| blob | 35021ea137fae1cbd26ced7b9748f2b64925217a |
1 /* Convert function calls to rtl insns, for GNU C compiler.
2 Copyright (C) 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
20 02111-1307, USA. */
44 /* Like PREFERRED_STACK_BOUNDARY but in units of bytes, not bits. */
45 #define STACK_BYTES (PREFERRED_STACK_BOUNDARY / BITS_PER_UNIT)
47 /* Data structure and subroutines used within expand_call. */
49 struct arg_data
50 {
51 /* Tree node for this argument. */
52 tree tree_value;
53 /* Mode for value; TYPE_MODE unless promoted. */
55 /* Current RTL value for argument, or 0 if it isn't precomputed. */
56 rtx value;
57 /* Initially-compute RTL value for argument; only for const functions. */
58 rtx initial_value;
59 /* Register to pass this argument in, 0 if passed on stack, or an
60 PARALLEL if the arg is to be copied into multiple non-contiguous
61 registers. */
62 rtx reg;
63 /* Register to pass this argument in when generating tail call sequence.
64 This is not the same register as for normal calls on machines with
65 register windows. */
66 rtx tail_call_reg;
67 /* If REG was promoted from the actual mode of the argument expression,
68 indicates whether the promotion is sign- or zero-extended. */
70 /* Number of registers to use. 0 means put the whole arg in registers.
71 Also 0 if not passed in registers. */
73 /* Nonzero if argument must be passed on stack.
74 Note that some arguments may be passed on the stack
75 even though pass_on_stack is zero, just because FUNCTION_ARG says so.
76 pass_on_stack identifies arguments that *cannot* go in registers. */
78 /* Some fields packaged up for locate_and_pad_parm. */
80 /* Location on the stack at which parameter should be stored. The store
81 has already been done if STACK == VALUE. */
82 rtx stack;
83 /* Location on the stack of the start of this argument slot. This can
84 differ from STACK if this arg pads downward. This location is known
85 to be aligned to FUNCTION_ARG_BOUNDARY. */
86 rtx stack_slot;
87 /* Place that this stack area has been saved, if needed. */
88 rtx save_area;
89 /* If an argument's alignment does not permit direct copying into registers,
90 copy in smaller-sized pieces into pseudos. These are stored in a
91 block pointed to by this field. The next field says how many
92 word-sized pseudos we made. */
95 };
97 /* A vector of one char per byte of stack space. A byte if nonzero if
98 the corresponding stack location has been used.
99 This vector is used to prevent a function call within an argument from
100 clobbering any stack already set up. */
103 /* Size of STACK_USAGE_MAP. */
106 /* A bitmap of virtual-incoming stack space. Bit is set if the corresponding
107 stack location's tail call argument has been already stored into the stack.
108 This bitmap is used to prevent sibling call optimization if function tries
109 to use parent's incoming argument slots when they have been already
110 overwritten with tail call arguments. */
113 /* stack_arg_under_construction is nonzero when an argument may be
114 initialized with a constructor call (including a C function that
115 returns a BLKmode struct) and expand_call must take special action
116 to make sure the object being constructed does not overlap the
117 argument list for the constructor call. */
125 CUMULATIVE_ARGS *);
153 #ifdef REG_PARM_STACK_SPACE
156 #endif
157 \f
158 /* If WHICH is 1, return 1 if EXP contains a call to the built-in function
159 `alloca'.
161 If WHICH is 0, return 1 if EXP contains a call to any function.
162 Actually, we only need return 1 if evaluating EXP would require pushing
163 arguments on the stack, but that is too difficult to compute, so we just
164 assume any function call might require the stack. */
168 static int
170 {
177 }
179 /* Recursive function to do the work of above function. */
181 static int
183 {
189 /* If this code is language-specific, we don't know what it will do. */
194 {
200 && (TYPE_RETURNS_STACK_DEPRESSED
214 {
215 tree tem;
220 }
230 calls_function_save_exprs);
235 {
236 tree local;
237 tree subblock;
245 subblock;
249 }
260 }
262 /* Only expressions and blocks can contain calls.
263 Blocks were handled above. */
273 }
274 \f
275 /* Force FUNEXP into a form suitable for the address of a CALL,
276 and return that as an rtx. Also load the static chain register
277 if FNDECL is a nested function.
279 CALL_FUSAGE points to a variable holding the prospective
280 CALL_INSN_FUNCTION_USAGE information. */
282 rtx
285 {
288 /* Make a valid memory address and copy constants through pseudo-regs,
289 but not for a constant address if -fno-function-cse. */
291 /* If we are using registers for parameters, force the
292 function address into a register now. */
297 {
298 #ifndef NO_FUNCTION_CSE
300 #ifdef NO_RECURSIVE_FUNCTION_CSE
302 #endif
304 #endif
305 }
308 {
313 }
316 }
318 /* Generate instructions to call function FUNEXP,
319 and optionally pop the results.
320 The CALL_INSN is the first insn generated.
322 FNDECL is the declaration node of the function. This is given to the
323 macro RETURN_POPS_ARGS to determine whether this function pops its own args.
325 FUNTYPE is the data type of the function. This is given to the macro
326 RETURN_POPS_ARGS to determine whether this function pops its own args.
327 We used to allow an identifier for library functions, but that doesn't
328 work when the return type is an aggregate type and the calling convention
329 says that the pointer to this aggregate is to be popped by the callee.
331 STACK_SIZE is the number of bytes of arguments on the stack,
332 ROUNDED_STACK_SIZE is that number rounded up to
333 PREFERRED_STACK_BOUNDARY; zero if the size is variable. This is
334 both to put into the call insn and to generate explicit popping
335 code if necessary.
337 STRUCT_VALUE_SIZE is the number of bytes wanted in a structure value.
338 It is zero if this call doesn't want a structure value.
340 NEXT_ARG_REG is the rtx that results from executing
341 FUNCTION_ARG (args_so_far, VOIDmode, void_type_node, 1)
342 just after all the args have had their registers assigned.
343 This could be whatever you like, but normally it is the first
344 arg-register beyond those used for args in this call,
345 or 0 if all the arg-registers are used in this call.
346 It is passed on to `gen_call' so you can put this info in the call insn.
348 VALREG is a hard register in which a value is returned,
349 or 0 if the call does not return a value.
351 OLD_INHIBIT_DEFER_POP is the value that `inhibit_defer_pop' had before
352 the args to this call were processed.
353 We restore `inhibit_defer_pop' to that value.
355 CALL_FUSAGE is either empty or an EXPR_LIST of USE expressions that
356 denote registers used by the called function. */
358 static void
360 tree funtype ATTRIBUTE_UNUSED,
361 HOST_WIDE_INT stack_size ATTRIBUTE_UNUSED,
362 HOST_WIDE_INT rounded_stack_size,
363 HOST_WIDE_INT struct_value_size ATTRIBUTE_UNUSED,
367 {
369 rtx call_insn;
372 #if defined (HAVE_call) && defined (HAVE_call_value)
373 rtx struct_value_size_rtx;
375 #endif
377 #ifdef CALL_POPS_ARGS
379 #endif
381 /* Ensure address is valid. SYMBOL_REF is already valid, so no need,
382 and we don't want to load it into a register as an optimization,
383 because prepare_call_address already did it if it should be done. */
387 #if defined (HAVE_sibcall_pop) && defined (HAVE_sibcall_value_pop)
391 {
393 rtx pat;
395 /* If this subroutine pops its own args, record that in the call insn
396 if possible, for the sake of frame pointer elimination. */
402 n_pop);
403 else
409 }
410 else
411 #endif
413 #if defined (HAVE_call_pop) && defined (HAVE_call_value_pop)
414 /* If the target has "call" or "call_value" insns, then prefer them
415 if no arguments are actually popped. If the target does not have
416 "call" or "call_value" insns, then we must use the popping versions
417 even if the call has no arguments to pop. */
418 #if defined (HAVE_call) && defined (HAVE_call_value)
421 #else
423 #endif
424 {
426 rtx pat;
428 /* If this subroutine pops its own args, record that in the call insn
429 if possible, for the sake of frame pointer elimination. */
435 else
441 }
442 else
443 #endif
445 #if defined (HAVE_sibcall) && defined (HAVE_sibcall_value)
448 {
452 rounded_stack_size_rtx,
454 else
457 struct_value_size_rtx));
458 }
459 else
460 #endif
462 #if defined (HAVE_call) && defined (HAVE_call_value)
464 {
469 NULL_RTX));
470 else
473 struct_value_size_rtx));
474 }
475 else
476 #endif
479 /* Find the call we just emitted. */
482 /* Mark memory as used for "pure" function call. */
484 call_fusage
485 = gen_rtx_EXPR_LIST
489 call_fusage);
491 /* Put the register usage information there. */
494 /* If this is a const call, then set the insn's unchanging bit. */
498 /* If this call can't throw, attach a REG_EH_REGION reg note to that
499 effect. */
503 else
504 {
507 /* If rn < 0, then either (1) tree-ssa not used or (2) doesn't
508 throw, which we already took care of. */
513 }
523 {
527 }
531 /* Restore this now, so that we do defer pops for this call's args
532 if the context of the call as a whole permits. */
536 {
545 }
548 {
549 /* If returning from the subroutine does not automatically pop the args,
550 we need an instruction to pop them sooner or later.
