1 /* Tail call optimization on trees.
2 Copyright (C) 2003-2013 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
22 #include "coretypes.h"
26 #include "basic-block.h"
28 #include "tree-flow.h"
29 #include "gimple-pretty-print.h"
31 #include "tree-pass.h"
33 #include "langhooks.h"
37 #include "common/common-target.h"
39 /* The file implements the tail recursion elimination. It is also used to
40 analyze the tail calls in general, passing the results to the rtl level
41 where they are used for sibcall optimization.
43 In addition to the standard tail recursion elimination, we handle the most
44 trivial cases of making the call tail recursive by creating accumulators.
45 For example the following function
50 return n + sum (n - 1);
67 To do this, we maintain two accumulators (a_acc and m_acc) that indicate
68 when we reach the return x statement, we should return a_acc + x * m_acc
69 instead. They are initially initialized to 0 and 1, respectively,
70 so the semantics of the function is obviously preserved. If we are
71 guaranteed that the value of the accumulator never change, we
74 There are three cases how the function may exit. The first one is
75 handled in adjust_return_value, the other two in adjust_accumulator_values
76 (the second case is actually a special case of the third one and we
77 present it separately just for clarity):
79 1) Just return x, where x is not in any of the remaining special shapes.
80 We rewrite this to a gimple equivalent of return m_acc * x + a_acc.
82 2) return f (...), where f is the current function, is rewritten in a
83 classical tail-recursion elimination way, into assignment of arguments
84 and jump to the start of the function. Values of the accumulators
87 3) return a + m * f(...), where a and m do not depend on call to f.
88 To preserve the semantics described before we want this to be rewritten
89 in such a way that we finally return
91 a_acc + (a + m * f(...)) * m_acc = (a_acc + a * m_acc) + (m * m_acc) * f(...).
93 I.e. we increase a_acc by a * m_acc, multiply m_acc by m and
94 eliminate the tail call to f. Special cases when the value is just
95 added or just multiplied are obtained by setting a = 0 or m = 1.
97 TODO -- it is possible to do similar tricks for other operations. */
99 /* A structure that describes the tailcall. */
103 /* The iterator pointing to the call statement. */
104 gimple_stmt_iterator call_gsi
;
106 /* True if it is a call to the current function. */
109 /* The return value of the caller is mult * f + add, where f is the return
110 value of the call. */
113 /* Next tailcall in the chain. */
114 struct tailcall
*next
;
117 /* The variables holding the value of multiplicative and additive
119 static tree m_acc
, a_acc
;
121 static bool suitable_for_tail_opt_p (void);
122 static bool optimize_tail_call (struct tailcall
*, bool);
123 static void eliminate_tail_call (struct tailcall
*);
124 static void find_tail_calls (basic_block
, struct tailcall
**);
126 /* Returns false when the function is not suitable for tail call optimization
127 from some reason (e.g. if it takes variable number of arguments). */
130 suitable_for_tail_opt_p (void)
137 /* Returns false when the function is not suitable for tail call optimization
138 from some reason (e.g. if it takes variable number of arguments).
