xref: /dflybsd-src/contrib/gcc-4.7/gcc/stack-ptr-mod.c (revision 04febcfb30580676d3e95f58a16c5137ee478b32)
1*e4b17023SJohn Marino /* Discover if the stack pointer is modified in a function.
2*e4b17023SJohn Marino    Copyright (C) 2007, 2008, 2009
3*e4b17023SJohn Marino    Free Software Foundation, Inc.
4*e4b17023SJohn Marino 
5*e4b17023SJohn Marino This file is part of GCC.
6*e4b17023SJohn Marino 
7*e4b17023SJohn Marino GCC is free software; you can redistribute it and/or modify it under
8*e4b17023SJohn Marino the terms of the GNU General Public License as published by the Free
9*e4b17023SJohn Marino Software Foundation; either version 3, or (at your option) any later
10*e4b17023SJohn Marino version.
11*e4b17023SJohn Marino 
12*e4b17023SJohn Marino GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13*e4b17023SJohn Marino WARRANTY; without even the implied warranty of MERCHANTABILITY or
14*e4b17023SJohn Marino FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15*e4b17023SJohn Marino for more details.
16*e4b17023SJohn Marino 
17*e4b17023SJohn Marino You should have received a copy of the GNU General Public License
18*e4b17023SJohn Marino along with GCC; see the file COPYING3.  If not see
19*e4b17023SJohn Marino <http://www.gnu.org/licenses/>.  */
20*e4b17023SJohn Marino 
21*e4b17023SJohn Marino #include "config.h"
22*e4b17023SJohn Marino #include "system.h"
23*e4b17023SJohn Marino #include "coretypes.h"
24*e4b17023SJohn Marino #include "tm.h"
25*e4b17023SJohn Marino #include "tree.h"
26*e4b17023SJohn Marino #include "rtl.h"
27*e4b17023SJohn Marino #include "regs.h"
28*e4b17023SJohn Marino #include "expr.h"
29*e4b17023SJohn Marino #include "tree-pass.h"
30*e4b17023SJohn Marino #include "basic-block.h"
31*e4b17023SJohn Marino #include "flags.h"
32*e4b17023SJohn Marino #include "output.h"
33*e4b17023SJohn Marino #include "df.h"
34*e4b17023SJohn Marino 
35*e4b17023SJohn Marino /* Determine if the stack pointer is constant over the life of the function.
36*e4b17023SJohn Marino    Only useful before prologues have been emitted.  */
37*e4b17023SJohn Marino 
38*e4b17023SJohn Marino static void
notice_stack_pointer_modification_1(rtx x,const_rtx pat ATTRIBUTE_UNUSED,void * data ATTRIBUTE_UNUSED)39*e4b17023SJohn Marino notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED,
40*e4b17023SJohn Marino 				     void *data ATTRIBUTE_UNUSED)
41*e4b17023SJohn Marino {
42*e4b17023SJohn Marino   if (x == stack_pointer_rtx
43*e4b17023SJohn Marino       /* The stack pointer is only modified indirectly as the result
44*e4b17023SJohn Marino 	 of a push until later.  See the comments in rtl.texi
45*e4b17023SJohn Marino 	 regarding Embedded Side-Effects on Addresses.  */
46*e4b17023SJohn Marino       || (MEM_P (x)
47*e4b17023SJohn Marino 	  && GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC
48*e4b17023SJohn Marino 	  && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx))
49*e4b17023SJohn Marino     current_function_sp_is_unchanging = 0;
50*e4b17023SJohn Marino }
51*e4b17023SJohn Marino 
52*e4b17023SJohn Marino static void
notice_stack_pointer_modification(void)53*e4b17023SJohn Marino notice_stack_pointer_modification (void)
54*e4b17023SJohn Marino {
55*e4b17023SJohn Marino   basic_block bb;
56*e4b17023SJohn Marino   rtx insn;
57*e4b17023SJohn Marino 
58*e4b17023SJohn Marino   /* Assume that the stack pointer is unchanging if alloca hasn't
59*e4b17023SJohn Marino      been used.  */
60*e4b17023SJohn Marino   current_function_sp_is_unchanging = !cfun->calls_alloca;
61*e4b17023SJohn Marino   if (current_function_sp_is_unchanging)
62*e4b17023SJohn Marino     FOR_EACH_BB (bb)
63*e4b17023SJohn Marino       FOR_BB_INSNS (bb, insn)
64*e4b17023SJohn Marino         {
65*e4b17023SJohn Marino 	  if (INSN_P (insn))
66*e4b17023SJohn Marino 	    {
67*e4b17023SJohn Marino 	      /* Check if insn modifies the stack pointer.  */
68*e4b17023SJohn Marino 	      note_stores (PATTERN (insn),
69*e4b17023SJohn Marino 			   notice_stack_pointer_modification_1,
70*e4b17023SJohn Marino 			   NULL);
71*e4b17023SJohn Marino 	      if (! current_function_sp_is_unchanging)
72*e4b17023SJohn Marino 		return;
73*e4b17023SJohn Marino 	    }
74*e4b17023SJohn Marino 	}
75*e4b17023SJohn Marino 
76*e4b17023SJohn Marino   /* The value coming into this pass was 0, and the exit block uses
77*e4b17023SJohn Marino      are based on this.  If the value is now 1, we need to redo the
78*e4b17023SJohn Marino      exit block uses.  */
79*e4b17023SJohn Marino   if (df && current_function_sp_is_unchanging)
80*e4b17023SJohn Marino     df_update_exit_block_uses ();
81*e4b17023SJohn Marino }
82*e4b17023SJohn Marino 
83*e4b17023SJohn Marino   /* Some targets can emit simpler epilogues if they know that sp was
84*e4b17023SJohn Marino      not ever modified during the function.  After reload, of course,
85*e4b17023SJohn Marino      we've already emitted the epilogue so there's no sense searching.  */
86*e4b17023SJohn Marino 
87*e4b17023SJohn Marino static unsigned int
rest_of_handle_stack_ptr_mod(void)88*e4b17023SJohn Marino rest_of_handle_stack_ptr_mod (void)
89*e4b17023SJohn Marino {
90*e4b17023SJohn Marino   notice_stack_pointer_modification ();
91*e4b17023SJohn Marino   return 0;
92*e4b17023SJohn Marino }
93*e4b17023SJohn Marino 
94*e4b17023SJohn Marino struct rtl_opt_pass pass_stack_ptr_mod =
95*e4b17023SJohn Marino {
96*e4b17023SJohn Marino  {
97*e4b17023SJohn Marino   RTL_PASS,
98*e4b17023SJohn Marino   "*stack_ptr_mod",                     /* name */
99*e4b17023SJohn Marino   NULL,                                 /* gate */
100*e4b17023SJohn Marino   rest_of_handle_stack_ptr_mod,         /* execute */
101*e4b17023SJohn Marino   NULL,                                 /* sub */
102*e4b17023SJohn Marino   NULL,                                 /* next */
103*e4b17023SJohn Marino   0,                                    /* static_pass_number */
104*e4b17023SJohn Marino   TV_NONE,                              /* tv_id */
105*e4b17023SJohn Marino   0,                                    /* properties_required */
106*e4b17023SJohn Marino   0,                                    /* properties_provided */
107*e4b17023SJohn Marino   0,                                    /* properties_destroyed */
108*e4b17023SJohn Marino   0,                                    /* todo_flags_start */
109*e4b17023SJohn Marino   0                                     /* todo_flags_finish */
110*e4b17023SJohn Marino  }
111*e4b17023SJohn Marino };
112