551 Perhaps do it now; perhaps just record how much space to pop later.
553 If returning from the subroutine does pop the args, indicate that the
554 stack pointer will be changed. */
557 {
559 /* Just pretend we did the pop. */
564 else
566 }
567 }
568 /* When we accumulate outgoing args, we must avoid any stack manipulations.
569 Restore the stack pointer to its original value now. Usually
570 ACCUMULATE_OUTGOING_ARGS targets don't get here, but there are exceptions.
571 On i386 ACCUMULATE_OUTGOING_ARGS can be enabled on demand, and
572 popping variants of functions exist as well.
574 ??? We may optimize similar to defer_pop above, but it is
575 probably not worthwhile.
577 ??? It will be worthwhile to enable combine_stack_adjustments even for
578 such machines. */
581 }
583 /* Determine if the function identified by NAME and FNDECL is one with
584 special properties we wish to know about.
586 For example, if the function might return more than one time (setjmp), then
587 set RETURNS_TWICE to a nonzero value.
589 Similarly set LONGJMP for if the function is in the longjmp family.
591 Set MAY_BE_ALLOCA for any memory allocation function that might allocate
592 space from the stack such as alloca. */
594 static int
596 {
599 /* Exclude functions not at the file scope, or not `extern',
600 since they are not the magic functions we would otherwise
601 think they are.
602 FIXME: this should be handled with attributes, not with this
603 hacky imitation of DECL_ASSEMBLER_NAME. It's (also) wrong
604 because you can declare fork() inside a function if you
605 wish. */
609 {
613 /* We assume that alloca will always be called by name. It
614 makes no sense to pass it as a pointer-to-function to
615 anything that does not understand its behavior. */
624 /* Disregard prefix _, __ or __x. */
626 {
631 else
633 }
636 {
649 }
659 }
662 }
664 /* Return nonzero when tree represent call to longjmp. */
666 int
668 {
670 }
672 /* Return true when exp contains alloca call. */
673 bool
675 {
684 }
686 /* Detect flags (function attributes) from the function decl or type node. */
688 int
690 {
695 {
700 {
705 }
707 /* The function exp may have the `malloc' attribute. */
711 /* The function exp may have the `pure' attribute. */
722 }
729 /* Mark if the function returns with the stack pointer depressed. We
730 cannot consider it pure or constant in that case. */
732 {
735 }
738 }
740 /* Detect flags from a CALL_EXPR. */
742 int
744 {
750 else
751 {
755 else
757 }
760 }
762 /* Precompute all register parameters as described by ARGS, storing values
763 into fields within the ARGS array.
765 NUM_ACTUALS indicates the total number elements in the ARGS array.
767 Set REG_PARM_SEEN if we encounter a register parameter. */
769 static void
771 {
778 {
782 {
789 /* ANSI doesn't require a sequence point here,
790 but PCC has one, so this will avoid some problems. */
792 }
794 /* If the value is a non-legitimate constant, force it into a
795 pseudo now. TLS symbols sometimes need a call to resolve. */
800 /* If we are to promote the function arg to a wider mode,
801 do it now. */
809 /* If the value is expensive, and we are inside an appropriately
810 short loop, put the value into a pseudo and then put the pseudo
811 into the hard reg.
813 For small register classes, also do this if this call uses
814 register parameters. This is to avoid reload conflicts while
815 loading the parameters registers. */
825 }
826 }
828 #ifdef REG_PARM_STACK_SPACE
830 /* The argument list is the property of the called routine and it
831 may clobber it. If the fixed area has been used for previous
832 parameters, we must save and restore it. */
834 static rtx
835 save_fixed_argument_area (int reg_parm_stack_space, rtx argblock, int *low_to_save, int *high_to_save)
836 {
840 /* Compute the boundary of the area that needs to be saved, if any. */
842 #ifdef ARGS_GROW_DOWNWARD
844 #endif
850 {
854 rtx stack_area;
855 rtx save_area;
858 ;
866 /* If we don't have the required alignment, must do this
867 in BLKmode. */
872 #ifdef ARGS_GROW_DOWNWARD
874 #else
876 #endif
880 delta)));
884 {
888 }
889 else
890 {
893 }
896 }
899 }
901 static void
903 {
906 rtx stack_area;
908 #ifdef ARGS_GROW_DOWNWARD
910 #else
912 #endif
920 else
923 BLOCK_OP_CALL_PARM);
924 }
927 /* If any elements in ARGS refer to parameters that are to be passed in
928 registers, but not in memory, and whose alignment does not permit a
929 direct copy into registers. Copy the values into a group of pseudos
930 which we will later copy into the appropriate hard registers.
932 Pseudos for each unaligned argument will be stored into the array
933 args[argnum].aligned_regs. The caller is responsible for deallocating
934 the aligned_regs array if it is nonzero. */
936 static void
938 {
946 {
954 /* Structures smaller than a word are normally aligned to the
955 least significant byte. On a BYTES_BIG_ENDIAN machine,
956 this means we must skip the empty high order bytes when
957 calculating the bit offset. */
959 #ifdef BLOCK_REG_PADDING
963 #else
964 && BYTES_BIG_ENDIAN
965 #endif
966 )
970 {
979 /* There is no need to restrict this code to loading items
980 in TYPE_ALIGN sized hunks. The bitfield instructions can
981 load up entire word sized registers efficiently.
983 ??? This may not be needed anymore.
984 We use to emit a clobber here but that doesn't let later
985 passes optimize the instructions we emit. By storing 0 into
986 the register later passes know the first AND to zero out the
987 bitfield being set in the register is unnecessary. The store
988 of 0 will be deleted as will at least the first AND. */
995 }
996 }
997 }
999 /* Fill in ARGS_SIZE and ARGS array based on the parameters found in
1000 ACTPARMS.
1002 NUM_ACTUALS is the total number of parameters.
1004 N_NAMED_ARGS is the total number of named arguments.
1006 FNDECL is the tree code for the target of this call (if known)
1008 ARGS_SO_FAR holds state needed by the target to know where to place
1009 the next argument.
1011 REG_PARM_STACK_SPACE is the number of bytes of stack space reserved
1012 for arguments which are passed in registers.
1014 OLD_STACK_LEVEL is a pointer to an rtx which olds the old stack level
1015 and may be modified by this routine.
1017 OLD_PENDING_ADJ, MUST_PREALLOCATE and FLAGS are pointers to integer
1018 flags which may may be modified by this routine.
1020 MAY_TAILCALL is cleared if we encounter an invisible pass-by-reference
1021 that requires allocation of stack space.
1023 CALL_FROM_THUNK_P is true if this call is the jump from a thunk to
1024 the thunked-to function. */
1026 static void
1037 {
1038 /* 1 if scanning parms front to back, -1 if scanning back to front. */
1041 /* Count arg position in order args appear. */
1045 tree p;
1050 /* In this loop, we consider args in the order they are written.
1051 We fill up ARGS from the front or from the back if necessary
1052 so that in any case the first arg to be pushed ends up at the front. */
1055 {
1057 /* In this case, must reverse order of args
1058 so that we compute and push the last arg first. */
1059 }
1060 else
1061 {
1063 }
1065 /* I counts args in order (to be) pushed; ARGPOS counts in order written. */
1067 {
1074 /* Replace erroneous argument with constant zero. */
1078 /* If TYPE is a transparent union, pass things the way we would
1079 pass the first field of the union. We have already verified that
1080 the modes are the same. */
1084 /* Decide where to pass this arg.
1086 args[i].reg is nonzero if all or part is passed in registers.
1088 args[i].partial is nonzero if part but not all is passed in registers,
1089 and the exact value says how many words are passed in registers.
1091 args[i].pass_on_stack is nonzero if the argument must at least be
1092 computed on the stack. It may then be loaded back into registers
1093 if args[i].reg is nonzero.
1095 These decisions are driven by the FUNCTION_... macros and must agree
1096 with those made by function.c. */
1098 /* See if this argument should be passed by invisible reference. */
1101 #ifdef FUNCTION_ARG_PASS_BY_REFERENCE
1104 #endif
1105 )
1106 {
1107 /* If we're compiling a thunk, pass through invisible
1108 references instead of making a copy. */
1110 #ifdef FUNCTION_ARG_CALLEE_COPIES
1113 /* If it's in a register, we must make a copy of it too. */
1114 /* ??? Is this a sufficient test? Is there a better one? */
1118 #endif
1119 )
1120 {
1121 /* C++ uses a TARGET_EXPR to indicate that we want to make a
1122 new object from the argument. If we are passing by
1123 invisible reference, the callee will do that for us, so we
1124 can strip off the TARGET_EXPR. This is not always safe,
1125 but it is safe in the only case where this is a useful
1126 optimization; namely, when the argument is a plain object.
1127 In that case, the frontend is just asking the backend to
1128 make a bitwise copy of the argument. */
1139 }
1141 {
1142 /* In the V3 C++ ABI, parameters are destroyed in the caller.
1143 We implement this by passing the address of the temporary
1144 rather than expanding it into another allocated slot. */
1150 }
1151 else
1152 {
1153 /* We make a copy of the object and pass the address to the
1154 function being called. */
1155 rtx copy;
1161 STACK_CHECK_MAX_VAR_SIZE))))
1162 {
1163 /* This is a variable-sized object. Make space on the stack
1164 for it. */
1168 {
1172 }
1175 allocate_dynamic_stack_space
1178 }
1179 else
1190 }
1191 }
1204 #ifdef FUNCTION_INCOMING_ARG
1205 /* If this is a sibling call and the machine has register windows, the
1206 register window has to be unwinded before calling the routine, so
1207 arguments have to go into the incoming registers. */
1210 #else
1212 #endif
1214 #ifdef FUNCTION_ARG_PARTIAL_NREGS
1219 #endif
1223 /* If FUNCTION_ARG returned a (parallel [(expr_list (nil) ...) ...]),
1224 it means that we are to pass this arg in the register(s) designated
1225 by the PARALLEL, but also to pass it in the stack. */
1230 /* If this is an addressable type, we must preallocate the stack
1231 since we must evaluate the object into its final location.
