2093 lines
65 KiB
C
2093 lines
65 KiB
C
/* SSA Dominator optimizations for trees
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Copyright (C) 2001-2016 Free Software Foundation, Inc.
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Contributed by Diego Novillo <dnovillo@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
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GCC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License 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 "fold-const.h"
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#include "cfganal.h"
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#include "cfgloop.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-into-ssa.h"
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#include "domwalk.h"
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#include "tree-ssa-propagate.h"
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#include "tree-ssa-threadupdate.h"
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#include "params.h"
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#include "tree-ssa-scopedtables.h"
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#include "tree-ssa-threadedge.h"
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#include "tree-ssa-dom.h"
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#include "gimplify.h"
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#include "tree-cfgcleanup.h"
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#include "dbgcnt.h"
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/* This file implements optimizations on the dominator tree. */
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/* Structure for recording known values of a conditional expression
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at the exits from its block. */
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struct cond_equivalence
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{
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struct hashable_expr cond;
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tree value;
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};
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/* Structure for recording edge equivalences.
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Computing and storing the edge equivalences instead of creating
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them on-demand can save significant amounts of time, particularly
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for pathological cases involving switch statements.
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These structures live for a single iteration of the dominator
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optimizer in the edge's AUX field. At the end of an iteration we
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free each of these structures. */
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struct edge_info
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{
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/* If this edge creates a simple equivalence, the LHS and RHS of
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the equivalence will be stored here. */
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tree lhs;
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tree rhs;
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/* Traversing an edge may also indicate one or more particular conditions
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are true or false. */
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vec<cond_equivalence> cond_equivalences;
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};
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/* Track whether or not we have changed the control flow graph. */
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static bool cfg_altered;
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/* Bitmap of blocks that have had EH statements cleaned. We should
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remove their dead edges eventually. */
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static bitmap need_eh_cleanup;
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static vec<gimple *> need_noreturn_fixup;
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/* Statistics for dominator optimizations. */
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struct opt_stats_d
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{
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long num_stmts;
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long num_exprs_considered;
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long num_re;
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long num_const_prop;
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long num_copy_prop;
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};
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static struct opt_stats_d opt_stats;
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/* Local functions. */
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static edge optimize_stmt (basic_block, gimple_stmt_iterator,
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class const_and_copies *,
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class avail_exprs_stack *);
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static tree lookup_avail_expr (gimple *, bool, class avail_exprs_stack *,
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bool = true);
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static void record_cond (cond_equivalence *, class avail_exprs_stack *);
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static void record_equality (tree, tree, class const_and_copies *);
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static void record_equivalences_from_phis (basic_block);
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static void record_equivalences_from_incoming_edge (basic_block,
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class const_and_copies *,
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class avail_exprs_stack *);
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static void eliminate_redundant_computations (gimple_stmt_iterator *,
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class const_and_copies *,
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class avail_exprs_stack *);
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static void record_equivalences_from_stmt (gimple *, int,
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class avail_exprs_stack *);
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static edge single_incoming_edge_ignoring_loop_edges (basic_block);
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static void dump_dominator_optimization_stats (FILE *file,
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hash_table<expr_elt_hasher> *);
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/* Free the edge_info data attached to E, if it exists. */
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void
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free_dom_edge_info (edge e)
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{
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struct edge_info *edge_info = (struct edge_info *)e->aux;
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if (edge_info)
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{
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edge_info->cond_equivalences.release ();
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free (edge_info);
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}
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}
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/* Allocate an EDGE_INFO for edge E and attach it to E.
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Return the new EDGE_INFO structure. */
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static struct edge_info *
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allocate_edge_info (edge e)
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{
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struct edge_info *edge_info;
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/* Free the old one, if it exists. */
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free_dom_edge_info (e);
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edge_info = XCNEW (struct edge_info);
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e->aux = edge_info;
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return edge_info;
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}
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/* Free all EDGE_INFO structures associated with edges in the CFG.
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If a particular edge can be threaded, copy the redirection
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target from the EDGE_INFO structure into the edge's AUX field
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as required by code to update the CFG and SSA graph for
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jump threading. */
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static void
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free_all_edge_infos (void)
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{
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basic_block bb;
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edge_iterator ei;
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edge e;
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FOR_EACH_BB_FN (bb, cfun)
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{
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FOR_EACH_EDGE (e, ei, bb->preds)
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{
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free_dom_edge_info (e);
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e->aux = NULL;
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}
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}
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}
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/* Build a cond_equivalence record indicating that the comparison
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CODE holds between operands OP0 and OP1 and push it to **P. */
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static void
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build_and_record_new_cond (enum tree_code code,
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tree op0, tree op1,
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vec<cond_equivalence> *p,
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bool val = true)
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{
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cond_equivalence c;
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struct hashable_expr *cond = &c.cond;
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gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
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cond->type = boolean_type_node;
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cond->kind = EXPR_BINARY;
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cond->ops.binary.op = code;
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cond->ops.binary.opnd0 = op0;
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cond->ops.binary.opnd1 = op1;
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c.value = val ? boolean_true_node : boolean_false_node;
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p->safe_push (c);
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}
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/* Record that COND is true and INVERTED is false into the edge information
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structure. Also record that any conditions dominated by COND are true
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as well.
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For example, if a < b is true, then a <= b must also be true. */
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static void
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record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
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{
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tree op0, op1;
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cond_equivalence c;
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if (!COMPARISON_CLASS_P (cond))
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return;
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op0 = TREE_OPERAND (cond, 0);
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op1 = TREE_OPERAND (cond, 1);
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switch (TREE_CODE (cond))
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{
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case LT_EXPR:
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case GT_EXPR:
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if (FLOAT_TYPE_P (TREE_TYPE (op0)))
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{
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build_and_record_new_cond (ORDERED_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (LTGT_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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}
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build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
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? LE_EXPR : GE_EXPR),
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op0, op1, &edge_info->cond_equivalences);
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build_and_record_new_cond (NE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (EQ_EXPR, op0, op1,
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&edge_info->cond_equivalences, false);
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break;
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case GE_EXPR:
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case LE_EXPR:
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if (FLOAT_TYPE_P (TREE_TYPE (op0)))
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{
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build_and_record_new_cond (ORDERED_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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}
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break;
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case EQ_EXPR:
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if (FLOAT_TYPE_P (TREE_TYPE (op0)))
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{
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build_and_record_new_cond (ORDERED_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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}
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build_and_record_new_cond (LE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (GE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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break;
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case UNORDERED_EXPR:
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build_and_record_new_cond (NE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (UNLE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (UNGE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (UNEQ_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (UNLT_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (UNGT_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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break;
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case UNLT_EXPR:
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case UNGT_EXPR:
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build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
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? UNLE_EXPR : UNGE_EXPR),
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op0, op1, &edge_info->cond_equivalences);
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build_and_record_new_cond (NE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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break;
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case UNEQ_EXPR:
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build_and_record_new_cond (UNLE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (UNGE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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break;
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case LTGT_EXPR:
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build_and_record_new_cond (NE_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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build_and_record_new_cond (ORDERED_EXPR, op0, op1,
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&edge_info->cond_equivalences);
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break;
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default:
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break;
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}
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/* Now store the original true and false conditions into the first
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two slots. */
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initialize_expr_from_cond (cond, &c.cond);
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c.value = boolean_true_node;
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edge_info->cond_equivalences.safe_push (c);
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/* It is possible for INVERTED to be the negation of a comparison,
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and not a valid RHS or GIMPLE_COND condition. This happens because
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invert_truthvalue may return such an expression when asked to invert
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a floating-point comparison. These comparisons are not assumed to
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obey the trichotomy law. */
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initialize_expr_from_cond (inverted, &c.cond);
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c.value = boolean_false_node;
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edge_info->cond_equivalences.safe_push (c);
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}
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/* We have finished optimizing BB, record any information implied by
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taking a specific outgoing edge from BB. */
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static void
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record_edge_info (basic_block bb)
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{
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gimple_stmt_iterator gsi = gsi_last_bb (bb);
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struct edge_info *edge_info;
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if (! gsi_end_p (gsi))
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{
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gimple *stmt = gsi_stmt (gsi);
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location_t loc = gimple_location (stmt);
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if (gimple_code (stmt) == GIMPLE_SWITCH)
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{
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gswitch *switch_stmt = as_a <gswitch *> (stmt);
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tree index = gimple_switch_index (switch_stmt);
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if (TREE_CODE (index) == SSA_NAME)
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{
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int i;
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int n_labels = gimple_switch_num_labels (switch_stmt);
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tree *info = XCNEWVEC (tree, last_basic_block_for_fn (cfun));
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edge e;
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edge_iterator ei;
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for (i = 0; i < n_labels; i++)
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{
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tree label = gimple_switch_label (switch_stmt, i);
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basic_block target_bb = label_to_block (CASE_LABEL (label));
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if (CASE_HIGH (label)
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|| !CASE_LOW (label)
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|| info[target_bb->index])
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info[target_bb->index] = error_mark_node;
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else
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info[target_bb->index] = label;
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}
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FOR_EACH_EDGE (e, ei, bb->succs)
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{
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basic_block target_bb = e->dest;
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tree label = info[target_bb->index];
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if (label != NULL && label != error_mark_node)
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{
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tree x = fold_convert_loc (loc, TREE_TYPE (index),
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CASE_LOW (label));
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edge_info = allocate_edge_info (e);
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edge_info->lhs = index;
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edge_info->rhs = x;
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}
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}
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free (info);
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}
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}
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/* A COND_EXPR may create equivalences too. */
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if (gimple_code (stmt) == GIMPLE_COND)
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{
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edge true_edge;
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edge false_edge;
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tree op0 = gimple_cond_lhs (stmt);
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tree op1 = gimple_cond_rhs (stmt);
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enum tree_code code = gimple_cond_code (stmt);
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extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
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/* Special case comparing booleans against a constant as we
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know the value of OP0 on both arms of the branch. i.e., we
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can record an equivalence for OP0 rather than COND.
