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"
29 #include "gimple-pretty-print.h"
31 #include "tree-pass.h"
33 #include "langhooks.h"
37 #include "common/common-target.h"
38 #include "ipa-utils.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)
138 /* Returns false when the function is not suitable for tail call optimization
139 from some reason (e.g. if it takes variable number of arguments).
140 This test must pass in addition to suitable_for_tail_opt_p in order to make
141 tail call discovery happen. */
144 suitable_for_tail_call_opt_p (void)
148 /* alloca (until we have stack slot life analysis) inhibits
149 sibling call optimizations, but not tail recursion. */
150 if (cfun
->calls_alloca
)
153 /* If we are using sjlj exceptions, we may need to add a call to
154 _Unwind_SjLj_Unregister at exit of the function. Which means
155 that we cannot do any sibcall transformations. */
156 if (targetm_common
.except_unwind_info (&global_options
) == UI_SJLJ
157 && current_function_has_exception_handlers ())
160 /* Any function that calls setjmp might have longjmp called from
161 any called function. ??? We really should represent this
162 properly in the CFG so that this needn't be special cased. */
163 if (cfun
->calls_setjmp
)
166 /* ??? It is OK if the argument of a function is taken in some cases,
167 but not in all cases. See PR15387 and PR19616. Revisit for 4.1. */
168 for (param
= DECL_ARGUMENTS (current_function_decl
);
170 param
= DECL_CHAIN (param
))
171 if (TREE_ADDRESSABLE (param
))
177 /* Checks whether the expression EXPR in stmt AT is independent of the
178 statement pointed to by GSI (in a sense that we already know EXPR's value
179 at GSI). We use the fact that we are only called from the chain of
180 basic blocks that have only single successor. Returns the expression
181 containing the value of EXPR at GSI. */
184 independent_of_stmt_p (tree expr
, gimple at
, gimple_stmt_iterator gsi
)
186 basic_block bb
, call_bb
, at_bb
;
190 if (is_gimple_min_invariant (expr
))
193 if (TREE_CODE (expr
) != SSA_NAME
)
196 /* Mark the blocks in the chain leading to the end. */
197 at_bb
= gimple_bb (at
);
198 call_bb
= gimple_bb (gsi_stmt (gsi
));
199 for (bb
= call_bb
; bb
!= at_bb
; bb
= single_succ (bb
))
205 at
= SSA_NAME_DEF_STMT (expr
);
208 /* The default definition or defined before the chain. */
214 for (; !gsi_end_p (gsi
); gsi_next (&gsi
))
215 if (gsi_stmt (gsi
) == at
)
218 if (!gsi_end_p (gsi
))
223 if (gimple_code (at
) != GIMPLE_PHI
)
229 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
234 expr
= PHI_ARG_DEF_FROM_EDGE (at
, e
);
235 if (TREE_CODE (expr
) != SSA_NAME
)
237 /* The value is a constant. */
242 /* Unmark the blocks. */
243 for (bb
= call_bb
; bb
!= at_bb
; bb
= single_succ (bb
))
250 /* Simulates the effect of an assignment STMT on the return value of the tail
251 recursive CALL passed in ASS_VAR. M and A are the multiplicative and the
252 additive factor for the real return value. */
255 process_assignment (gimple stmt
, gimple_stmt_iterator call
, tree
*m
,
256 tree
*a
, tree
*ass_var
)
258 tree op0
, op1
= NULL_TREE
, non_ass_var
= NULL_TREE
;
259 tree dest
= gimple_assign_lhs (stmt
);
260 enum tree_code code
= gimple_assign_rhs_code (stmt
);
261 enum gimple_rhs_class rhs_class
= get_gimple_rhs_class (code
);
262 tree src_var
= gimple_assign_rhs1 (stmt
);
264 /* See if this is a simple copy operation of an SSA name to the function
265 result. In that case we may have a simple tail call. Ignore type
266 conversions that can never produce extra code between the function
267 call and the function return. */
268 if ((rhs_class
== GIMPLE_SINGLE_RHS
|| gimple_assign_cast_p (stmt
))
269 && (TREE_CODE (src_var
) == SSA_NAME
))
271 /* Reject a tailcall if the type conversion might need
273 if (gimple_assign_cast_p (stmt
)
274 && TYPE_MODE (TREE_TYPE (dest
)) != TYPE_MODE (TREE_TYPE (src_var
)))
277 if (src_var
!= *ass_var
)
286 case GIMPLE_BINARY_RHS
:
287 op1
= gimple_assign_rhs2 (stmt
);
291 case GIMPLE_UNARY_RHS
:
292 op0
= gimple_assign_rhs1 (stmt
);
299 /* Accumulator optimizations will reverse the order of operations.
