1 /* Tail call optimization on trees.
2 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
28 #include "hard-reg-set.h"
29 #include "basic-block.h"
31 #include "tree-flow.h"
32 #include "tree-dump.h"
33 #include "diagnostic.h"
35 #include "tree-pass.h"
37 #include "langhooks.h"
40 /* The file implements the tail recursion elimination. It is also used to
41 analyze the tail calls in general, passing the results to the rtl level
42 where they are used for sibcall optimization.
44 In addition to the standard tail recursion elimination, we handle the most
45 trivial cases of making the call tail recursive by creating accumulators.
46 For example the following function
51 return n + sum (n - 1);
68 To do this, we maintain two accumulators (a_acc and m_acc) that indicate
69 when we reach the return x statement, we should return a_acc + x * m_acc
70 instead. They are initially initialized to 0 and 1, respectively,
71 so the semantics of the function is obviously preserved. If we are
72 guaranteed that the value of the accumulator never change, we
75 There are three cases how the function may exit. The first one is
76 handled in adjust_return_value, the other two in adjust_accumulator_values
77 (the second case is actually a special case of the third one and we
78 present it separately just for clarity):
80 1) Just return x, where x is not in any of the remaining special shapes.
81 We rewrite this to a gimple equivalent of return m_acc * x + a_acc.
83 2) return f (...), where f is the current function, is rewritten in a
84 classical tail-recursion elimination way, into assignment of arguments
85 and jump to the start of the function. Values of the accumulators
88 3) return a + m * f(...), where a and m do not depend on call to f.
89 To preserve the semantics described before we want this to be rewritten
90 in such a way that we finally return
92 a_acc + (a + m * f(...)) * m_acc = (a_acc + a * m_acc) + (m * m_acc) * f(...).
94 I.e. we increase a_acc by a * m_acc, multiply m_acc by m and
95 eliminate the tail call to f. Special cases when the value is just
96 added or just multiplied are obtained by setting a = 0 or m = 1.
98 TODO -- it is possible to do similar tricks for other operations. */
100 /* A structure that describes the tailcall. */
104 /* The iterator pointing to the call statement. */
105 gimple_stmt_iterator call_gsi
;
107 /* True if it is a call to the current function. */
110 /* The return value of the caller is mult * f + add, where f is the return
111 value of the call. */
114 /* Next tailcall in the chain. */
115 struct tailcall
*next
;
118 /* The variables holding the value of multiplicative and additive
120 static tree m_acc
, a_acc
;
122 static bool suitable_for_tail_opt_p (void);
123 static bool optimize_tail_call (struct tailcall
*, bool);
124 static void eliminate_tail_call (struct tailcall
*);
125 static void find_tail_calls (basic_block
, struct tailcall
**);
127 /* Returns false when the function is not suitable for tail call optimization
128 from some reason (e.g. if it takes variable number of arguments). */
131 suitable_for_tail_opt_p (void)
133 referenced_var_iterator rvi
;
139 /* No local variable nor structure field should be call-used. */
140 FOR_EACH_REFERENCED_VAR (var
, rvi
)
142 if (!is_global_var (var
)
143 && is_call_used (var
))
149 /* Returns false when the function is not suitable for tail call optimization
150 from some reason (e.g. if it takes variable number of arguments).
