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/* Const/copy propagation and SSA_NAME replacement support routines.
Copyright (C) 2004 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 2, 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 COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "flags.h"
#include "rtl.h"
#include "tm_p.h"
#include "ggc.h"
#include "basic-block.h"
#include "output.h"
#include "errors.h"
#include "expr.h"
#include "function.h"
#include "diagnostic.h"
#include "timevar.h"
#include "tree-dump.h"
#include "tree-flow.h"
#include "tree-pass.h"
#include "langhooks.h"
/* This file provides a handful of interfaces for performing const/copy
propagation and simple expression replacement which keep variable
annotations up-to-date.
We require that for any copy operation where the RHS and LHS have
a non-null memory tag that the memory tag be the same. It is OK
for one or both of the memory tags to be NULL.
We also require tracking if a variable is dereferenced in a load or
store operation.
We enforce these requirements by having all copy propagation and
replacements of one SSA_NAME with a different SSA_NAME to use the
APIs defined in this file. */
/* Given two SSA_NAMEs, replace the annotations for the one referred to by OP
with VAR's annmoptations.
If OP is a pointer, copy the memory tag used originally by OP into
VAR. This is needed in cases where VAR had never been dereferenced in the
program.
If FOR_PROPAGATION is true, then perform additional checks to ensure
that const/copy propagation of var for OP is valid. */
static void
replace_ssa_names_ann (tree op,
tree var,
bool for_propagation ATTRIBUTE_UNUSED)
{
#if defined ENABLE_CHECKING
if (for_propagation && !may_propagate_copy (op, var))
abort ();
#endif
/* If VAR doesn't have a memory tag, copy the one from the original
operand. Also copy the dereferenced flags. */
if (POINTER_TYPE_P (TREE_TYPE (op)))
{
var_ann_t new_ann = var_ann (SSA_NAME_VAR (var));
var_ann_t orig_ann = var_ann (SSA_NAME_VAR (op));
if (new_ann->type_mem_tag == NULL_TREE)
new_ann->type_mem_tag = orig_ann->type_mem_tag;
else if (orig_ann->type_mem_tag == NULL_TREE)
orig_ann->type_mem_tag = new_ann->type_mem_tag;
else if (new_ann->type_mem_tag != orig_ann->type_mem_tag)
abort ();
}
}
/* Common code for propagate_value and replace_exp.
Replace use operand OP_P with VAL. FOR_PROPAGATION indicates if the
replacement is done to propagate a value or not. */
static void
replace_exp_1 (use_operand_p op_p, tree val, bool for_propagation)
{
if (TREE_CODE (val) == SSA_NAME)
{
if (TREE_CODE (USE_FROM_PTR (op_p)) == SSA_NAME)
replace_ssa_names_ann (USE_FROM_PTR (op_p), val, for_propagation);
SET_USE (op_p, val);
}
else
SET_USE (op_p, lhd_unsave_expr_now (val));
}
/* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
into the operand pointed by OP_P.
Use this version for const/copy propagation as it will perform additional
checks to ensure validity of the const/copy propagation. */
void
propagate_value (use_operand_p op_p, tree val)
{
replace_exp_1 (op_p, val, true);
}
/* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
into the tree pointed by OP_P.
Use this version for const/copy propagation when SSA operands are not
available. It will perform the additional checks to ensure validity of
the const/copy propagation, but will not update any operand information.
Be sure to mark the stmt as modified. */
void
propagate_tree_value (tree *op_p, tree val)
{
if (TREE_CODE (val) == SSA_NAME)
{
if (TREE_CODE (*op_p) == SSA_NAME)
replace_ssa_names_ann (*op_p, val, true);
*op_p = val;
}
else
*op_p = lhd_unsave_expr_now (val);
}
/* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME).
Use this version when not const/copy propagating values. For example,
PRE uses this version when building expressions as they would appear
in specific blocks taking into account actions of PHI nodes. */
void
replace_exp (use_operand_p op_p, tree val)
{
replace_exp_1 (op_p, val, false);
}
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