300 We can only do that for floating-point types if we're assuming
301 that addition and multiplication are associative. */
302 if (!flag_associative_math
)
303 if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl
))))
306 if (rhs_class
== GIMPLE_UNARY_RHS
)
308 else if (op0
== *ass_var
309 && (non_ass_var
= independent_of_stmt_p (op1
, stmt
, call
)))
311 else if (op1
== *ass_var
312 && (non_ass_var
= independent_of_stmt_p (op0
, stmt
, call
)))
324 case POINTER_PLUS_EXPR
:
337 *m
= build_minus_one_cst (TREE_TYPE (op0
));
343 *a
= fold_build1 (NEGATE_EXPR
, TREE_TYPE (non_ass_var
), non_ass_var
);
346 *m
= build_minus_one_cst (TREE_TYPE (non_ass_var
));
347 *a
= fold_build1 (NEGATE_EXPR
, TREE_TYPE (non_ass_var
), non_ass_var
);
353 /* TODO -- Handle POINTER_PLUS_EXPR. */
360 /* Propagate VAR through phis on edge E. */
363 propagate_through_phis (tree var
, edge e
)
365 basic_block dest
= e
->dest
;
366 gimple_stmt_iterator gsi
;
368 for (gsi
= gsi_start_phis (dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
370 gimple phi
= gsi_stmt (gsi
);
371 if (PHI_ARG_DEF_FROM_EDGE (phi
, e
) == var
)
372 return PHI_RESULT (phi
);
377 /* Finds tailcalls falling into basic block BB. The list of found tailcalls is
378 added to the start of RET. */
381 find_tail_calls (basic_block bb
, struct tailcall
**ret
)
383 tree ass_var
= NULL_TREE
, ret_var
, func
, param
;
384 gimple stmt
, call
= NULL
;
385 gimple_stmt_iterator gsi
, agsi
;
394 if (!single_succ_p (bb
))
397 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
399 stmt
= gsi_stmt (gsi
);
401 /* Ignore labels, returns, clobbers and debug stmts. */
402 if (gimple_code (stmt
) == GIMPLE_LABEL
403 || gimple_code (stmt
) == GIMPLE_RETURN
404 || gimple_clobber_p (stmt
)
405 || is_gimple_debug (stmt
))
408 /* Check for a call. */
409 if (is_gimple_call (stmt
))
412 ass_var
= gimple_call_lhs (stmt
);
416 /* If the statement references memory or volatile operands, fail. */
417 if (gimple_references_memory_p (stmt
)
418 || gimple_has_volatile_ops (stmt
))
425 /* Recurse to the predecessors. */
426 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
427 find_tail_calls (e
->src
, ret
);
432 /* If the LHS of our call is not just a simple register, we can't
433 transform this into a tail or sibling call. This situation happens,
434 in (e.g.) "*p = foo()" where foo returns a struct. In this case
435 we won't have a temporary here, but we need to carry out the side
436 effect anyway, so tailcall is impossible.