151 This test must pass in addition to suitable_for_tail_opt_p in order to make
152 tail call discovery happen. */
155 suitable_for_tail_call_opt_p (void)
159 /* alloca (until we have stack slot life analysis) inhibits
160 sibling call optimizations, but not tail recursion. */
161 if (cfun
->calls_alloca
)
164 /* If we are using sjlj exceptions, we may need to add a call to
165 _Unwind_SjLj_Unregister at exit of the function. Which means
166 that we cannot do any sibcall transformations. */
167 if (USING_SJLJ_EXCEPTIONS
&& current_function_has_exception_handlers ())
170 /* Any function that calls setjmp might have longjmp called from
171 any called function. ??? We really should represent this
172 properly in the CFG so that this needn't be special cased. */
173 if (cfun
->calls_setjmp
)
176 /* ??? It is OK if the argument of a function is taken in some cases,
177 but not in all cases. See PR15387 and PR19616. Revisit for 4.1. */
178 for (param
= DECL_ARGUMENTS (current_function_decl
);
180 param
= TREE_CHAIN (param
))
181 if (TREE_ADDRESSABLE (param
))
187 /* Checks whether the expression EXPR in stmt AT is independent of the
188 statement pointed to by GSI (in a sense that we already know EXPR's value
189 at GSI). We use the fact that we are only called from the chain of
190 basic blocks that have only single successor. Returns the expression
191 containing the value of EXPR at GSI. */
194 independent_of_stmt_p (tree expr
, gimple at
, gimple_stmt_iterator gsi
)
196 basic_block bb
, call_bb
, at_bb
;
200 if (is_gimple_min_invariant (expr
))
203 if (TREE_CODE (expr
) != SSA_NAME
)
206 /* Mark the blocks in the chain leading to the end. */
207 at_bb
= gimple_bb (at
);
208 call_bb
= gimple_bb (gsi_stmt (gsi
));
209 for (bb
= call_bb
; bb
!= at_bb
; bb
= single_succ (bb
))
215 at
= SSA_NAME_DEF_STMT (expr
);
218 /* The default definition or defined before the chain. */
224 for (; !gsi_end_p (gsi
); gsi_next (&gsi
))
225 if (gsi_stmt (gsi
) == at
)
228 if (!gsi_end_p (gsi
))
233 if (gimple_code (at
) != GIMPLE_PHI
)
239 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
244 expr
= PHI_ARG_DEF_FROM_EDGE (at
, e
);
245 if (TREE_CODE (expr
) != SSA_NAME
)
247 /* The value is a constant. */
252 /* Unmark the blocks. */
253 for (bb
= call_bb
; bb
!= at_bb
; bb
= single_succ (bb
))
260 /* Simulates the effect of an assignment STMT on the return value of the tail
261 recursive CALL passed in ASS_VAR. M and A are the multiplicative and the
262 additive factor for the real return value. */
265 process_assignment (gimple stmt
, gimple_stmt_iterator call
, tree
*m
,
266 tree
*a
, tree
*ass_var
)
268 tree op0
, op1
, non_ass_var
;
269 tree dest
= gimple_assign_lhs (stmt
);
270 enum tree_code code
= gimple_assign_rhs_code (stmt
);
271 enum gimple_rhs_class rhs_class
= get_gimple_rhs_class (code
);
272 tree src_var
= gimple_assign_rhs1 (stmt
);
274 /* See if this is a simple copy operation of an SSA name to the function
275 result. In that case we may have a simple tail call. Ignore type
276 conversions that can never produce extra code between the function
277 call and the function return. */
278 if ((rhs_class
== GIMPLE_SINGLE_RHS
|| gimple_assign_cast_p (stmt
))
279 && (TREE_CODE (src_var
) == SSA_NAME
))
281 /* Reject a tailcall if the type conversion might need
283 if (gimple_assign_cast_p (stmt
)
284 && TYPE_MODE (TREE_TYPE (dest
)) != TYPE_MODE (TREE_TYPE (src_var
)))
287 if (src_var
!= *ass_var
)
294 if (rhs_class
!= GIMPLE_BINARY_RHS
)
297 /* Accumulator optimizations will reverse the order of operations.
