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
)))
338 /* TODO -- Handle other codes (NEGATE_EXPR, MINUS_EXPR,
339 POINTER_PLUS_EXPR). */
346 /* Propagate VAR through phis on edge E. */
349 propagate_through_phis (tree var
, edge e
)
351 basic_block dest
= e
->dest
;
352 gimple_stmt_iterator gsi
;
354 for (gsi
= gsi_start_phis (dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
356 gimple phi
= gsi_stmt (gsi
);
357 if (PHI_ARG_DEF_FROM_EDGE (phi
, e
) == var
)
358 return PHI_RESULT (phi
);
363 /* Finds tailcalls falling into basic block BB. The list of found tailcalls is
364 added to the start of RET. */
367 find_tail_calls (basic_block bb
, struct tailcall
**ret
)
369 tree ass_var
= NULL_TREE
, ret_var
, func
, param
;
370 gimple stmt
, call
= NULL
;
371 gimple_stmt_iterator gsi
, agsi
;
379 if (!single_succ_p (bb
))
382 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
384 stmt
= gsi_stmt (gsi
);
387 if (gimple_code (stmt
) == GIMPLE_LABEL
|| is_gimple_debug (stmt
))
390 /* Check for a call. */
391 if (is_gimple_call (stmt
))
394 ass_var
= gimple_call_lhs (stmt
);
398 /* If the statement references memory or volatile operands, fail. */
399 if (gimple_references_memory_p (stmt
)
400 || gimple_has_volatile_ops (stmt
))
407 /* Recurse to the predecessors. */
408 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
409 find_tail_calls (e
->src
, ret
);
414 /* If the LHS of our call is not just a simple register, we can't
415 transform this into a tail or sibling call. This situation happens,
416 in (e.g.) "*p = foo()" where foo returns a struct. In this case
417 we won't have a temporary here, but we need to carry out the side
418 effect anyway, so tailcall is impossible.
420 ??? In some situations (when the struct is returned in memory via
421 invisible argument) we could deal with this, e.g. by passing 'p'
422 itself as that argument to foo, but it's too early to do this here,
423 and expand_call() will not handle it anyway. If it ever can, then
424 we need to revisit this here, to allow that situation. */
425 if (ass_var
&& !is_gimple_reg (ass_var
))
428 /* We found the call, check whether it is suitable. */
429 tail_recursion
= false;
430 func
= gimple_call_fndecl (call
);
431 if (func
== current_function_decl
)
434 for (param
= DECL_ARGUMENTS (func
), idx
= 0;
435 param
&& idx
< gimple_call_num_args (call
);
436 param
= TREE_CHAIN (param
), idx
++)
438 arg
= gimple_call_arg (call
, idx
);
441 /* Make sure there are no problems with copying. The parameter
442 have a copyable type and the two arguments must have reasonably
443 equivalent types. The latter requirement could be relaxed if
444 we emitted a suitable type conversion statement. */
445 if (!is_gimple_reg_type (TREE_TYPE (param
))
446 || !useless_type_conversion_p (TREE_TYPE (param
),
450 /* The parameter should be a real operand, so that phi node
451 created for it at the start of the function has the meaning
452 of copying the value. This test implies is_gimple_reg_type
453 from the previous condition, however this one could be
454 relaxed by being more careful with copying the new value
455 of the parameter (emitting appropriate GIMPLE_ASSIGN and
456 updating the virtual operands). */
457 if (!is_gimple_reg (param
))
461 if (idx
== gimple_call_num_args (call
) && !param
)
462 tail_recursion
= true;
465 /* Now check the statements after the call. None of them has virtual
466 operands, so they may only depend on the call through its return
467 value. The return value should also be dependent on each of them,
468 since we are running after dce. */
476 tree tmp_a
= NULL_TREE
;
477 tree tmp_m
= NULL_TREE
;
480 while (gsi_end_p (agsi
))
482 ass_var
= propagate_through_phis (ass_var
, single_succ_edge (abb
));
483 abb
