+++ /dev/null
-/* SSA Dominator optimizations for trees
- Copyright (C) 2001-2016 Free Software Foundation, Inc.
- Contributed by Diego Novillo <dnovillo@redhat.com>
-
-This file is part of GCC.
-
-GCC is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 3, or (at your option)
-any later version.
-
-GCC is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING3. If not see
-<http://www.gnu.org/licenses/>. */
-
-#include "config.h"
-#include "system.h"
-#include "coretypes.h"
-#include "backend.h"
-#include "tree.h"
-#include "gimple.h"
-#include "tree-pass.h"
-#include "ssa.h"
-#include "gimple-pretty-print.h"
-#include "fold-const.h"
-#include "cfganal.h"
-#include "cfgloop.h"
-#include "gimple-fold.h"
-#include "tree-eh.h"
-#include "gimple-iterator.h"
-#include "tree-cfg.h"
-#include "tree-into-ssa.h"
-#include "domwalk.h"
-#include "tree-ssa-propagate.h"
-#include "tree-ssa-threadupdate.h"
-#include "params.h"
-#include "tree-ssa-scopedtables.h"
-#include "tree-ssa-threadedge.h"
-#include "tree-ssa-dom.h"
-#include "gimplify.h"
-#include "tree-cfgcleanup.h"
-#include "dbgcnt.h"
-
-/* This file implements optimizations on the dominator tree. */
-
-/* Structure for recording known values of a conditional expression
- at the exits from its block. */
-
-struct cond_equivalence
-{
- struct hashable_expr cond;
- tree value;
-};
-
-/* Structure for recording edge equivalences.
-
- Computing and storing the edge equivalences instead of creating
- them on-demand can save significant amounts of time, particularly
- for pathological cases involving switch statements.
-
- These structures live for a single iteration of the dominator
- optimizer in the edge's AUX field. At the end of an iteration we
- free each of these structures. */
-
-struct edge_info
-{
- /* If this edge creates a simple equivalence, the LHS and RHS of
- the equivalence will be stored here. */
- tree lhs;
- tree rhs;
-
- /* Traversing an edge may also indicate one or more particular conditions
- are true or false. */
- vec<cond_equivalence> cond_equivalences;
-};
-
-/* Track whether or not we have changed the control flow graph. */
-static bool cfg_altered;
-
-/* Bitmap of blocks that have had EH statements cleaned. We should
- remove their dead edges eventually. */
-static bitmap need_eh_cleanup;
-static vec<gimple *> need_noreturn_fixup;
-
-/* Statistics for dominator optimizations. */
-struct opt_stats_d
-{
- long num_stmts;
- long num_exprs_considered;
- long num_re;
- long num_const_prop;
- long num_copy_prop;
-};
-
-static struct opt_stats_d opt_stats;
-
-/* Local functions. */
-static edge optimize_stmt (basic_block, gimple_stmt_iterator,
- class const_and_copies *,
- class avail_exprs_stack *);
-static tree lookup_avail_expr (gimple *, bool, class avail_exprs_stack *);
-static void record_cond (cond_equivalence *, class avail_exprs_stack *);
-static void record_equality (tree, tree, class const_and_copies *);
-static void record_equivalences_from_phis (basic_block);
-static void record_equivalences_from_incoming_edge (basic_block,
- class const_and_copies *,
- class avail_exprs_stack *);
-static void eliminate_redundant_computations (gimple_stmt_iterator *,
- class const_and_copies *,
- class avail_exprs_stack *);
-static void record_equivalences_from_stmt (gimple *, int,
- class avail_exprs_stack *);
-static edge single_incoming_edge_ignoring_loop_edges (basic_block);
-static void dump_dominator_optimization_stats (FILE *file,
- hash_table<expr_elt_hasher> *);
-
-
-/* Free the edge_info data attached to E, if it exists. */
-
-void
-free_dom_edge_info (edge e)
-{
- struct edge_info *edge_info = (struct edge_info *)e->aux;
-
- if (edge_info)
- {
- edge_info->cond_equivalences.release ();
- free (edge_info);
- }
-}
-
-/* Allocate an EDGE_INFO for edge E and attach it to E.
- Return the new EDGE_INFO structure. */
-
-static struct edge_info *
-allocate_edge_info (edge e)
-{
- struct edge_info *edge_info;
-
- /* Free the old one, if it exists. */
- free_dom_edge_info (e);
-
- edge_info = XCNEW (struct edge_info);
-
- e->aux = edge_info;
- return edge_info;
-}
-
-/* Free all EDGE_INFO structures associated with edges in the CFG.