298 We can only do that for floating-point types if we're assuming
299 that addition and multiplication are associative. */
300 if (!flag_associative_math
)
301 if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl
))))
304 /* We only handle the code like
311 TODO -- Extend it for cases where the linear transformation of the output
312 is expressed in a more complicated way. */
314 op0
= gimple_assign_rhs1 (stmt
);
315 op1
= gimple_assign_rhs2 (stmt
);
318 && (non_ass_var
= independent_of_stmt_p (op1
, stmt
, call
)))
320 else if (op1
== *ass_var
321 && (non_ass_var
= independent_of_stmt_p (op0
, stmt
, call
)))
329 /* There should be no previous addition. TODO -- it should be fairly
330 straightforward to lift this restriction -- just allow storing
331 more complicated expressions in *A, and gimplify it in
332 adjust_accumulator_values. */
340 /* Similar remark applies here. Handling multiplication after addition
341 is just slightly more complicated -- we need to multiply both *A and
349 /* TODO -- Handle other codes (NEGATE_EXPR, MINUS_EXPR,
350 POINTER_PLUS_EXPR). */
357 /* Propagate VAR through phis on edge E. */
360 propagate_through_phis (tree var
, edge e
)
362 basic_block dest
= e
->dest
;
363 gimple_stmt_iterator gsi
;
365 for (gsi
= gsi_start_phis (dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
367 gimple phi
= gsi_stmt (gsi
);
368 if (PHI_ARG_DEF_FROM_EDGE (phi
, e
) == var
)
369 return PHI_RESULT (phi
);
374 /* Finds tailcalls falling into basic block BB. The list of found tailcalls is
375 added to the start of RET. */
378 find_tail_calls (basic_block bb
, struct tailcall
**ret
)
380 tree ass_var
= NULL_TREE
, ret_var
, func
, param
;
381 gimple stmt
, call
= NULL
;
382 gimple_stmt_iterator gsi
, agsi
;
390 if (!single_succ_p (bb
))
393 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
395 stmt
= gsi_stmt (gsi
);
398 if (gimple_code (stmt
) == GIMPLE_LABEL
)
401 /* Check for a call. */
402 if (is_gimple_call (stmt
))
405 ass_var
= gimple_call_lhs (stmt
);
409 /* If the statement references memory or volatile operands, fail. */
410 if (gimple_references_memory_p (stmt
)
411 || gimple_has_volatile_ops (stmt
))
418 /* Recurse to the predecessors. */
419 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
420 find_tail_calls (e
->src
, ret
);
425 /* If the LHS of our call is not just a simple register, we can't
426 transform this into a tail or sibling call. This situation happens,
427 in (e.g.) "*p = foo()" where foo returns a struct. In this case
428 we won't have a temporary here, but we need to carry out the side
429 effect anyway, so tailcall is impossible.
431 ??? In some situations (when the struct is returned in memory via
432 invisible argument) we could deal with this, e.g. by passing 'p'
433 itself as that argument to foo, but it's too early to do this here,
434 and expand_call() will not handle it anyway. If it ever can, then
435 we need to revisit this here, to allow that situation. */
436 if (ass_var
&& !is_gimple_reg (ass_var
))
439 /* We found the call, check whether it is suitable. */
440 tail_recursion
= false;
441 func
= gimple_call_fndecl (call
);
442 if (func
== current_function_decl
)
445 for (param
= DECL_ARGUMENTS (func
), idx
= 0;
446 param
&& idx
< gimple_call_num_args (call
);
447 param
= TREE_CHAIN (param
), idx
++)
449 arg
= gimple_call_arg (call
, idx
);
452 /* Make sure there are no problems with copying. The parameter