= single_succ (abb
);
484 agsi
= gsi_start_bb (abb
);
487 stmt
= gsi_stmt (agsi
);
489 if (gimple_code (stmt
) == GIMPLE_LABEL
)
492 if (gimple_code (stmt
) == GIMPLE_RETURN
)
495 if (is_gimple_debug (stmt
))
498 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
501 /* This is a gimple assign. */
502 if (! process_assignment (stmt
, gsi
, &tmp_m
, &tmp_a
, &ass_var
))
508 a
= fold_build2 (PLUS_EXPR
, TREE_TYPE (tmp_a
), a
, tmp_a
);
515 m
= fold_build2 (MULT_EXPR
, TREE_TYPE (tmp_m
), m
, tmp_m
);
520 a
= fold_build2 (MULT_EXPR
, TREE_TYPE (tmp_m
), a
, tmp_m
);
524 /* See if this is a tail call we can handle. */
525 ret_var
= gimple_return_retval (stmt
);
527 /* We may proceed if there either is no return value, or the return value
528 is identical to the call's return. */
530 && (ret_var
!= ass_var
))
533 /* If this is not a tail recursive call, we cannot handle addends or
535 if (!tail_recursion
&& (m
|| a
))
538 nw
= XNEW (struct tailcall
);
542 nw
->tail_recursion
= tail_recursion
;
551 /* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */
554 add_successor_phi_arg (edge e
, tree var
, tree phi_arg
)
556 gimple_stmt_iterator gsi
;
558 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
559 if (PHI_RESULT (gsi_stmt (gsi
)) == var
)
562 gcc_assert (!gsi_end_p (gsi
));
563 add_phi_arg (gsi_stmt (gsi
), phi_arg
, e
, UNKNOWN_LOCATION
);
566 /* Creates a GIMPLE statement which computes the operation specified by
567 CODE, OP0 and OP1 to a new variable with name LABEL and inserts the
568 statement in the position specified by GSI and UPDATE. Returns the
569 tree node of the statement's result. */
572 adjust_return_value_with_ops (enum tree_code code
, const char *label
,
573 tree op0
, tree op1
, gimple_stmt_iterator gsi
,
574 enum gsi_iterator_update update
)
577 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
578 tree tmp
= create_tmp_var (ret_type
, label
);
579 gimple stmt
= gimple_build_assign_with_ops (code
, tmp
, op0
, op1
);
582 if (TREE_CODE (ret_type
) == COMPLEX_TYPE
583 || TREE_CODE (ret_type
) == VECTOR_TYPE
)
584 DECL_GIMPLE_REG_P (tmp
) = 1;
585 add_referenced_var (tmp
);
586 result
= make_ssa_name (tmp
, stmt
);
587 gimple_assign_set_lhs (stmt
, result
);
589 gsi_insert_before (&gsi
, stmt
, update
);
593 /* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by
594 the computation specified by CODE and OP1 and insert the statement
595 at the position specified by GSI as a new statement. Returns new SSA name
596 of updated accumulator. */
599 update_accumulator_with_ops (enum tree_code code
, tree acc
, tree op1
,
600 gimple_stmt_iterator gsi
)
602 gimple stmt
= gimple_build_assign_with_ops (code
, SSA_NAME_VAR (acc
), acc
,
604 tree var
= make_ssa_name (SSA_NAME_VAR (acc
), stmt
);
605 gimple_assign_set_lhs (stmt
, var
);
607 gsi_insert_after (&gsi
, stmt
, GSI_NEW_STMT
);
611 /* Adjust the accumulator values according to A and M after GSI, and update
612 the phi nodes on edge BACK. */
615 adjust_accumulator_values (gimple_stmt_iterator gsi
, tree m
, tree a
, edge back
)
617 tree var
, a_acc_arg
, m_acc_arg
;
620 m
= force_gimple_operand_gsi (&gsi
, m
, true, NULL
, true, GSI_SAME_STMT
);
622 a
= force_gimple_operand_gsi (&gsi
, a
, true, NULL
, true, GSI_SAME_STMT
);
630 if (integer_onep (a
))
633 var
= adjust_return_value_with_ops (MULT_EXPR
, "acc_tmp", m_acc
,
634 a
, gsi
, GSI_NEW_STMT
);
639 a_acc_arg
= update_accumulator_with_ops (PLUS_EXPR
, a_acc
, var
, gsi
);
643 m_acc_arg
= update_accumulator_with_ops (MULT_EXPR
, m_acc
, m
, gsi
);
646 add_successor_phi_arg (back
, a_acc
, a_acc_arg
);
649 add_successor_phi_arg (back
, m_acc
, m_acc_arg
);
652 /* Adjust value of the return at the end of BB according to M and A
656 adjust_return_value (basic_block bb
, tree m