- If a particular edge can be threaded, copy the redirection
- target from the EDGE_INFO structure into the edge's AUX field
- as required by code to update the CFG and SSA graph for
- jump threading. */
-
-static void
-free_all_edge_infos (void)
-{
- basic_block bb;
- edge_iterator ei;
- edge e;
-
- FOR_EACH_BB_FN (bb, cfun)
- {
- FOR_EACH_EDGE (e, ei, bb->preds)
- {
- free_dom_edge_info (e);
- e->aux = NULL;
- }
- }
-}
-
-/* Build a cond_equivalence record indicating that the comparison
- CODE holds between operands OP0 and OP1 and push it to **P. */
-
-static void
-build_and_record_new_cond (enum tree_code code,
- tree op0, tree op1,
- vec<cond_equivalence> *p,
- bool val = true)
-{
- cond_equivalence c;
- struct hashable_expr *cond = &c.cond;
-
- gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
-
- cond->type = boolean_type_node;
- cond->kind = EXPR_BINARY;
- cond->ops.binary.op = code;
- cond->ops.binary.opnd0 = op0;
- cond->ops.binary.opnd1 = op1;
-
- c.value = val ? boolean_true_node : boolean_false_node;
- p->safe_push (c);
-}
-
-/* Record that COND is true and INVERTED is false into the edge information
- structure. Also record that any conditions dominated by COND are true
- as well.
-
- For example, if a < b is true, then a <= b must also be true. */
-
-static void
-record_conditions (struct edge_info *edge_info, tree cond, tree inverted)
-{
- tree op0, op1;
- cond_equivalence c;
-
- if (!COMPARISON_CLASS_P (cond))
- return;
-
- op0 = TREE_OPERAND (cond, 0);
- op1 = TREE_OPERAND (cond, 1);
-
- switch (TREE_CODE (cond))
- {
- case LT_EXPR:
- case GT_EXPR:
- if (FLOAT_TYPE_P (TREE_TYPE (op0)))
- {
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (LTGT_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- }
-
- build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
- ? LE_EXPR : GE_EXPR),
- op0, op1, &edge_info->cond_equivalences);
- build_and_record_new_cond (NE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (EQ_EXPR, op0, op1,
- &edge_info->cond_equivalences, false);
- break;
-
- case GE_EXPR:
- case LE_EXPR:
- if (FLOAT_TYPE_P (TREE_TYPE (op0)))
- {
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- }
- break;
-
- case EQ_EXPR:
- if (FLOAT_TYPE_P (TREE_TYPE (op0)))
- {
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- }
- build_and_record_new_cond (LE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (GE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- break;
-
- case UNORDERED_EXPR:
- build_and_record_new_cond (NE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (UNLE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (UNGE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (UNEQ_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (UNLT_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (UNGT_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- break;
-
- case UNLT_EXPR:
- case UNGT_EXPR:
- build_and_record_new_cond ((TREE_CODE (cond) == UNLT_EXPR
- ? UNLE_EXPR : UNGE_EXPR),
- op0, op1, &edge_info->cond_equivalences);
- build_and_record_new_cond (NE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- break;
-
- case UNEQ_EXPR:
- build_and_record_new_cond (UNLE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (UNGE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- break;
-
- case LTGT_EXPR:
- build_and_record_new_cond (NE_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences);
- break;
-
- default:
- break;
- }
-
- /* Now store the original true and false conditions into the first
- two slots. */
- initialize_expr_from_cond (cond, &c.cond);
- c.value = boolean_true_node;
- edge_info->cond_equivalences.safe_push (c);
-
- /* It is possible for INVERTED to be the negation of a comparison,
- and not a valid RHS or GIMPLE_COND condition. This happens because
- invert_truthvalue may return such an expression when asked to invert
- a floating-point comparison. These comparisons are not assumed to
- obey the trichotomy law. */
- initialize_expr_from_cond (inverted, &c.cond);
- c.value = boolean_false_node;
- edge_info->cond_equivalences.safe_push (c);
-}
-
-/* Return TRUE is OP, an SSA_NAME has a range of values [0..1], false
- otherwise.