453 have a copyable type and the two arguments must have reasonably
454 equivalent types. The latter requirement could be relaxed if
455 we emitted a suitable type conversion statement. */
456 if (!is_gimple_reg_type (TREE_TYPE (param
))
457 || !useless_type_conversion_p (TREE_TYPE (param
),
461 /* The parameter should be a real operand, so that phi node
462 created for it at the start of the function has the meaning
463 of copying the value. This test implies is_gimple_reg_type
464 from the previous condition, however this one could be
465 relaxed by being more careful with copying the new value
466 of the parameter (emitting appropriate GIMPLE_ASSIGN and
467 updating the virtual operands). */
468 if (!is_gimple_reg (param
))
472 if (idx
== gimple_call_num_args (call
) && !param
)
473 tail_recursion
= true;
476 /* Now check the statements after the call. None of them has virtual
477 operands, so they may only depend on the call through its return
478 value. The return value should also be dependent on each of them,
479 since we are running after dce. */
489 while (gsi_end_p (agsi
))
491 ass_var
= propagate_through_phis (ass_var
, single_succ_edge (abb
));
492 abb
= single_succ (abb
);
493 agsi
= gsi_start_bb (abb
);
496 stmt
= gsi_stmt (agsi
);
498 if (gimple_code (stmt
) == GIMPLE_LABEL
)
501 if (gimple_code (stmt
) == GIMPLE_RETURN
)
504 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
507 /* This is a gimple assign. */
508 if (! process_assignment (stmt
, gsi
, &m
, &a
, &ass_var
))
512 /* See if this is a tail call we can handle. */
513 ret_var
= gimple_return_retval (stmt
);
515 /* We may proceed if there either is no return value, or the return value
516 is identical to the call's return. */
518 && (ret_var
!= ass_var
))
521 /* If this is not a tail recursive call, we cannot handle addends or
523 if (!tail_recursion
&& (m
|| a
))
526 nw
= XNEW (struct tailcall
);
530 nw
->tail_recursion
= tail_recursion
;
539 /* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */
542 add_successor_phi_arg (edge e
, tree var
, tree phi_arg
)
544 gimple_stmt_iterator gsi
;
546 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
547 if (PHI_RESULT (gsi_stmt (gsi
)) == var
)
550 gcc_assert (!gsi_end_p (gsi
));
551 add_phi_arg (gsi_stmt (gsi
), phi_arg
, e
);
554 /* Creates a GIMPLE statement which computes the operation specified by
555 CODE, OP0 and OP1 to a new variable with name LABEL and inserts the
556 statement in the position specified by GSI and UPDATE. Returns the
557 tree node of the statement's result. */
560 adjust_return_value_with_ops (enum tree_code code
, const char *label
,
561 tree op0
, tree op1
, gimple_stmt_iterator gsi
,
562 enum gsi_iterator_update update
)
565 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
566 tree tmp
= create_tmp_var (ret_type
, label
);
567 gimple stmt
= gimple_build_assign_with_ops (code
, tmp
, op0
, op1
);
570 add_referenced_var (tmp
);
571 result
= make_ssa_name (tmp
, stmt
);
572 gimple_assign_set_lhs (stmt
, result
);
574 gsi_insert_before (&gsi
, stmt
, update
);
578 /* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by
579 the computation specified by CODE and OP1 and insert the statement
580 at the position specified by GSI as a new statement. Returns new SSA name
581 of updated accumulator. */
584 update_accumulator_with_ops (enum tree_code code
, tree acc
, tree op1
,
585 gimple_stmt_iterator gsi
)
587 gimple stmt
= gimple_build_assign_with_ops (code
, SSA_NAME_VAR (acc
), acc
