/* * Copyright (c) 2006, 2025, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code 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 * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "memory/allocation.inline.hpp" #include "opto/castnode.hpp" #include "opto/cfgnode.hpp" #include "opto/connode.hpp" #include "opto/convertnode.hpp" #include "opto/loopnode.hpp" #include "opto/opaquenode.hpp" #include "opto/predicates.hpp" #include "opto/rootnode.hpp" // Multiversioning: // A loop is cloned, and a selector If decides which loop is taken at run-time: the true-path-loop (original) or the // false-path-loop (cloned). // // Use-cases: // - Speculative compilation: // The selector If checks some assumptions which allow stronger optimization in the true-path-loop. If the assumptions // do not hold, we can still execute in the false-path-loop, although with fewer optimizations. // See: PhaseIdealLoop::maybe_multiversion_for_auto_vectorization_runtime_checks // PhaseIdealLoop::create_new_if_for_multiversion // // - Unswitching: // The selector If has the same (loop invariant) condition as some unswitching candidate If inside the loop. This // allows us to constant-fold the unswitching candidate If to true in the true-path-loop and to false in the // false-path-loop, thus eliminating the unswitching candidate If from the loop. // // // Loop Unswitching is a loop optimization to move an invariant, non-loop-exiting test in the loop body before the loop. // Such a test is either always true or always false in all loop iterations and could therefore only be executed once. // To achieve that, we duplicate the loop and change the original and cloned loop as follows: // - Original loop -> true-path-loop: // The true-path of the invariant, non-loop-exiting test in the original loop // is kept while the false-path is killed. We call this unswitched loop version // the true-path-loop. // - Cloned loop -> false-path-loop: // The false-path of the invariant, non-loop-exiting test in the cloned loop // is kept while the true-path is killed. We call this unswitched loop version // the false-path loop. // // The invariant, non-loop-exiting test can now be moved before both loops (to only execute it once) and turned into a // loop selector If node to select at runtime which unswitched loop version should be executed. // - Loop selector true? Execute the true-path-loop. // - Loop selector false? Execute the false-path-loop. // // Note that even though an invariant test that exits the loop could also be optimized with Loop Unswitching, it is more // efficient to simply peel the loop which achieves the same result in a simpler manner (also see policy_peeling()). // // The following graphs summarizes the Loop Unswitching optimization. // We start with the original loop: // // [Predicates] // | // Original Loop // stmt1 // if (invariant-test) // if-path // else // else-path // stmt2 // Endloop // // // which is unswitched into a true-path-loop and a false-path-loop together with a loop selector: // // // [Initialized Assertion Predicates] // | // loop selector If (invariant-test) // / \ // true? false? // / \ // [Cloned Parse Predicates] [Cloned Parse Predicates] // [Cloned Template [Cloned Template // Assertion Predicates] Assertion Predicates] // | | // True-Path-Loop False-Path-Loop // cloned stmt1 cloned stmt1 // cloned if-path cloned else-path // cloned stmt2 cloned stmt2 // Endloop Endloop // Return true if the loop should be unswitched or false otherwise. bool IdealLoopTree::policy_unswitching(PhaseIdealLoop* phase) const { if (!LoopUnswitching) { return false; } if (!