1233 If this is to be passed in both registers and the stack, it is simpler
1234 to preallocate. */
1239 /* If this is an addressable type, we cannot pre-evaluate it. Thus,
1240 we cannot consider this function call constant. */
1244 /* Compute the stack-size of this argument. */
1249 #ifdef STACK_PARMS_IN_REG_PARM_AREA
1251 #else
1253 #endif
1256 #ifdef BLOCK_REG_PADDING
1257 else
1258 /* The argument is passed entirely in registers. See at which
1259 end it should be padded. */
1263 #endif
1265 /* Update ARGS_SIZE, the total stack space for args so far. */
1271 /* Increment ARGS_SO_FAR, which has info about which arg-registers
1272 have been used, etc. */
1276 }
1277 }
1279 /* Update ARGS_SIZE to contain the total size for the argument block.
1280 Return the original constant component of the argument block's size.
1282 REG_PARM_STACK_SPACE holds the number of bytes of stack space reserved
1283 for arguments passed in registers. */
1285 static int
1289 {
1292 /* For accumulate outgoing args mode we don't need to align, since the frame
1293 will be already aligned. Align to STACK_BOUNDARY in order to prevent
1294 backends from generating misaligned frame sizes. */
1298 /* Compute the actual size of the argument block required. The variable
1299 and constant sizes must be combined, the size may have to be rounded,
1300 and there may be a minimum required size. */
1303 {
1309 {
1310 /* We don't handle this case yet. To handle it correctly we have
1311 to add the delta, round and subtract the delta.
1312 Currently no machine description requires this support. */
1316 }
1319 {
1320 args_size->var
1324 #ifndef OUTGOING_REG_PARM_STACK_SPACE
1325 /* The area corresponding to register parameters is not to count in
1326 the size of the block we need. So make the adjustment. */
1327 args_size->var
1330 #endif
1331 }
1332 }
1333 else
1334 {
1339 + stack_pointer_delta
1341 / preferred_stack_boundary
1346 reg_parm_stack_space);
1348 #ifndef OUTGOING_REG_PARM_STACK_SPACE
1350 #endif
1351 }
1353 }
1355 /* Precompute parameters as needed for a function call.
1357 FLAGS is mask of ECF_* constants.
1359 NUM_ACTUALS is the number of arguments.
1361 ARGS is an array containing information for each argument; this
1362 routine fills in the INITIAL_VALUE and VALUE fields for each
1363 precomputed argument. */
1365 static void
1367 {
1370 /* If this is a libcall, then precompute all arguments so that we do not
1371 get extraneous instructions emitted as part of the libcall sequence.
1373 If this target defines ACCUMULATE_OUTGOING_ARGS to true, then we must
1374 precompute all arguments that contain function calls. Otherwise,
1375 computing arguments for a subcall may clobber arguments for this call.
1377 If this target defines ACCUMULATE_OUTGOING_ARGS to false, then we only
1378 need to precompute arguments that change the stack pointer, such as calls
1379 to alloca, and calls that do not pop all of their arguments. */
1384 {
1387 /* If this is an addressable type, we cannot pre-evaluate it. */
1394 /* ANSI doesn't require a sequence point here,
1395 but PCC has one, so this will avoid some problems. */
1403 {
1407 #if defined(PROMOTE_FUNCTION_MODE) && !defined(PROMOTE_MODE)
1408 /* CSE will replace this only if it contains args[i].value
1409 pseudo, so convert it down to the declared mode using
1410 a SUBREG. */
1413 {
1419 }
1420 #endif
1421 }
1422 }
1423 }
1425 /* Given the current state of MUST_PREALLOCATE and information about
1426 arguments to a function call in NUM_ACTUALS, ARGS and ARGS_SIZE,
1427 compute and return the final value for MUST_PREALLOCATE. */
1429 static int
1430 finalize_must_preallocate (int must_preallocate, int num_actuals, struct arg_data *args, struct args_size *args_size)
1431 {
1432 /* See if we have or want to preallocate stack space.
1434 If we would have to push a partially-in-regs parm
1435 before other stack parms, preallocate stack space instead.
1437 If the size of some parm is not a multiple of the required stack
1438 alignment, we must preallocate.
1440 If the total size of arguments that would otherwise create a copy in
1441 a temporary (such as a CALL) is more than half the total argument list
1442 size, preallocation is faster.
1444 Another reason to preallocate is if we have a machine (like the m88k)
1445 where stack alignment is required to be maintained between every
1446 pair of insns, not just when the call is made. However, we assume here
1447 that such machines either do not have push insns (and hence preallocation
1448 would occur anyway) or the problem is taken care of with
1449 PUSH_ROUNDING. */
1452 {
1458 {
1469 copy_to_evaluate_size
1471 }
1476 }
1478 }
1480 /* If we preallocated stack space, compute the address of each argument
1481 and store it into the ARGS array.
1483 We need not ensure it is a valid memory address here; it will be
1484 validized when it is used.
1486 ARGBLOCK is an rtx for the address of the outgoing arguments. */
1488 static void
1490 {
1492 {
1500 {
1503 rtx addr;
1505 /* Skip this parm if it will not be passed on the stack. */
1511 else
1522 else
1531 /* Function incoming arguments may overlap with sibling call
1532 outgoing arguments and we cannot allow reordering of reads
1533 from function arguments with stores to outgoing arguments
1534 of sibling calls. */
1537 }
1538 }
1539 }
1541 /* Given a FNDECL and EXP, return an rtx suitable for use as a target address
1542 in a call instruction.
1544 FNDECL is the tree node for the target function. For an indirect call
1545 FNDECL will be NULL_TREE.
1547 ADDR is the operand 0 of CALL_EXPR for this call. */
1549 static rtx
1551 {
1552 rtx funexp;
1554 /* Get the function to call, in the form of RTL. */
1556 {
1557 /* If this is the first use of the function, see if we need to
1558 make an external definition for it. */
1560 {
1563 }
1565 /* Get a SYMBOL_REF rtx for the function address. */
1567 }
1568 else
1569 /* Generate an rtx (probably a pseudo-register) for the address. */
1570 {
1575 }
1577 }
1579 /* Do the register loads required for any wholly-register parms or any
1580 parms which are passed both on the stack and in a register. Their
1581 expressions were already evaluated.
1583 Mark all register-parms as living through the call, putting these USE
1584 insns in the CALL_INSN_FUNCTION_USAGE field.
1586 When IS_SIBCALL, perform the check_sibcall_overlap_argument_overlap
1587 checking, setting *SIBCALL_FAILURE if appropriate. */
1589 static void
1593 {
1597 {
1601 {
1606 /* Set to non-negative if must move a word at a time, even if just
1607 one word (e.g, partial == 1 && mode == DFmode). Set to -1 if
1608 we just use a normal move insn. This value can be zero if the
1609 argument is a zero size structure with no fields. */
1614 {
1617 }
1618 else
1621 /* Handle calls that pass values in multiple non-contiguous
1622 locations. The Irix 6 ABI has examples of this. */
1625 {
1629 }
1631 /* If simple case, just do move. If normal partial, store_one_arg
1632 has already loaded the register for us. In all other cases,
1633 load the register(s) from memory. */
1636 {
1638 #ifdef BLOCK_REG_PADDING
1639 /* Handle case where we have a value that needs shifting
1640 up to the msb. eg. a QImode value and we're padding
1641 upward on a BYTES_BIG_ENDIAN machine. */
1645 {
1646 rtx x;
1649 /* Assigning REG here rather than a temp makes CALL_FUSAGE
1650 report the whole reg as used. Strictly speaking, the
1651 call only uses SIZE bytes at the msb end, but it doesn't
1652 seem worth generating rtl to say that. */
1658 }
1659 #endif
1660 }
1662 /* If we have pre-computed the values to put in the registers in
1663 the case of non-aligned structures, copy them in now. */
1671 {
1674 /* Handle a BLKmode that needs shifting. */
1676 #ifdef BLOCK_REG_PADDING
1678 #else
1679 && BYTES_BIG_ENDIAN
1680 #endif
1681 )
1682 {
1694 }
1695 else
1697 }
1699 /* When a parameter is a block, and perhaps in other cases, it is
1700 possible that it did a load from an argument slot that was
1701 already clobbered. */
1706 /* Handle calls that pass values in multiple non-contiguous
1707 locations. The Irix 6 ABI has examples of this. */
1712 else
1714 }
1715 }
1716 }
1718 /* We need to pop PENDING_STACK_ADJUST bytes. But, if the arguments
1719 wouldn't fill up an even multiple of PREFERRED_UNIT_STACK_BOUNDARY
1720 bytes, then we would need to push some additional bytes to pad the
1721 arguments. So, we compute an adjust to the stack pointer for an
1722 amount that will leave the stack under-aligned by UNADJUSTED_ARGS_SIZE
1723 bytes. Then, when the arguments are pushed the stack will be perfectly
1724 aligned. ARGS_SIZE->CONSTANT is set to the number of bytes that should
1725 be popped after the call. Returns the adjustment. */
1727 static int
1731 {
1732 /* The number of bytes to pop so that the stack will be
1733 under-aligned by UNADJUSTED_ARGS_SIZE bytes. */
1734 HOST_WIDE_INT adjustment;
1735 /* The alignment of the stack after the arguments are pushed, if we
1736 just pushed the arguments without adjust the stack here. */
1737 HOST_WIDE_INT unadjusted_alignment;
1739 unadjusted_alignment
1743 /* We want to get rid of as many of the PENDING_STACK_ADJUST bytes
1744 as possible -- leaving just enough left to cancel out the
1745 UNADJUSTED_ALIGNMENT. In other words, we want to ensure that the
1746 PENDING_STACK_ADJUST is non-negative, and congruent to
1747 -UNADJUSTED_ALIGNMENT modulo the PREFERRED_UNIT_STACK_BOUNDARY. */
1749 /* Begin by trying to pop all the bytes. */
1750 unadjusted_alignment
1751 = (unadjusted_alignment
1754 /* Push enough additional bytes that the stack will be aligned
1755 after the arguments are pushed. */
1757 {
1760 else
1762 }
1764 /* Now, sets ARGS_SIZE->CONSTANT so that we pop the right number of
1765 bytes after the call. The right number is the entire
1766 PENDING_STACK_ADJUST less our ADJUSTMENT plus the amount required
1767 by the arguments in the first place. */
1768 args_size->constant
1772 }
1774 /* Scan X expression if it does not dereference any argument slots
1775 we already clobbered by tail call arguments (as noted in stored_args_map
1776 bitmap).