139 This test must pass in addition to suitable_for_tail_opt_p in order to make
140 tail call discovery happen. */
143 suitable_for_tail_call_opt_p (void)
147 /* alloca (until we have stack slot life analysis) inhibits
148 sibling call optimizations, but not tail recursion. */
149 if (cfun
->calls_alloca
)
152 /* If we are using sjlj exceptions, we may need to add a call to
153 _Unwind_SjLj_Unregister at exit of the function. Which means
154 that we cannot do any sibcall transformations. */
155 if (targetm_common
.except_unwind_info (&global_options
) == UI_SJLJ
156 && current_function_has_exception_handlers ())
159 /* Any function that calls setjmp might have longjmp called from
160 any called function. ??? We really should represent this
161 properly in the CFG so that this needn't be special cased. */
162 if (cfun
->calls_setjmp
)
165 /* ??? It is OK if the argument of a function is taken in some cases,
166 but not in all cases. See PR15387 and PR19616. Revisit for 4.1. */
167 for (param
= DECL_ARGUMENTS (current_function_decl
);
169 param
= DECL_CHAIN (param
))
170 if (TREE_ADDRESSABLE (param
))
176 /* Checks whether the expression EXPR in stmt AT is independent of the
177 statement pointed to by GSI (in a sense that we already know EXPR's value
178 at GSI). We use the fact that we are only called from the chain of
179 basic blocks that have only single successor. Returns the expression
180 containing the value of EXPR at GSI. */
183 independent_of_stmt_p (tree expr
, gimple at
, gimple_stmt_iterator gsi
)
185 basic_block bb
, call_bb
, at_bb
;
189 if (is_gimple_min_invariant (expr
))
192 if (TREE_CODE (expr
) != SSA_NAME
)
195 /* Mark the blocks in the chain leading to the end. */
196 at_bb
= gimple_bb (at
);
197 call_bb
= gimple_bb (gsi_stmt (gsi
));
198 for (bb
= call_bb
; bb
!= at_bb
; bb
= single_succ (bb
))
204 at
= SSA_NAME_DEF_STMT (expr
);
207 /* The default definition or defined before the chain. */
213 for (; !gsi_end_p (gsi
); gsi_next (&gsi
))
214 if (gsi_stmt (gsi
) == at
)
217 if (!gsi_end_p (gsi
))
222 if (gimple_code (at
) != GIMPLE_PHI
)
228 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
233 expr
= PHI_ARG_DEF_FROM_EDGE (at
, e
);
234 if (TREE_CODE (expr
) != SSA_NAME
)
236 /* The value is a constant. */
241 /* Unmark the blocks. */
242 for (bb
= call_bb
; bb
!= at_bb
; bb
= single_succ (bb
))
249 /* Simulates the effect of an assignment STMT on the return value of the tail
250 recursive CALL passed in ASS_VAR. M and A are the multiplicative and the
251 additive factor for the real return value. */
254 process_assignment (gimple stmt
, gimple_stmt_iterator call
, tree
*m
,
255 tree
*a
, tree
*ass_var
)
257 tree op0
, op1
= NULL_TREE
, non_ass_var
= NULL_TREE
;
258 tree dest
= gimple_assign_lhs (stmt
);
259 enum tree_code code
= gimple_assign_rhs_code (stmt
);
260 enum gimple_rhs_class rhs_class
= get_gimple_rhs_class (code
);
261 tree src_var
= gimple_assign_rhs1 (stmt
);
263 /* See if this is a simple copy operation of an SSA name to the function
264 result. In that case we may have a simple tail call. Ignore type
265 conversions that can never produce extra code between the function
266 call and the function return. */
267 if ((rhs_class
== GIMPLE_SINGLE_RHS
|| gimple_assign_cast_p (stmt
))
268 && (TREE_CODE (src_var
) == SSA_NAME
))
270 /* Reject a tailcall if the type conversion might need
272 if (gimple_assign_cast_p (stmt
)
273 && TYPE_MODE (TREE_TYPE (dest
)) != TYPE_MODE (TREE_TYPE (src_var
)))
276 if (src_var
!= *ass_var
)
285 case GIMPLE_BINARY_RHS
:
286 op1
= gimple_assign_rhs2 (stmt
);
290 case GIMPLE_UNARY_RHS
:
291 op0
= gimple_assign_rhs1 (stmt
);
298 /* Accumulator optimizations will reverse the order of operations.