, tree a
)
659 gimple ret_stmt
= gimple_seq_last_stmt (bb_seq (bb
));
660 gimple_stmt_iterator gsi
= gsi_last_bb (bb
);
662 gcc_assert (gimple_code (ret_stmt
) == GIMPLE_RETURN
);
664 retval
= gimple_return_retval (ret_stmt
);
665 if (!retval
|| retval
== error_mark_node
)
669 retval
= adjust_return_value_with_ops (MULT_EXPR
, "mul_tmp", m_acc
, retval
,
672 retval
= adjust_return_value_with_ops (PLUS_EXPR
, "acc_tmp", a_acc
, retval
,
674 gimple_return_set_retval (ret_stmt
, retval
);
675 update_stmt (ret_stmt
);
678 /* Subtract COUNT and FREQUENCY from the basic block and it's
681 decrease_profile (basic_block bb
, gcov_type count
, int frequency
)
687 bb
->frequency
-= frequency
;
688 if (bb
->frequency
< 0)
690 if (!single_succ_p (bb
))
692 gcc_assert (!EDGE_COUNT (bb
->succs
));
695 e
= single_succ_edge (bb
);
701 /* Returns true if argument PARAM of the tail recursive call needs to be copied
702 when the call is eliminated. */
705 arg_needs_copy_p (tree param
)
709 if (!is_gimple_reg (param
) || !var_ann (param
))
712 /* Parameters that are only defined but never used need not be copied. */
713 def
= gimple_default_def (cfun
, param
);
720 /* Eliminates tail call described by T. TMP_VARS is a list of
721 temporary variables used to copy the function arguments. */
724 eliminate_tail_call (struct tailcall
*t
)
730 basic_block bb
, first
;
733 gimple_stmt_iterator gsi
;
736 stmt
= orig_stmt
= gsi_stmt (t
->call_gsi
);
737 bb
= gsi_bb (t
->call_gsi
);
739 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
741 fprintf (dump_file
, "Eliminated tail recursion in bb %d : ",
743 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
744 fprintf (dump_file
, "\n");
747 gcc_assert (is_gimple_call (stmt
));
749 first
= single_succ (ENTRY_BLOCK_PTR
);
751 /* Remove the code after call_gsi that will become unreachable. The
752 possibly unreachable code in other blocks is removed later in
756 while (!gsi_end_p (gsi
))
758 gimple t
= gsi_stmt (gsi
);
759 /* Do not remove the return statement, so that redirect_edge_and_branch
760 sees how the block ends. */
761 if (gimple_code (t
) == GIMPLE_RETURN
)
764 gsi_remove (&gsi
, true);
768 /* Number of executions of function has reduced by the tailcall. */
769 e
= single_succ_edge (gsi_bb (t
->call_gsi
));
770 decrease_profile (EXIT_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
771 decrease_profile (ENTRY_BLOCK_PTR
, e
->count
, EDGE_FREQUENCY (e
));
772 if (e
->dest
!= EXIT_BLOCK_PTR
)
773 decrease_profile (e
->dest
, e
->count
, EDGE_FREQUENCY (e
));
775 /* Replace the call by a jump to the start of function. */
776 e
= redirect_edge_and_branch (single_succ_edge (gsi_bb (t
->call_gsi
)),
779 PENDING_STMT (e
) = NULL
;
781 /* Add phi node entries for arguments. The ordering of the phi nodes should
782 be the same as the ordering of the arguments. */
783 for (param
= DECL_ARGUMENTS (current_function_decl
),
784 idx
= 0, gsi
= gsi_start_phis (first
);
786 param
= TREE_CHAIN (param
), idx
++)
788 if (!arg_needs_copy_p (param
))
791 arg
= gimple_call_arg (stmt
, idx
);
792 phi
= gsi_stmt (gsi
);
793 gcc_assert (param
== SSA_NAME_VAR (PHI_RESULT (phi
)));
795 add_phi_arg (phi
, arg
, e
, gimple_location (stmt
));
799 /* Update the values of accumulators. */
800 adjust_accumulator_values (t
->call_gsi
, t
->mult
, t
->add
, e
);
802 call
= gsi_stmt (t
->call_gsi
);
803 rslt
= gimple_call_lhs (call
);
804 if (rslt
!= NULL_TREE
)
806 /* Result of the call will no longer be defined. So adjust the
807 SSA_NAME_DEF_STMT accordingly. */
808 SSA_NAME_DEF_STMT (rslt
) = gimple_build_nop ();
811 gsi_remove (&t
->call_gsi
, true);
815 /* Add phi nodes for the virtual operands defined in the function to the
816 header of the loop created by tail recursion elimination.