1777 Return nonzero if X expression dereferences such argument slots,
1778 zero otherwise. */
1780 static int
1782 {
1783 RTX_CODE code;
1794 {
1799 current_function_internal_arg_pointer
1802 else
1805 #ifdef ARGS_GROW_DOWNWARD
1807 #endif
1815 }
1817 /* Scan all subexpressions. */
1820 {
1822 {
1825 }
1827 {
1831 }
1832 }
1834 }
1836 /* Scan sequence after INSN if it does not dereference any argument slots
1837 we already clobbered by tail call arguments (as noted in stored_args_map
1838 bitmap). If MARK_STORED_ARGS_MAP, add stack slots for ARG to
1839 stored_args_map bitmap afterwards (when ARG is a register MARK_STORED_ARGS_MAP
1840 should be 0). Return nonzero if sequence after INSN dereferences such argument
1841 slots, zero otherwise. */
1843 static int
1845 {
1850 else
1859 {
1860 #ifdef ARGS_GROW_DOWNWARD
1862 #else
1864 #endif
1868 }
1870 }
1872 static tree
1874 {
1876 {
1885 {
1891 }
1896 }
1898 }
1901 /* If function value *VALUE was returned at the most significant end of a
1902 register, shift it towards the least significant end and convert it to
1903 TYPE's mode. Return true and update *VALUE if some action was needed.
1905 TYPE is the type of the function's return value, which is known not
1906 to have mode BLKmode. */
1908 static bool
1910 {
1912 {
1913 HOST_WIDE_INT shift;
1918 {
1923 }
1924 }
1926 }
1928 /* Remove all REG_EQUIV notes found in the insn chain. */
1930 static void
1932 {
1933 rtx insn;
1936 {
1938 {
1941 {
1942 /* Remove the note and keep looking at the notes for
1943 this insn. */
1946 }
1948 }
1949 }
1950 }
1952 /* Clear RTX_UNCHANGING_P flag of incoming argument MEMs. */
1954 static void
1956 {
1957 RTX_CODE code;
1967 {
1972 current_function_internal_arg_pointer
1976 }
1978 /* Scan all subexpressions. */
1981 {
1987 }
1988 }
1991 /* Generate all the code for a function call
1992 and return an rtx for its value.
1993 Store the value in TARGET (specified as an rtx) if convenient.
1994 If the value is stored in TARGET then TARGET is returned.
1995 If IGNORE is nonzero, then we ignore the value of the function call. */
1997 rtx
1999 {
2000 /* Nonzero if we are currently expanding a call. */
2003 /* List of actual parameters. */
2005 /* RTX for the function to be called. */
2006 rtx funexp;
2007 /* Sequence of insns to perform a normal "call". */
2009 /* Sequence of insns to perform a tail "call". */
2011 /* Data type of the function. */
2012 tree funtype;
2013 tree type_arg_types;
2014 /* Declaration of the function being called,
2015 or 0 if the function is computed (not known by name). */
2017 /* The type of the function being called. */
2018 tree fntype;
2022 /* Register in which non-BLKmode value will be returned,
2023 or 0 if no value or if value is BLKmode. */
2024 rtx valreg;
2025 /* Address where we should return a BLKmode value;
2026 0 if value not BLKmode. */
2028 /* Nonzero if that address is being passed by treating it as
2029 an extra, implicit first parameter. Otherwise,
2030 it is passed by being copied directly into struct_value_rtx. */
2032 /* Size of aggregate value wanted, or zero if none wanted
2033 or if we are using the non-reentrant PCC calling convention
2034 or expecting the value in registers. */
2036 /* Nonzero if called function returns an aggregate in memory PCC style,
2037 by returning the address of where to find it. */
2041 /* Number of actual parameters in this call, including struct value addr. */
2043 /* Number of named args. Args after this are anonymous ones
2044 and they must all go on the stack. */
2047 /* Vector of information about each argument.
2048 Arguments are numbered in the order they will be pushed,
2049 not the order they are written. */
2052 /* Total size in bytes of all the stack-parms scanned so far. */
2055 /* Size of arguments before any adjustments (such as rounding). */
2057 /* Data on reg parms scanned so far. */
2058 CUMULATIVE_ARGS args_so_far;
2059 /* Nonzero if a reg parm has been scanned. */
2061 /* Nonzero if this is an indirect function call. */
2063 /* Nonzero if we must avoid push-insns in the args for this call.
2064 If stack space is allocated for register parameters, but not by the
2065 caller, then it is preallocated in the fixed part of the stack frame.
2066 So the entire argument block must then be preallocated (i.e., we
2067 ignore PUSH_ROUNDING in that case). */
2071 /* Size of the stack reserved for parameter registers. */
2074 /* Address of space preallocated for stack parms
2075 (on machines that lack push insns), or 0 if space not preallocated. */
2078 /* Mask of ECF_ flags. */
2080 #ifdef REG_PARM_STACK_SPACE
2081 /* Define the boundary of the register parm stack space that needs to be
2082 saved, if any. */
2085 #endif
2092 /* State variables to track stack modifications. */
2098 /* Some stack pointer alterations we make are performed via
2099 allocate_dynamic_stack_space. This modifies the stack_pointer_delta,
2100 which we then also need to save/restore along the way. */
2103 rtx call_fusage;
2107 /* The alignment of the stack, in bits. */
2108 HOST_WIDE_INT preferred_stack_boundary;
2109 /* The alignment of the stack, in bytes. */
2110 HOST_WIDE_INT preferred_unit_stack_boundary;
2111 /* The static chain value to use for this call. */
2112 rtx static_chain_value;
2113 /* See if this is "nothrow" function call. */
2117 /* See if we can find a DECL-node for the actual function, and get the
2118 function attributes (flags) from the function decl or type node. */
2121 {
2124 }
2125 else
2126 {
2129 }
2133 /* Warn if this value is an aggregate type,
2134 regardless of which calling convention we are using for it. */
2138 /* If the result of a pure or const function call is ignored (or void),
2139 and none of its arguments are volatile, we can avoid expanding the
2140 call and just evaluate the arguments for side-effects. */
2144 {
2146 tree arg;
2150 {
2153 }
2156 {
2161 }
2162 }
2164 #ifdef REG_PARM_STACK_SPACE
2166 #endif
2168 #ifndef OUTGOING_REG_PARM_STACK_SPACE
2171 #endif
2173 /* Set up a place to return a structure. */
2175 /* Cater to broken compilers. */
2177 {
2178 /* This call returns a big structure. */
2181 #ifdef PCC_STATIC_STRUCT_RETURN
2182 {
2184 }
2186 {
2190 {
2191 /* The structure value address arg is already in actparms.
2192 Pull it out. It might be nice to just leave it there, but
2193 we need to set structure_value_addr. */
2198 }
2201 else
2202 {
2203 /* For variable-sized objects, we must be called with a target
2204 specified. If we were to allocate space on the stack here,
2205 we would have no way of knowing when to free it. */
2211 }
2212 }
2214 }
2216 /* Figure out the amount to which the stack should be aligned. */
2219 {
2223 }
2225 /* Operand 0 is a pointer-to-function; get the type of the function. */
2231 /* Munge the tree to split complex arguments into their imaginary
2232 and real parts. */
2234 {
2237 }
2238 else
2244 /* If struct_value_rtx is 0, it means pass the address
2245 as if it were an extra parameter. */
2247 {
2248 /* If structure_value_addr is a REG other than
2249 virtual_outgoing_args_rtx, we can use always use it. If it
2250 is not a REG, we must always copy it into a register.
2251 If it is virtual_outgoing_args_rtx, we must copy it to another
2252 register in some cases. */
2254 || (ACCUMULATE_OUTGOING_ARGS
2255 && stack_arg_under_construction
2261 actparms
2264 temp),
2265 actparms);
2267 }
2269 /* Count the arguments and set NUM_ACTUALS. */
2271 num_actuals++;
2273 /* Compute number of named args.
