445 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
446 RET_SMALL, const, EF_, 0, 0);
448 EXTFUN(stg_gc_ut_1_0_entry)
457 EXTFUN(stg_gc_ut_1_0)
463 Sp[0] = (W_)&stg_gc_ut_1_0_info;
468 /*---- R1 contains a non-pointer: ------ */
470 INFO_TABLE_SRT_BITMAP(stg_gc_ut_0_1_info, stg_gc_ut_0_1_entry, 3/*BITMAP*/,
471 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
472 RET_SMALL, const, EF_, 0, 0);
474 EXTFUN(stg_gc_ut_0_1_entry)
483 EXTFUN(stg_gc_ut_0_1)
487 Sp[0] = (W_)&stg_gc_ut_0_1_info;
494 /* -----------------------------------------------------------------------------
495 Standard top-level fast-entry heap checks.
497 - we want to make the stack look like it should at the slow entry
498 point for the function. That way we can just push the slow
499 entry point on the stack and return using ThreadRunGHC.
501 - The compiler will generate code to fill in any tags on the stack,
502 in case we arrived directly at the fast entry point and these tags
505 - The rest is hopefully handled by jumping to a canned sequence.
506 We currently have canned sequences for 0-8 pointer registers. If
507 any registers contain non-pointers, we must reduce to an all-pointers
508 situation by pushing as many registers on the stack as necessary.
510 eg. if R1, R2 contain pointers and R3 contains a word, the heap check
511 failure sequence looks like this:
518 after pushing R3, we have pointers in R1 and R2 which corresponds
519 to the 2-pointer canned sequence.
521 -------------------------------------------------------------------------- */
523 /*- 0 Regs -------------------------------------------------------------------*/
534 /*- 1 Reg --------------------------------------------------------------------*/
546 /*- 1 Reg (non-ptr) ----------------------------------------------------------*/
553 Sp[1] = WORD_TAG; /* ToDo: or maybe its an int? */
559 /*- 2 Regs--------------------------------------------------------------------*/
572 /*- 3 Regs -------------------------------------------------------------------*/
586 /*- 4 Regs -------------------------------------------------------------------*/
601 /*- 5 Regs -------------------------------------------------------------------*/
617 /*- 6 Regs -------------------------------------------------------------------*/
634 /*- 7 Regs -------------------------------------------------------------------*/
652 /*- 8 Regs -------------------------------------------------------------------*/
671 /* -----------------------------------------------------------------------------
672 Generic Heap Check Code.
674 Called with Liveness mask in R9, Return address in R10.
675 Stack must be consistent (tagged, and containing all necessary info pointers
678 We also define an stg_gen_yield here, because it's very similar.
679 -------------------------------------------------------------------------- */
681 #if SIZEOF_DOUBLE > SIZEOF_VOID_P
683 #define RESTORE_EVERYTHING \
684 D2 = PK_DBL(Sp+16); \
685 D1 = PK_DBL(Sp+14); \
686 F4 = PK_FLT(Sp+13); \
687 F3 = PK_FLT(Sp+12); \
688 F2 = PK_FLT(Sp+11); \
689 F1 = PK_FLT(Sp+10); \
700 #define RET_OFFSET (-17)
702 #define SAVE_EVERYTHING \
703 ASSIGN_DBL(Sp-2,D2); \
704 ASSIGN_DBL(Sp-4,D1); \
705 ASSIGN_FLT(Sp-5,F4); \
706 ASSIGN_FLT(Sp-6,F3); \
707 ASSIGN_FLT(Sp-7,F2); \
708 ASSIGN_FLT(Sp-8,F1); \
717 Sp[-17] = R10.w; /* return address */ \
718 Sp[-18] = R9.w; /* liveness mask */ \
719 Sp[-19] = (W_)&stg_gen_chk_info; \
724 #define RESTORE_EVERYTHING \
725 D2 = PK_DBL(Sp+15); \
726 D1 = PK_DBL(Sp+14); \
727 F4 = PK_FLT(Sp+13); \
728 F3 = PK_FLT(Sp+12); \
729 F2 = PK_FLT(Sp+11); \
730 F1 = PK_FLT(Sp+10); \
741 #define RET_OFFSET (-15)
743 #define SAVE_EVERYTHING \
744 ASSIGN_DBL(Sp-1,D2); \
745 ASSIGN_DBL(Sp-2,D1); \
746 ASSIGN_FLT(Sp-3,F4); \
747 ASSIGN_FLT(Sp-4,F3); \
748 ASSIGN_FLT(Sp-5,F2); \
749 ASSIGN_FLT(Sp-6,F1); \
758 Sp[-15] = R10.w; /* return address */ \
759 Sp[-16] = R9.w; /* liveness mask */ \
760 Sp[-17] = (W_)&stg_gen_chk_info; \
765 INFO_TABLE_SRT_BITMAP(stg_gen_chk_info, stg_gen_chk_ret, 0,
766 0/*SRT*/, 0/*SRT_OFF*/, 0/*SRT_LEN*/,
767 RET_DYN, const, EF_, 0, 0);
769 /* bitmap in the above info table is unused, the real one is on the stack.
776 JMP_(Sp[RET_OFFSET]);
789 * stg_gen_hp is used by MAYBE_GC, where we can't use GC_GENERIC
790 * because we've just failed doYouWantToGC(), not a standard heap
791 * check. GC_GENERIC would end up returning StackOverflow.
809 FN_(stg_yield_to_Hugs)
812 /* No need to save everything - no live registers */