| /* Discover if the stack pointer is modified in a function. |
| Copyright (C) 2007, 2008, 2009 |
| Free Software Foundation, Inc. |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify it under |
| the terms of the GNU General Public License as published by the Free |
| Software Foundation; either version 3, or (at your option) any later |
| version. |
| |
| GCC is distributed in the hope that it will be useful, but WITHOUT ANY |
| WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GCC; see the file COPYING3. If not see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "tm.h" |
| #include "tree.h" |
| #include "rtl.h" |
| #include "regs.h" |
| #include "expr.h" |
| #include "tree-pass.h" |
| #include "basic-block.h" |
| #include "flags.h" |
| #include "output.h" |
| #include "df.h" |
| |
| /* Determine if the stack pointer is constant over the life of the function. |
| Only useful before prologues have been emitted. */ |
| |
| static void |
| notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, |
| void *data ATTRIBUTE_UNUSED) |
| { |
| if (x == stack_pointer_rtx |
| /* The stack pointer is only modified indirectly as the result |
| of a push until later. See the comments in rtl.texi |
| regarding Embedded Side-Effects on Addresses. */ |
| || (MEM_P (x) |
| && GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC |
| && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx)) |
| current_function_sp_is_unchanging = 0; |
| } |
| |
| static void |
| notice_stack_pointer_modification (void) |
| { |
| basic_block bb; |
| rtx insn; |
| |
| /* Assume that the stack pointer is unchanging if alloca hasn't |
| been used. */ |
| current_function_sp_is_unchanging = !cfun->calls_alloca; |
| if (current_function_sp_is_unchanging) |
| FOR_EACH_BB (bb) |
| FOR_BB_INSNS (bb, insn) |
| { |
| if (INSN_P (insn)) |
| { |
| /* Check if insn modifies the stack pointer. */ |
| note_stores (PATTERN (insn), |
| notice_stack_pointer_modification_1, |
| NULL); |
| if (! current_function_sp_is_unchanging) |
| return; |
| } |
| } |
| |
| /* The value coming into this pass was 0, and the exit block uses |
| are based on this. If the value is now 1, we need to redo the |
| exit block uses. */ |
| if (df && current_function_sp_is_unchanging) |
| df_update_exit_block_uses (); |
| } |
| |
| /* Some targets can emit simpler epilogues if they know that sp was |
| not ever modified during the function. After reload, of course, |
| we've already emitted the epilogue so there's no sense searching. */ |
| |
| static unsigned int |
| rest_of_handle_stack_ptr_mod (void) |
| { |
| notice_stack_pointer_modification (); |
| return 0; |
| } |
| |
| struct rtl_opt_pass pass_stack_ptr_mod = |
| { |
| { |
| RTL_PASS, |
| "*stack_ptr_mod", /* name */ |
| NULL, /* gate */ |
| rest_of_handle_stack_ptr_mod, /* execute */ |
| NULL, /* sub */ |
| NULL, /* next */ |
| 0, /* static_pass_number */ |
| TV_NONE, /* tv_id */ |
| 0, /* properties_required */ |
| 0, /* properties_provided */ |
| 0, /* properties_destroyed */ |
| 0, /* todo_flags_start */ |
| 0 /* todo_flags_finish */ |
| } |
| }; |