-
- This can be because it is a boolean type, any type with
- a single bit of precision, or has known range of [0..1]
- via VRP analysis. */
-
-static bool
-ssa_name_has_boolean_range (tree op)
-{
- /* Boolean types always have a range [0..1]. */
- if (TREE_CODE (TREE_TYPE (op)) == BOOLEAN_TYPE)
- return true;
-
- /* An integral type with a single bit of precision. */
- if (INTEGRAL_TYPE_P (TREE_TYPE (op))
- && TYPE_PRECISION (TREE_TYPE (op)) == 1)
- return true;
-
- /* An integral type with more precision, but the object
- only takes on values [0..1] as determined by VRP
- analysis. */
- wide_int min, max;
- if (INTEGRAL_TYPE_P (TREE_TYPE (op))
- && get_range_info (op, &min, &max) == VR_RANGE
- && wi::eq_p (min, 0)
- && wi::eq_p (max, 1))
- return true;
-
- return false;
-}
-
-/* We have finished optimizing BB, record any information implied by
- taking a specific outgoing edge from BB. */
-
-static void
-record_edge_info (basic_block bb)
-{
- gimple_stmt_iterator gsi = gsi_last_bb (bb);
- struct edge_info *edge_info;
-
- if (! gsi_end_p (gsi))
- {
- gimple *stmt = gsi_stmt (gsi);
- location_t loc = gimple_location (stmt);
-
- if (gimple_code (stmt) == GIMPLE_SWITCH)
- {
- gswitch *switch_stmt = as_a <gswitch *> (stmt);
- tree index = gimple_switch_index (switch_stmt);
-
- if (TREE_CODE (index) == SSA_NAME)
- {
- int i;
- int n_labels = gimple_switch_num_labels (switch_stmt);
- tree *info = XCNEWVEC (tree, last_basic_block_for_fn (cfun));
- edge e;
- edge_iterator ei;
-
- for (i = 0; i < n_labels; i++)
- {
- tree label = gimple_switch_label (switch_stmt, i);
- basic_block target_bb = label_to_block (CASE_LABEL (label));
- if (CASE_HIGH (label)
- || !CASE_LOW (label)
- || info[target_bb->index])
- info[target_bb->index] = error_mark_node;
- else
- info[target_bb->index] = label;
- }
-
- FOR_EACH_EDGE (e, ei, bb->succs)
- {
- basic_block target_bb = e->dest;
- tree label = info[target_bb->index];
-
- if (label != NULL && label != error_mark_node)
- {
- tree x = fold_convert_loc (loc, TREE_TYPE (index),
- CASE_LOW (label));
- edge_info = allocate_edge_info (e);
- edge_info->lhs = index;
- edge_info->rhs = x;
- }
- }
- free (info);
- }
- }
-
- /* A COND_EXPR may create equivalences too. */
- if (gimple_code (stmt) == GIMPLE_COND)
- {
- edge true_edge;
- edge false_edge;
-
- tree op0 = gimple_cond_lhs (stmt);
- tree op1 = gimple_cond_rhs (stmt);
- enum tree_code code = gimple_cond_code (stmt);
-
- extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
-
- /* Special case comparing booleans against a constant as we
- know the value of OP0 on both arms of the branch. i.e., we
- can record an equivalence for OP0 rather than COND. */
- if ((code == EQ_EXPR || code == NE_EXPR)
- && TREE_CODE (op0) == SSA_NAME
- && ssa_name_has_boolean_range (op0)
- && is_gimple_min_invariant (op1))
- {
- tree true_val = fold_convert (TREE_TYPE (op0),
- boolean_true_node);
- tree false_val = fold_convert (TREE_TYPE (op0),
- boolean_false_node);
- if (code == EQ_EXPR)
- {
- edge_info = allocate_edge_info (true_edge);
- edge_info->lhs = op0;
- edge_info->rhs = (integer_zerop (op1) ? false_val : true_val);
-
- edge_info = allocate_edge_info (false_edge);
- edge_info->lhs = op0;
- edge_info->rhs = (integer_zerop (op1) ? true_val : false_val);
- }
- else
- {
- edge_info = allocate_edge_info (true_edge);
- edge_info->lhs = op0;
- edge_info->rhs = (integer_zerop (op1) ? true_val : false_val);
-
- edge_info = allocate_edge_info (false_edge);
- edge_info->lhs = op0;
- edge_info->rhs = (integer_zerop (op1) ? false_val : true_val);
- }
- }
- else if (is_gimple_min_invariant (op0)
- && (TREE_CODE (op1) == SSA_NAME
- || is_gimple_min_invariant (op1)))
- {
- tree cond = build2 (code, boolean_type_node, op0, op1);
- tree inverted = invert_truthvalue_loc (loc, cond);
- bool can_infer_simple_equiv
- = !(HONOR_SIGNED_ZEROS (op0)
- && real_zerop (op0));
- struct edge_info *edge_info;
-
- edge_info = allocate_edge_info (true_edge);
- record_conditions (edge_info, cond, inverted);
-
- if (can_infer_simple_equiv && code == EQ_EXPR)
- {
- edge_info->lhs = op1;
- edge_info->rhs = op0;
- }
-
- edge_info = allocate_edge_info (false_edge);
- record_conditions (edge_info, inverted, cond);
-
- if (can_infer_simple_equiv && TREE_CODE (inverted) == EQ_EXPR)
- {
- edge_info->lhs = op1;
- edge_info->rhs = op0;
- }
- }
-