2274 Normally, don't include the last named arg if anonymous args follow.
2275 We do include the last named arg if
2276 targetm.calls.strict_argument_naming() returns nonzero.
2277 (If no anonymous args follow, the result of list_length is actually
2278 one too large. This is harmless.)
2280 If targetm.calls.pretend_outgoing_varargs_named() returns
2281 nonzero, and targetm.calls.strict_argument_naming() returns zero,
2282 this machine will be able to place unnamed args that were passed
2283 in registers into the stack. So treat all args as named. This
2284 allows the insns emitting for a specific argument list to be
2285 independent of the function declaration.
2287 If targetm.calls.pretend_outgoing_varargs_named() returns zero,
2288 we do not have any reliable way to pass unnamed args in
2289 registers, so we must force them into memory. */
2294 n_named_args
2296 /* Don't include the last named arg. */
2298 /* Count the struct value address, if it is passed as a parm. */
2300 else
2301 /* If we know nothing, treat all args as named. */
2304 /* Start updating where the next arg would go.
2306 On some machines (such as the PA) indirect calls have a different
2307 calling convention than normal calls. The fourth argument in
2308 INIT_CUMULATIVE_ARGS tells the backend if this is an indirect call
2309 or not. */
2312 /* Make a vector to hold all the information about each arg. */
2316 /* Build up entries in the ARGS array, compute the size of the
2317 arguments into ARGS_SIZE, etc. */
2326 {
2327 /* If this function requires a variable-sized argument list, don't
2328 try to make a cse'able block for this call. We may be able to
2329 do this eventually, but it is too complicated to keep track of
2330 what insns go in the cse'able block and which don't. */
2334 }
2336 /* Now make final decision about preallocating stack space. */
2341 /* If the structure value address will reference the stack pointer, we
2342 must stabilize it. We don't need to do this if we know that we are
2343 not going to adjust the stack pointer in processing this call. */
2348 structure_value_addr))
2353 /* Tail calls can make things harder to debug, and we're traditionally
2354 pushed these optimizations into -O2. Don't try if we're already
2355 expanding a call, as that means we're an argument. Don't try if
2356 there's cleanups, as we know there's code to follow the call.
2358 If rtx_equal_function_value_matters is false, that means we've
2359 finished with regular parsing. Which means that some of the
2360 machinery we use to generate tail-calls is no longer in place.
2361 This is most often true of sjlj-exceptions, which we couldn't
2362 tail-call to anyway.
2364 If current_nesting_level () == 0, we're being called after
2365 the function body has been expanded. This can happen when
2366 setting up trampolines in expand_function_end. */
2368 || !flag_optimize_sibling_calls
2369 || !rtx_equal_function_value_matters
2376 /* Rest of purposes for tail call optimizations to fail. */
2378 #ifdef HAVE_sibcall_epilogue
2379 !HAVE_sibcall_epilogue
2380 #else
2381 1
2382 #endif
2383 || !try_tail_call
2384 /* Doing sibling call optimization needs some work, since
2385 structure_value_addr can be allocated on the stack.
2386 It does not seem worth the effort since few optimizable
2387 sibling calls will return a structure. */
2389 /* Check whether the target is able to optimize the call
2390 into a sibcall. */
2392 /* Functions that do not return exactly once may not be sibcall
2393 optimized. */
2396 /* If the called function is nested in the current one, it might access
2397 some of the caller's arguments, but could clobber them beforehand if
2398 the argument areas are shared. */
2400 /* If this function requires more stack slots than the current
2401 function, we cannot change it into a sibling call. */
2403 /* If the callee pops its own arguments, then it must pop exactly
2404 the same number of arguments as the current function. */
2408 current_function_args_size))
2413 {
2416 /* Ok, we're going to give the tail call the old college try.
2417 This means we're going to evaluate the function arguments
2418 up to three times. There are two degrees of badness we can
2419 encounter, those that can be unsaved and those that can't.
2420 (See unsafe_for_reeval commentary for details.)
2422 Generate a new argument list. Pass safe arguments through
2423 unchanged. For the easy badness wrap them in UNSAVE_EXPRs.
2424 For hard badness, evaluate them now and put their resulting
2425 rtx in a temporary VAR_DECL.
2427 initialize_argument_information has ordered the array for the
2428 order to be pushed, and we must remember this when reconstructing
2429 the original argument order. */
2432 {
2436 }
2437 else
2438 {
2442 }
2445 {
2447 }
2448 /* Do the same for the function address if it is an expression. */
2451 /* Expanding one of those dangerous arguments could have added
2452 cleanups, but otherwise give it a whirl. */
2455 }
2458 /* Ensure current function's preferred stack boundary is at least
2459 what we need. We don't have to increase alignment for recursive
2460 functions. */
2469 function_call_count++;
2471 /* We want to make two insn chains; one for a sibling call, the other
2472 for a normal call. We will select one of the two chains after
2473 initial RTL generation is complete. */
2475 {
2477 /* We want to emit any pending stack adjustments before the tail
2478 recursion "call". That way we know any adjustment after the tail
2479 recursion call can be ignored if we indeed use the tail
2480 call expansion. */
2483 rtx insns;
2487 {
2488 /* Emit any queued insns now; otherwise they would end up in
2489 only one of the alternates. */
2492 /* State variables we need to save and restore between
2493 iterations. */
2496 }
2499 else
2502 /* Other state variables that we must reinitialize each time
2503 through the loop (that are not initialized by the loop itself). */
2507 /* Start a new sequence for the normal call case.
2509 From this point on, if the sibling call fails, we want to set
2510 sibcall_failure instead of continuing the loop. */
2514 {
2515 /* We know at this point that there are not currently any
2516 pending cleanups. If, however, in the process of evaluating
2517 the arguments we were to create some, we'll need to be
2518 able to get rid of them. */
2520 }
2522 /* Don't let pending stack adjusts add up to too much.
2523 Also, do all pending adjustments now if there is any chance
2524 this might be a call to alloca or if we are expanding a sibling
2525 call sequence or if we are calling a function that is to return
2526 with stack pointer depressed. */
2533 /* When calling a const function, we must pop the stack args right away,
2534 so that the pop is deleted or moved with the call. */
2536 NO_DEFER_POP;
2538 /* Precompute any arguments as needed. */
2542 /* Now we are about to start emitting insns that can be deleted
2543 if a libcall is deleted. */
2548 /* Compute the actual size of the argument block required. The variable
2549 and constant sizes must be combined, the size may have to be rounded,
2550 and there may be a minimum required size. When generating a sibcall
2551 pattern, do not round up, since we'll be re-using whatever space our
2552 caller provided. */
2553 unadjusted_args_size
2561 /* The argument block when performing a sibling call is the
2562 incoming argument block. */
2564 {
2566 argblock
2567 #ifdef STACK_GROWS_DOWNWARD
2569 #else
2571 #endif
2574 }
2576 /* If we have no actual push instructions, or shouldn't use them,
2577 make space for all args right now. */
2579 {
2581 {
2586 /* stack_arg_under_construction says whether a stack arg is
2587 being constructed at the old stack level. Pushing the stack
2588 gets a clean outgoing argument block. */
2591 }
2593 }
2594 else
2595 {
2596 /* Note that we must go through the motions of allocating an argument
2597 block even if the size is zero because we may be storing args
2598 in the area reserved for register arguments, which may be part of
2599 the stack frame. */
2603 /* Store the maximum argument space used. It will be pushed by
2604 the prologue (if ACCUMULATE_OUTGOING_ARGS, or stack overflow
2605 checking). */
2611 {
2613 {
2614 /* Since the stack pointer will never be pushed, it is
2615 possible for the evaluation of a parm to clobber
2616 something we have already written to the stack.
2617 Since most function calls on RISC machines do not use
2618 the stack, this is uncommon, but must work correctly.
2620 Therefore, we save any area of the stack that was already
2621 written and that we are using. Here we set up to do this
2622 by making a new stack usage map from the old one. The
2623 actual save will be done by store_one_arg.
2625 Another approach might be to try to reorder the argument
2626 evaluations to avoid this conflicting stack usage. */
2628 #ifndef OUTGOING_REG_PARM_STACK_SPACE
2629 /* Since we will be writing into the entire argument area,
2630 the map must be allocated for its entire size, not just
2631 the part that is the responsibility of the caller. */
2633 #endif
2635 #ifdef ARGS_GROW_DOWNWARD
2638 #else
2640 needed);
2641 #endif
2646 initial_highest_arg_in_use);
2650 (highest_outgoing_arg_in_use
2654 /* The address of the outgoing argument list must not be
2655 copied to a register here, because argblock would be left
2656 pointing to the wrong place after the call to
2657 allocate_dynamic_stack_space below. */
2660 }
2661 else
2662 {
2664 {
2665 /* Try to reuse some or all of the pending_stack_adjust
2666 to get this space. */
2667 needed
2668 = (combine_pending_stack_adjustment_and_call
2671 preferred_unit_stack_boundary));
2673 /* combine_pending_stack_adjustment_and_call computes
2674 an adjustment before the arguments are allocated.