_head->is_Loop()) { return false; } // If nodes are depleted, some transform has miscalculated its needs. assert(!phase->exceeding_node_budget(), "sanity"); // check for vectorized loops, any unswitching was already applied if (_head->is_CountedLoop() && _head->as_CountedLoop()->is_unroll_only()) { return false; } LoopNode* head = _head->as_Loop(); if (head->unswitch_count() + 1 > head->unswitch_max()) { return false; } if (phase->find_unswitch_candidate(this) == nullptr) { return false; } // Too speculative if running low on nodes. return phase->may_require_nodes(est_loop_clone_sz(2)); } // Find an invariant test in the loop body that does not exit the loop. If multiple tests are found, we pick the first // one in the loop body. Return the "unswitch candidate" If to apply Loop Unswitching on. IfNode* PhaseIdealLoop::find_unswitch_candidate(const IdealLoopTree* loop) const { LoopNode* head = loop->_head->as_Loop(); IfNode* unswitch_candidate = nullptr; Node* n = head->in(LoopNode::LoopBackControl); while (n != head) { Node* n_dom = idom(n); if (n->is_Region()) { if (n_dom->is_If()) { IfNode* iff = n_dom->as_If(); if (iff->in(1)->is_Bool()) { BoolNode* bol = iff->in(1)->as_Bool(); if (bol->in(1)->is_Cmp()) { // If condition is invariant and not a loop exit, // then found reason to unswitch. if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) { assert(iff->Opcode() == Op_If || iff->is_RangeCheck() || iff->is_BaseCountedLoopEnd(), "valid ifs"); unswitch_candidate = iff; } } } } } n = n_dom; } return unswitch_candidate; } // LoopSelector is used for loop multiversioning and unswitching. This class creates an If node (i.e. loop selector) // that selects if the true-path-loop or the false-path-loop should be executed at runtime. class LoopSelector : public StackObj { // Cached fields for construction. PhaseIdealLoop* const _phase; IdealLoopTree* const _outer_loop; Node* const _original_loop_entry; const uint _dom_depth; // of original_loop_entry // Constructed selector if with its projections. IfNode* const _selector; IfTrueNode* const _true_path_loop_proj; IfFalseNode* const _false_path_loop_proj; enum PathToLoop { TRUE_PATH, FALSE_PATH }; public: // For multiversioning: create a new selector (multiversion_if) from a bol condition. LoopSelector(IdealLoopTree* loop, Node* bol, float prob, float fcnt) : _phase(loop->_phase), _outer_loop(loop->skip_strip_mined()->_parent), _original_loop_entry(loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl)), _dom_depth(_phase->dom_depth(_original_loop_entry)), _selector(create_multiversioning_if(bol, prob, fcnt)), // multiversioning _true_path_loop_proj(create_proj_to_loop(TRUE_PATH)->as_IfTrue()), _false_path_loop_proj(create_proj_to_loop(FALSE_PATH)->as_IfFalse()) { } // For unswitching: create an unswitching if before the loop, from a pre-existing // unswitching_candidate inside the loop. LoopSelector(IdealLoopTree* loop, IfNode* unswitch_candidate) : _phase(loop->_phase), _outer_loop(loop->skip_strip_mined()->_parent), _original_loop_entry(loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl)), _dom_depth(_phase->dom_depth(_original_loop_entry)), _selector(create_unswitching_if(unswitch_candidate)), // unswitching _true_path_loop_proj(create_proj_to_loop(TRUE_PATH)->as_IfTrue()), _false_path_loop_proj(create_proj_to_loop(FALSE_PATH)->as_IfFalse()) { } NONCOPYABLE(LoopSelector); IfNode* create_multiversioning_if(Node* bol, float prob, float fcnt) { _phase->igvn().rehash_node_delayed(_original_loop_entry); IfNode* selector_if = new IfNode(_original_loop_entry, bol, prob, fcnt); _phase->register_node(selector_if, _outer_loop, _original_loop_entry, _dom_depth); return selector_if; } IfNode* create_unswitching_if(IfNode* unswitch_candidate) { _phase->igvn().rehash_node_delayed(_original_loop_entry); BoolNode* unswitch_candidate_bool = unswitch_candidate->in(1)->as_Bool(); IfNode* selector_if = IfNode::make_with_same_profile(unswitch_candidate, _original_loop_entry, unswitch_candidate_bool); _phase->register_node(selector_if, _outer_loop, _original_loop_entry, _dom_depth); return selector_if; } private: IfProjNode* create_proj_to_loop(const PathToLoop path_to_loop) { IfProjNode* proj_to_loop; if (path_to_loop == TRUE_PATH) { proj_to_loop = new IfTrueNode(_selector); } else { proj_to_loop = new IfFalseNode(_selector); } _phase->register_node(proj_to_loop, _outer_loop, _selector, _dom_depth); return proj_to_loop; } public: IfNode* selector() const { return _selector; } IfTrueNode* true_path_loop_proj() const { return _true_path_loop_proj; } IfFalseNode* false_path_loop_proj() const { return _false_path_loop_proj; } }; // This class creates an If node (i.e. loop selector) that selects if the true-path-loop or the false-path-loop should be // executed at runtime. This is done by finding an invariant and non-loop-exiting unswitch candidate If node (guaranteed // to exist at this point) to perform Loop Unswitching on. class UnswitchedLoopSelector : public StackObj { IfNode* const _unswitch_candidate; const LoopSelector _loop_selector; public: UnswitchedLoopSelector(IdealLoopTree* loop) : _unswitch_candidate(find_unswitch_candidate(loop)), _loop_selector(loop, _unswitch_candidate) {} NONCOPYABLE(UnswitchedLoopSelector); private: static IfNode* find_unswitch_candidate(IdealLoopTree* loop) { IfNode* unswitch_candidate = loop->_phase->find_unswitch_candidate(loop); assert(unswitch_candidate != nullptr, "guaranteed to exist by policy_unswitching"); assert(loop->_phase->is_member(loop, unswitch_candidate), "must be inside original loop"); return unswitch_candidate; } public: IfNode* unswitch_candidate() const { return _unswitch_candidate; } const LoopSelector& loop_selector() const { return _loop_selector; } }; // Class to unswitch the original loop and create Predicates at the new unswitched loop versions. The newly cloned loop // becomes the false-path-loop while original loop becomes the true-path-loop. class OriginalLoop : public StackObj { LoopNode* const _loop_head; LoopNode* const _outer_loop_head; // OuterStripMinedLoopNode if loop strip mined, else just the loop head. IdealLoopTree* const _loop; Node_List& _old_new; PhaseIdealLoop* const _phase; public: OriginalLoop(IdealLoopTree* loop, Node_List& old_new) : _loop_head(loop->_head->as_Loop()), _outer_loop_head(loop->_head->as_Loop()->skip_strip_mined()), _loop(loop), _old_new(old_new), _phase(loop->_phase) {} NONCOPYABLE(OriginalLoop); // Unswitch the original loop on the invariant loop selector by creating a true-path-loop and a false-path-loop. // Remove the unswitch candidate If from both unswitched loop versions which are now covered by the loop selector If. void unswitch(const UnswitchedLoopSelector& unswitched_loop_selector) { multiversion(unswitched_loop_selector.loop_selector()); remove_unswitch_candidate_from_loops(unswitched_loop_selector); } // Multiversion the original loop. The loop selector if selects between the original loop (true-path-loop), and // a copy of it (false-path-loop). void multiversion(const LoopSelector& loop_selector) { const uint first_false_path_loop_node_index = _phase->C->unique(); clone_loop(loop_selector); move_parse_and_template_assertion_predicates_to_unswitched_loops(loop_selector, first_false_path_loop_node_index); DEBUG_ONLY(verify_loop_versions(_loop->_head->as_Loop(), loop_selector);) _phase->recompute_dom_depth(); } private: void clone_loop(const LoopSelector& loop_selector) { _phase->clone_loop(_loop, _old_new, _phase->dom_depth(_outer_loop_head), PhaseIdealLoop::CloneIncludesStripMined, loop_selector.selector()); fix_loop_entries(loop_selector); } void