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However, don't do this if the constant isn't zero or one.
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Such conditionals will get optimized more thoroughly during
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the domwalk. */
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if ((code == EQ_EXPR || code == NE_EXPR)
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&& TREE_CODE (op0) == SSA_NAME
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&& ssa_name_has_boolean_range (op0)
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&& is_gimple_min_invariant (op1)
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&& (integer_zerop (op1) || integer_onep (op1)))
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{
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tree true_val = constant_boolean_node (true, TREE_TYPE (op0));
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tree false_val = constant_boolean_node (false, TREE_TYPE (op0));
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if (code == EQ_EXPR)
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{
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edge_info = allocate_edge_info (true_edge);
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edge_info->lhs = op0;
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edge_info->rhs = (integer_zerop (op1) ? false_val : true_val);
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edge_info = allocate_edge_info (false_edge);
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edge_info->lhs = op0;
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edge_info->rhs = (integer_zerop (op1) ? true_val : false_val);
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}
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else
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{
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edge_info = allocate_edge_info (true_edge);
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edge_info->lhs = op0;
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edge_info->rhs = (integer_zerop (op1) ? true_val : false_val);
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edge_info = allocate_edge_info (false_edge);
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edge_info->lhs = op0;
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edge_info->rhs = (integer_zerop (op1) ? false_val : true_val);
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}
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}
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else if (is_gimple_min_invariant (op0)
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&& (TREE_CODE (op1) == SSA_NAME
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|| is_gimple_min_invariant (op1)))
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{
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tree cond = build2 (code, boolean_type_node, op0, op1);
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tree inverted = invert_truthvalue_loc (loc, cond);
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bool can_infer_simple_equiv
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= !(HONOR_SIGNED_ZEROS (op0)
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&& real_zerop (op0));
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struct edge_info *edge_info;
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edge_info = allocate_edge_info (true_edge);
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record_conditions (edge_info, cond, inverted);
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if (can_infer_simple_equiv && code == EQ_EXPR)
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{
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edge_info->lhs = op1;
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edge_info->rhs = op0;
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}
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edge_info = allocate_edge_info (false_edge);
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record_conditions (edge_info, inverted, cond);
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if (can_infer_simple_equiv && TREE_CODE (inverted) == EQ_EXPR)
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{
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edge_info->lhs = op1;
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edge_info->rhs = op0;
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}
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}
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else if (TREE_CODE (op0) == SSA_NAME
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&& (TREE_CODE (op1) == SSA_NAME
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|| is_gimple_min_invariant (op1)))
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{
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tree cond = build2 (code, boolean_type_node, op0, op1);
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tree inverted = invert_truthvalue_loc (loc, cond);
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bool can_infer_simple_equiv
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= !(HONOR_SIGNED_ZEROS (op1)
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&& (TREE_CODE (op1) == SSA_NAME || real_zerop (op1)));
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struct edge_info *edge_info;
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edge_info = allocate_edge_info (true_edge);
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record_conditions (edge_info, cond, inverted);
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if (can_infer_simple_equiv && code == EQ_EXPR)
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{
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edge_info->lhs = op0;
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edge_info->rhs = op1;
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}
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edge_info = allocate_edge_info (false_edge);
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record_conditions (edge_info, inverted, cond);
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if (can_infer_simple_equiv && TREE_CODE (inverted) == EQ_EXPR)
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{
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edge_info->lhs = op0;
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edge_info->rhs = op1;
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}
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}
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}
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/* ??? TRUTH_NOT_EXPR can create an equivalence too. */
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}
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}
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class dom_opt_dom_walker : public dom_walker
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{
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public:
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dom_opt_dom_walker (cdi_direction direction,
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class const_and_copies *const_and_copies,
|
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class avail_exprs_stack *avail_exprs_stack)
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|
: dom_walker (direction, true),
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m_const_and_copies (const_and_copies),
|
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m_avail_exprs_stack (avail_exprs_stack),
|
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m_dummy_cond (NULL) {}
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|
|
virtual edge before_dom_children (basic_block);
|
|
virtual void after_dom_children (basic_block);
|
|
|
|
private:
|
|
void thread_across_edge (edge);
|
|
|
|
/* Unwindable equivalences, both const/copy and expression varieties. */
|
|
class const_and_copies *m_const_and_copies;
|
|
class avail_exprs_stack *m_avail_exprs_stack;
|
|
|
|
gcond *m_dummy_cond;
|
|
};
|
|
|
|
/* Jump threading, redundancy elimination and const/copy propagation.
|
|
|
|
This pass may expose new symbols that need to be renamed into SSA. For
|
|
every new symbol exposed, its corresponding bit will be set in
|
|
VARS_TO_RENAME. */
|
|
|
|
namespace {
|
|
|
|
const pass_data pass_data_dominator =
|
|
{
|
|
GIMPLE_PASS, /* type */
|
|
"dom", /* name */
|
|
OPTGROUP_NONE, /* optinfo_flags */
|
|
TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
|
|
( PROP_cfg | PROP_ssa ), /* properties_required */
|
|
0, /* properties_provided */
|
|
0, /* properties_destroyed */
|
|
0, /* todo_flags_start */
|
|
( TODO_cleanup_cfg | TODO_update_ssa ), /* todo_flags_finish */
|
|
};
|
|
|
|
class pass_dominator : public gimple_opt_pass
|
|
{
|
|
public:
|
|
pass_dominator (gcc::context *ctxt)
|
|
: gimple_opt_pass (pass_data_dominator, ctxt),
|
|
may_peel_loop_headers_p (false)
|
|
{}
|
|
|
|
/* opt_pass methods: */
|
|
opt_pass * clone () { return new pass_dominator (m_ctxt); }
|
|
void set_pass_param (unsigned int n, bool param)
|
|
{
|
|
gcc_assert (n == 0);
|
|
may_peel_loop_headers_p = param;
|
|
}
|
|
virtual bool gate (function *) { return flag_tree_dom != 0; }
|
|
virtual unsigned int execute (function *);
|
|
|
|
private:
|
|
/* This flag is used to prevent loops from being peeled repeatedly in jump
|
|
threading; it will be removed once we preserve loop structures throughout
|
|
the compilation -- we will be able to mark the affected loops directly in
|
|
jump threading, and avoid peeling them next time. */
|
|
bool may_peel_loop_headers_p;
|
|
}; // class pass_dominator
|
|
|
|
unsigned int
|
|
pass_dominator::execute (function *fun)
|
|
{
|
|
memset (&opt_stats, 0, sizeof (opt_stats));
|
|
|
|
/* Create our hash tables. */
|
|
hash_table<expr_elt_hasher> *avail_exprs
|
|
= new hash_table<expr_elt_hasher> (1024);
|
|
class avail_exprs_stack *avail_exprs_stack
|
|
= new class avail_exprs_stack (avail_exprs);
|
|
class const_and_copies *const_and_copies = new class const_and_copies ();
|
|
need_eh_cleanup = BITMAP_ALLOC (NULL);
|
|
need_noreturn_fixup.create (0);
|
|
|
|
calculate_dominance_info (CDI_DOMINATORS);
|
|
cfg_altered = false;
|
|
|
|
/* We need to know loop structures in order to avoid destroying them
|
|
in jump threading. Note that we still can e.g. thread through loop
|
|
headers to an exit edge, or through loop header to the loop body, assuming
|
|
that we update the loop info.
|
|
|
|
TODO: We don't need to set LOOPS_HAVE_PREHEADERS generally, but due
|
|
to several overly conservative bail-outs in jump threading, case
|
|
gcc.dg/tree-ssa/pr21417.c can't be threaded if loop preheader is
|
|
missing. We should improve jump threading in future then
|
|
LOOPS_HAVE_PREHEADERS won't be needed here. */
|
|
loop_optimizer_init (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES);
|
|
|
|
/* Initialize the value-handle array. */
|
|
threadedge_initialize_values ();
|
|
|
|
/* We need accurate information regarding back edges in the CFG
|
|
for jump threading; this may include back edges that are not part of
|
|
a single loop. */
|
|
mark_dfs_back_edges ();
|
|
|
|
/* We want to create the edge info structures before the dominator walk
|
|
so that they'll be in place for the jump threader, particularly when
|
|
threading through a join block.