438 ??? In some situations (when the struct is returned in memory via
439 invisible argument) we could deal with this, e.g. by passing 'p'
440 itself as that argument to foo, but it's too early to do this here,
441 and expand_call() will not handle it anyway. If it ever can, then
442 we need to revisit this here, to allow that situation. */
443 if (ass_var
&& !is_gimple_reg (ass_var
))
446 /* We found the call, check whether it is suitable. */
447 tail_recursion
= false;
448 func
= gimple_call_fndecl (call
);
449 if (func
&& recursive_call_p (current_function_decl
, func
))
453 for (param
= DECL_ARGUMENTS (func
), idx
= 0;
454 param
&& idx
< gimple_call_num_args (call
);
455 param
= DECL_CHAIN (param
), idx
++)
457 arg
= gimple_call_arg (call
, idx
);
460 /* Make sure there are no problems with copying. The parameter
461 have a copyable type and the two arguments must have reasonably
462 equivalent types. The latter requirement could be relaxed if
463 we emitted a suitable type conversion statement. */
464 if (!is_gimple_reg_type (TREE_TYPE (param
))
465 || !useless_type_conversion_p (TREE_TYPE (param
),
469 /* The parameter should be a real operand, so that phi node
470 created for it at the start of the function has the meaning
471 of copying the value. This test implies is_gimple_reg_type
472 from the previous condition, however this one could be
473 relaxed by being more careful with copying the new value
474 of the parameter (emitting appropriate GIMPLE_ASSIGN and
475 updating the virtual operands). */
476 if (!is_gimple_reg (param
))
480 if (idx
== gimple_call_num_args (call
) && !param
)
481 tail_recursion
= true;
484 /* Make sure the tail invocation of this function does not refer
485 to local variables. */
486 FOR_EACH_LOCAL_DECL (cfun
, idx
, var
)
488 if (TREE_CODE (var
) != PARM_DECL
489 && auto_var_in_fn_p (var
, cfun
->decl
)
490 && (ref_maybe_used_by_stmt_p (call
, var
)
491 || call_may_clobber_ref_p (call
, var
)))
495 /* Now check the statements after the call. None of them has virtual
496 operands, so they may only depend on the call through its return
497 value. The return value should also be dependent on each of them,
498 since we are running after dce. */
506 tree tmp_a
= NULL_TREE
;
507 tree tmp_m
= NULL_TREE
;
510 while (gsi_end_p (agsi
))
512 ass_var
= propagate_through_phis (ass_var
, single_succ_edge (abb
));
513 abb
= single_succ (abb
);
514 agsi
= gsi_start_bb (abb
);
517 stmt
= gsi_stmt (agsi
);
519 if (gimple_code (stmt
) == GIMPLE_LABEL
)
522 if (gimple_code (stmt
) == GIMPLE_RETURN
)
525 if (gimple_clobber_p (stmt
))
528 if (is_gimple_debug (stmt
))
531 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
534 /* This is a gimple assign. */
535 if (! process_assignment (stmt
, gsi
, &tmp_m
, &tmp_a
, &ass_var
))
540 tree type
= TREE_TYPE (tmp_a
);
542 a
= fold_build2 (PLUS_EXPR
, type
, fold_convert (type
, a
), tmp_a
);
548 tree type
= TREE_TYPE (tmp_m
);
550 m
= fold_build2 (MULT_EXPR
, type
, fold_convert (type
, m
), tmp_m
);
555 a
= fold_build2 (MULT_EXPR
, type
, fold_convert (type
, a
), tmp_m
);
559 /* See if this is a tail call we can handle. */
560 ret_var
= gimple_return_retval (stmt
);
562 /* We may proceed if there either is no return value, or the return value
563 is identical to the call's return. */
565 && (ret_var
!= ass_var
))
568 /* If this is not a tail recursive call, we cannot handle addends or
570 if (!tail_recursion
&& (m
|| a
))