fix_loop_entries(const LoopSelector& loop_selector) const { _phase->replace_loop_entry(_outer_loop_head, loop_selector.true_path_loop_proj()); LoopNode* false_path_loop_strip_mined_head = old_to_new(_outer_loop_head)->as_Loop(); _phase->replace_loop_entry(false_path_loop_strip_mined_head, loop_selector.false_path_loop_proj()); } // Moves the Parse And Template Assertion Predicates to the true and false path loop. They are inserted between the // loop heads and the loop selector If projections. The old Parse and Template Assertion Predicates before // the unswitched loop selector are killed. void move_parse_and_template_assertion_predicates_to_unswitched_loops( const LoopSelector& loop_selector, const uint first_false_path_loop_node_index) const { const NodeInOriginalLoopBody node_in_true_path_loop_body(first_false_path_loop_node_index, _old_new); const NodeInClonedLoopBody node_in_false_path_loop_body(first_false_path_loop_node_index); CloneUnswitchedLoopPredicatesVisitor clone_unswitched_loop_predicates_visitor(_loop_head, old_to_new(_loop_head)->as_Loop(), node_in_true_path_loop_body, node_in_false_path_loop_body, _phase); Node* source_loop_entry = loop_selector.selector()->in(0); PredicateIterator predicate_iterator(source_loop_entry); predicate_iterator.for_each(clone_unswitched_loop_predicates_visitor); } #ifdef ASSERT void verify_loop_versions(LoopNode* true_path_loop_head, const LoopSelector& loop_selector) const { verify_loop_version(true_path_loop_head, loop_selector.true_path_loop_proj()); verify_loop_version(old_to_new(true_path_loop_head)->as_Loop(), loop_selector.false_path_loop_proj()); } static void verify_loop_version(LoopNode* loop_head, IfProjNode* loop_selector_if_proj) { Node* entry = loop_head->skip_strip_mined()->in(LoopNode::EntryControl); const Predicates predicates(entry); // When skipping all predicates, we should end up at 'loop_selector_if_proj'. assert(loop_selector_if_proj == predicates.entry(), "should end up at loop selector If"); } #endif // ASSERT Node* old_to_new(const Node* old) const { return _old_new[old->_idx]; } // Remove the unswitch candidate If nodes in both unswitched loop versions which are now dominated by the loop selector // If node. Keep the true-path-path in the true-path-loop and the false-path-path in the false-path-loop by setting // the bool input accordingly. The unswitch candidate If nodes are folded in the next IGVN round. void remove_unswitch_candidate_from_loops(const UnswitchedLoopSelector& unswitched_loop_selector) { const LoopSelector& loop_selector = unswitched_loop_selector.loop_selector();; IfNode* unswitch_candidate = unswitched_loop_selector.unswitch_candidate(); _phase->igvn().rehash_node_delayed(unswitch_candidate); _phase->dominated_by(loop_selector.true_path_loop_proj(), unswitch_candidate); IfNode* unswitch_candidate_clone = _old_new[unswitch_candidate->_idx]->as_If(); _phase->igvn().rehash_node_delayed(unswitch_candidate_clone); _phase->dominated_by(loop_selector.false_path_loop_proj(), unswitch_candidate_clone); } }; // See comments below file header for more information about Loop Unswitching. void PhaseIdealLoop::do_unswitching(IdealLoopTree* loop, Node_List& old_new) { assert(LoopUnswitching, "LoopUnswitching must be enabled"); LoopNode* original_head = loop->_head->as_Loop(); if (has_control_dependencies_from_predicates(original_head)) { NOT_PRODUCT(trace_loop_unswitching_impossible(original_head);) return; } NOT_PRODUCT(trace_loop_unswitching_count(loop, original_head);) C->print_method(PHASE_BEFORE_LOOP_UNSWITCHING, 4, original_head); revert_to_normal_loop(original_head); const UnswitchedLoopSelector unswitched_loop_selector(loop); OriginalLoop