2675 Account for them and see whether or not the stack
2676 needs to go up or down. */
2680 {
2681 /* We're releasing stack space. */
2682 /* ??? We can avoid any adjustment at all if we're
2683 already aligned. FIXME. */
2687 }
2688 else
2689 /* We need to allocate space. We'll do that in
2690 push_block below. */
2692 }
2694 /* Special case this because overhead of `push_block' in
2695 this case is non-trivial. */
2698 else
2699 {
2701 #ifdef ARGS_GROW_DOWNWARD
2703 #endif
2704 }
2706 /* We only really need to call `copy_to_reg' in the case
2707 where push insns are going to be used to pass ARGBLOCK
2708 to a function call in ARGS. In that case, the stack
2709 pointer changes value from the allocation point to the
2710 call point, and hence the value of
2711 VIRTUAL_OUTGOING_ARGS_RTX changes as well. But might
2712 as well always do it. */
2714 }
2715 }
2716 }
2719 {
2720 /* The save/restore code in store_one_arg handles all
2721 cases except one: a constructor call (including a C
2722 function returning a BLKmode struct) to initialize
2723 an argument. */
2725 {
2726 #ifndef OUTGOING_REG_PARM_STACK_SPACE
2729 #else
2731 #endif
2733 {
2735 NULL_RTX);
2739 /* stack_arg_under_construction says whether a stack
2740 arg is being constructed at the old stack level.
2741 Pushing the stack gets a clean outgoing argument
2742 block. */
2743 old_stack_arg_under_construction
2746 /* Make a new map for the new argument list. */
2750 }
2752 BITS_PER_UNIT);
2753 }
2755 /* If argument evaluation might modify the stack pointer,
2756 copy the address of the argument list to a register. */
2759 {
2762 }
2763 }
2767 /* If we push args individually in reverse order, perform stack alignment
2768 before the first push (the last arg). */
2771 {
2772 /* When the stack adjustment is pending, we get better code
2773 by combining the adjustments. */
2777 {
2778 pending_stack_adjust
2779 = (combine_pending_stack_adjustment_and_call
2782 preferred_unit_stack_boundary));
2784 }
2788 }
2789 /* Now that the stack is properly aligned, pops can't safely
2790 be deferred during the evaluation of the arguments. */
2791 NO_DEFER_POP;
2795 /* Figure out the register where the value, if any, will come back. */
2799 {
2803 else
2805 }
2807 /* Precompute all register parameters. It isn't safe to compute anything
2808 once we have started filling any specific hard regs. */
2814 else
2817 #ifdef REG_PARM_STACK_SPACE
2818 /* Save the fixed argument area if it's part of the caller's frame and
2819 is clobbered by argument setup for this call. */
2823 #endif
2825 /* Now store (and compute if necessary) all non-register parms.
2826 These come before register parms, since they can require block-moves,
2827 which could clobber the registers used for register parms.
2828 Parms which have partial registers are not stored here,
2829 but we do preallocate space here if they want that. */
2833 {
2838 reg_parm_stack_space)
2850 call_fusage);
2851 }
2853 /* If we have a parm that is passed in registers but not in memory
2854 and whose alignment does not permit a direct copy into registers,
2855 make a group of pseudos that correspond to each register that we
2856 will later fill. */
2860 /* Now store any partially-in-registers parm.
2861 This is the last place a block-move can happen. */
2865 {
2870 reg_parm_stack_space)
2875 }
2877 /* If we pushed args in forward order, perform stack alignment
2878 after pushing the last arg. */
2883 /* If register arguments require space on the stack and stack space
2884 was not preallocated, allocate stack space here for arguments
2885 passed in registers. */
2886 #ifdef OUTGOING_REG_PARM_STACK_SPACE
2890 #endif
2892 /* Pass the function the address in which to return a
2893 structure value. */
2895 {
2896 structure_value_addr
2901 NULL_RTX)));
2905 }
2913 /* Perform postincrements before actually calling the function. */
2916 /* Save a pointer to the last insn before the call, so that we can
2917 later safely search backwards to find the CALL_INSN. */
2920 /* Set up next argument register. For sibling calls on machines
2921 with register windows this should be the incoming register. */
2922 #ifdef FUNCTION_INCOMING_ARG
2926 else
2927 #endif
2931 /* All arguments and registers used for the call must be set up by
2932 now! */
2934 /* Stack must be properly aligned now. */
2938 /* Generate the actual call instruction. */
2944 /* If call is cse'able, make appropriate pair of reg-notes around it.
2945 Test valreg so we don't crash; may safely ignore `const'
2946 if return type is void. Disable for PARALLEL return values, because
2947 we have no way to move such values into a pseudo register. */
2949 {
2950 rtx insns;
2951 rtx insn;
2956 /* Expansion of block moves possibly introduced a loop that may
2957 not appear inside libcall block. */
2963 {
2966 }
2967 else
2968 {
2972 /* Mark the return value as a pointer if needed. */
2979 && fndecl
2987 else
2988 {
2989 /* Construct an "equal form" for the value which
2990 mentions all the arguments in order as well as
2991 the function name. */
3002 note);
3003 }
3007 }
3008 }
3010 {
3014 /* The return value from a malloc-like function is a pointer. */
3020 /* The return value from a malloc-like function can not alias
3021 anything else. */
3026 /* Write out the sequence. */
3031 }
3033 /* For calls to `setjmp', etc., inform flow.c it should complain
3034 if nonvolatile values are live. For functions that cannot return,
3035 inform flow that control does not fall through. */
3038 {
3039 /* The barrier must be emitted
3040 immediately after the CALL_INSN. Some ports emit more
3041 than just a CALL_INSN above, so we must search for it here. */
3045 {
3047 /* There was no CALL_INSN? */
3050 }
3054 /* Stack adjustments after a noreturn call are dead code.
3055 However when NO_DEFER_POP is in effect, we must preserve
3056 stack_pointer_delta. */
3058 {
3061 }
3062 }
3067 /* If value type not void, return an rtx for the value. */
3069 /* If there are cleanups to be called, don't use a hard reg as target.
3070 We need to double check this and see if it matters anymore. */
3072 {
3077 }
3083 {
3085 {
3086 target
3089 structure_value_addr));
3091 }
3092 }
3094 {
3095 /* This is the special C++ case where we need to
3096 know what the true target was. We take care to
3097 never use this value more than once in one expression. */
3101 }
3102 /* Handle calls that return values in multiple non-contiguous locations.
3103 The Irix 6 ABI has examples of this. */
3105 {
3107 {
3108 /* This will only be assigned once, so it can be readonly. */
3115 }
3121 /* We can not support sibling calls for this case. */
3123 }
3127 {
3128 /* TARGET and VALREG cannot be equal at this point because the
3129 latter would not have REG_FUNCTION_VALUE_P true, while the
3130 former would if it were referring to the same register.
3132 If they refer to the same register, this move will be a no-op,
3133 except when function inlining is being done. */
3136 /* If we are setting a MEM, this code must be executed. Since it is
3137 emitted after the call insn, sibcall optimization cannot be
3138 performed in that case. */
3141 }
3143 {
3146 /* We can not support sibling calls for this case. */
3148 }
3149 else
3150 {
3155 }
3158 {
3159 /* If we promoted this return value, make the proper SUBREG. TARGET
3160 might be const0_rtx here, so be careful. */
3164 {
3169 /* If we don't promote as expected, something is wrong. */
3177 {
3184 }
3188 }
3189 }
3191 /* If size of args is variable or this was a constructor call for a stack
3192 argument, restore saved stack-pointer value. */
3195 {
3203 }
3205 {
3206 #ifdef REG_PARM_STACK_SPACE
3210 #endif
3212 /* If we saved any argument areas, restore them. */
3215 {
3217 rtx stack_area
3224 else
3227 BLOCK_OP_CALL_PARM);
3228 }
3232 }
3234 /* If this was alloca, record the new stack level for nonlocal gotos.
3235 Check for the handler slots since we might not have a save area
3236 for non-local gotos. */
3241 /* Free up storage we no longer need. */
3247 {
3248 /* Undo the fake expand_start_target_temps we did earlier. If
3249 there had been any cleanups created, we've already set
3250 sibcall_failure. */
3252 }
3254 /* If this function is returning into a memory location marked as
3255 readonly, it means it is initializing that location. We normally treat
3256 functions as not clobbering such locations, so we need to specify that
3257 this one does. We do this by adding the appropriate CLOBBER to the
3258 CALL_INSN function usage list. This cannot be done by emitting a
3259 standalone CLOBBER after the call because the latter would be ignored
3260 by at least the delay slot scheduling pass. We do this now instead of
3261 adding to call_fusage before the call to emit_call_1 because TARGET
3262 may be modified in the meantime. */
3265 add_function_usage_to
3268 NULL_RTX));
3274 {
3277 /* Restore the pending stack adjustment now that we have
3278 finished generating the sibling call sequence. */
3283 /* Prepare arg structure for next iteration. */
3285 {
3289 }
3292 }
3293 else
3294 {
3297 /* Verify that we've deallocated all the stack we used. */
3302 }
3304 /* If something prevents making this a sibling call,
3305 zero out the sequence. */
3308 else
3310 }
3312 /* If tail call production suceeded, we need to remove REG_EQUIV notes on
3313 arguments too, as argument area is now clobbered by the call. */
3315 {
3318 }
3319 else
3322 currently_expanding_call--;
3324 /* If this function returns with the stack pointer depressed, ensure
3325 this block saves and restores the stack pointer, show it was
3326 changed, and adjust for any outgoing arg space. */
3328 {
3333 }
3336 }
3338 /* A sibling call sequence invalidates any REG_EQUIV notes made for
3339 this function's incoming arguments.
3341 At the start of RTL generation we know the only REG_EQUIV notes
3342 in the rtl chain are those for incoming arguments, so we can safely
3343 flush any REG_EQUIV note.