299 We can only do that for floating-point types if we're assuming
300 that addition and multiplication are associative. */
301 if (!flag_associative_math
)
302 if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl
))))
305 if (rhs_class
== GIMPLE_UNARY_RHS
)
307 else if (op0
== *ass_var
308 && (non_ass_var
= independent_of_stmt_p (op1
, stmt
, call
)))
310 else if (op1
== *ass_var
311 && (non_ass_var
= independent_of_stmt_p (op0
, stmt
, call
)))
329 *m
= build_minus_one_cst (TREE_TYPE (op0
));
335 *a
= fold_build1 (NEGATE_EXPR
, TREE_TYPE (non_ass_var
), non_ass_var
);
338 *m
= build_minus_one_cst (TREE_TYPE (non_ass_var
));
339 *a
= fold_build1 (NEGATE_EXPR
, TREE_TYPE (non_ass_var
), non_ass_var
);
345 /* TODO -- Handle POINTER_PLUS_EXPR. */
352 /* Propagate VAR through phis on edge E. */
355 propagate_through_phis (tree var
, edge e
)
357 basic_block dest
= e
->dest
;
358 gimple_stmt_iterator gsi
;
360 for (gsi
= gsi_start_phis (dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
362 gimple phi
= gsi_stmt (gsi
);
363 if (PHI_ARG_DEF_FROM_EDGE (phi
, e
) == var
)
364 return PHI_RESULT (phi
);
369 /* Finds tailcalls falling into basic block BB. The list of found tailcalls is
370 added to the start of RET. */
373 find_tail_calls (basic_block bb
, struct tailcall
**ret
)
375 tree ass_var
= NULL_TREE
, ret_var
, func
, param
;
376 gimple stmt
, call
= NULL
;
377 gimple_stmt_iterator gsi
, agsi
;
386 if (!single_succ_p (bb
))
389 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
391 stmt
= gsi_stmt (gsi
);
393 /* Ignore labels, returns, clobbers and debug stmts. */
394 if (gimple_code (stmt
) == GIMPLE_LABEL
395 || gimple_code (stmt
) == GIMPLE_RETURN
396 || gimple_clobber_p (stmt
)
397 || is_gimple_debug (stmt
))
400 /* Check for a call. */
401 if (is_gimple_call (stmt
))
404 ass_var
= gimple_call_lhs (stmt
);
408 /* If the statement references memory or volatile operands, fail. */
409 if (gimple_references_memory_p (stmt
)
410 || gimple_has_volatile_ops (stmt
))
417 /* Recurse to the predecessors. */
418 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
419 find_tail_calls (e
->src
, ret
);
424 /* If the LHS of our call is not just a simple register, we can't
425 transform this into a tail or sibling call. This situation happens,
426 in (e.g.) "*p = foo()" where foo returns a struct. In this case
427 we won't have a temporary here, but we need to carry out the side
428 effect anyway, so tailcall is impossible.
430 ??? In some situations (when the struct is returned in memory via
431 invisible argument) we could deal with this, e.g. by passing 'p'
432 itself as that argument to foo, but it's too early to do this here,
433 and expand_call() will not handle it anyway. If it ever can, then
434 we need to revisit this here, to allow that situation. */
435 if (ass_var
&& !is_gimple_reg (ass_var
))
438 /* We found the call, check whether it is suitable. */
439 tail_recursion
= false;
440 func
= gimple_call_fndecl (call
);
441 if (func
== current_function_decl
)
445 for (param
= DECL_ARGUMENTS (func
), idx
= 0;
446 param
&& idx
< gimple_call_num_args (call
);
447 param
= DECL_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 /* Make sure the tail invocation of this function does not refer
477 to local variables. */
478 FOR_EACH_LOCAL_DECL (cfun
, idx
, var
)
480 if (TREE_CODE (var
) != PARM_DECL
481 && auto_var_in_fn_p (var
, cfun
->decl
)
482 && (ref_maybe_used_by_stmt_p (call
, var
)
483 || call_may_clobber_ref_p (call
, var
)))
487 /* Now check the statements after the call. None of them has virtual
488 operands, so they may only depend on the call through its return
489 value. The return value should also be dependent on each of them,