original_loop(loop, old_new); original_loop.unswitch(unswitched_loop_selector); hoist_invariant_check_casts(loop, old_new, unswitched_loop_selector); add_unswitched_loop_version_bodies_to_igvn(loop, old_new); LoopNode* new_head = old_new[original_head->_idx]->as_Loop(); increment_unswitch_counts(original_head, new_head); NOT_PRODUCT(trace_loop_unswitching_result(unswitched_loop_selector, original_head, new_head);) C->print_method(PHASE_AFTER_LOOP_UNSWITCHING, 4, new_head); C->set_major_progress(); } void PhaseIdealLoop::do_multiversioning(IdealLoopTree* lpt, Node_List& old_new) { #ifndef PRODUCT if (TraceLoopOpts || TraceLoopMultiversioning) { tty->print("Multiversion "); lpt->dump_head(); } #endif assert(LoopMultiversioning, "LoopMultiversioning must be enabled"); CountedLoopNode* original_head = lpt->_head->as_CountedLoop(); C->print_method(PHASE_BEFORE_LOOP_MULTIVERSIONING, 4, original_head); Node* one = _igvn.intcon(1); set_ctrl(one, C->root()); Node* opaque = new OpaqueMultiversioningNode(C, one); set_ctrl(opaque, C->root()); _igvn.register_new_node_with_optimizer(opaque); _igvn.set_type(opaque, TypeInt::BOOL); const LoopSelector loop_selector(lpt, opaque, PROB_LIKELY_MAG(3), COUNT_UNKNOWN); OriginalLoop original_loop(lpt, old_new); original_loop.multiversion(loop_selector); add_unswitched_loop_version_bodies_to_igvn(lpt, old_new); CountedLoopNode* new_head = old_new[original_head->_idx]->as_CountedLoop(); original_head->set_multiversion_fast_loop(); new_head->set_multiversion_delayed_slow_loop(); NOT_PRODUCT(trace_loop_multiversioning_result(loop_selector, original_head, new_head);) C->print_method(PHASE_AFTER_LOOP_MULTIVERSIONING, 4, new_head); C->set_major_progress(); } // Create a new if in the multiversioning pattern, adding an additional condition for the // multiversioning fast-loop. // // Before: // entry opaque // | | // multiversion_if // | | // +----------------+ +---------------+ // | | // multiversion_fast_proj multiversion_slow_proj // | // +--------+ // | // slow_path // // // After: // entry opaque <-- to be replaced by caller // | | // new_if // | | // | +-----------------------------+ // | | // new_if_true opaque new_if_false // | | | // multiversion_if | // | | | // +----------------+ +---------------+ | // | | | // multiversion_fast_proj new_multiversion_slow_proj | // | | // +------+ | // | | // region // | // slow_path // IfTrueNode* PhaseIdealLoop::create_new_if_for_multiversion(IfTrueNode* multiversioning_fast_proj) { // Give all nodes in the old sub-graph a name. IfNode* multiversion_if = multiversioning_fast_proj->in(0)->as_If(); Node* entry = multiversion_if->in(0); OpaqueMultiversioningNode* opaque = multiversion_if->in(1)->as_OpaqueMultiversioning(); IfFalseNode* multiversion_slow_proj = multiversion_if->proj_out(0)->as_IfFalse(); Node* slow_path = multiversion_slow_proj->unique_ctrl_out(); // The slow_loop may still be delayed, and waiting for runtime-checks to be added to the // multiversion_if. Now that we have at least one condition for the multiversioning, // we should resume optimizations for the slow loop. opaque->notify_slow_loop_that_it_can_resume_optimizations(); // Create new_if with its projections. IfNode* new_if = IfNode::make_with_same_profile(multiversion_if, entry, opaque); IdealLoopTree* lp = get_loop(entry); register_control(new_if, lp, entry); IfTrueNode* new_if_true = new IfTrueNode(new_if); IfFalseNode* new_if_false = new IfFalseNode(new_if); register_control(new_if_true, lp, new_if); register_control(new_if_false, lp, new_if); // Hook new_if_true into multiversion_if. _igvn.replace_input_of(multiversion_if, 0, new_if_true); // Clone multiversion_slow_path - this allows us to easily carry