- else if (TREE_CODE (op0) == SSA_NAME
- && (TREE_CODE (op1) == SSA_NAME
- || is_gimple_min_invariant (op1)))
- {
- tree cond = build2 (code, boolean_type_node, op0, op1);
- tree inverted = invert_truthvalue_loc (loc, cond);
- bool can_infer_simple_equiv
- = !(HONOR_SIGNED_ZEROS (op1)
- && (TREE_CODE (op1) == SSA_NAME || real_zerop (op1)));
- struct edge_info *edge_info;
-
- edge_info = allocate_edge_info (true_edge);
- record_conditions (edge_info, cond, inverted);
-
- if (can_infer_simple_equiv && code == EQ_EXPR)
- {
- edge_info->lhs = op0;
- edge_info->rhs = op1;
- }
-
- edge_info = allocate_edge_info (false_edge);
- record_conditions (edge_info, inverted, cond);
-
- if (can_infer_simple_equiv && TREE_CODE (inverted) == EQ_EXPR)
- {
- edge_info->lhs = op0;
- edge_info->rhs = op1;
- }
- }
- }
-
- /* ??? TRUTH_NOT_EXPR can create an equivalence too. */
- }
-}
-
-
-class dom_opt_dom_walker : public dom_walker
-{
-public:
- dom_opt_dom_walker (cdi_direction direction,
- class const_and_copies *const_and_copies,
- class avail_exprs_stack *avail_exprs_stack)
- : dom_walker (direction, true),
- m_const_and_copies (const_and_copies),
- m_avail_exprs_stack (avail_exprs_stack),
- m_dummy_cond (NULL) {}
-
- 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;
-}
-
-/* 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;
- tree lhs = edge_info->lhs;
- tree rhs = edge_info->rhs;
-
- /* If we have a simple NAME = VALUE equivalence, record it. */
- if (lhs)
- record_equality (lhs, rhs, const_and_copies);
-
- /* 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 (lhs
- && TREE_CODE (lhs) == SSA_NAME
- && 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);
- }
- }
- }
-
- /* If LHS is an SSA_NAME with a new equivalency then try if
- stmts with uses of that LHS that dominate the edge destination
- simplify and allow further equivalences to be recorded. */
- if (lhs && TREE_CODE (lhs) == SSA_NAME)
- {
- use_operand_p use_p;
- imm_use_iterator iter;
- FOR_EACH_IMM_USE_FAST (use_p, iter, lhs)
- {
- gimple *use_stmt = USE_STMT (use_p);
-
- /* Only bother to record more equivalences for lhs that
- can be directly used by e->dest.
- ??? 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. */
- if (e->dest == gimple_bb (use_stmt)
- || !dominated_by_p (CDI_DOMINATORS,
- e->dest, gimple_bb (use_stmt)))
- continue;
- tree lhs2 = gimple_get_lhs (use_stmt);
- if (lhs2 && TREE_CODE (lhs2) == 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 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);
- }
-}
-
-/* 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 ();
-
- /* Traversing E may result in equivalences we can utilize. */
- record_temporary_equivalences (e, m_const_and_copies, m_avail_exprs_stack);
-
- /* 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;
-}
-
-/* Return the loop depth of the basic block of the defining statement of X.
- This number should not be treated as absolutely correct because the loop
- information may not be completely up-to-date when dom runs. However, it
- will be relatively correct, and as more passes are taught to keep loop info
- up to date, the result will become more and more accurate. */
-
-static int
-loop_depth_of_name (tree x)
-{
- gimple *defstmt;
- basic_block defbb;
-
- /* If it's not an SSA_NAME, we have no clue where the definition is. */
- if (TREE_CODE (x) != SSA_NAME)
- return 0;
-
- /* Otherwise return the loop depth of the defining statement's bb.
- Note that there may not actually be a bb for this statement, if the
- ssa_name is live on entry. */
- defstmt = SSA_NAME_DEF_STMT (x);
- defbb = gimple_bb (defstmt);
- if (!defbb)
- return 0;
-
- return bb_loop_depth (defbb);
-}
-
-/* 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)
- /* ??? When threading over backedges the following is important
- for correctness. See PR61757. */
- || (loop_depth_of_name (x) < loop_depth_of_name (y)))
- 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
- && (TREE_CODE (new_val) == SSA_NAME
- || is_gimple_min_invariant (new_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);
- }
- }
-
- 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);
- 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)
-{
- 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)), 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;
-}
projects / thirdparty / gcc.git / blobdiff