573 /* For pointers only allow additions. */
574 if (m
&& POINTER_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl
))))
577 nw
= XNEW (struct tailcall
);
581 nw
->tail_recursion
= tail_recursion
;
590 /* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */
593 add_successor_phi_arg (edge e
, tree var
, tree phi_arg
)
595 gimple_stmt_iterator gsi
;
597 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
598 if (PHI_RESULT (gsi_stmt (gsi
)) == var
)
601 gcc_assert (!gsi_end_p (gsi
));
602 add_phi_arg (gsi_stmt (gsi
), phi_arg
, e
, UNKNOWN_LOCATION
);
605 /* Creates a GIMPLE statement which computes the operation specified by
606 CODE, ACC and OP1 to a new variable with name LABEL and inserts the
607 statement in the position specified by GSI. Returns the
608 tree node of the statement's result. */
611 adjust_return_value_with_ops (enum tree_code code
, const char *label
,
612 tree acc
, tree op1
, gimple_stmt_iterator gsi
)
615 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
616 tree result
= make_temp_ssa_name (ret_type
, NULL
, label
);
619 if (POINTER_TYPE_P (ret_type
))
621 gcc_assert (code
== PLUS_EXPR
&& TREE_TYPE (acc
) == sizetype
);
622 code
= POINTER_PLUS_EXPR
;
624 if (types_compatible_p (TREE_TYPE (acc
), TREE_TYPE (op1
))
625 && code
!= POINTER_PLUS_EXPR
)
626 stmt
= gimple_build_assign_with_ops (code
, result
, acc
, op1
);
630 if (code
== POINTER_PLUS_EXPR
)
631 tem
= fold_build2 (code
, TREE_TYPE (op1
), op1
, acc
);
633 tem
= fold_build2 (code
, TREE_TYPE (op1
),
634 fold_convert (TREE_TYPE (op1
), acc
), op1
);
635 tree rhs
= fold_convert (ret_type
, tem
);
636 rhs
= force_gimple_operand_gsi (&gsi
, rhs
,
637 false, NULL
, true, GSI_SAME_STMT
);
638 stmt
= gimple_build_assign (result
, rhs
);
641 gsi_insert_before (&gsi
, stmt
, GSI_NEW_STMT
);
645 /* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by
646 the computation specified by CODE and OP1 and insert the statement
647 at the position specified by GSI as a new statement. Returns new SSA name
648 of updated accumulator. */
651 update_accumulator_with_ops (enum tree_code code
, tree acc
, tree op1
,
652 gimple_stmt_iterator gsi
)
655 tree var
= copy_ssa_name (acc
, NULL
);
656 if (types_compatible_p (TREE_TYPE (acc
), TREE_TYPE (op1
)))
657 stmt
= gimple_build_assign_with_ops (code
, var
, acc
, op1
);
660 tree rhs
= fold_convert (TREE_TYPE (acc
),
663 fold_convert (TREE_TYPE (op1
), acc
),
665 rhs
= force_gimple_operand_gsi (&gsi
, rhs
,
666 false, NULL
, false, GSI_CONTINUE_LINKING
);
667 stmt
= gimple_build_assign (var
, rhs
);
669 gsi_insert_after (&gsi
, stmt
, GSI_NEW_STMT
);
673 /* Adjust the accumulator values according to A and M after GSI, and update
674 the phi nodes on edge BACK. */
677 adjust_accumulator_values (gimple_stmt_iterator gsi
, tree m
, tree a
, edge back
)
679 tree var
, a_acc_arg
, m_acc_arg
;
682 m
= force_gimple_operand_gsi (&gsi
, m
, true, NULL
, true, GSI_SAME_STMT
);
684 a
= force_gimple_operand_gsi (&gsi
, a
, true, NULL
, true, GSI_SAME_STMT
);
692 if (integer_onep (a
))
695 var
= adjust_return_value_with_ops (MULT_EXPR
, "acc_tmp", m_acc
,
701 a_acc_arg
= update_accumulator_with_ops (PLUS_EXPR
, a_acc
, var
, gsi
);
705 m_acc_arg
= update_accumulator_with_ops (MULT_EXPR
, m_acc
, m
, gsi
);
708 add_successor_phi_arg (back
, a_acc
, a_acc_arg
);
711 add_successor_phi_arg (back
, m_acc
, m_acc_arg
);
714 /* Adjust value of the return at the end of BB according to M and A
718 adjust_return_value (basic_block bb