the dependencies to // the new region below. IfFalseNode* new_multiversion_slow_proj = multiversion_slow_proj->clone()->as_IfFalse(); register_control(new_multiversion_slow_proj, lp, multiversion_if); // Create new Region. RegionNode* region = new RegionNode(1); region->add_req(new_multiversion_slow_proj); region->add_req(new_if_false); register_control(region, lp, new_multiversion_slow_proj); // Hook region into slow_path, in stead of the multiversion_slow_proj. // This also moves all other dependencies of the multiversion_slow_proj to the region. _igvn.replace_node(multiversion_slow_proj, region); return new_if_true; } OpaqueMultiversioningNode* find_multiversion_opaque_from_multiversion_if_false(Node* maybe_multiversion_if_false) { IfFalseNode* multiversion_if_false = maybe_multiversion_if_false->isa_IfFalse(); if (multiversion_if_false == nullptr) { return nullptr; } IfNode* multiversion_if = multiversion_if_false->in(0)->isa_If(); if (multiversion_if == nullptr) { return nullptr; } return multiversion_if->in(1)->isa_OpaqueMultiversioning(); } bool PhaseIdealLoop::try_resume_optimizations_for_delayed_slow_loop(IdealLoopTree* lpt) { CountedLoopNode* cl = lpt->_head->as_CountedLoop(); assert(cl->is_multiversion_delayed_slow_loop(), "must currently be delayed"); // Find multiversion_if. Node* entry = cl->skip_strip_mined()->in(LoopNode::EntryControl); const Predicates predicates(entry); Node* slow_path = predicates.entry(); // Find opaque. OpaqueMultiversioningNode* opaque = nullptr; if (slow_path->is_Region()) { for (uint i = 1; i < slow_path->req(); i++) { Node* n = slow_path->in(i); opaque = find_multiversion_opaque_from_multiversion_if_false(n); if (opaque != nullptr) { break; } } } else { opaque = find_multiversion_opaque_from_multiversion_if_false(slow_path); } assert(opaque != nullptr, "must have found multiversion opaque node"); if (opaque == nullptr) { return false; } // We may still be delayed, if there were not yet any runtime-checks added // for the multiversioning. We may never add any, and then this loop would // fold away. So we wait until some runtime-checks are added, then we know // that this loop will be reachable and it is worth optimizing further. if (opaque->is_delayed_slow_loop()) { return false; } // Clear away the "delayed" status, i.e. resume optimizations. cl->set_no_multiversion(); cl->set_multiversion_slow_loop(); #ifndef PRODUCT if (TraceLoopOpts) { tty->print("Resume Optimizations "); lpt->dump_head(); } #endif return true; } bool PhaseIdealLoop::has_control_dependencies_from_predicates(LoopNode* head) { Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl); const Predicates predicates(entry); if (predicates.has_any()) { assert(entry->is_IfProj(), "sanity - must be ifProj since there is at least one predicate"); if (entry->outcnt() > 1) { // Bailout if there are predicates from which there are additional control dependencies (i.e. from loop // entry 'entry') to previously partially peeled statements since this case is not handled and can lead // to a wrong execution. Remove this bailout, once this is fixed. return true; } } return false; } #ifndef PRODUCT void PhaseIdealLoop::trace_loop_unswitching_impossible(const LoopNode* original_head) { if (TraceLoopUnswitching) { tty->print_cr("Loop Unswitching \"%d %s\" not possible due to control dependencies", original_head->_idx, original_head->Name()); } } void PhaseIdealLoop::trace_loop_unswitching_count(IdealLoopTree* loop, LoopNode* original_head) { if (TraceLoopOpts) { tty->print("Unswitch %d ", original_head->unswitch_count() + 1); loop->dump_head(); } } void PhaseIdealLoop::trace_loop_unswitching_result(const UnswitchedLoopSelector& unswitched_loop_selector, const