|
|
|
|
The conditions will be lazily updated with global equivalences as
|
|
we reach them during the dominator walk. */
|
|
basic_block bb;
|
|
FOR_EACH_BB_FN (bb, fun)
|
|
record_edge_info (bb);
|
|
|
|
/* Recursively walk the dominator tree optimizing statements. */
|
|
dom_opt_dom_walker walker (CDI_DOMINATORS,
|
|
const_and_copies,
|
|
avail_exprs_stack);
|
|
walker.walk (fun->cfg->x_entry_block_ptr);
|
|
|
|
/* Look for blocks where we cleared EDGE_EXECUTABLE on an outgoing
|
|
edge. When found, remove jump threads which contain any outgoing
|
|
edge from the affected block. */
|
|
if (cfg_altered)
|
|
{
|
|
FOR_EACH_BB_FN (bb, fun)
|
|
{
|
|
edge_iterator ei;
|
|
edge e;
|
|
|
|
/* First see if there are any edges without EDGE_EXECUTABLE
|
|
set. */
|
|
bool found = false;
|
|
FOR_EACH_EDGE (e, ei, bb->succs)
|
|
{
|
|
if ((e->flags & EDGE_EXECUTABLE) == 0)
|
|
{
|
|
found = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* If there were any such edges found, then remove jump threads
|
|
containing any edge leaving BB. */
|
|
if (found)
|
|
FOR_EACH_EDGE (e, ei, bb->succs)
|
|
remove_jump_threads_including (e);
|
|
}
|
|
}
|
|
|
|
{
|
|
gimple_stmt_iterator gsi;
|
|
basic_block bb;
|
|
FOR_EACH_BB_FN (bb, fun)
|
|
{
|
|
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
update_stmt_if_modified (gsi_stmt (gsi));
|
|
}
|
|
}
|
|
|
|
/* If we exposed any new variables, go ahead and put them into
|
|
SSA form now, before we handle jump threading. This simplifies
|
|
interactions between rewriting of _DECL nodes into SSA form
|
|
and rewriting SSA_NAME nodes into SSA form after block
|
|
duplication and CFG manipulation. */
|
|
update_ssa (TODO_update_ssa);
|
|
|
|
free_all_edge_infos ();
|
|
|
|
/* Thread jumps, creating duplicate blocks as needed. */
|
|
cfg_altered |= thread_through_all_blocks (may_peel_loop_headers_p);
|
|
|
|
if (cfg_altered)
|
|
free_dominance_info (CDI_DOMINATORS);
|
|
|
|
/* Removal of statements may make some EH edges dead. Purge
|
|
such edges from the CFG as needed. */
|
|
if (!bitmap_empty_p (need_eh_cleanup))
|
|
{
|
|
unsigned i;
|
|
bitmap_iterator bi;
|
|
|
|
/* Jump threading may have created forwarder blocks from blocks
|
|
needing EH cleanup; the new successor of these blocks, which
|
|
has inherited from the original block, needs the cleanup.
|
|
Don't clear bits in the bitmap, as that can break the bitmap
|
|
iterator. */
|
|
EXECUTE_IF_SET_IN_BITMAP (need_eh_cleanup, 0, i, bi)
|
|
{
|
|
basic_block bb = BASIC_BLOCK_FOR_FN (fun, i);
|
|
if (bb == NULL)
|
|
continue;
|
|
while (single_succ_p (bb)
|
|
&& (single_succ_edge (bb)->flags & EDGE_EH) == 0)
|
|
bb = single_succ (bb);
|
|
if (bb == EXIT_BLOCK_PTR_FOR_FN (fun))
|
|
continue;
|
|
if ((unsigned) bb->index != i)
|
|
bitmap_set_bit (need_eh_cleanup, bb->index);
|
|
}
|
|
|
|
gimple_purge_all_dead_eh_edges (need_eh_cleanup);
|
|
bitmap_clear (need_eh_cleanup);
|
|
}
|
|
|
|
/* Fixup stmts that became noreturn calls. This may require splitting
|
|
blocks and thus isn't possible during the dominator walk or before
|
|
jump threading finished. Do this in reverse order so we don't
|
|
inadvertedly remove a stmt we want to fixup by visiting a dominating
|
|
now noreturn call first. */
|
|
while (!need_noreturn_fixup.is_empty ())
|
|
{
|
|
gimple *stmt = need_noreturn_fixup.pop ();
|
|
if (dump_file && dump_flags & TDF_DETAILS)
|
|
{
|
|
fprintf (dump_file, "Fixing up noreturn call ");
|
|
print_gimple_stmt (dump_file, stmt, 0, 0);
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
fixup_noreturn_call (stmt);
|
|
}
|
|
|
|
statistics_counter_event (fun, "Redundant expressions eliminated",
|
|
opt_stats.num_re);
|
|
statistics_counter_event (fun, "Constants propagated",
|
|
opt_stats.num_const_prop);
|
|
statistics_counter_event (fun, "Copies propagated",
|
|
opt_stats.num_copy_prop);
|
|
|
|
/* Debugging dumps. */
|
|
if (dump_file && (dump_flags & TDF_STATS))
|
|
dump_dominator_optimization_stats (dump_file, avail_exprs);
|
|
|
|
loop_optimizer_finalize ();
|
|
|
|
/* Delete our main hashtable. */
|
|
delete avail_exprs;
|
|
avail_exprs = NULL;
|
|
|
|
/* Free asserted bitmaps and stacks. */
|
|
BITMAP_FREE (need_eh_cleanup);
|
|
need_noreturn_fixup.release ();
|
|
delete avail_exprs_stack;
|
|
delete const_and_copies;
|
|
|
|
/* Free the value-handle array. */
|
|
threadedge_finalize_values ();
|
|
|
|
return 0;
|
|
}
|
|
|
|
} // anon namespace
|
|
|
|
gimple_opt_pass *
|
|
make_pass_dominator (gcc::context *ctxt)
|
|
{
|
|
return new pass_dominator (ctxt);
|
|
}
|
|
|
|
|
|
/* Given a conditional statement CONDSTMT, convert the
|
|
condition to a canonical form. */
|
|
|
|
static void
|
|
canonicalize_comparison (gcond *condstmt)
|
|
{
|
|
tree op0;
|
|
tree op1;
|
|
enum tree_code code;
|
|
|
|
gcc_assert (gimple_code (condstmt) == GIMPLE_COND);
|
|
|
|
op0 = gimple_cond_lhs (condstmt);
|
|
op1 = gimple_cond_rhs (condstmt);
|
|
|
|
code = gimple_cond_code (condstmt);
|
|
|
|
/* If it would be profitable to swap the operands, then do so to
|
|
canonicalize the statement, enabling better optimization.
|
|
|
|
By placing canonicalization of such expressions here we
|
|
transparently keep statements in canonical form, even
|
|
when the statement is modified. */
|
|
if (tree_swap_operands_p (op0, op1, false))
|
|
{
|
|
/* For relationals we need to swap the operands
|
|
and change the code. */
|
|
if (code == LT_EXPR
|
|
|| code == GT_EXPR
|
|
|| code == LE_EXPR
|
|
|| code == GE_EXPR)
|
|
{
|
|
code = swap_tree_comparison (code);
|
|
|
|
gimple_cond_set_code (condstmt, code);
|
|
gimple_cond_set_lhs (condstmt, op1);
|
|
gimple_cond_set_rhs (condstmt, op0);
|
|
|
|
update_stmt (condstmt);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* A trivial wrapper so that we can present the generic jump
|
|
threading code with a simple API for simplifying statements. */
|
|
static tree
|
|
simplify_stmt_for_jump_threading (gimple *stmt,
|
|
gimple *within_stmt ATTRIBUTE_UNUSED,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
return lookup_avail_expr (stmt, false, avail_exprs_stack);
|
|
}
|
|
|
|
/* Valueize hook for gimple_fold_stmt_to_constant_1. */
|
|
|
|
static tree
|
|
dom_valueize (tree t)
|
|
{
|
|
if (TREE_CODE (t) == SSA_NAME)
|
|
{
|
|
tree tem = SSA_NAME_VALUE (t);
|
|
if (tem)
|
|
return tem;
|
|
}
|
|
return t;
|
|
}
|
|
|
|
/* We have just found an equivalence for LHS on an edge E.
|
|
Look backwards to other uses of LHS and see if we can derive
|
|
additional equivalences that are valid on edge E. */
|
|
static void
|
|
back_propagate_equivalences (tree lhs, edge e,
|
|
class const_and_copies *const_and_copies)
|
|
{
|
|
use_operand_p use_p;
|
|
imm_use_iterator iter;
|
|
bitmap domby = NULL;
|
|
basic_block dest = e->dest;
|
|
|
|
/* Iterate over the uses of LHS to see if any dominate E->dest.
|
|
If so, they may create useful equivalences too.
|
|
|
|
??? If the code gets re-organized to a worklist to catch more
|
|
indirect opportunities and it is made to handle PHIs then this
|
|
should only consider use_stmts in basic-blocks we have already visited. */
|
|
FOR_EACH_IMM_USE_FAST (use_p, iter, lhs)
|
|
{
|
|
gimple *use_stmt = USE_STMT (use_p);
|
|
|
|
/* Often the use is in DEST, which we trivially know we can't use.
|
|
This is cheaper than the dominator set tests below. */
|
|
if (dest == gimple_bb (use_stmt))
|
|
continue;
|
|
|
|
/* Filter out statements that can never produce a useful
|
|
equivalence. */
|
|
tree lhs2 = gimple_get_lhs (use_stmt);
|
|
if (!lhs2 || TREE_CODE (lhs2) != SSA_NAME)
|
|
continue;
|
|
|
|
/* Profiling has shown the domination tests here can be fairly
|
|
expensive. We get significant improvements by building the
|
|
set of blocks that dominate BB. We can then just test
|
|
for set membership below.
|
|
|
|
We also initialize the set lazily since often the only uses
|
|
are going to be in the same block as DEST. */
|
|
if (!domby)
|
|
{
|
|
domby = BITMAP_ALLOC (NULL);
|
|
basic_block bb = get_immediate_dominator (CDI_DOMINATORS, dest);
|
|
while (bb)
|
|
{
|
|
bitmap_set_bit (domby, bb->index);
|
|
bb = get_immediate_dominator (CDI_DOMINATORS, bb);
|
|
}
|
|
}
|
|
|
|
/* This tests if USE_STMT does not dominate DEST. */
|
|
if (!bitmap_bit_p (domby, gimple_bb (use_stmt)->index))
|
|
continue;
|
|
|
|
/* At this point USE_STMT dominates DEST and may result in a
|
|
useful equivalence. Try to simplify its RHS to a constant
|
|
or SSA_NAME. */
|
|
tree res = gimple_fold_stmt_to_constant_1 (use_stmt, dom_valueize,
|
|
no_follow_ssa_edges);
|
|
if (res && (TREE_CODE (res) == SSA_NAME || is_gimple_min_invariant (res)))
|
|
record_equality (lhs2, res, const_and_copies);
|
|
}
|
|
|
|
if (domby)
|
|
BITMAP_FREE (domby);
|
|
}
|
|
|
|
/* Record into CONST_AND_COPIES and AVAIL_EXPRS_STACK any equivalences implied
|
|
by traversing edge E (which are cached in E->aux).
