| /* Discover if the stack pointer is modified in a function. |
| Copyright (C) 2007-2021 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 "backend.h" |
| #include "rtl.h" |
| #include "df.h" |
| #include "memmodel.h" |
| #include "emit-rtl.h" |
| #include "tree-pass.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)) |
| crtl->sp_is_unchanging = 0; |
| } |
| |
| /* 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. */ |
| |
| namespace { |
| |
| const pass_data pass_data_stack_ptr_mod = |
| { |
| RTL_PASS, /* type */ |
| "*stack_ptr_mod", /* name */ |
| OPTGROUP_NONE, /* optinfo_flags */ |
| TV_NONE, /* tv_id */ |
| 0, /* properties_required */ |
| 0, /* properties_provided */ |
| 0, /* properties_destroyed */ |
| 0, /* todo_flags_start */ |
| 0, /* todo_flags_finish */ |
| }; |
| |
| class pass_stack_ptr_mod : public rtl_opt_pass |
| { |
| public: |
| pass_stack_ptr_mod (gcc::context *ctxt) |
| : rtl_opt_pass (pass_data_stack_ptr_mod, ctxt) |
| {} |
| |
| /* opt_pass methods: */ |
| virtual unsigned int execute (function *); |
| |
| }; // class pass_stack_ptr_mod |
| |
| unsigned int |
| pass_stack_ptr_mod::execute (function *fun) |
| { |
| basic_block bb; |
| rtx_insn *insn; |
| |
| /* Assume that the stack pointer is unchanging if alloca hasn't |
| been used. */ |
| crtl->sp_is_unchanging = !fun->calls_alloca; |
| if (crtl->sp_is_unchanging) |
| FOR_EACH_BB_FN (bb, fun) |
| FOR_BB_INSNS (bb, insn) |
| { |
| if (INSN_P (insn)) |
| { |
| /* Check if insn modifies the stack pointer. */ |
| note_stores (insn, notice_stack_pointer_modification_1, NULL); |
| if (! crtl->sp_is_unchanging) |
| return 0; |
| } |
| } |
| |
| /* 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 && crtl->sp_is_unchanging) |
| df_update_exit_block_uses (); |
| |
| return 0; |
| } |
| |
| } // anon namespace |
| |
| rtl_opt_pass * |
| make_pass_stack_ptr_mod (gcc::context *ctxt) |
| { |
| return new pass_stack_ptr_mod (ctxt); |
| } |