LoopNode* original_head, const LoopNode* new_head) { if (TraceLoopUnswitching) { IfNode* unswitch_candidate = unswitched_loop_selector.unswitch_candidate(); IfNode* loop_selector = unswitched_loop_selector.loop_selector().selector(); tty->print_cr("Loop Unswitching:"); tty->print_cr("- Unswitch-Candidate-If: %d %s", unswitch_candidate->_idx, unswitch_candidate->Name()); tty->print_cr("- Loop-Selector-If: %d %s", loop_selector->_idx, loop_selector->Name()); tty->print_cr("- True-Path-Loop (=Orig): %d %s", original_head->_idx, original_head->Name()); tty->print_cr("- False-Path-Loop (=Clone): %d %s", new_head->_idx, new_head->Name()); } } void PhaseIdealLoop::trace_loop_multiversioning_result(const LoopSelector& loop_selector, const LoopNode* original_head, const LoopNode* new_head) { if (TraceLoopMultiversioning) { IfNode* selector_if = loop_selector.selector(); tty->print_cr("Loop Multiversioning:"); tty->print_cr("- Loop-Selector-If: %d %s", selector_if->_idx, selector_if->Name()); tty->print_cr("- True-Path-Loop (=Orig / Fast): %d %s", original_head->_idx, original_head->Name()); tty->print_cr("- False-Path-Loop (=Clone / Slow): %d %s", new_head->_idx, new_head->Name()); } } #endif // When unswitching a counted loop, we need to convert it back to a normal loop since it's not a proper pre, main or, // post loop anymore after loop unswitching. We also lose the multiversion structure, with access to the multiversion_if. void PhaseIdealLoop::revert_to_normal_loop(const LoopNode* loop_head) { CountedLoopNode* cl = loop_head->isa_CountedLoop(); if (cl == nullptr) { return; } if (!cl->is_normal_loop()) { cl->set_normal_loop(); } if (cl->is_multiversion()) { cl->set_no_multiversion(); } } // Hoist invariant CheckCastPPNodes out of each unswitched loop version to the appropriate loop selector If projection. void PhaseIdealLoop::hoist_invariant_check_casts(const IdealLoopTree* loop, const Node_List& old_new, const UnswitchedLoopSelector& unswitched_loop_selector) { IfNode* unswitch_candidate = unswitched_loop_selector.unswitch_candidate(); IfNode* loop_selector = unswitched_loop_selector.loop_selector().selector(); ResourceMark rm; GrowableArray loop_invariant_check_casts; for (DUIterator_Fast imax, i = unswitch_candidate->fast_outs(imax); i < imax; i++) { IfProjNode* proj = unswitch_candidate->fast_out(i)->as_IfProj(); // Copy to a worklist for easier manipulation for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) { CheckCastPPNode* check_cast = proj->fast_out(j)->isa_CheckCastPP(); if (check_cast != nullptr && loop->is_invariant(check_cast->in(1))) { loop_invariant_check_casts.push(check_cast); } } IfProjNode* loop_selector_if_proj = loop_selector->proj_out(proj->_con)->as_IfProj(); while (loop_invariant_check_casts.length() > 0) { CheckCastPPNode* cast = loop_invariant_check_casts.pop(); Node* cast_clone = cast->clone(); cast_clone->set_req(0, loop_selector_if_proj); _igvn.replace_input_of(cast, 1, cast_clone); register_new_node(cast_clone, loop_selector_if_proj); // Same for the clone Node* use_clone = old_new[cast->_idx]; _igvn.replace_input_of(use_clone, 1, cast_clone); } } } // Enable more optimizations possibilities in the next IGVN round. void PhaseIdealLoop::add_unswitched_loop_version_bodies_to_igvn(IdealLoopTree* loop, const Node_List& old_new) { loop->record_for_igvn(); for(int i = loop->_body.size() - 1; i >= 0 ; i--) { Node* n = loop->_body[i]; Node* n_clone = old_new[n->_idx]; _igvn._worklist.push(n_clone); } } void PhaseIdealLoop::increment_unswitch_counts(LoopNode* original_head, LoopNode* new_head) { const int unswitch_count = original_head->unswitch_count() + 1; original_head->set_unswitch_count(unswitch_count); new_head->set_unswitch_count(unswitch_count); }