, tree m
, tree a
)
721 gimple ret_stmt
= gimple_seq_last_stmt (bb_seq (bb
));
722 gimple_stmt_iterator gsi
= gsi_last_bb (bb
);
724 gcc_assert (gimple_code (ret_stmt
) == GIMPLE_RETURN
);
726 retval
= gimple_return_retval (ret_stmt
);
727 if (!retval
|| retval
== error_mark_node
)
731 retval
= adjust_return_value_with_ops (MULT_EXPR
, "mul_tmp", m_acc
, retval
,
734 retval
= adjust_return_value_with_ops (PLUS_EXPR
, "acc_tmp", a_acc
, retval
,
736 gimple_return_set_retval (ret_stmt
, retval
);
737 update_stmt (ret_stmt
);
740 /* Subtract COUNT and FREQUENCY from the basic block and it's
743 decrease_profile (basic_block bb
, gcov_type count
, int frequency
)
749 bb
->frequency
-= frequency
;
750 if (bb
->frequency
< 0)
752 if (!single_succ_p (bb
))
754 gcc_assert (!EDGE_COUNT (bb
->succs
));
757 e
= single_succ_edge (bb
);
763 /* Returns true if argument PARAM of the tail recursive call needs to be copied
764 when the call is eliminated. */
767 arg_needs_copy_p (tree param
)
771 if (!is_gimple_reg (param
))
774 /* Parameters that are only defined but never used need not be copied. */
775 def
= ssa_default_def (cfun
, param
);
782 /* Eliminates tail call described by T. TMP_VARS is a list of
783 temporary variables used to copy the function arguments. */
786 eliminate_tail_call (struct tailcall
*t
)
792 basic_block bb
, first
;
795 gimple_stmt_iterator gsi
;
798 stmt
= orig_stmt
= gsi_stmt (t
->call_gsi
);
799 bb
= gsi_bb (t
->call_gsi
);
801 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
803 fprintf (dump_file
, "Eliminated tail recursion in bb %d : ",
805 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
806 fprintf (dump_file
, "\n");
809 gcc_assert (is_gimple_call (stmt
));
811 first
= single_succ (ENTRY_BLOCK_PTR
);
813 /* Remove the code after call_gsi that will become unreachable. The
814 possibly unreachable code in other blocks is removed later in
818 while (!gsi_end_p (gsi
))
820 gimple t
= gsi_stmt (gsi
);
821 /* Do not remove the return statement, so that redirect_edge_and_branch
822 sees how the block ends. */
823 if (gimple_code (t
) == GIMPLE_RETURN
)
826 gsi_remove (&gsi
, true);
830 /* Number of executions of function has reduced by the tailcall. */
831 e
= single_succ_edge (gsi_bb (t
->call_gsi
));
832 decrease_profile (EXIT_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
833 decrease_profile (ENTRY_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
834 if (e
->dest
!= EXIT_BLOCK_PTR
)
835 decrease_profile (e
->dest
, e
->count
, EDGE_FREQUENCY (e
));
837 /* Replace the call by a jump to the start of function. */
838 e
= redirect_edge_and_branch (single_succ_edge (gsi_bb (t
->call_gsi
)),
841 PENDING_STMT (e
) = NULL
;
843 /* Add phi node entries for arguments. The ordering of the phi nodes should
844 be the same as the ordering of the arguments. */
845 for (param
= DECL_ARGUMENTS (current_function_decl
),
846 idx
= 0, gsi
= gsi_start_phis (first
);
848 param
= DECL_CHAIN (param
), idx
++)
850 if (!arg_needs_copy_p (param
))
853 arg
= gimple_call_arg (stmt
, idx
);
854 phi
= gsi_stmt (gsi
);
855 gcc_assert (param
== SSA_NAME_VAR (PHI_RESULT (phi
)));
857 add_phi_arg (phi
, arg
, e
, gimple_location (stmt
));
861 /* Update the values of accumulators. */
862 adjust_accumulator_values (t
->call_gsi
, t
->mult
, t
->add
, e
);
864 call
= gsi_stmt (t
->call_gsi
);
865 rslt
= gimple_call_lhs (call
);
866 if (rslt
!= NULL_TREE
)
868 /* Result of the call will no longer be defined. So adjust the