|
|
|
|
Callers are responsible for managing the unwinding markers. */
|
|
void
|
|
record_temporary_equivalences (edge e,
|
|
class const_and_copies *const_and_copies,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
int i;
|
|
struct edge_info *edge_info = (struct edge_info *) e->aux;
|
|
|
|
/* If we have info associated with this edge, record it into
|
|
our equivalence tables. */
|
|
if (edge_info)
|
|
{
|
|
cond_equivalence *eq;
|
|
/* If we have 0 = COND or 1 = COND equivalences, record them
|
|
into our expression hash tables. */
|
|
for (i = 0; edge_info->cond_equivalences.iterate (i, &eq); ++i)
|
|
record_cond (eq, avail_exprs_stack);
|
|
|
|
tree lhs = edge_info->lhs;
|
|
if (!lhs || TREE_CODE (lhs) != SSA_NAME)
|
|
return;
|
|
|
|
/* Record the simple NAME = VALUE equivalence. */
|
|
tree rhs = edge_info->rhs;
|
|
record_equality (lhs, rhs, const_and_copies);
|
|
|
|
/* We already recorded that LHS = RHS, with canonicalization,
|
|
value chain following, etc.
|
|
|
|
We also want to return RHS = LHS, but without any canonicalization
|
|
or value chain following. */
|
|
if (TREE_CODE (rhs) == SSA_NAME)
|
|
const_and_copies->record_const_or_copy_raw (rhs, lhs,
|
|
SSA_NAME_VALUE (rhs));
|
|
|
|
/* If LHS is an SSA_NAME and RHS is a constant integer and LHS was
|
|
set via a widening type conversion, then we may be able to record
|
|
additional equivalences. */
|
|
if (TREE_CODE (rhs) == INTEGER_CST)
|
|
{
|
|
gimple *defstmt = SSA_NAME_DEF_STMT (lhs);
|
|
|
|
if (defstmt
|
|
&& is_gimple_assign (defstmt)
|
|
&& CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (defstmt)))
|
|
{
|
|
tree old_rhs = gimple_assign_rhs1 (defstmt);
|
|
|
|
/* If the conversion widens the original value and
|
|
the constant is in the range of the type of OLD_RHS,
|
|
then convert the constant and record the equivalence.
|
|
|
|
Note that int_fits_type_p does not check the precision
|
|
if the upper and lower bounds are OK. */
|
|
if (INTEGRAL_TYPE_P (TREE_TYPE (old_rhs))
|
|
&& (TYPE_PRECISION (TREE_TYPE (lhs))
|
|
> TYPE_PRECISION (TREE_TYPE (old_rhs)))
|
|
&& int_fits_type_p (rhs, TREE_TYPE (old_rhs)))
|
|
{
|
|
tree newval = fold_convert (TREE_TYPE (old_rhs), rhs);
|
|
record_equality (old_rhs, newval, const_and_copies);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Any equivalence found for LHS may result in additional
|
|
equivalences for other uses of LHS that we have already
|
|
processed. */
|
|
back_propagate_equivalences (lhs, e, const_and_copies);
|
|
}
|
|
}
|
|
|
|
/* Wrapper for common code to attempt to thread an edge. For example,
|
|
it handles lazily building the dummy condition and the bookkeeping
|
|
when jump threading is successful. */
|
|
|
|
void
|
|
dom_opt_dom_walker::thread_across_edge (edge e)
|
|
{
|
|
if (! m_dummy_cond)
|
|
m_dummy_cond =
|
|
gimple_build_cond (NE_EXPR,
|
|
integer_zero_node, integer_zero_node,
|
|
NULL, NULL);
|
|
|
|
/* Push a marker on both stacks so we can unwind the tables back to their
|
|
current state. */
|
|
m_avail_exprs_stack->push_marker ();
|
|
m_const_and_copies->push_marker ();
|
|
|
|
/* With all the edge equivalences in the tables, go ahead and attempt
|
|
to thread through E->dest. */
|
|
::thread_across_edge (m_dummy_cond, e, false,
|
|
m_const_and_copies, m_avail_exprs_stack,
|
|
simplify_stmt_for_jump_threading);
|
|
|
|
/* And restore the various tables to their state before
|
|
we threaded this edge.
|
|
|
|
XXX The code in tree-ssa-threadedge.c will restore the state of
|
|
the const_and_copies table. We we just have to restore the expression
|
|
table. */
|
|
m_avail_exprs_stack->pop_to_marker ();
|
|
}
|
|
|
|
/* PHI nodes can create equivalences too.
|
|
|
|
Ignoring any alternatives which are the same as the result, if
|
|
all the alternatives are equal, then the PHI node creates an
|
|
equivalence. */
|
|
|
|
static void
|
|
record_equivalences_from_phis (basic_block bb)
|
|
{
|
|
gphi_iterator gsi;
|
|
|
|
for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
{
|
|
gphi *phi = gsi.phi ();
|
|
|
|
tree lhs = gimple_phi_result (phi);
|
|
tree rhs = NULL;
|
|
size_t i;
|
|
|
|
for (i = 0; i < gimple_phi_num_args (phi); i++)
|
|
{
|
|
tree t = gimple_phi_arg_def (phi, i);
|
|
|
|
/* Ignore alternatives which are the same as our LHS. Since
|
|
LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
|
|
can simply compare pointers. */
|
|
if (lhs == t)
|
|
continue;
|
|
|
|
/* If the associated edge is not marked as executable, then it
|
|
can be ignored. */
|
|
if ((gimple_phi_arg_edge (phi, i)->flags & EDGE_EXECUTABLE) == 0)
|
|
continue;
|
|
|
|
t = dom_valueize (t);
|
|
|
|
/* If we have not processed an alternative yet, then set
|
|
RHS to this alternative. */
|
|
if (rhs == NULL)
|
|
rhs = t;
|
|
/* If we have processed an alternative (stored in RHS), then
|
|
see if it is equal to this one. If it isn't, then stop
|
|
the search. */
|
|
else if (! operand_equal_for_phi_arg_p (rhs, t))
|
|
break;
|
|
}
|
|
|
|
/* If we had no interesting alternatives, then all the RHS alternatives
|
|
must have been the same as LHS. */
|
|
if (!rhs)
|
|
rhs = lhs;
|
|
|
|
/* If we managed to iterate through each PHI alternative without
|
|
breaking out of the loop, then we have a PHI which may create
|
|
a useful equivalence. We do not need to record unwind data for
|
|
this, since this is a true assignment and not an equivalence
|
|
inferred from a comparison. All uses of this ssa name are dominated
|
|
by this assignment, so unwinding just costs time and space. */
|
|
if (i == gimple_phi_num_args (phi)
|
|
&& may_propagate_copy (lhs, rhs))
|
|
set_ssa_name_value (lhs, rhs);
|
|
}
|
|
}
|
|
|
|
/* Ignoring loop backedges, if BB has precisely one incoming edge then
|
|
return that edge. Otherwise return NULL. */
|
|
static edge
|
|
single_incoming_edge_ignoring_loop_edges (basic_block bb)
|
|
{
|
|
edge retval = NULL;
|
|
edge e;
|
|
edge_iterator ei;
|
|
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
{
|
|
/* A loop back edge can be identified by the destination of
|
|
the edge dominating the source of the edge. */
|
|
if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
|
|
continue;
|
|
|
|
/* We can safely ignore edges that are not executable. */
|
|
if ((e->flags & EDGE_EXECUTABLE) == 0)
|
|
continue;
|
|
|
|
/* If we have already seen a non-loop edge, then we must have
|
|
multiple incoming non-loop edges and thus we return NULL. */
|
|
if (retval)
|
|
return NULL;
|
|
|
|
/* This is the first non-loop incoming edge we have found. Record
|
|
it. */
|
|
retval = e;
|
|
}
|
|
|
|
return retval;
|
|
}
|
|
|
|
/* Record any equivalences created by the incoming edge to BB into
|
|
CONST_AND_COPIES and AVAIL_EXPRS_STACK. If BB has more than one
|
|
incoming edge, then no equivalence is created. */
|
|
|
|
static void
|
|
record_equivalences_from_incoming_edge (basic_block bb,
|
|
class const_and_copies *const_and_copies,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
edge e;
|
|
basic_block parent;
|
|
|
|
/* If our parent block ended with a control statement, then we may be
|
|
able to record some equivalences based on which outgoing edge from
|
|
the parent was followed. */
|
|
parent = get_immediate_dominator (CDI_DOMINATORS, bb);
|
|
|
|
e = single_incoming_edge_ignoring_loop_edges (bb);
|
|
|
|
/* If we had a single incoming edge from our parent block, then enter
|
|
any data associated with the edge into our tables. */
|
|
if (e && e->src == parent)
|
|
record_temporary_equivalences (e, const_and_copies, avail_exprs_stack);
|
|
}
|
|
|
|
/* Dump statistics for the hash table HTAB. */
|
|
|
|
static void
|
|
htab_statistics (FILE *file, const hash_table<expr_elt_hasher> &htab)
|
|
{
|
|
fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
|
|
(long) htab.size (),
|
|
(long) htab.elements (),
|
|
htab.collisions ());
|
|
}
|
|
|
|
/* Dump SSA statistics on FILE. */
|
|
|
|
static void
|
|
dump_dominator_optimization_stats (FILE *file,
|
|
hash_table<expr_elt_hasher> *avail_exprs)
|
|
{
|
|
fprintf (file, "Total number of statements: %6ld\n\n",
|
|
opt_stats.num_stmts);
|
|
fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
|
|
opt_stats.num_exprs_considered);
|
|
|
|
fprintf (file, "\nHash table statistics:\n");
|
|
|
|
fprintf (file, " avail_exprs: ");
|
|
htab_statistics (file, *avail_exprs);
|
|
}
|
|
|
|
|
|
/* Enter condition equivalence P into AVAIL_EXPRS_HASH.
