1 /* Analyze functions to determine if callers need to allocate a frame header
2 on the stack. The frame header is used by callees to save their arguments.
3 This optimization is specific to TARGET_OLDABI targets. For TARGET_NEWABI
4 targets, if a frame header is required, it is allocated by the callee.
7 Copyright (C) 2015-2024 Free Software Foundation, Inc.
9 This file is part of GCC.
11 GCC is free software; you can redistribute it and/or modify it
12 under the terms of the GNU General Public License as published by the
13 Free Software Foundation; either version 3, or (at your option) any
16 GCC is distributed in the hope that it will be useful, but WITHOUT
17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
18 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
21 You should have received a copy of the GNU General Public License
22 along with GCC; see the file COPYING3. If not see
23 <http://www.gnu.org/licenses/>. */
26 #define IN_TARGET_CODE 1
31 #include "coretypes.h"
34 #include "tree-core.h"
35 #include "tree-pass.h"
37 #include "target-globals.h"
38 #include "profile-count.h"
41 #include "basic-block.h"
43 #include "gimple-iterator.h"
44 #include "gimple-walk.h"
46 static unsigned int frame_header_opt (void);
50 const pass_data pass_data_ipa_frame_header_opt
=
53 "frame-header-opt", /* name */
54 OPTGROUP_NONE
, /* optinfo_flags */
55 TV_CGRAPHOPT
, /* tv_id */
56 0, /* properties_required */
57 0, /* properties_provided */
58 0, /* properties_destroyed */
59 0, /* todo_flags_start */
60 0, /* todo_flags_finish */
63 class pass_ipa_frame_header_opt
: public ipa_opt_pass_d
66 pass_ipa_frame_header_opt (gcc::context
*ctxt
)
67 : ipa_opt_pass_d (pass_data_ipa_frame_header_opt
, ctxt
,
68 NULL
, /* generate_summary */
69 NULL
, /* write_summary */
70 NULL
, /* read_summary */
71 NULL
, /* write_optimization_summary */
72 NULL
, /* read_optimization_summary */
73 NULL
, /* stmt_fixup */
74 0, /* function_transform_todo_flags_start */
75 NULL
, /* function_transform */
76 NULL
) /* variable_transform */
79 /* opt_pass methods: */
80 virtual bool gate (function
*)
82 /* This optimization has no affect if TARGET_NEWABI. If optimize
83 is not at least 1 then the data needed for the optimization is
84 not available and nothing will be done anyway. */
85 return TARGET_OLDABI
&& flag_frame_header_optimization
&& optimize
> 0;
88 virtual unsigned int execute (function
*) { return frame_header_opt (); }
90 }; // class pass_ipa_frame_header_opt
94 static ipa_opt_pass_d
*
95 make_pass_ipa_frame_header_opt (gcc::context
*ctxt
)
97 return new pass_ipa_frame_header_opt (ctxt
);
101 mips_register_frame_header_opt (void)
103 opt_pass
*p
= make_pass_ipa_frame_header_opt (g
);
104 struct register_pass_info f
= { p
, "comdats", 1, PASS_POS_INSERT_AFTER
};
109 /* Return true if it is certain that this is a leaf function. False if it is
110 not a leaf function or if it is impossible to tell. */
113 is_leaf_function (function
*fn
)
116 gimple_stmt_iterator gsi
;
118 /* If we do not have a cfg for this function be conservative and assume
119 it is not a leaf function. */
123 FOR_EACH_BB_FN (bb
, fn
)
124 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
125 if (is_gimple_call (gsi_stmt (gsi
)))
130 /* Return true if this function has inline assembly code or if we cannot
131 be certain that it does not. False if we know that there is no inline
135 has_inlined_assembly (function
*fn
)
138 gimple_stmt_iterator gsi
;
140 /* If we do not have a cfg for this function be conservative and assume
141 it is may have inline assembly. */
145 FOR_EACH_BB_FN (bb
, fn
)
146 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
147 if (gimple_code (gsi_stmt (gsi
)) == GIMPLE_ASM
)
153 /* Return true if this function will use the stack space allocated by its
154 caller or if we cannot determine for certain that it does not. */
157 needs_frame_header_p (function
*fn
)
161 if (fn
->decl
== NULL
)
167 for (t
= DECL_ARGUMENTS (fn
->decl
); t
; t
= TREE_CHAIN (t
))
169 if (!use_register_for_decl (t
))
172 /* Some 64-bit types may get copied to general registers using the frame
173 header, see mips_output_64bit_xfer. Checking for SImode only may be
174 overly restrictive but it is guaranteed to be safe. */
175 if (DECL_MODE (t
) != SImode
)
182 /* Return true if the argument stack space allocated by function FN is used.
183 Return false if the space is needed or if the need for the space cannot
187 callees_functions_use_frame_header (function
*fn
)
190 gimple_stmt_iterator gsi
;
198 FOR_EACH_BB_FN (bb
, fn
)
200 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
202 stmt
= gsi_stmt (gsi
);
203 if (is_gimple_call (stmt
))
205 called_fn_tree
= gimple_call_fndecl (stmt
);
206 if (called_fn_tree
!= NULL
)
208 called_fn
= DECL_STRUCT_FUNCTION (called_fn_tree
);
209 if (called_fn
== NULL
210 || DECL_WEAK (called_fn_tree
)
211 || has_inlined_assembly (called_fn
)
212 || !is_leaf_function (called_fn
)
213 || !called_fn
->machine
->does_not_use_frame_header
)
224 /* Set the callers_may_not_allocate_frame flag for any function which
225 function FN calls because FN may not allocate a frame header. */
228 set_callers_may_not_allocate_frame (function
*fn
)
231 gimple_stmt_iterator gsi
;
239 FOR_EACH_BB_FN (bb
, fn
)
241 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
243 stmt
= gsi_stmt (gsi
);
244 if (is_gimple_call (stmt
))
246 called_fn_tree
= gimple_call_fndecl (stmt
);
247 if (called_fn_tree
!= NULL
)
249 called_fn
= DECL_STRUCT_FUNCTION (called_fn_tree
);
250 if (called_fn
!= NULL
)
251 called_fn
->machine
->callers_may_not_allocate_frame
= true;
259 /* Scan each function to determine those that need its frame headers. Perform
260 a second scan to determine if the allocation can be skipped because none of
261 their callees require the frame header. */
266 struct cgraph_node
*node
;
269 FOR_EACH_DEFINED_FUNCTION (node
)
271 fn
= node
->get_fun ();
273 fn
->machine
->does_not_use_frame_header
= !needs_frame_header_p (fn
);
276 FOR_EACH_DEFINED_FUNCTION (node
)
278 fn
= node
->get_fun ();
280 fn
->machine
->optimize_call_stack
281 = !callees_functions_use_frame_header (fn
) && !is_leaf_function (fn
);
284 FOR_EACH_DEFINED_FUNCTION (node
)
286 fn
= node
->get_fun ();
287 if (fn
!= NULL
&& fn
->machine
->optimize_call_stack
)
288 set_callers_may_not_allocate_frame (fn
);