490 since we are running after dce. */
498 tree tmp_a
= NULL_TREE
;
499 tree tmp_m
= NULL_TREE
;
502 while (gsi_end_p (agsi
))
504 ass_var
= propagate_through_phis (ass_var
, single_succ_edge (abb
));
505 abb
= single_succ (abb
);
506 agsi
= gsi_start_bb (abb
);
509 stmt
= gsi_stmt (agsi
);
511 if (gimple_code (stmt
) == GIMPLE_LABEL
)
514 if (gimple_code (stmt
) == GIMPLE_RETURN
)
517 if (gimple_clobber_p (stmt
))
520 if (is_gimple_debug (stmt
))
523 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
526 /* This is a gimple assign. */
527 if (! process_assignment (stmt
, gsi
, &tmp_m
, &tmp_a
, &ass_var
))
532 tree type
= TREE_TYPE (tmp_a
);
534 a
= fold_build2 (PLUS_EXPR
, type
, fold_convert (type
, a
), tmp_a
);
540 tree type
= TREE_TYPE (tmp_m
);
542 m
= fold_build2 (MULT_EXPR
, type
, fold_convert (type
, m
), tmp_m
);
547 a
= fold_build2 (MULT_EXPR
, type
, fold_convert (type
, a
), tmp_m
);
551 /* See if this is a tail call we can handle. */
552 ret_var
= gimple_return_retval (stmt
);
554 /* We may proceed if there either is no return value, or the return value
555 is identical to the call's return. */
557 && (ret_var
!= ass_var
))
560 /* If this is not a tail recursive call, we cannot handle addends or
562 if (!tail_recursion
&& (m
|| a
))
565 nw
= XNEW (struct tailcall
);
569 nw
->tail_recursion
= tail_recursion
;
578 /* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */
581 add_successor_phi_arg (edge e
, tree var
, tree phi_arg
)
583 gimple_stmt_iterator gsi
;
585 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
586 if (PHI_RESULT (gsi_stmt (gsi
)) == var
)
589 gcc_assert (!gsi_end_p (gsi
));
590 add_phi_arg (gsi_stmt (gsi
), phi_arg
, e
, UNKNOWN_LOCATION
);
593 /* Creates a GIMPLE statement which computes the operation specified by
594 CODE, ACC and OP1 to a new variable with name LABEL and inserts the
595 statement in the position specified by GSI. Returns the
596 tree node of the statement's result. */
599 adjust_return_value_with_ops (enum tree_code code
, const char *label
,
600 tree acc
, tree op1
, gimple_stmt_iterator gsi
)
603 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
604 tree result
= make_temp_ssa_name (ret_type
, NULL
, label
);
607 if (types_compatible_p (TREE_TYPE (acc
), TREE_TYPE (op1
)))
608 stmt
= gimple_build_assign_with_ops (code
, result
, acc
, op1
);
611 tree rhs
= fold_convert (TREE_TYPE (acc
),
614 fold_convert (TREE_TYPE (op1
), acc
),
616 rhs
= force_gimple_operand_gsi (&gsi
, rhs
,
617 false, NULL
, true, GSI_SAME_STMT
);
618 stmt
= gimple_build_assign (result
, rhs
);
621 gsi_insert_before (&gsi
, stmt
, GSI_NEW_STMT
);
625 /* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by
626 the computation specified by CODE and OP1 and insert the statement
627 at the position specified by GSI as a new statement. Returns new SSA name
628 of updated accumulator. */
631 update_accumulator_with_ops (enum tree_code code
, tree acc
, tree op1
,
632 gimple_stmt_iterator gsi
)
635 tree var
= copy_ssa_name (acc
, NULL
);
636 if (types_compatible_p (TREE_TYPE (acc
), TREE_TYPE (op1
)))
637 stmt
= gimple_build_assign_with_ops (code
, var
, acc
, op1
);
640 tree rhs
= fold_convert (TREE_TYPE (acc
),
643 fold_convert (TREE_TYPE (op1
), acc
),
645 rhs
= force_gimple_operand_gsi (&gsi
, rhs
,
646 false, NULL
, false, GSI_CONTINUE_LINKING
);
647 stmt
= gimple_build_assign (var
, rhs
);
649 gsi_insert_after (&gsi
, stmt
, GSI_NEW_STMT
);
653 /* Adjust the accumulator values according to A and M after GSI, and update
654 the phi nodes on edge BACK. */
657 adjust_accumulator_values (gimple_stmt_iterator gsi
, tree m
, tree a
, edge back
)
659 tree var
, a_acc_arg
, m_acc_arg
;
662 m
= force_gimple_operand_gsi (&gsi
, m
, true, NULL