3345 This is (slight) overkill. We could keep track of the highest
3346 argument we clobber and be more selective in removing notes, but it
3347 does not seem to be worth the effort. */
3348 void
3350 {
3351 rtx insn;
3352 tree arg;
3356 /* A sibling call sequence also may invalidate RTX_UNCHANGING_P
3357 flag of some incoming arguments MEM RTLs, because it can write into
3358 those slots. We clear all those bits now.
3360 This is (slight) overkill, we could keep track of which arguments
3361 we actually write into. */
3363 {
3366 }
3368 /* Similarly, invalidate RTX_UNCHANGING_P for any incoming
3369 arguments passed in registers. */
3371 arg;
3373 {
3376 }
3377 }
3379 /* Traverse an argument list in VALUES and expand all complex
3380 arguments into their components. */
3381 tree
3383 {
3384 tree p;
3386 /* Before allocating memory, check for the common case of no complex. */
3388 {
3393 }
3396 found:
3400 {
3402 tree complex_type;
3410 {
3411 tree subtype;
3425 /* Skip the newly created node. */
3427 }
3428 }
3431 }
3433 /* Traverse a list of TYPES and expand all complex types into their
3434 components. */
3435 tree
3437 {
3438 tree p;
3440 /* Before allocating memory, check for the common case of no complex. */
3442 {
3447 }
3450 found:
3454 {
3459 {
3462 /* Rewrite complex type with component type. */
3466 /* Add another component type for the imaginary part. */
3471 /* Skip the newly created node. */
3473 }
3474 }
3477 }
3478 \f
3479 /* Output a library call to function FUN (a SYMBOL_REF rtx).
3480 The RETVAL parameter specifies whether return value needs to be saved, other
3481 parameters are documented in the emit_library_call function below. */
3483 static rtx
3487 {
3488 /* Total size in bytes of all the stack-parms scanned so far. */
3490 /* Size of arguments before any adjustments (such as rounding). */
3493 rtx fun;
3497 CUMULATIVE_ARGS args_so_far;
3498 struct arg
3499 {
3500 rtx value;
3502 rtx reg;
3505 rtx save_area;
3506 };
3511 rtx valreg;
3517 rtx before_call;
3520 #ifdef REG_PARM_STACK_SPACE
3521 /* Define the boundary of the register parm stack space that needs to be
3522 save, if any. */
3525 #endif
3527 /* Size of the stack reserved for parameter registers. */
3533 #ifdef REG_PARM_STACK_SPACE
3535 #endif
3537 /* By default, library functions can not throw. */
3541 {
3568 }
3571 /* Ensure current function's preferred stack boundary is at least
3572 what we need. */
3576 /* If this kind of value comes back in memory,
3577 decide where in memory it should come back. */
3579 {
3582 {
3583 #ifdef PCC_STATIC_STRUCT_RETURN
3584 rtx pointer_reg
3594 else
3596 #endif
3597 /* This call returns a big structure. */
3599 }
3600 }
3601 else
3604 /* ??? Unfinished: must pass the memory address as an argument. */
3606 /* Copy all the libcall-arguments out of the varargs data
3607 and into a vector ARGVEC.
3609 Compute how to pass each argument. We only support a very small subset
3610 of the full argument passing conventions to limit complexity here since
3611 library functions shouldn't have many args. */
3616 #ifdef INIT_CUMULATIVE_LIBCALL_ARGS
3618 #else
3620 #endif
3627 /* Now we are about to start emitting insns that can be deleted
3628 if a libcall is deleted. */
3634 /* If there's a structure value address to be passed,
3635 either pass it in the special place, or pass it as an extra argument. */
3637 {
3639 nargs++;
3641 /* Make sure it is a reasonable operand for a move or push insn. */
3651 #ifdef FUNCTION_ARG_PARTIAL_NREGS
3654 #endif
3657 #ifdef STACK_PARMS_IN_REG_PARM_AREA
3659 #else
3661 #endif
3670 count++;
3671 }
3674 {
3678 /* We cannot convert the arg value to the mode the library wants here;
3679 must do it earlier where we know the signedness of the arg. */
3684 /* There's no need to call protect_from_queue, because
3685 either emit_move_insn or emit_push_insn will do that. */
3687 /* Make sure it is a reasonable operand for a move or push insn. */
3692 #ifdef FUNCTION_ARG_PASS_BY_REFERENCE
3694 {
3695 rtx slot;
3697 #ifdef FUNCTION_ARG_CALLEE_COPIES
3700 #endif
3701 ;
3703 /* loop.c won't look at CALL_INSN_FUNCTION_USAGE of const/pure
3704 functions, so we have to pretend this isn't such a function. */
3706 {
3710 }
3713 /* If this was a CONST function, it is now PURE since
3714 it now reads memory. */
3716 {
3719 }
3724 {
3728 }
3729 else
3730 {
3733 slot
3739 }
3743 call_fusage);
3747 slot),
3748 call_fusage);
3752 }
3753 #endif
3760 #ifdef FUNCTION_ARG_PARTIAL_NREGS
3763 #else
3765 #endif
3768 #ifdef STACK_PARMS_IN_REG_PARM_AREA
3770 #else
3772 #endif
3784 }
3786 /* If this machine requires an external definition for library
3787 functions, write one out. */
3792 + stack_pointer_delta
3794 / STACK_BYTES
3799 reg_parm_stack_space);
3801 #ifndef OUTGOING_REG_PARM_STACK_SPACE
3803 #endif
3809 {
3810 /* Since the stack pointer will never be pushed, it is possible for
3811 the evaluation of a parm to clobber something we have already
3812 written to the stack. Since most function calls on RISC machines
3813 do not use the stack, this is uncommon, but must work correctly.
3815 Therefore, we save any area of the stack that was already written
3816 and that we are using. Here we set up to do this by making a new
3817 stack usage map from the old one.
3819 Another approach might be to try to reorder the argument
3820 evaluations to avoid this conflicting stack usage. */
3824 #ifndef OUTGOING_REG_PARM_STACK_SPACE
3825 /* Since we will be writing into the entire argument area, the
3826 map must be allocated for its entire size, not just the part that
3827 is the responsibility of the caller. */
3829 #endif
3831 #ifdef ARGS_GROW_DOWNWARD
3834 #else
3836 needed);
3837 #endif
3842 initial_highest_arg_in_use);
3849 /* We must be careful to use virtual regs before they're instantiated,
3850 and real regs afterwards. Loop optimization, for example, can create
3851 new libcalls after we've instantiated the virtual regs, and if we
3852 use virtuals anyway, they won't match the rtl patterns. */
3856 else
3858 }
3859 else
3860 {
3863 }
3865 /* If we push args individually in reverse order, perform stack alignment
3866 before the first push (the last arg). */
3872 {
3875 }
3876 else
3877 {
3880 }
3882 #ifdef REG_PARM_STACK_SPACE
3884 {
3885 /* The argument list is the property of the called routine and it
3886 may clobber it. If the fixed area has been used for previous
3887 parameters, we must save and restore it. */
3890 }
3891 #endif
3893 /* Push the args that need to be pushed. */
3895 /* ARGNUM indexes the ARGVEC array in the order in which the arguments
3896 are to be pushed. */
3898 {
3906 {
3908 {
3909 /* If this is being stored into a pre-allocated, fixed-size,
3910 stack area, save any previous data at that location. */
3912 #ifdef ARGS_GROW_DOWNWARD
3913 /* stack_slot is negative, but we want to index stack_usage_map
3914 with positive values. */
3917 #else
3920 #endif
3923 /* Don't worry about things in the fixed argument area;
3924 it has already been saved. */
3928 i++;
3931 {
3932 /* We need to make a save area. */
3933 unsigned int size
3935 enum machine_mode save_mode
3937 rtx adr
3940 rtx stack_area
3944 {
3951 stack_area,
3953 BLOCK_OP_CALL_PARM);
3954 }
3955 else
3956 {
3960 }
3961 }
3962 }
3967 reg_parm_stack_space,
3970 /* Now mark the segment we just used. */
3975 NO_DEFER_POP;
3976 }
3977 }
3979 /* If we pushed args in forward order, perform stack alignment
3980 after pushing the last arg. */
3987 else
3992 /* Now load any reg parms into their regs. */
3994 /* ARGNUM indexes the ARGVEC array in the order in which the arguments
3995 are to be pushed. */
3997 {
4002 /* Handle calls that pass values in multiple non-contiguous
4003 locations. The PA64 has examples of this for library calls. */
4009 NO_DEFER_POP;
4010 }
4012 /* Any regs containing parms remain in use through the call. */
4014 {
4020 }
4022 /* Pass the function the address in which to return a structure value. */
4024 {
4028 NULL_RTX)));
4031 }
4033 /* Don't allow popping to be deferred, since then
4034 cse'ing of library calls could delete a call and leave the pop. */
4035 NO_DEFER_POP;
4039 /* Stack must be properly aligned now. */
4045 /* We pass the old value of inhibit_defer_pop + 1 to emit_call_1, which
4046 will set inhibit_defer_pop to that value. */
4047 /* The return type is needed to decide how many bytes the function pops.