|
|
|
|
This indicates that a conditional expression has a known
|
|
boolean value. */
|
|
|
|
static void
|
|
record_cond (cond_equivalence *p,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
class expr_hash_elt *element = new expr_hash_elt (&p->cond, p->value);
|
|
expr_hash_elt **slot;
|
|
|
|
hash_table<expr_elt_hasher> *avail_exprs = avail_exprs_stack->avail_exprs ();
|
|
slot = avail_exprs->find_slot_with_hash (element, element->hash (), INSERT);
|
|
if (*slot == NULL)
|
|
{
|
|
*slot = element;
|
|
avail_exprs_stack->record_expr (element, NULL, '1');
|
|
}
|
|
else
|
|
delete element;
|
|
}
|
|
|
|
/* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
|
|
This constrains the cases in which we may treat this as assignment. */
|
|
|
|
static void
|
|
record_equality (tree x, tree y, class const_and_copies *const_and_copies)
|
|
{
|
|
tree prev_x = NULL, prev_y = NULL;
|
|
|
|
if (tree_swap_operands_p (x, y, false))
|
|
std::swap (x, y);
|
|
|
|
/* Most of the time tree_swap_operands_p does what we want. But there
|
|
are cases where we know one operand is better for copy propagation than
|
|
the other. Given no other code cares about ordering of equality
|
|
comparison operators for that purpose, we just handle the special cases
|
|
here. */
|
|
if (TREE_CODE (x) == SSA_NAME && TREE_CODE (y) == SSA_NAME)
|
|
{
|
|
/* If one operand is a single use operand, then make it
|
|
X. This will preserve its single use properly and if this
|
|
conditional is eliminated, the computation of X can be
|
|
eliminated as well. */
|
|
if (has_single_use (y) && ! has_single_use (x))
|
|
std::swap (x, y);
|
|
}
|
|
if (TREE_CODE (x) == SSA_NAME)
|
|
prev_x = SSA_NAME_VALUE (x);
|
|
if (TREE_CODE (y) == SSA_NAME)
|
|
prev_y = SSA_NAME_VALUE (y);
|
|
|
|
/* If one of the previous values is invariant, or invariant in more loops
|
|
(by depth), then use that.
|
|
Otherwise it doesn't matter which value we choose, just so
|
|
long as we canonicalize on one value. */
|
|
if (is_gimple_min_invariant (y))
|
|
;
|
|
else if (is_gimple_min_invariant (x))
|
|
prev_x = x, x = y, y = prev_x, prev_x = prev_y;
|
|
else if (prev_x && is_gimple_min_invariant (prev_x))
|
|
x = y, y = prev_x, prev_x = prev_y;
|
|
else if (prev_y)
|
|
y = prev_y;
|
|
|
|
/* After the swapping, we must have one SSA_NAME. */
|
|
if (TREE_CODE (x) != SSA_NAME)
|
|
return;
|
|
|
|
/* For IEEE, -0.0 == 0.0, so we don't necessarily know the sign of a
|
|
variable compared against zero. If we're honoring signed zeros,
|
|
then we cannot record this value unless we know that the value is
|
|
nonzero. */
|
|
if (HONOR_SIGNED_ZEROS (x)
|
|
&& (TREE_CODE (y) != REAL_CST
|
|
|| real_equal (&dconst0, &TREE_REAL_CST (y))))
|
|
return;
|
|
|
|
const_and_copies->record_const_or_copy (x, y, prev_x);
|
|
}
|
|
|
|
/* Returns true when STMT is a simple iv increment. It detects the
|
|
following situation:
|
|
|
|
i_1 = phi (..., i_2)
|
|
i_2 = i_1 +/- ... */
|
|
|
|
bool
|
|
simple_iv_increment_p (gimple *stmt)
|
|
{
|
|
enum tree_code code;
|
|
tree lhs, preinc;
|
|
gimple *phi;
|
|
size_t i;
|
|
|
|
if (gimple_code (stmt) != GIMPLE_ASSIGN)
|
|
return false;
|
|
|
|
lhs = gimple_assign_lhs (stmt);
|
|
if (TREE_CODE (lhs) != SSA_NAME)
|
|
return false;
|
|
|
|
code = gimple_assign_rhs_code (stmt);
|
|
if (code != PLUS_EXPR
|
|
&& code != MINUS_EXPR
|
|
&& code != POINTER_PLUS_EXPR)
|
|
return false;
|
|
|
|
preinc = gimple_assign_rhs1 (stmt);
|
|
if (TREE_CODE (preinc) != SSA_NAME)
|
|
return false;
|
|
|
|
phi = SSA_NAME_DEF_STMT (preinc);
|
|
if (gimple_code (phi) != GIMPLE_PHI)
|
|
return false;
|
|
|
|
for (i = 0; i < gimple_phi_num_args (phi); i++)
|
|
if (gimple_phi_arg_def (phi, i) == lhs)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Propagate know values from SSA_NAME_VALUE into the PHI nodes of the
|
|
successors of BB. */
|
|
|
|
static void
|
|
cprop_into_successor_phis (basic_block bb,
|
|
class const_and_copies *const_and_copies)
|
|
{
|
|
edge e;
|
|
edge_iterator ei;
|
|
|
|
FOR_EACH_EDGE (e, ei, bb->succs)
|
|
{
|
|
int indx;
|
|
gphi_iterator gsi;
|
|
|
|
/* If this is an abnormal edge, then we do not want to copy propagate
|
|
into the PHI alternative associated with this edge. */
|
|
if (e->flags & EDGE_ABNORMAL)
|
|
continue;
|
|
|
|
gsi = gsi_start_phis (e->dest);
|
|
if (gsi_end_p (gsi))
|
|
continue;
|
|
|
|
/* We may have an equivalence associated with this edge. While
|
|
we can not propagate it into non-dominated blocks, we can
|
|
propagate them into PHIs in non-dominated blocks. */
|
|
|
|
/* Push the unwind marker so we can reset the const and copies
|
|
table back to its original state after processing this edge. */
|
|
const_and_copies->push_marker ();
|
|
|
|
/* Extract and record any simple NAME = VALUE equivalences.
|
|
|
|
Don't bother with [01] = COND equivalences, they're not useful
|
|
here. */
|
|
struct edge_info *edge_info = (struct edge_info *) e->aux;
|
|
if (edge_info)
|
|
{
|
|
tree lhs = edge_info->lhs;
|
|
tree rhs = edge_info->rhs;
|
|
|
|
if (lhs && TREE_CODE (lhs) == SSA_NAME)
|
|
const_and_copies->record_const_or_copy (lhs, rhs);
|
|
}
|
|
|
|
indx = e->dest_idx;
|
|
for ( ; !gsi_end_p (gsi); gsi_next (&gsi))
|
|
{
|
|
tree new_val;
|
|
use_operand_p orig_p;
|
|
tree orig_val;
|
|
gphi *phi = gsi.phi ();
|
|
|
|
/* The alternative may be associated with a constant, so verify
|
|
it is an SSA_NAME before doing anything with it. */
|
|
orig_p = gimple_phi_arg_imm_use_ptr (phi, indx);
|
|
orig_val = get_use_from_ptr (orig_p);
|
|
if (TREE_CODE (orig_val) != SSA_NAME)
|
|
continue;
|
|
|
|
/* If we have *ORIG_P in our constant/copy table, then replace
|
|
ORIG_P with its value in our constant/copy table. */
|
|
new_val = SSA_NAME_VALUE (orig_val);
|
|
if (new_val
|
|
&& new_val != orig_val
|
|
&& may_propagate_copy (orig_val, new_val))
|
|
propagate_value (orig_p, new_val);
|
|
}
|
|
|
|
const_and_copies->pop_to_marker ();
|
|
}
|
|
}
|
|
|
|
edge
|
|
dom_opt_dom_walker::before_dom_children (basic_block bb)
|
|
{
|
|
gimple_stmt_iterator gsi;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, "\n\nOptimizing block #%d\n\n", bb->index);
|
|
|
|
/* Push a marker on the stacks of local information so that we know how
|
|
far to unwind when we finalize this block. */
|
|
m_avail_exprs_stack->push_marker ();
|
|
m_const_and_copies->push_marker ();
|
|
|
|
record_equivalences_from_incoming_edge (bb, m_const_and_copies,
|
|
m_avail_exprs_stack);
|
|
|
|
/* PHI nodes can create equivalences too. */
|
|
record_equivalences_from_phis (bb);
|
|
|
|
/* Create equivalences from redundant PHIs. PHIs are only truly
|
|
redundant when they exist in the same block, so push another
|
|
marker and unwind right afterwards. */
|
|
m_avail_exprs_stack->push_marker ();
|
|
for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
eliminate_redundant_computations (&gsi, m_const_and_copies,
|
|
m_avail_exprs_stack);
|
|
m_avail_exprs_stack->pop_to_marker ();
|
|
|
|
edge taken_edge = NULL;
|
|
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
taken_edge
|
|
= optimize_stmt (bb, gsi, m_const_and_copies, m_avail_exprs_stack);
|
|
|
|
/* Now prepare to process dominated blocks. */
|
|
record_edge_info (bb);
|
|
cprop_into_successor_phis (bb, m_const_and_copies);
|
|
if (taken_edge && !dbg_cnt (dom_unreachable_edges))
|
|
return NULL;
|
|
|
|
return taken_edge;
|
|
}
|
|
|
|
/* We have finished processing the dominator children of BB, perform
|
|
any finalization actions in preparation for leaving this node in
|
|
the dominator tree. */
|
|
|
|
void
|
|
dom_opt_dom_walker::after_dom_children (basic_block bb)
|
|
{
|
|
gimple *last;
|
|
|
|
/* If we have an outgoing edge to a block with multiple incoming and
|
|
outgoing edges, then we may be able to thread the edge, i.e., we
|
|
may be able to statically determine which of the outgoing edges
|
|
will be traversed when the incoming edge from BB is traversed. */
|
|
if (single_succ_p (bb)
|
|
&& (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0
|
|
&& potentially_threadable_block (single_succ (bb)))
|
|
{
|
|
thread_across_edge (single_succ_edge (bb));
|
|
}
|
|
else if ((last = last_stmt (bb))
|
|
&& gimple_code (last) == GIMPLE_COND
|
|
&& EDGE_COUNT (bb->succs) == 2
|
|
&& (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
|
|
&& (EDGE_SUCC (bb, 1)->flags & EDGE_ABNORMAL) == 0)
|
|
{
|
|
edge true_edge, false_edge;
|
|
|
|
extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
|
|
|
|
/* Only try to thread the edge if it reaches a target block with
|
|
more than one predecessor and more than one successor. */
|
|
if (potentially_threadable_block (true_edge->dest))
|
|
thread_across_edge (true_edge);
|
|
|
|
/* Similarly for the ELSE arm. */
|
|
if (potentially_threadable_block (false_edge->dest))
|
|
thread_across_edge (false_edge);
|
|
|
|
}
|
|
|
|
/* These remove expressions local to BB from the tables. */
|
|
m_avail_exprs_stack->pop_to_marker ();
|
|
m_const_and_copies->pop_to_marker ();
|
|
}
|
|
|
|
/* Search for redundant computations in STMT. If any are found, then
|
|
replace them with the variable holding the result of the computation.