, true, GSI_SAME_STMT
);
664 a
= force_gimple_operand_gsi (&gsi
, a
, true, NULL
, true, GSI_SAME_STMT
);
672 if (integer_onep (a
))
675 var
= adjust_return_value_with_ops (MULT_EXPR
, "acc_tmp", m_acc
,
681 a_acc_arg
= update_accumulator_with_ops (PLUS_EXPR
, a_acc
, var
, gsi
);
685 m_acc_arg
= update_accumulator_with_ops (MULT_EXPR
, m_acc
, m
, gsi
);
688 add_successor_phi_arg (back
, a_acc
, a_acc_arg
);
691 add_successor_phi_arg (back
, m_acc
, m_acc_arg
);
694 /* Adjust value of the return at the end of BB according to M and A
698 adjust_return_value (basic_block bb
, tree m
, tree a
)
701 gimple ret_stmt
= gimple_seq_last_stmt (bb_seq (bb
));
702 gimple_stmt_iterator gsi
= gsi_last_bb (bb
);
704 gcc_assert (gimple_code (ret_stmt
) == GIMPLE_RETURN
);
706 retval
= gimple_return_retval (ret_stmt
);
707 if (!retval
|| retval
== error_mark_node
)
711 retval
= adjust_return_value_with_ops (MULT_EXPR
, "mul_tmp", m_acc
, retval
,
714 retval
= adjust_return_value_with_ops (PLUS_EXPR
, "acc_tmp", a_acc
, retval
,
716 gimple_return_set_retval (ret_stmt
, retval
);
717 update_stmt (ret_stmt
);
720 /* Subtract COUNT and FREQUENCY from the basic block and it's
723 decrease_profile (basic_block bb
, gcov_type count
, int frequency
)
729 bb
->frequency
-= frequency
;
730 if (bb
->frequency
< 0)
732 if (!single_succ_p (bb
))
734 gcc_assert (!EDGE_COUNT (bb
->succs
));
737 e
= single_succ_edge (bb
);
743 /* Returns true if argument PARAM of the tail recursive call needs to be copied
744 when the call is eliminated. */
747 arg_needs_copy_p (tree param
)
751 if (!is_gimple_reg (param
))
754 /* Parameters that are only defined but never used need not be copied. */
755 def
= ssa_default_def (cfun
, param
);
762 /* Eliminates tail call described by T. TMP_VARS is a list of
763 temporary variables used to copy the function arguments. */
766 eliminate_tail_call (struct tailcall
*t
)
772 basic_block bb
, first
;
775 gimple_stmt_iterator gsi
;
778 stmt
= orig_stmt
= gsi_stmt (t
->call_gsi
);
779 bb
= gsi_bb (t
->call_gsi
);
781 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
783 fprintf (dump_file
, "Eliminated tail recursion in bb %d : ",
785 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
786 fprintf (dump_file
, "\n");
789 gcc_assert (is_gimple_call (stmt
));
791 first
= single_succ (ENTRY_BLOCK_PTR
);
793 /* Remove the code after call_gsi that will become unreachable. The
794 possibly unreachable code in other blocks is removed later in
798 while (!gsi_end_p (gsi
))
800 gimple t
= gsi_stmt (gsi
);
801 /* Do not remove the return statement, so that redirect_edge_and_branch
802 sees how the block ends. */
803 if (gimple_code (t
) == GIMPLE_RETURN
)
806 gsi_remove (&gsi
, true);
810 /* Number of executions of function has reduced by the tailcall. */
811 e
= single_succ_edge (gsi_bb (t
->call_gsi
));
812 decrease_profile (EXIT_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
813 decrease_profile (ENTRY_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
814 if (e
->dest
!= EXIT_BLOCK_PTR
)
815 decrease_profile (e
->dest
, e
->count
, EDGE_FREQUENCY (e
));
817 /* Replace the call by a jump to the start of function. */
818 e
= redirect_edge_and_branch (single_succ_edge (gsi_bb (t
->call_gsi
)),
821 PENDING_STMT (e
) = NULL
;
823 /* Add phi node entries for arguments. The ordering of the phi nodes should
824 be the same as the ordering of the arguments. */
825 for (param
= DECL_ARGUMENTS (current_function_decl
),
826 idx
= 0, gsi
= gsi_start_phis (first
);
828 param
= DECL_CHAIN (param
), idx
++)
830 if (!arg_needs_copy_p (param
))
833 arg
= gimple_call_arg (stmt
, idx
);
834 phi
= gsi_stmt (gsi
);
835 gcc_assert (param
== SSA_NAME_VAR (PHI_RESULT (phi
)));
837 add_phi_arg (phi