,
589 tree var
= make_ssa_name (SSA_NAME_VAR (acc
), stmt
);
590 gimple_assign_set_lhs (stmt
, var
);
592 gsi_insert_after (&gsi
, stmt
, GSI_NEW_STMT
);
596 /* Adjust the accumulator values according to A and M after GSI, and update
597 the phi nodes on edge BACK. */
600 adjust_accumulator_values (gimple_stmt_iterator gsi
, tree m
, tree a
, edge back
)
602 tree var
, a_acc_arg
= a_acc
, m_acc_arg
= m_acc
;
608 if (integer_onep (a
))
611 var
= adjust_return_value_with_ops (MULT_EXPR
, "acc_tmp", m_acc
,
612 a
, gsi
, GSI_NEW_STMT
);
617 a_acc_arg
= update_accumulator_with_ops (PLUS_EXPR
, a_acc
, var
, gsi
);
621 m_acc_arg
= update_accumulator_with_ops (MULT_EXPR
, m_acc
, m
, gsi
);
624 add_successor_phi_arg (back
, a_acc
, a_acc_arg
);
627 add_successor_phi_arg (back
, m_acc
, m_acc_arg
);
630 /* Adjust value of the return at the end of BB according to M and A
634 adjust_return_value (basic_block bb
, tree m
, tree a
)
637 gimple ret_stmt
= gimple_seq_last_stmt (bb_seq (bb
));
638 gimple_stmt_iterator gsi
= gsi_last_bb (bb
);
640 gcc_assert (gimple_code (ret_stmt
) == GIMPLE_RETURN
);
642 retval
= gimple_return_retval (ret_stmt
);
643 if (!retval
|| retval
== error_mark_node
)
647 retval
= adjust_return_value_with_ops (MULT_EXPR
, "mul_tmp", m_acc
, retval
,
650 retval
= adjust_return_value_with_ops (PLUS_EXPR
, "acc_tmp", a_acc
, retval
,
652 gimple_return_set_retval (ret_stmt
, retval
);
653 update_stmt (ret_stmt
);
656 /* Subtract COUNT and FREQUENCY from the basic block and it's
659 decrease_profile (basic_block bb
, gcov_type count
, int frequency
)
665 bb
->frequency
-= frequency
;
666 if (bb
->frequency
< 0)
668 if (!single_succ_p (bb
))
670 gcc_assert (!EDGE_COUNT (bb
->succs
));
673 e
= single_succ_edge (bb
);
679 /* Returns true if argument PARAM of the tail recursive call needs to be copied
680 when the call is eliminated. */
683 arg_needs_copy_p (tree param
)
687 if (!is_gimple_reg (param
) || !var_ann (param
))
690 /* Parameters that are only defined but never used need not be copied. */
691 def
= gimple_default_def (cfun
, param
);
698 /* Eliminates tail call described by T. TMP_VARS is a list of
699 temporary variables used to copy the function arguments. */
702 eliminate_tail_call (struct tailcall
*t
)
708 basic_block bb
, first
;
711 gimple_stmt_iterator gsi
;
714 stmt
= orig_stmt
= gsi_stmt (t
->call_gsi
);
715 bb
= gsi_bb (t
->call_gsi
);
717 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
719 fprintf (dump_file
, "Eliminated tail recursion in bb %d : ",
721 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
722 fprintf (dump_file
, "\n");
725 gcc_assert (is_gimple_call (stmt
));
727 first
= single_succ (ENTRY_BLOCK_PTR
);
729 /* Remove the code after call_gsi that will become unreachable. The
730 possibly unreachable code in other blocks is removed later in
734 while (!gsi_end_p (gsi
))
736 gimple t
= gsi_stmt (gsi
);
737 /* Do not remove the return statement, so that redirect_edge_and_branch
738 sees how the block ends. */
739 if (gimple_code (t
) == GIMPLE_RETURN
)
742 gsi_remove (&gsi
, true);
746 /* Number of executions of function has reduced by the tailcall. */
747 e
= single_succ_edge (gsi_bb (t
->call_gsi
));
748 decrease_profile (EXIT_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
749 decrease_profile (ENTRY_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
750 if (e
->dest
!= EXIT_BLOCK_PTR
)
751 decrease_profile (e
->dest
, e
->count
, EDGE_FREQUENCY (e