869 SSA_NAME_DEF_STMT accordingly. */
870 SSA_NAME_DEF_STMT (rslt
) = gimple_build_nop ();
873 gsi_remove (&t
->call_gsi
, true);
877 /* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also
878 mark the tailcalls for the sibcall optimization. */
881 optimize_tail_call (struct tailcall
*t
, bool opt_tailcalls
)
883 if (t
->tail_recursion
)
885 eliminate_tail_call (t
);
891 gimple stmt
= gsi_stmt (t
->call_gsi
);
893 gimple_call_set_tail (stmt
, true);
894 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
896 fprintf (dump_file
, "Found tail call ");
897 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
898 fprintf (dump_file
, " in bb %i\n", (gsi_bb (t
->call_gsi
))->index
);
905 /* Creates a tail-call accumulator of the same type as the return type of the
906 current function. LABEL is the name used to creating the temporary
907 variable for the accumulator. The accumulator will be inserted in the
908 phis of a basic block BB with single predecessor with an initial value
909 INIT converted to the current function return type. */
912 create_tailcall_accumulator (const char *label
, basic_block bb
, tree init
)
914 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
915 if (POINTER_TYPE_P (ret_type
))
918 tree tmp
= make_temp_ssa_name (ret_type
, NULL
, label
);
921 phi
= create_phi_node (tmp
, bb
);
922 /* RET_TYPE can be a float when -ffast-maths is enabled. */
923 add_phi_arg (phi
, fold_convert (ret_type
, init
), single_pred_edge (bb
),
925 return PHI_RESULT (phi
);
928 /* Optimizes tail calls in the function, turning the tail recursion
932 tree_optimize_tail_calls_1 (bool opt_tailcalls
)
935 bool phis_constructed
= false;
936 struct tailcall
*tailcalls
= NULL
, *act
, *next
;
937 bool changed
= false;
938 basic_block first
= single_succ (ENTRY_BLOCK_PTR
);
943 if (!suitable_for_tail_opt_p ())
946 opt_tailcalls
= suitable_for_tail_call_opt_p ();
948 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
950 /* Only traverse the normal exits, i.e. those that end with return
952 stmt
= last_stmt (e
->src
);
955 && gimple_code (stmt
) == GIMPLE_RETURN
)
956 find_tail_calls (e
->src
, &tailcalls
);
959 /* Construct the phi nodes and accumulators if necessary. */
960 a_acc
= m_acc
= NULL_TREE
;
961 for (act
= tailcalls
; act
; act
= act
->next
)
963 if (!act
->tail_recursion
)
966 if (!phis_constructed
)
968 /* Ensure that there is only one predecessor of the block
969 or if there are existing degenerate PHI nodes. */
970 if (!single_pred_p (first
)
971 || !gimple_seq_empty_p (phi_nodes (first
)))
972 first
= split_edge (single_succ_edge (ENTRY_BLOCK_PTR
));
974 /* Copy the args if needed. */
975 for (param
= DECL_ARGUMENTS (current_function_decl
);
977 param
= DECL_CHAIN (param
))
978 if (arg_needs_copy_p (param
))
980 tree name
= ssa_default_def (cfun
, param
);
981 tree new_name
= make_ssa_name (param
, SSA_NAME_DEF_STMT (name
));
984 set_ssa_default_def (cfun
, param
, new_name
);
985 phi
= create_phi_node (name
, first
);
986 add_phi_arg (phi
, new_name
, single_pred_edge (first
),
987 EXPR_LOCATION (param
));
989 phis_constructed
= true;
992 if (act
->add
&& !a_acc
)
993 a_acc
= create_tailcall_accumulator ("add_acc", first
,
996 if (act
->mult
&& !m_acc
)
997 m_acc
= create_tailcall_accumulator ("mult_acc", first
,
1003 /* When the tail call elimination using accumulators is performed,
1004 statements adding the accumulated value are inserted at all exits.
