118 lines
3.2 KiB
C
118 lines
3.2 KiB
C
/* Discover if the stack pointer is modified in a function.
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Copyright (C) 2007-2017 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "backend.h"
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#include "rtl.h"
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#include "df.h"
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#include "memmodel.h"
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#include "emit-rtl.h"
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#include "tree-pass.h"
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/* Determine if the stack pointer is constant over the life of the function.
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Only useful before prologues have been emitted. */
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static void
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notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED,
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void *data ATTRIBUTE_UNUSED)
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{
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if (x == stack_pointer_rtx
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/* The stack pointer is only modified indirectly as the result
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of a push until later. See the comments in rtl.texi
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regarding Embedded Side-Effects on Addresses. */
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|| (MEM_P (x)
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&& GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC
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&& XEXP (XEXP (x, 0), 0) == stack_pointer_rtx))
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crtl->sp_is_unchanging = 0;
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}
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/* Some targets can emit simpler epilogues if they know that sp was
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not ever modified during the function. After reload, of course,
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we've already emitted the epilogue so there's no sense searching. */
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namespace {
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const pass_data pass_data_stack_ptr_mod =
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{
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RTL_PASS, /* type */
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"*stack_ptr_mod", /* name */
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OPTGROUP_NONE, /* optinfo_flags */
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TV_NONE, /* tv_id */
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0, /* properties_required */
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0, /* properties_provided */
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0, /* properties_destroyed */
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0, /* todo_flags_start */
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0, /* todo_flags_finish */
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};
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class pass_stack_ptr_mod : public rtl_opt_pass
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{
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public:
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pass_stack_ptr_mod (gcc::context *ctxt)
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: rtl_opt_pass (pass_data_stack_ptr_mod, ctxt)
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{}
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/* opt_pass methods: */
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virtual unsigned int execute (function *);
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}; // class pass_stack_ptr_mod
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unsigned int
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pass_stack_ptr_mod::execute (function *fun)
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{
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basic_block bb;
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rtx_insn *insn;
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/* Assume that the stack pointer is unchanging if alloca hasn't
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been used. */
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crtl->sp_is_unchanging = !fun->calls_alloca;
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if (crtl->sp_is_unchanging)
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FOR_EACH_BB_FN (bb, fun)
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FOR_BB_INSNS (bb, insn)
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{
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if (INSN_P (insn))
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{
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/* Check if insn modifies the stack pointer. */
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note_stores (PATTERN (insn),
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notice_stack_pointer_modification_1,
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NULL);
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if (! crtl->sp_is_unchanging)
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return 0;
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}
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}
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/* The value coming into this pass was 0, and the exit block uses
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are based on this. If the value is now 1, we need to redo the
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exit block uses. */
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if (df && crtl->sp_is_unchanging)
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df_update_exit_block_uses ();
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return 0;
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}
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} // anon namespace
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rtl_opt_pass *
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make_pass_stack_ptr_mod (gcc::context *ctxt)
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{
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return new pass_stack_ptr_mod (ctxt);
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}
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