, arg
, e
, gimple_location (stmt
));
841 /* Update the values of accumulators. */
842 adjust_accumulator_values (t
->call_gsi
, t
->mult
, t
->add
, e
);
844 call
= gsi_stmt (t
->call_gsi
);
845 rslt
= gimple_call_lhs (call
);
846 if (rslt
!= NULL_TREE
)
848 /* Result of the call will no longer be defined. So adjust the
849 SSA_NAME_DEF_STMT accordingly. */
850 SSA_NAME_DEF_STMT (rslt
) = gimple_build_nop ();
853 gsi_remove (&t
->call_gsi
, true);
857 /* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also
858 mark the tailcalls for the sibcall optimization. */
861 optimize_tail_call (struct tailcall
*t
, bool opt_tailcalls
)
863 if (t
->tail_recursion
)
865 eliminate_tail_call (t
);
871 gimple stmt
= gsi_stmt (t
->call_gsi
);
873 gimple_call_set_tail (stmt
, true);
874 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
876 fprintf (dump_file
, "Found tail call ");
877 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
878 fprintf (dump_file
, " in bb %i\n", (gsi_bb (t
->call_gsi
))->index
);
885 /* Creates a tail-call accumulator of the same type as the return type of the
886 current function. LABEL is the name used to creating the temporary
887 variable for the accumulator. The accumulator will be inserted in the
888 phis of a basic block BB with single predecessor with an initial value
889 INIT converted to the current function return type. */
892 create_tailcall_accumulator (const char *label
, basic_block bb
, tree init
)
894 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
895 tree tmp
= make_temp_ssa_name (ret_type
, NULL
, label
);
898 phi
= create_phi_node (tmp
, bb
);
899 /* RET_TYPE can be a float when -ffast-maths is enabled. */
900 add_phi_arg (phi
, fold_convert (ret_type
, init
), single_pred_edge (bb
),
902 return PHI_RESULT (phi
);
905 /* Optimizes tail calls in the function, turning the tail recursion
909 tree_optimize_tail_calls_1 (bool opt_tailcalls
)
912 bool phis_constructed
= false;
913 struct tailcall
*tailcalls
= NULL
, *act
, *next
;
914 bool changed
= false;
915 basic_block first
= single_succ (ENTRY_BLOCK_PTR
);
920 if (!suitable_for_tail_opt_p ())
923 opt_tailcalls
= suitable_for_tail_call_opt_p ();
925 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
927 /* Only traverse the normal exits, i.e. those that end with return
929 stmt
= last_stmt (e
->src
);
932 && gimple_code (stmt
) == GIMPLE_RETURN
)
933 find_tail_calls (e
->src
, &tailcalls
);
936 /* Construct the phi nodes and accumulators if necessary. */
937 a_acc
= m_acc
= NULL_TREE
;
938 for (act
= tailcalls
; act
; act
= act
->next
)
940 if (!act
->tail_recursion
)
943 if (!phis_constructed
)
945 /* Ensure that there is only one predecessor of the block
946 or if there are existing degenerate PHI nodes. */
947 if (!single_pred_p (first
)
948 || !gimple_seq_empty_p (phi_nodes (first
)))
949 first
= split_edge (single_succ_edge (ENTRY_BLOCK_PTR
));
951 /* Copy the args if needed. */
952 for (param
= DECL_ARGUMENTS (current_function_decl
);
954 param
= DECL_CHAIN (param
))
955 if (arg_needs_copy_p (param
))
957 tree name
= ssa_default_def (cfun
, param
);
958 tree new_name
= make_ssa_name (param
, SSA_NAME_DEF_STMT (name
));
961 set_ssa_default_def (cfun
, param
, new_name
);
962 phi
= create_phi_node (name
, first
);
963 add_phi_arg (phi
, new_name
, single_pred_edge (first
),
964 EXPR_LOCATION (param
));
966 phis_constructed
= true;
969 if (act
->add
&& !a_acc
)
970 a_acc
= create_tailcall_accumulator ("add_acc", first
,
973 if (act
->mult
&& !m_acc
)
974 m_acc
= create_tailcall_accumulator ("mult_acc", first
,
980 /* When the tail call elimination using accumulators is performed,
981 statements adding the accumulated value are inserted at all exits.