|
|
|
|
If safe, record this expression into AVAIL_EXPRS_STACK and
|
|
CONST_AND_COPIES. */
|
|
|
|
static void
|
|
eliminate_redundant_computations (gimple_stmt_iterator* gsi,
|
|
class const_and_copies *const_and_copies,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
tree expr_type;
|
|
tree cached_lhs;
|
|
tree def;
|
|
bool insert = true;
|
|
bool assigns_var_p = false;
|
|
|
|
gimple *stmt = gsi_stmt (*gsi);
|
|
|
|
if (gimple_code (stmt) == GIMPLE_PHI)
|
|
def = gimple_phi_result (stmt);
|
|
else
|
|
def = gimple_get_lhs (stmt);
|
|
|
|
/* Certain expressions on the RHS can be optimized away, but can not
|
|
themselves be entered into the hash tables. */
|
|
if (! def
|
|
|| TREE_CODE (def) != SSA_NAME
|
|
|| SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
|
|
|| gimple_vdef (stmt)
|
|
/* Do not record equivalences for increments of ivs. This would create
|
|
overlapping live ranges for a very questionable gain. */
|
|
|| simple_iv_increment_p (stmt))
|
|
insert = false;
|
|
|
|
/* Check if the expression has been computed before. */
|
|
cached_lhs = lookup_avail_expr (stmt, insert, avail_exprs_stack);
|
|
|
|
opt_stats.num_exprs_considered++;
|
|
|
|
/* Get the type of the expression we are trying to optimize. */
|
|
if (is_gimple_assign (stmt))
|
|
{
|
|
expr_type = TREE_TYPE (gimple_assign_lhs (stmt));
|
|
assigns_var_p = true;
|
|
}
|
|
else if (gimple_code (stmt) == GIMPLE_COND)
|
|
expr_type = boolean_type_node;
|
|
else if (is_gimple_call (stmt))
|
|
{
|
|
gcc_assert (gimple_call_lhs (stmt));
|
|
expr_type = TREE_TYPE (gimple_call_lhs (stmt));
|
|
assigns_var_p = true;
|
|
}
|
|
else if (gswitch *swtch_stmt = dyn_cast <gswitch *> (stmt))
|
|
expr_type = TREE_TYPE (gimple_switch_index (swtch_stmt));
|
|
else if (gimple_code (stmt) == GIMPLE_PHI)
|
|
/* We can't propagate into a phi, so the logic below doesn't apply.
|
|
Instead record an equivalence between the cached LHS and the
|
|
PHI result of this statement, provided they are in the same block.
|
|
This should be sufficient to kill the redundant phi. */
|
|
{
|
|
if (def && cached_lhs)
|
|
const_and_copies->record_const_or_copy (def, cached_lhs);
|
|
return;
|
|
}
|
|
else
|
|
gcc_unreachable ();
|
|
|
|
if (!cached_lhs)
|
|
return;
|
|
|
|
/* It is safe to ignore types here since we have already done
|
|
type checking in the hashing and equality routines. In fact
|
|
type checking here merely gets in the way of constant
|
|
propagation. Also, make sure that it is safe to propagate
|
|
CACHED_LHS into the expression in STMT. */
|
|
if ((TREE_CODE (cached_lhs) != SSA_NAME
|
|
&& (assigns_var_p
|
|
|| useless_type_conversion_p (expr_type, TREE_TYPE (cached_lhs))))
|
|
|| may_propagate_copy_into_stmt (stmt, cached_lhs))
|
|
{
|
|
gcc_checking_assert (TREE_CODE (cached_lhs) == SSA_NAME
|
|
|| is_gimple_min_invariant (cached_lhs));
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, " Replaced redundant expr '");
|
|
print_gimple_expr (dump_file, stmt, 0, dump_flags);
|
|
fprintf (dump_file, "' with '");
|
|
print_generic_expr (dump_file, cached_lhs, dump_flags);
|
|
fprintf (dump_file, "'\n");
|
|
}
|
|
|
|
opt_stats.num_re++;
|
|
|
|
if (assigns_var_p
|
|
&& !useless_type_conversion_p (expr_type, TREE_TYPE (cached_lhs)))
|
|
cached_lhs = fold_convert (expr_type, cached_lhs);
|
|
|
|
propagate_tree_value_into_stmt (gsi, cached_lhs);
|
|
|
|
/* Since it is always necessary to mark the result as modified,
|
|
perhaps we should move this into propagate_tree_value_into_stmt
|
|
itself. */
|
|
gimple_set_modified (gsi_stmt (*gsi), true);
|
|
}
|
|
}
|
|
|
|
/* STMT, a GIMPLE_ASSIGN, may create certain equivalences, in either
|
|
the available expressions table or the const_and_copies table.
|
|
Detect and record those equivalences into AVAIL_EXPRS_STACK.