4048 Signedness plays no role in that, so for simplicity, we pretend it's
4049 always signed. We also assume that the list of arguments passed has
4050 no impact, so we pretend it is unknown. */
4056 struct_value_size,
4058 valreg,
4061 /* For calls to `setjmp', etc., inform flow.c it should complain
4062 if nonvolatile values are live. For functions that cannot return,
4063 inform flow that control does not fall through. */
4066 {
4067 /* The barrier note must be emitted
4068 immediately after the CALL_INSN. Some ports emit more than
4069 just a CALL_INSN above, so we must search for it here. */
4073 {
4075 /* There was no CALL_INSN? */
4078 }
4081 }
4083 /* Now restore inhibit_defer_pop to its actual original value. */
4084 OK_DEFER_POP;
4086 /* If call is cse'able, make appropriate pair of reg-notes around it.
4087 Test valreg so we don't crash; may safely ignore `const'
4088 if return type is void. Disable for PARALLEL return values, because
4089 we have no way to move such values into a pseudo register. */
4091 {
4092 rtx insns;
4095 {
4099 }
4100 else
4101 {
4103 rtx temp;
4107 {
4112 }
4116 /* Construct an "equal form" for the value which mentions all the
4117 arguments in order as well as the function name. */
4130 note);
4135 }
4136 }
4139 /* Copy the value to the right place. */
4141 {
4143 {
4148 }
4150 {
4154 }
4157 else
4159 }
4162 {
4163 #ifdef REG_PARM_STACK_SPACE
4167 #endif
4169 /* If we saved any argument areas, restore them. */
4172 {
4183 BLOCK_OP_CALL_PARM);
4184 else
4186 }
4190 }
4194 }
4195 \f
4196 /* Output a library call to function FUN (a SYMBOL_REF rtx)
4197 (emitting the queue unless NO_QUEUE is nonzero),
4198 for a value of mode OUTMODE,
4199 with NARGS different arguments, passed as alternating rtx values
4200 and machine_modes to convert them to.
4201 The rtx values should have been passed through protect_from_queue already.
4203 FN_TYPE should be LCT_NORMAL for `normal' calls, LCT_CONST for `const'
4204 calls, LCT_PURE for `pure' calls, LCT_CONST_MAKE_BLOCK for `const' calls
4205 which should be enclosed in REG_LIBCALL/REG_RETVAL notes,
4206 LCT_PURE_MAKE_BLOCK for `purep' calls which should be enclosed in
4207 REG_LIBCALL/REG_RETVAL notes with extra (use (memory (scratch)),
4208 or other LCT_ value for other types of library calls. */
4210 void
4213 {
4219 }
4220 \f
4221 /* Like emit_library_call except that an extra argument, VALUE,
4222 comes second and says where to store the result.
4223 (If VALUE is zero, this function chooses a convenient way
4224 to return the value.
4226 This function returns an rtx for where the value is to be found.
4227 If VALUE is nonzero, VALUE is returned. */
4229 rtx
4233 {
4234 rtx result;
4243 }
4244 \f
4245 /* Store a single argument for a function call
4246 into the register or memory area where it must be passed.
4247 *ARG describes the argument value and where to pass it.
4249 ARGBLOCK is the address of the stack-block for all the arguments,
4250 or 0 on a machine where arguments are pushed individually.
4252 MAY_BE_ALLOCA nonzero says this could be a call to `alloca'
4253 so must be careful about how the stack is used.
4255 VARIABLE_SIZE nonzero says that this was a variable-sized outgoing
4256 argument stack. This is used if ACCUMULATE_OUTGOING_ARGS to indicate
4257 that we need not worry about saving and restoring the stack.
4259 FNDECL is the declaration of the function we are calling.
4261 Return nonzero if this arg should cause sibcall failure,
4262 zero otherwise. */
4264 static int
4267 {
4278 /* Push a new temporary level for any temporaries we make for
4279 this argument. */
4283 {
4284 /* If this is being stored into a pre-allocated, fixed-size, stack area,
4285 save any previous data at that location. */
4287 {
4288 #ifdef ARGS_GROW_DOWNWARD
4289 /* stack_slot is negative, but we want to index stack_usage_map
4290 with positive values. */
4293 else
4297 #else
4300 else
4304 #endif
4307 /* Don't worry about things in the fixed argument area;
4308 it has already been saved. */
4312 i++;
4315 {
4316 /* We need to make a save area. */
4323 {
4332 BLOCK_OP_CALL_PARM);
4333 }
4334 else
4335 {
4338 }
4339 }
4340 }
4341 }
4343 /* If this isn't going to be placed on both the stack and in registers,
4344 set up the register and number of words. */
4346 {
4349 else
4352 }
4355 /* Being passed entirely in a register. We shouldn't be called in
4356 this case. */
4359 /* If this arg needs special alignment, don't load the registers
4360 here. */
4364 /* If this is being passed partially in a register, we can't evaluate
4365 it directly into its stack slot. Otherwise, we can. */
4367 {
4368 /* stack_arg_under_construction is nonzero if a function argument is
4369 being evaluated directly into the outgoing argument list and
4370 expand_call must take special action to preserve the argument list
4371 if it is called recursively.
4373 For scalar function arguments stack_usage_map is sufficient to
4374 determine which stack slots must be saved and restored. Scalar
4375 arguments in general have pass_on_stack == 0.
4377 If this argument is initialized by a function which takes the
4378 address of the argument (a C++ constructor or a C function
4379 returning a BLKmode structure), then stack_usage_map is
4380 insufficient and expand_call must push the stack around the
4381 function call. Such arguments have pass_on_stack == 1.
4383 Note that it is always safe to set stack_arg_under_construction,
4384 but this generates suboptimal code if set when not needed. */
4387 stack_arg_under_construction++;
4390 (partial
4395 /* If we are promoting object (or for any other reason) the mode
4396 doesn't agree, convert the mode. */
4403 stack_arg_under_construction--;
4404 }
4406 /* Don't allow anything left on stack from computation
4407 of argument to alloca. */
4412 /* If the value is already in the stack slot, we are done. */
4413 ;
4415 {
4418 /* Argument is a scalar, not entirely passed in registers.
4419 (If part is passed in registers, arg->partial says how much
4420 and emit_push_insn will take care of putting it there.)
4422 Push it, and if its size is less than the
4423 amount of space allocated to it,
4424 also bump stack pointer by the additional space.
4425 Note that in C the default argument promotions
4426 will prevent such mismatches. */
4429 /* Compute how much space the push instruction will push.
4430 On many machines, pushing a byte will advance the stack
4431 pointer by a halfword. */
4432 #ifdef PUSH_ROUNDING
4434 #endif
4437 /* Compute how much space the argument should get:
4438 round up to a multiple of the alignment for arguments. */
4444 /* This isn't already where we want it on the stack, so put it there.
4445 This can either be done with push or copy insns. */
4451 /* Unless this is a partially-in-register argument, the argument is now
4452 in the stack. */
4455 }
4456 else
4457 {
4458 /* BLKmode, at least partly to be pushed. */
4462 rtx size_rtx;
4464 /* Pushing a nonscalar.
4465 If part is passed in registers, PARTIAL says how much
4466 and emit_push_insn will take care of putting it there. */
4468 /* Round its size up to a multiple
4469 of the allocation unit for arguments. */
4472 {
4475 }
4476 else
4477 {
4478 /* PUSH_ROUNDING has no effect on us, because
4479 emit_push_insn for BLKmode is careful to avoid it. */
4481 {
4482 /* Use the size of the elt to compute excess. */
4487 }
4488 else
4494 }
4496 /* Some types will require stricter alignment, which will be
4497 provided for elsewhere in argument layout. */
4500 /* When an argument is padded down, the block is aligned to
4501 PARM_BOUNDARY, but the actual argument isn't. */
4503 {
4507 {
4510 }
4511 }
4514 {
4515 /* emit_push_insn might not work properly if arg->value and
4516 argblock + arg->locate.offset areas overlap. */
4523 current_function_internal_arg_pointer
4525 {
4529 /* expand_call should ensure this. */
4534 {
4537 }
4539 {
4542 }
4543 }
4544 }
4551 /* Unless this is a partially-in-register argument, the argument is now
4552 in the stack.
4554 ??? Unlike the case above, in which we want the actual
4555 address of the data, so that we can load it directly into a
4556 register, here we want the address of the stack slot, so that
4557 it's properly aligned for word-by-word copying or something
4558 like that. It's not clear that this is always correct. */
4561 }
4563 /* Mark all slots this store used. */
4569 /* Once we have pushed something, pops can't safely
4570 be deferred during the rest of the arguments. */
4571 NO_DEFER_POP;
4573 /* ANSI doesn't require a sequence point here,
4574 but PCC has one, so this will avoid some problems. */
4577 /* Free any temporary slots made in processing this argument. Show
4578 that we might have taken the address of something and pushed that
4579 as an operand. */
4585 }
4587 /* Nonzero if we do not know how to pass TYPE solely in registers.
4588 We cannot do so in the following cases:
4590 - if the type has variable size
4591 - if the type is marked as addressable (it is required to be constructed
4592 into the stack)
4593 - if the padding and mode of the type is such that a copy into a register
4594 would put it into the wrong part of the register.
4596 Which padding can't be supported depends on the byte endianness.
4598 A value in a register is implicitly padded at the most significant end.
4599 On a big-endian machine, that is the lower end in memory.
4600 So a value padded in memory at the upper end can't go in a register.
4601 For a little-endian machine, the reverse is true. */
4603 bool
4605 {
4609 /* If the type has variable size... */
4613 /* If the type is marked as addressable (it is required
4614 to be constructed into the stack)... */
4618 /* If the padding and mode of the type is such that a copy into
4619 a register would put it into the wrong part of the register. */
4627 }