982 This turns all other tail calls to non-tail ones. */
983 opt_tailcalls
= false;
986 for (; tailcalls
; tailcalls
= next
)
988 next
= tailcalls
->next
;
989 changed
|= optimize_tail_call (tailcalls
, opt_tailcalls
);
995 /* Modify the remaining return statements. */
996 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
998 stmt
= last_stmt (e
->src
);
1001 && gimple_code (stmt
) == GIMPLE_RETURN
)
1002 adjust_return_value (e
->src
, m_acc
, a_acc
);
1008 /* We may have created new loops. Make them magically appear. */
1010 loops_state_set (LOOPS_NEED_FIXUP
);
1011 free_dominance_info (CDI_DOMINATORS
);
1014 /* Add phi nodes for the virtual operands defined in the function to the
1015 header of the loop created by tail recursion elimination. Do so
1016 by triggering the SSA renamer. */
1017 if (phis_constructed
)
1018 mark_virtual_operands_for_renaming (cfun
);
1021 return TODO_cleanup_cfg
| TODO_update_ssa_only_virtuals
;
1026 execute_tail_recursion (void)
1028 return tree_optimize_tail_calls_1 (false);
1032 gate_tail_calls (void)
1034 return flag_optimize_sibling_calls
!= 0 && dbg_cnt (tail_call
);
1038 execute_tail_calls (void)
1040 return tree_optimize_tail_calls_1 (true);
1045 const pass_data pass_data_tail_recursion
=
1047 GIMPLE_PASS
, /* type */
1049 OPTGROUP_NONE
, /* optinfo_flags */
1050 true, /* has_gate */
1051 true, /* has_execute */
1052 TV_NONE
, /* tv_id */
1053 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1054 0, /* properties_provided */
1055 0, /* properties_destroyed */
1056 0, /* todo_flags_start */
1057 TODO_verify_ssa
, /* todo_flags_finish */
1060 class pass_tail_recursion
: public gimple_opt_pass
1063 pass_tail_recursion(gcc::context
*ctxt
)
1064 : gimple_opt_pass(pass_data_tail_recursion
, ctxt
)
1067 /* opt_pass methods: */
1068 opt_pass
* clone () { return new pass_tail_recursion (ctxt_
); }
1069 bool gate () { return gate_tail_calls (); }
1070 unsigned int execute () { return execute_tail_recursion (); }
1072 }; // class pass_tail_recursion
1077 make_pass_tail_recursion (gcc::context
*ctxt
)
1079 return new pass_tail_recursion (ctxt
);
1084 const pass_data pass_data_tail_calls
=
1086 GIMPLE_PASS
, /* type */
1088 OPTGROUP_NONE
, /* optinfo_flags */
1089 true, /* has_gate */
1090 true, /* has_execute */
1091 TV_NONE
, /* tv_id */
1092 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1093 0, /* properties_provided */
1094 0, /* properties_destroyed */
1095 0, /* todo_flags_start */
1096 TODO_verify_ssa
, /* todo_flags_finish */
1099 class pass_tail_calls
: public gimple_opt_pass
1102 pass_tail_calls(gcc::context
*ctxt
)
1103 : gimple_opt_pass(pass_data_tail_calls
, ctxt
)
1106 /* opt_pass methods: */
1107 bool gate () { return gate_tail_calls (); }
1108 unsigned int execute () { return execute_tail_calls (); }
1110 }; // class pass_tail_calls
1115 make_pass_tail_calls (gcc::context
*ctxt
)
1117 return new pass_tail_calls (ctxt
);