818 Originally, we used to add phi nodes only for call clobbered variables,
819 as the value of the non-call clobbered ones obviously cannot be used
820 or changed within the recursive call. However, the local variables
821 from multiple calls now share the same location, so the virtual ssa form
822 requires us to say that the location dies on further iterations of the loop,
823 which requires adding phi nodes.
826 add_virtual_phis (void)
828 referenced_var_iterator rvi
;
831 /* The problematic part is that there is no way how to know what
832 to put into phi nodes (there in fact does not have to be such
833 ssa name available). A solution would be to have an artificial
834 use/kill for all virtual operands in EXIT node. Unless we have
835 this, we cannot do much better than to rebuild the ssa form for
836 possibly affected virtual ssa names from scratch. */
838 FOR_EACH_REFERENCED_VAR (var
, rvi
)
840 if (!is_gimple_reg (var
) && gimple_default_def (cfun
, var
) != NULL_TREE
)
841 mark_sym_for_renaming (var
);
845 /* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also
846 mark the tailcalls for the sibcall optimization. */
849 optimize_tail_call (struct tailcall
*t
, bool opt_tailcalls
)
851 if (t
->tail_recursion
)
853 eliminate_tail_call (t
);
859 gimple stmt
= gsi_stmt (t
->call_gsi
);
861 gimple_call_set_tail (stmt
, true);
862 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
864 fprintf (dump_file
, "Found tail call ");
865 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
866 fprintf (dump_file
, " in bb %i\n", (gsi_bb (t
->call_gsi
))->index
);
873 /* Creates a tail-call accumulator of the same type as the return type of the
874 current function. LABEL is the name used to creating the temporary
875 variable for the accumulator. The accumulator will be inserted in the
876 phis of a basic block BB with single predecessor with an initial value
877 INIT converted to the current function return type. */
880 create_tailcall_accumulator (const char *label
, basic_block bb
, tree init
)
882 tree ret_type
= TREE_TYPE (DECL_RESULT (current_function_decl
));
883 tree tmp
= create_tmp_var (ret_type
, label
);
886 if (TREE_CODE (ret_type
) == COMPLEX_TYPE
887 || TREE_CODE (ret_type
) == VECTOR_TYPE
)
888 DECL_GIMPLE_REG_P (tmp
) = 1;
889 add_referenced_var (tmp
);
890 phi
= create_phi_node (tmp
, bb
);
891 /* RET_TYPE can be a float when -ffast-maths is enabled. */
892 add_phi_arg (phi
, fold_convert (ret_type
, init
), single_pred_edge (bb
),
894 return PHI_RESULT (phi
);
897 /* Optimizes tail calls in the function, turning the tail recursion
901 tree_optimize_tail_calls_1 (bool opt_tailcalls
)
904 bool phis_constructed
= false;
905 struct tailcall
*tailcalls
= NULL
, *act
, *next
;
906 bool changed
= false;
907 basic_block first
= single_succ (ENTRY_BLOCK_PTR
);
912 if (!suitable_for_tail_opt_p ())
915 opt_tailcalls
= suitable_for_tail_call_opt_p ();
917 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