|
|
|
|
We handle only very simple copy equivalences here. The heavy
|
|
lifing is done by eliminate_redundant_computations. */
|
|
|
|
static void
|
|
record_equivalences_from_stmt (gimple *stmt, int may_optimize_p,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
tree lhs;
|
|
enum tree_code lhs_code;
|
|
|
|
gcc_assert (is_gimple_assign (stmt));
|
|
|
|
lhs = gimple_assign_lhs (stmt);
|
|
lhs_code = TREE_CODE (lhs);
|
|
|
|
if (lhs_code == SSA_NAME
|
|
&& gimple_assign_single_p (stmt))
|
|
{
|
|
tree rhs = gimple_assign_rhs1 (stmt);
|
|
|
|
/* If the RHS of the assignment is a constant or another variable that
|
|
may be propagated, register it in the CONST_AND_COPIES table. We
|
|
do not need to record unwind data for this, since this is a true
|
|
assignment and not an equivalence inferred from a comparison. All
|
|
uses of this ssa name are dominated by this assignment, so unwinding
|
|
just costs time and space. */
|
|
if (may_optimize_p
|
|
&& (TREE_CODE (rhs) == SSA_NAME
|
|
|| is_gimple_min_invariant (rhs)))
|
|
{
|
|
rhs = dom_valueize (rhs);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "==== ASGN ");
|
|
print_generic_expr (dump_file, lhs, 0);
|
|
fprintf (dump_file, " = ");
|
|
print_generic_expr (dump_file, rhs, 0);
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
|
|
set_ssa_name_value (lhs, rhs);
|
|
}
|
|
}
|
|
|
|
/* Make sure we can propagate &x + CST. */
|
|
if (lhs_code == SSA_NAME
|
|
&& gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
|
|
&& TREE_CODE (gimple_assign_rhs1 (stmt)) == ADDR_EXPR
|
|
&& TREE_CODE (gimple_assign_rhs2 (stmt)) == INTEGER_CST)
|
|
{
|
|
tree op0 = gimple_assign_rhs1 (stmt);
|
|
tree op1 = gimple_assign_rhs2 (stmt);
|
|
tree new_rhs
|
|
= build_fold_addr_expr (fold_build2 (MEM_REF,
|
|
TREE_TYPE (TREE_TYPE (op0)),
|
|
unshare_expr (op0),
|
|
fold_convert (ptr_type_node,
|
|
op1)));
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "==== ASGN ");
|
|
print_generic_expr (dump_file, lhs, 0);
|
|
fprintf (dump_file, " = ");
|
|
print_generic_expr (dump_file, new_rhs, 0);
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
|
|
set_ssa_name_value (lhs, new_rhs);
|
|
}
|
|
|
|
/* A memory store, even an aliased store, creates a useful
|
|
equivalence. By exchanging the LHS and RHS, creating suitable
|
|
vops and recording the result in the available expression table,
|
|
we may be able to expose more redundant loads. */
|
|
if (!gimple_has_volatile_ops (stmt)
|
|
&& gimple_references_memory_p (stmt)
|
|
&& gimple_assign_single_p (stmt)
|
|
&& (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
|
|
|| is_gimple_min_invariant (gimple_assign_rhs1 (stmt)))
|
|
&& !is_gimple_reg (lhs))
|
|
{
|
|
tree rhs = gimple_assign_rhs1 (stmt);
|
|
gassign *new_stmt;
|
|
|
|
/* Build a new statement with the RHS and LHS exchanged. */
|
|
if (TREE_CODE (rhs) == SSA_NAME)
|
|
{
|
|
/* NOTE tuples. The call to gimple_build_assign below replaced
|
|
a call to build_gimple_modify_stmt, which did not set the
|
|
SSA_NAME_DEF_STMT on the LHS of the assignment. Doing so
|
|
may cause an SSA validation failure, as the LHS may be a
|
|
default-initialized name and should have no definition. I'm
|
|
a bit dubious of this, as the artificial statement that we
|
|
generate here may in fact be ill-formed, but it is simply
|
|
used as an internal device in this pass, and never becomes
|
|
part of the CFG. */
|
|
gimple *defstmt = SSA_NAME_DEF_STMT (rhs);
|
|
new_stmt = gimple_build_assign (rhs, lhs);
|
|
SSA_NAME_DEF_STMT (rhs) = defstmt;
|
|
}
|
|
else
|
|
new_stmt = gimple_build_assign (rhs, lhs);
|
|
|
|
gimple_set_vuse (new_stmt, gimple_vdef (stmt));
|
|
|
|
/* Finally enter the statement into the available expression
|
|
table. */
|
|
lookup_avail_expr (new_stmt, true, avail_exprs_stack);
|
|
}
|
|
}
|
|
|
|
/* Replace *OP_P in STMT with any known equivalent value for *OP_P from
|
|
CONST_AND_COPIES. */
|
|
|
|
static void
|
|
cprop_operand (gimple *stmt, use_operand_p op_p)
|
|
{
|
|
tree val;
|
|
tree op = USE_FROM_PTR (op_p);
|
|
|
|
/* If the operand has a known constant value or it is known to be a
|
|
copy of some other variable, use the value or copy stored in
|
|
CONST_AND_COPIES. */
|
|
val = SSA_NAME_VALUE (op);
|
|
if (val && val != op)
|
|
{
|
|
/* Do not replace hard register operands in asm statements. */
|
|
if (gimple_code (stmt) == GIMPLE_ASM
|
|
&& !may_propagate_copy_into_asm (op))
|
|
return;
|
|
|
|
/* Certain operands are not allowed to be copy propagated due
|
|
to their interaction with exception handling and some GCC
|
|
extensions. */
|
|
if (!may_propagate_copy (op, val))
|
|
return;
|
|
|
|
/* Do not propagate copies into BIVs.
|
|
See PR23821 and PR62217 for how this can disturb IV and
|
|
number of iteration analysis. */
|
|
if (TREE_CODE (val) != INTEGER_CST)
|
|
{
|
|
gimple *def = SSA_NAME_DEF_STMT (op);
|
|
if (gimple_code (def) == GIMPLE_PHI
|
|
&& gimple_bb (def)->loop_father->header == gimple_bb (def))
|
|
return;
|
|
}
|
|
|
|
/* Dump details. */
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, " Replaced '");
|
|
print_generic_expr (dump_file, op, dump_flags);
|
|
fprintf (dump_file, "' with %s '",
|
|
(TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
|
|
print_generic_expr (dump_file, val, dump_flags);
|
|
fprintf (dump_file, "'\n");
|
|
}
|
|
|
|
if (TREE_CODE (val) != SSA_NAME)
|
|
opt_stats.num_const_prop++;
|
|
else
|
|
opt_stats.num_copy_prop++;
|
|
|
|
propagate_value (op_p, val);
|
|
|
|
/* And note that we modified this statement. This is now
|
|
safe, even if we changed virtual operands since we will
|
|
rescan the statement and rewrite its operands again. */
|
|
gimple_set_modified (stmt, true);
|
|
}
|
|
}
|
|
|
|
/* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
|
|
known value for that SSA_NAME (or NULL if no value is known).
|
|
|
|
Propagate values from CONST_AND_COPIES into the uses, vuses and
|
|
vdef_ops of STMT. */
|
|
|
|
static void
|
|
cprop_into_stmt (gimple *stmt)
|
|
{
|
|
use_operand_p op_p;
|
|
ssa_op_iter iter;
|
|
|
|
FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_USE)
|
|
cprop_operand (stmt, op_p);
|
|
}
|
|
|
|
/* Optimize the statement in block BB pointed to by iterator SI
|
|
using equivalences from CONST_AND_COPIES and AVAIL_EXPRS_STACK.
|
|
|
|
We try to perform some simplistic global redundancy elimination and
|
|
constant propagation:
|
|
|
|
1- To detect global redundancy, we keep track of expressions that have
|
|
been computed in this block and its dominators. If we find that the
|
|
same expression is computed more than once, we eliminate repeated
|
|
computations by using the target of the first one.
|
|
|
|
2- Constant values and copy assignments. This is used to do very
|
|
simplistic constant and copy propagation. When a constant or copy
|
|
assignment is found, we map the value on the RHS of the assignment to
|
|
the variable in the LHS in the CONST_AND_COPIES table. */
|
|
|
|
static edge
|
|
optimize_stmt (basic_block bb, gimple_stmt_iterator si,
|
|
class const_and_copies *const_and_copies,
|
|
class avail_exprs_stack *avail_exprs_stack)
|
|
{
|
|
gimple *stmt, *old_stmt;
|
|
bool may_optimize_p;
|
|
bool modified_p = false;
|
|
bool was_noreturn;
|
|
edge retval = NULL;
|
|
|
|
old_stmt = stmt = gsi_stmt (si);
|
|
was_noreturn = is_gimple_call (stmt) && gimple_call_noreturn_p (stmt);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "Optimizing statement ");
|
|
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
|
|
}
|
|
|
|
if (gimple_code (stmt) == GIMPLE_COND)
|
|
canonicalize_comparison (as_a <gcond *> (stmt));
|
|
|
|
update_stmt_if_modified (stmt);
|
|
opt_stats.num_stmts++;
|
|
|
|
/* Const/copy propagate into USES, VUSES and the RHS of VDEFs. */
|
|
cprop_into_stmt (stmt);
|
|
|
|
/* If the statement has been modified with constant replacements,
|
|
fold its RHS before checking for redundant computations. */
|
|
if (gimple_modified_p (stmt))
|
|
{
|
|
tree rhs = NULL;
|
|
|
|
/* Try to fold the statement making sure that STMT is kept
|
|
up to date. */
|
|
if (fold_stmt (&si))
|
|
{
|
|
stmt = gsi_stmt (si);
|
|
gimple_set_modified (stmt, true);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, " Folded to: ");
|
|
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
|
|
}
|
|
}
|
|
|
|
/* We only need to consider cases that can yield a gimple operand. */
|
|
if (gimple_assign_single_p (stmt))
|
|
rhs = gimple_assign_rhs1 (stmt);
|
|
else if (gimple_code (stmt) == GIMPLE_GOTO)
|
|
rhs = gimple_goto_dest (stmt);
|
|
else if (gswitch *swtch_stmt = dyn_cast <gswitch *> (stmt))
|
|
/* This should never be an ADDR_EXPR. */
|
|
rhs = gimple_switch_index (swtch_stmt);
|
|
|
|
if (rhs && TREE_CODE (rhs) == ADDR_EXPR)
|
|
recompute_tree_invariant_for_addr_expr (rhs);
|
|
|
|
/* Indicate that maybe_clean_or_replace_eh_stmt needs to be called,
|
|
even if fold_stmt updated the stmt already and thus cleared
|
|
gimple_modified_p flag on it. */
|
|
modified_p = true;
|
|
}
|
|
|
|
/* Check for redundant computations. Do this optimization only
|
|
for assignments that have no volatile ops and conditionals. */
|
|
may_optimize_p = (!gimple_has_side_effects (stmt)
|
|
&& (is_gimple_assign (stmt)
|
|
|| (is_gimple_call (stmt)
|
|
&& gimple_call_lhs (stmt) != NULL_TREE)
|
|
|| gimple_code (stmt) == GIMPLE_COND
|
|
|| gimple_code (stmt) == GIMPLE_SWITCH));
|
|
|
|
if (may_optimize_p)
|
|
{
|
|
if (gimple_code (stmt) == GIMPLE_CALL)
|
|
{
|
|
/* Resolve __builtin_constant_p. If it hasn't been
|
|
folded to integer_one_node by now, it's fairly
|
|
certain that the value simply isn't constant. */
|
|
tree callee = gimple_call_fndecl (stmt);
|
|
if (callee
|
|
&& DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
|
|
&& DECL_FUNCTION_CODE (callee) == BUILT_IN_CONSTANT_P)
|
|
{
|
|
propagate_tree_value_into_stmt (&si, integer_zero_node);
|
|
stmt = gsi_stmt (si);
|
|
}
|
|
}
|
|
|
|
if (gimple_code (stmt) == GIMPLE_COND)
|
|
{
|
|
tree lhs = gimple_cond_lhs (stmt);
|
|
tree rhs = gimple_cond_rhs (stmt);
|
|
|
|
/* If the LHS has a range [0..1] and the RHS has a range ~[0..1],
|
|
then this conditional is computable at compile time. We can just
|
|
shove either 0 or 1 into the LHS, mark the statement as modified
|
|
and all the right things will just happen below.
