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321 lines
8.0 KiB
C++
321 lines
8.0 KiB
C++
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/* Context-aware pointer equivalence tracker.
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Copyright (C) 2020-2022 Free Software Foundation, Inc.
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Contributed by Aldy Hernandez <aldyh@redhat.com>
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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 "tree.h"
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#include "gimple.h"
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#include "tree-pass.h"
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#include "ssa.h"
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#include "gimple-pretty-print.h"
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#include "cfganal.h"
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#include "gimple-fold.h"
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#include "tree-eh.h"
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#include "gimple-iterator.h"
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#include "tree-cfg.h"
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#include "tree-ssa-loop-manip.h"
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#include "tree-ssa-loop.h"
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#include "cfgloop.h"
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#include "tree-scalar-evolution.h"
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#include "tree-ssa-propagate.h"
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#include "alloc-pool.h"
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#include "domwalk.h"
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#include "tree-cfgcleanup.h"
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#include "vr-values.h"
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#include "gimple-range.h"
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#include "fold-const.h"
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#include "value-pointer-equiv.h"
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// Unwindable SSA equivalence table for pointers.
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//
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// The main query point is get_replacement() which returns what a
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// given SSA can be replaced with in the current scope.
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class ssa_equiv_stack
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{
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public:
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ssa_equiv_stack ();
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void enter (basic_block);
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void leave (basic_block);
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void push_replacement (tree name, tree replacement);
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tree get_replacement (tree name);
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private:
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auto_vec<std::pair <tree, tree>> m_stack;
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auto_vec<tree> m_replacements;
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const std::pair <tree, tree> m_marker = std::make_pair (NULL, NULL);
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};
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ssa_equiv_stack::ssa_equiv_stack ()
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{
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m_replacements.safe_grow_cleared (num_ssa_names + 1);
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}
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// Pushes a marker at the given point.
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void
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ssa_equiv_stack::enter (basic_block)
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{
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m_stack.safe_push (m_marker);
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}
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// Pops the stack to the last marker, while performing replacements
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// along the way.
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void
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ssa_equiv_stack::leave (basic_block)
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{
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gcc_checking_assert (!m_stack.is_empty ());
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while (m_stack.last () != m_marker)
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{
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std::pair<tree, tree> e = m_stack.pop ();
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m_replacements[SSA_NAME_VERSION (e.first)] = e.second;
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}
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m_stack.pop ();
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}
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// Set the equivalence of NAME to REPLACEMENT.
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void
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ssa_equiv_stack::push_replacement (tree name, tree replacement)
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{
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unsigned v = SSA_NAME_VERSION (name);
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if (v >= m_replacements.length ())
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m_replacements.safe_grow_cleared (num_ssa_names + 1);
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tree old = m_replacements[v];
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m_replacements[v] = replacement;
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m_stack.safe_push (std::make_pair (name, old));
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}
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// Return the equivalence of NAME.
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tree
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ssa_equiv_stack::get_replacement (tree name)
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{
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unsigned v = SSA_NAME_VERSION (name);
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if (v >= m_replacements.length ())
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m_replacements.safe_grow_cleared (num_ssa_names + 1);
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return m_replacements[v];
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}
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pointer_equiv_analyzer::pointer_equiv_analyzer (gimple_ranger *r)
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{
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m_ranger = r;
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m_global_points.safe_grow_cleared (num_ssa_names + 1);
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m_cond_points = new ssa_equiv_stack;
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}
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pointer_equiv_analyzer::~pointer_equiv_analyzer ()
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{
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delete m_cond_points;
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}
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// Set the global pointer equivalency for SSA to POINTEE.
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void
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pointer_equiv_analyzer::set_global_equiv (tree ssa, tree pointee)
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{
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unsigned v = SSA_NAME_VERSION (ssa);
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if (v >= m_global_points.length ())
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m_global_points.safe_grow_cleared (num_ssa_names + 1);
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m_global_points[v] = pointee;
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}
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// Set the conditional pointer equivalency for SSA to POINTEE.
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void
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pointer_equiv_analyzer::set_cond_equiv (tree ssa, tree pointee)
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{
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m_cond_points->push_replacement (ssa, pointee);
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}
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// Return the current pointer equivalency info for SSA, or NULL if
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// none is available. Note that global info takes priority over
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// conditional info.
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tree
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pointer_equiv_analyzer::get_equiv (tree ssa)
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{
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unsigned v = SSA_NAME_VERSION (ssa);
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if (v >= m_global_points.length ())
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m_global_points.safe_grow_cleared (num_ssa_names + 1);
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tree ret = m_global_points[v];
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if (ret)
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return ret;
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return m_cond_points->get_replacement (ssa);
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}
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// Method to be called on entry to a BB.