));
753 /* Replace the call by a jump to the start of function. */
754 e
= redirect_edge_and_branch (single_succ_edge (gsi_bb (t
->call_gsi
)),
757 PENDING_STMT (e
) = NULL
;
759 /* Add phi node entries for arguments. The ordering of the phi nodes should
760 be the same as the ordering of the arguments. */
761 for (param
= DECL_ARGUMENTS (current_function_decl
),
762 idx
= 0, gsi
= gsi_start_phis (first
);
764 param
= TREE_CHAIN (param
), idx
++)
766 if (!arg_needs_copy_p (param
))
769 arg
= gimple_call_arg (stmt
, idx
);
770 phi
= gsi_stmt (gsi
);
771 gcc_assert (param
== SSA_NAME_VAR (PHI_RESULT (phi
)));
773 add_phi_arg (phi
, arg
, e
);
777 /* Update the values of accumulators. */
778 adjust_accumulator_values (t
->call_gsi
, t
->mult
, t
->add
, e
);
780 call
= gsi_stmt (t
->call_gsi
);
781 rslt
= gimple_call_lhs (call
);
782 if (rslt
!= NULL_TREE
)
784 /* Result of the call will no longer be defined. So adjust the
785 SSA_NAME_DEF_STMT accordingly. */
786 SSA_NAME_DEF_STMT (rslt
) = gimple_build_nop ();
789 gsi_remove (&t
->call_gsi
, true);
793 /* Add phi nodes for the virtual operands defined in the function to the
794 header of the loop created by tail recursion elimination.
796 Originally, we used to add phi nodes only for call clobbered variables,
797 as the value of the non-call clobbered ones obviously cannot be used
798 or changed within the recursive call. However, the local variables
799 from multiple calls now share the same location, so the virtual ssa form
800 requires us to say that the location dies on further iterations of the loop,
801 which requires adding phi nodes.
804 add_virtual_phis (void)
806 referenced_var_iterator rvi
;
809 /* The problematic part is that there is no way how to know what
810 to put into phi nodes (there in fact does not have to be such
811 ssa name available). A solution would be to have an artificial
812 use/kill for all virtual operands in EXIT node. Unless we have
813 this, we cannot do much better than to rebuild the ssa form for
814 possibly affected virtual ssa names from scratch. */
816 FOR_EACH_REFERENCED_VAR (var
, rvi
)
818 if (!is_gimple_reg (var
) && gimple_default_def (cfun
, var
) != NULL_TREE
)
819 mark_sym_for_renaming (var
);
823 /* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also
824 mark the tailcalls for the sibcall optimization. */
827 optimize_tail_call (struct tailcall
*t
, bool opt_tailcalls
)
829 if (t
->tail_recursion
)
831 eliminate_tail_call (t
);
837 gimple stmt
= gsi_stmt (t
->call_gsi
);
839 gimple_call_set_tail (stmt
, true);
840 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
842 fprintf (dump_file
, "Found tail call ");
843 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
844 fprintf (dump_file
, " in bb %i\n", (gsi_bb (t
->call_gsi
))->index
);
851 /* Creates a tail-call accumulator of the same type as the return type of the
852 current function. LABEL is the name used to creating the temporary
853 variable for the accumulator. The accumulator will be inserted in the
854 phis of a basic block BB with single predecessor with an initial value
855 INIT converted to the current function return type. */
858 create_tailcall_accumulator (const char *label
, basic_block bb
, tree init
)
860 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
861 tree tmp
= create_tmp_var (ret_type
, label
);
864 add_referenced_var (tmp
);
865 phi
= create_phi_node (tmp
, bb
);
866 /* RET_TYPE can be a float when -ffast-maths is enabled. */