|
|
|
|
Note this would apply to any case where LHS has a range
|
|
narrower than its type implies and RHS is outside that
|
|
narrower range. Future work. */
|
|
if (TREE_CODE (lhs) == SSA_NAME
|
|
&& ssa_name_has_boolean_range (lhs)
|
|
&& TREE_CODE (rhs) == INTEGER_CST
|
|
&& ! (integer_zerop (rhs) || integer_onep (rhs)))
|
|
{
|
|
gimple_cond_set_lhs (as_a <gcond *> (stmt),
|
|
fold_convert (TREE_TYPE (lhs),
|
|
integer_zero_node));
|
|
gimple_set_modified (stmt, true);
|
|
}
|
|
}
|
|
|
|
update_stmt_if_modified (stmt);
|
|
eliminate_redundant_computations (&si, const_and_copies,
|
|
avail_exprs_stack);
|
|
stmt = gsi_stmt (si);
|
|
|
|
/* Perform simple redundant store elimination. */
|
|
if (gimple_assign_single_p (stmt)
|
|
&& TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME)
|
|
{
|
|
tree lhs = gimple_assign_lhs (stmt);
|
|
tree rhs = gimple_assign_rhs1 (stmt);
|
|
tree cached_lhs;
|
|
gassign *new_stmt;
|
|
rhs = dom_valueize (rhs);
|
|
/* Build a new statement with the RHS and LHS exchanged. */
|
|
if (TREE_CODE (rhs) == SSA_NAME)
|
|
{
|
|
gimple *defstmt = SSA_NAME_DEF_STMT (rhs);
|
|
new_stmt = gimple_build_assign (rhs, lhs);
|
|
SSA_NAME_DEF_STMT (rhs) = defstmt;
|
|
}
|
|
else
|
|
new_stmt = gimple_build_assign (rhs, lhs);
|
|
gimple_set_vuse (new_stmt, gimple_vuse (stmt));
|
|
cached_lhs = lookup_avail_expr (new_stmt, false, avail_exprs_stack,
|
|
false);
|
|
if (cached_lhs
|
|
&& rhs == cached_lhs)
|
|
{
|
|
basic_block bb = gimple_bb (stmt);
|
|
unlink_stmt_vdef (stmt);
|
|
if (gsi_remove (&si, true))
|
|
{
|
|
bitmap_set_bit (need_eh_cleanup, bb->index);
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, " Flagged to clear EH edges.\n");
|
|
}
|
|
release_defs (stmt);
|
|
return retval;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Record any additional equivalences created by this statement. */
|
|
if (is_gimple_assign (stmt))
|
|
record_equivalences_from_stmt (stmt, may_optimize_p, avail_exprs_stack);
|
|
|
|
/* If STMT is a COND_EXPR or SWITCH_EXPR and it was modified, then we may
|
|
know where it goes. */
|
|
if (gimple_modified_p (stmt) || modified_p)
|
|
{
|
|
tree val = NULL;
|
|
|
|
update_stmt_if_modified (stmt);
|
|
|
|
if (gimple_code (stmt) == GIMPLE_COND)
|
|
val = fold_binary_loc (gimple_location (stmt),
|
|
gimple_cond_code (stmt), boolean_type_node,
|
|
gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
|
|
else if (gswitch *swtch_stmt = dyn_cast <gswitch *> (stmt))
|
|
val = gimple_switch_index (swtch_stmt);
|
|
|
|
if (val && TREE_CODE (val) == INTEGER_CST)
|
|
{
|
|
retval = find_taken_edge (bb, val);
|
|
if (retval)
|
|
{
|
|
/* Fix the condition to be either true or false. */
|
|
if (gimple_code (stmt) == GIMPLE_COND)
|
|
{
|
|
if (integer_zerop (val))
|
|
gimple_cond_make_false (as_a <gcond *> (stmt));
|
|
else if (integer_onep (val))
|
|
gimple_cond_make_true (as_a <gcond *> (stmt));
|
|
else
|
|
gcc_unreachable ();
|
|
}
|
|
|
|
/* Further simplifications may be possible. */
|
|
cfg_altered = true;
|
|
}
|
|
}
|
|
|
|
/* If we simplified a statement in such a way as to be shown that it
|
|
cannot trap, update the eh information and the cfg to match. */
|
|
if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt))
|
|
{
|
|
bitmap_set_bit (need_eh_cleanup, bb->index);
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, " Flagged to clear EH edges.\n");
|
|
}
|
|
|
|
if (!was_noreturn
|
|
&& is_gimple_call (stmt) && gimple_call_noreturn_p (stmt))
|
|
need_noreturn_fixup.safe_push (stmt);
|
|
}
|
|
return retval;
|
|
}
|
|
|
|
/* Helper for walk_non_aliased_vuses. Determine if we arrived at
|
|
the desired memory state. */
|
|
|
|
static void *
|
|
vuse_eq (ao_ref *, tree vuse1, unsigned int cnt, void *data)
|
|
{
|
|
tree vuse2 = (tree) data;
|
|
if (vuse1 == vuse2)
|
|
return data;
|
|
|
|
/* This bounds the stmt walks we perform on reference lookups
|
|
to O(1) instead of O(N) where N is the number of dominating
|
|
stores leading to a candidate. We re-use the SCCVN param
|
|
for this as it is basically the same complexity. */
|
|
if (cnt > (unsigned) PARAM_VALUE (PARAM_SCCVN_MAX_ALIAS_QUERIES_PER_ACCESS))
|
|
return (void *)-1;
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/* Search for an existing instance of STMT in the AVAIL_EXPRS_STACK table.
|
|
If found, return its LHS. Otherwise insert STMT in the table and
|
|
return NULL_TREE.
|
|
|
|
Also, when an expression is first inserted in the table, it is also
|
|
is also added to AVAIL_EXPRS_STACK, so that it can be removed when
|
|
we finish processing this block and its children. */
|
|
|
|
static tree
|
|
lookup_avail_expr (gimple *stmt, bool insert,
|
|
class avail_exprs_stack *avail_exprs_stack, bool tbaa_p)
|
|
{
|
|
expr_hash_elt **slot;
|
|
tree lhs;
|
|
|
|
/* Get LHS of phi, assignment, or call; else NULL_TREE. */
|
|
if (gimple_code (stmt) == GIMPLE_PHI)
|
|
lhs = gimple_phi_result (stmt);
|
|
else
|
|
lhs = gimple_get_lhs (stmt);
|
|
|
|
class expr_hash_elt element (stmt, lhs);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "LKUP ");
|
|
element.print (dump_file);
|
|
}
|
|
|
|
/* Don't bother remembering constant assignments and copy operations.
|
|
Constants and copy operations are handled by the constant/copy propagator
|
|
in optimize_stmt. */
|
|
if (element.expr()->kind == EXPR_SINGLE
|
|
&& (TREE_CODE (element.expr()->ops.single.rhs) == SSA_NAME
|
|
|| is_gimple_min_invariant (element.expr()->ops.single.rhs)))
|
|
return NULL_TREE;
|
|
|
|
/* Finally try to find the expression in the main expression hash table. */
|
|
hash_table<expr_elt_hasher> *avail_exprs = avail_exprs_stack->avail_exprs ();
|
|
slot = avail_exprs->find_slot (&element, (insert ? INSERT : NO_INSERT));
|
|
if (slot == NULL)
|
|
{
|
|
return NULL_TREE;
|
|
}
|
|
else if (*slot == NULL)
|
|
{
|
|
class expr_hash_elt *element2 = new expr_hash_elt (element);
|
|
*slot = element2;
|
|
|
|
avail_exprs_stack->record_expr (element2, NULL, '2');
|
|
return NULL_TREE;
|
|
}
|
|
|
|
/* If we found a redundant memory operation do an alias walk to
|
|
check if we can re-use it. */
|
|
if (gimple_vuse (stmt) != (*slot)->vop ())
|
|
{
|
|
tree vuse1 = (*slot)->vop ();
|
|
tree vuse2 = gimple_vuse (stmt);
|
|
/* If we have a load of a register and a candidate in the
|
|
hash with vuse1 then try to reach its stmt by walking
|
|
up the virtual use-def chain using walk_non_aliased_vuses.
|
|
But don't do this when removing expressions from the hash. */
|
|
ao_ref ref;
|
|
if (!(vuse1 && vuse2
|
|
&& gimple_assign_single_p (stmt)
|
|
&& TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
|
|
&& (ao_ref_init (&ref, gimple_assign_rhs1 (stmt)),
|
|
ref.base_alias_set = ref.ref_alias_set = tbaa_p ? -1 : 0, true)
|
|
&& walk_non_aliased_vuses (&ref, vuse2,
|
|
vuse_eq, NULL, NULL, vuse1) != NULL))
|
|
{
|
|
if (insert)
|
|
{
|
|
class expr_hash_elt *element2 = new expr_hash_elt (element);
|
|
|
|
/* Insert the expr into the hash by replacing the current
|
|
entry and recording the value to restore in the
|
|
avail_exprs_stack. */
|
|
avail_exprs_stack->record_expr (element2, *slot, '2');
|
|
*slot = element2;
|
|
}
|
|
return NULL_TREE;
|
|
}
|
|
}
|
|
|
|
/* Extract the LHS of the assignment so that it can be used as the current
|
|
definition of another variable. */
|
|
lhs = (*slot)->lhs ();
|
|
|
|
lhs = dom_valueize (lhs);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "FIND: ");
|
|
print_generic_expr (dump_file, lhs, 0);
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
|
|
return lhs;
|
|
}
|