1005 This turns all other tail calls to non-tail ones. */
1006 opt_tailcalls
= false;
1009 for (; tailcalls
; tailcalls
= next
)
1011 next
= tailcalls
->next
;
1012 changed
|= optimize_tail_call (tailcalls
, opt_tailcalls
);
1018 /* Modify the remaining return statements. */
1019 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
1021 stmt
= last_stmt (e
->src
);
1024 && gimple_code (stmt
) == GIMPLE_RETURN
)
1025 adjust_return_value (e
->src
, m_acc
, a_acc
);
1031 /* We may have created new loops. Make them magically appear. */
1033 loops_state_set (LOOPS_NEED_FIXUP
);
1034 free_dominance_info (CDI_DOMINATORS
);
1037 /* Add phi nodes for the virtual operands defined in the function to the
1038 header of the loop created by tail recursion elimination. Do so
1039 by triggering the SSA renamer. */
1040 if (phis_constructed
)
1041 mark_virtual_operands_for_renaming (cfun
);
1044 return TODO_cleanup_cfg
| TODO_update_ssa_only_virtuals
;
1049 execute_tail_recursion (void)
1051 return tree_optimize_tail_calls_1 (false);
1055 gate_tail_calls (void)
1057 return flag_optimize_sibling_calls
!= 0 && dbg_cnt (tail_call
);
1061 execute_tail_calls (void)
1063 return tree_optimize_tail_calls_1 (true);
1068 const pass_data pass_data_tail_recursion
=
1070 GIMPLE_PASS
, /* type */
1072 OPTGROUP_NONE
, /* optinfo_flags */
1073 true, /* has_gate */
1074 true, /* has_execute */
1075 TV_NONE
, /* tv_id */
1076 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1077 0, /* properties_provided */
1078 0, /* properties_destroyed */
1079 0, /* todo_flags_start */
1080 TODO_verify_ssa
, /* todo_flags_finish */
1083 class pass_tail_recursion
: public gimple_opt_pass
1086 pass_tail_recursion(gcc::context
*ctxt
)
1087 : gimple_opt_pass(pass_data_tail_recursion
, ctxt
)
1090 /* opt_pass methods: */
1091 opt_pass
* clone () { return new pass_tail_recursion (ctxt_
); }
1092 bool gate () { return gate_tail_calls (); }
1093 unsigned int execute () { return execute_tail_recursion (); }
1095 }; // class pass_tail_recursion
1100 make_pass_tail_recursion (gcc::context
*ctxt
)
1102 return new pass_tail_recursion (ctxt
);
1107 const pass_data pass_data_tail_calls
=
1109 GIMPLE_PASS
, /* type */
1111 OPTGROUP_NONE
, /* optinfo_flags */
1112 true, /* has_gate */
1113 true, /* has_execute */
1114 TV_NONE
, /* tv_id */
1115 ( PROP_cfg
| PROP_ssa
), /* properties_required */
1116 0, /* properties_provided */
1117 0, /* properties_destroyed */
1118 0, /* todo_flags_start */
1119 TODO_verify_ssa
, /* todo_flags_finish */
1122 class pass_tail_calls
: public gimple_opt_pass
1125 pass_tail_calls(gcc::context
*ctxt
)
1126 : gimple_opt_pass(pass_data_tail_calls
, ctxt
)
1129 /* opt_pass methods: */
1130 bool gate () { return gate_tail_calls (); }
1131 unsigned int execute () { return execute_tail_calls (); }
1133 }; // class pass_tail_calls
1138 make_pass_tail_calls (gcc::context
*ctxt
)
1140 return new pass_tail_calls (ctxt
);