867 add_phi_arg (phi
, fold_convert (ret_type
, init
), single_pred_edge (bb
));
868 return PHI_RESULT (phi
);
871 /* Optimizes tail calls in the function, turning the tail recursion
875 tree_optimize_tail_calls_1 (bool opt_tailcalls
)
878 bool phis_constructed
= false;
879 struct tailcall
*tailcalls
= NULL
, *act
, *next
;
880 bool changed
= false;
881 basic_block first
= single_succ (ENTRY_BLOCK_PTR
);
886 if (!suitable_for_tail_opt_p ())
889 opt_tailcalls
= suitable_for_tail_call_opt_p ();
891 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
893 /* Only traverse the normal exits, i.e. those that end with return
895 stmt
= last_stmt (e
->src
);
898 && gimple_code (stmt
) == GIMPLE_RETURN
)
899 find_tail_calls (e
->src
, &tailcalls
);
902 /* Construct the phi nodes and accumulators if necessary. */
903 a_acc
= m_acc
= NULL_TREE
;
904 for (act
= tailcalls
; act
; act
= act
->next
)
906 if (!act
->tail_recursion
)
909 if (!phis_constructed
)
911 /* Ensure that there is only one predecessor of the block
912 or if there are existing degenerate PHI nodes. */
913 if (!single_pred_p (first
)
914 || !gimple_seq_empty_p (phi_nodes (first
)))
915 first
= split_edge (single_succ_edge (ENTRY_BLOCK_PTR
));
917 /* Copy the args if needed. */
918 for (param
= DECL_ARGUMENTS (current_function_decl
);
920 param
= TREE_CHAIN (param
))
921 if (arg_needs_copy_p (param
))
923 tree name
= gimple_default_def (cfun
, param
);
924 tree new_name
= make_ssa_name (param
, SSA_NAME_DEF_STMT (name
));
927 set_default_def (param
, new_name
);
928 phi
= create_phi_node (name
, first
);
929 SSA_NAME_DEF_STMT (name
) = phi
;
930 add_phi_arg (phi
, new_name
, single_pred_edge (first
));
932 phis_constructed
= true;
935 if (act
->add
&& !a_acc
)
936 a_acc
= create_tailcall_accumulator ("add_acc", first
,
939 if (act
->mult
&& !m_acc
)
940 m_acc
= create_tailcall_accumulator ("mult_acc", first
,
944 for (; tailcalls
; tailcalls
= next
)
946 next
= tailcalls
->next
;
947 changed
|= optimize_tail_call (tailcalls
, opt_tailcalls
);
953 /* Modify the remaining return statements. */
954 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
956 stmt
= last_stmt (e
->src
);
959 && gimple_code (stmt
) == GIMPLE_RETURN
)
960 adjust_return_value (e
->src
, m_acc
, a_acc
);
965 free_dominance_info (CDI_DOMINATORS
);
967 if (phis_constructed
)
970 return TODO_cleanup_cfg
| TODO_update_ssa_only_virtuals
;
975 execute_tail_recursion (void)
977 return tree_optimize_tail_calls_1 (false);
981 gate_tail_calls (void)
983 return flag_optimize_sibling_calls
!= 0 && dbg_cnt (tail_call
);
987 execute_tail_calls (void)
989 return tree_optimize_tail_calls_1 (true);
992 struct gimple_opt_pass pass_tail_recursion
=
997 gate_tail_calls
, /* gate */
998 execute_tail_recursion
, /* execute */
1001 0, /* static_pass_number */
1002 TV_NONE
, /* tv_id */
1003 PROP_cfg
| PROP_ssa
, /* properties_required */
1004 0, /* properties_provided */
1005 0, /* properties_destroyed */
1006 0, /* todo_flags_start */
1007 TODO_dump_func
| TODO_verify_ssa
/* todo_flags_finish */
1011 struct gimple_opt_pass pass_tail_calls
=
1016 gate_tail_calls
, /* gate */
1017 execute_tail_calls
, /* execute */
1020 0, /* static_pass_number */
1021 TV_NONE
, /* tv_id */
1022 PROP_cfg
| PROP_ssa
, /* properties_required */
1023 0, /* properties_provided */
1024 0, /* properties_destroyed */
1025 0, /* todo_flags_start */
1026 TODO_dump_func
| TODO_verify_ssa
/* todo_flags_finish */