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void
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pointer_equiv_analyzer::enter (basic_block bb)
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{
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m_cond_points->enter (bb);
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for (gphi_iterator iter = gsi_start_phis (bb);
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!gsi_end_p (iter);
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gsi_next (&iter))
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{
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gphi *phi = iter.phi ();
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tree lhs = gimple_phi_result (phi);
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if (!POINTER_TYPE_P (TREE_TYPE (lhs)))
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continue;
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tree arg0 = gimple_phi_arg_def (phi, 0);
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if (TREE_CODE (arg0) == SSA_NAME && !is_gimple_min_invariant (arg0))
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arg0 = get_equiv (arg0);
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if (arg0 && is_gimple_min_invariant (arg0))
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{
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// If all the PHI args point to the same place, set the
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// pointer equivalency info for the PHI result. This can
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// happen for passes that create redundant PHIs like
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// PHI<&foo, &foo> or PHI<&foo>.
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for (size_t i = 1; i < gimple_phi_num_args (phi); ++i)
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{
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tree argi = gimple_phi_arg_def (phi, i);
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if (TREE_CODE (argi) == SSA_NAME
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&& !is_gimple_min_invariant (argi))
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argi = get_equiv (argi);
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if (!argi || !operand_equal_p (arg0, argi))
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return;
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}
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set_global_equiv (lhs, arg0);
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}
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}
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edge pred = single_pred_edge_ignoring_loop_edges (bb, false);
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if (pred)
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visit_edge (pred);
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}
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// Method to be called on exit from a BB.
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void
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pointer_equiv_analyzer::leave (basic_block bb)
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{
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m_cond_points->leave (bb);
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}
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// Helper function to return the pointer equivalency information for
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// EXPR from a gimple statement with CODE. This returns either the
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// cached pointer equivalency info for an SSA, or an invariant in case
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// EXPR is one (i.e. &foo). Returns NULL if EXPR is neither an SSA
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// nor an invariant.
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tree
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pointer_equiv_analyzer::get_equiv_expr (tree_code code, tree expr)
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{
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if (code == SSA_NAME)
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return get_equiv (expr);
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if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS
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&& is_gimple_min_invariant (expr))
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return expr;
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return NULL;
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}
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// Hack to provide context to the gimple fold callback.
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static struct
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{
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gimple *m_stmt;
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gimple_ranger *m_ranger;
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pointer_equiv_analyzer *m_pta;
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} x_fold_context;
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// Gimple fold callback.
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static tree
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pta_valueize (tree name)
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{
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tree ret
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= x_fold_context.m_ranger->value_of_expr (name, x_fold_context.m_stmt);
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if (!ret && supported_pointer_equiv_p (name))
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ret = x_fold_context.m_pta->get_equiv (name);
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return ret ? ret : name;
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}
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// Method to be called on gimple statements during traversal of the IL.
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void
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pointer_equiv_analyzer::visit_stmt (gimple *stmt)
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{
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if (gimple_code (stmt) != GIMPLE_ASSIGN)
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return;
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tree lhs = gimple_assign_lhs (stmt);
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if (!supported_pointer_equiv_p (lhs))
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return;
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tree rhs = gimple_assign_rhs1 (stmt);
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rhs = get_equiv_expr (gimple_assign_rhs_code (stmt), rhs);
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if (rhs)
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{
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set_global_equiv (lhs, rhs);
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return;
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}
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// If we couldn't find anything, try fold.
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x_fold_context = { stmt, m_ranger, this};
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rhs = gimple_fold_stmt_to_constant_1 (stmt, pta_valueize, pta_valueize);
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if (rhs)
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{
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rhs = get_equiv_expr (TREE_CODE (rhs), rhs);
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if (rhs)
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{
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set_global_equiv (lhs, rhs);
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return;
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}
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}
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}
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// If the edge in E is a conditional that sets a pointer equality, set the
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// conditional pointer equivalency information.
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void
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pointer_equiv_analyzer::visit_edge (edge e)
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{
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gimple *stmt = last_stmt (e->src);
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tree lhs;
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// Recognize: x_13 [==,!=] &foo.
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if (stmt
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&& gimple_code (stmt) == GIMPLE_COND
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&& (lhs = gimple_cond_lhs (stmt))
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&& TREE_CODE (lhs) == SSA_NAME
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&& POINTER_TYPE_P (TREE_TYPE (lhs))
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&& TREE_CODE (gimple_cond_rhs (stmt)) == ADDR_EXPR)
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{
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tree_code code = gimple_cond_code (stmt);
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if ((code == EQ_EXPR && e->flags & EDGE_TRUE_VALUE)
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|| ((code == NE_EXPR && e->flags & EDGE_FALSE_VALUE)))
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set_cond_equiv (lhs, gimple_cond_rhs (stmt));
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}
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}
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