919 /* Only traverse the normal exits, i.e. those that end with return
921 stmt
= last_stmt (e
->src
);
924 && gimple_code (stmt
) == GIMPLE_RETURN
)
925 find_tail_calls (e
->src
, &tailcalls
);
928 /* Construct the phi nodes and accumulators if necessary. */
929 a_acc
= m_acc
= NULL_TREE
;
930 for (act
= tailcalls
; act
; act
= act
->next
)
932 if (!act
->tail_recursion
)
935 if (!phis_constructed
)
937 /* Ensure that there is only one predecessor of the block
938 or if there are existing degenerate PHI nodes. */
939 if (!single_pred_p (first
)
940 || !gimple_seq_empty_p (phi_nodes (first
)))
941 first
= split_edge (single_succ_edge (ENTRY_BLOCK_PTR
));
943 /* Copy the args if needed. */
944 for (param
= DECL_ARGUMENTS (current_function_decl
);
946 param
= TREE_CHAIN (param
))
947 if (arg_needs_copy_p (param
))
949 tree name
= gimple_default_def (cfun
, param
);
950 tree new_name
= make_ssa_name (param
, SSA_NAME_DEF_STMT (name
));
953 set_default_def (param
, new_name
);
954 phi
= create_phi_node (name
, first
);
955 SSA_NAME_DEF_STMT (name
) = phi
;
956 add_phi_arg (phi
, new_name
, single_pred_edge (first
),
957 EXPR_LOCATION (param
));
959 phis_constructed
= true;
962 if (act
->add
&& !a_acc
)
963 a_acc
= create_tailcall_accumulator ("add_acc", first
,
966 if (act
->mult
&& !m_acc
)
967 m_acc
= create_tailcall_accumulator ("mult_acc", first
,
971 for (; tailcalls
; tailcalls
= next
)
973 next
= tailcalls
->next
;
974 changed
|= optimize_tail_call (tailcalls
, opt_tailcalls
);
980 /* Modify the remaining return statements. */
981 FOR_EACH_EDGE (e
, ei
, EXIT_BLOCK_PTR
->preds
)
983 stmt
= last_stmt (e
->src
);
986 && gimple_code (stmt
) == GIMPLE_RETURN
)
987 adjust_return_value (e
->src
, m_acc
, a_acc
);
992 free_dominance_info (CDI_DOMINATORS
);
994 if (phis_constructed
)
997 return TODO_cleanup_cfg
| TODO_update_ssa_only_virtuals
;
1002 execute_tail_recursion (void)
1004 return tree_optimize_tail_calls_1 (false);
1008 gate_tail_calls (void)
1010 return flag_optimize_sibling_calls
!= 0 && dbg_cnt (tail_call
);
1014 execute_tail_calls (void)
1016 return tree_optimize_tail_calls_1 (true);
1019 struct gimple_opt_pass pass_tail_recursion
=
1024 gate_tail_calls
, /* gate */
1025 execute_tail_recursion
, /* execute */
1028 0, /* static_pass_number */
1029 TV_NONE
, /* tv_id */
1030 PROP_cfg
| PROP_ssa
, /* properties_required */
1031 0, /* properties_provided */
1032 0, /* properties_destroyed */
1033 0, /* todo_flags_start */
1034 TODO_dump_func
| TODO_verify_ssa
/* todo_flags_finish */
1038 struct gimple_opt_pass pass_tail_calls
=
1043 gate_tail_calls
, /* gate */
1044 execute_tail_calls
, /* execute */
1047 0, /* static_pass_number */
1048 TV_NONE
, /* tv_id */
1049 PROP_cfg
| PROP_ssa
, /* properties_required */
1050 0, /* properties_provided */
1051 0, /* properties_destroyed */
1052 0, /* todo_flags_start */
1053 TODO_dump_func
| TODO_verify_ssa
/* todo_flags_finish */