/* * Copyright (c) 1997, 2013, 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 "precompiled.hpp" #include "libadt/vectset.hpp" #include "memory/allocation.inline.hpp" #include "opto/block.hpp" #include "opto/c2compiler.hpp" #include "opto/callnode.hpp" #include "opto/cfgnode.hpp" #include "opto/machnode.hpp" #include "opto/opcodes.hpp" #include "opto/phaseX.hpp" #include "opto/rootnode.hpp" #include "opto/runtime.hpp" #include "runtime/deoptimization.hpp" #ifdef TARGET_ARCH_MODEL_x86_32 # include "adfiles/ad_x86_32.hpp" #endif #ifdef TARGET_ARCH_MODEL_x86_64 # include "adfiles/ad_x86_64.hpp" #endif #ifdef TARGET_ARCH_MODEL_sparc # include "adfiles/ad_sparc.hpp" #endif #ifdef TARGET_ARCH_MODEL_zero # include "adfiles/ad_zero.hpp" #endif #ifdef TARGET_ARCH_MODEL_arm # include "adfiles/ad_arm.hpp" #endif #ifdef TARGET_ARCH_MODEL_ppc_32 # include "adfiles/ad_ppc_32.hpp" #endif #ifdef TARGET_ARCH_MODEL_ppc_64 # include "adfiles/ad_ppc_64.hpp" #endif // Portions of code courtesy of Clifford Click // Optimization - Graph Style // To avoid float value underflow #define MIN_BLOCK_FREQUENCY 1.e-35f //----------------------------schedule_node_into_block------------------------- // Insert node n into block b. Look for projections of n and make sure they // are in b also. void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) { // Set basic block of n, Add n to b, map_node_to_block(n, b); b->add_inst(n); // After Matching, nearly any old Node may have projections trailing it. // These are usually machine-dependent flags. In any case, they might // float to another block below this one. Move them up. for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { Node* use = n->fast_out(i); if (use->is_Proj()) { Block* buse = get_block_for_node(use); if (buse != b) { // In wrong block? if (buse != NULL) { buse->find_remove(use); // Remove from wrong block } map_node_to_block(use, b); b->add_inst(use); } } } } //----------------------------replace_block_proj_ctrl------------------------- // Nodes that have is_block_proj() nodes as their control need to use // the appropriate Region for their actual block as their control since // the projection will be in a predecessor block. void PhaseCFG::replace_block_proj_ctrl( Node *n ) { const Node *in0 = n->in(0); assert(in0 != NULL, "Only control-dependent"); const Node *p = in0->is_block_proj(); if (p != NULL && p != n) { // Control from a block projection? assert(!n->pinned() || n->is_MachConstantBase(), "only pinned MachConstantBase node is expected here"); // Find trailing Region Block *pb = get_block_for_node(in0); // Block-projection already has basic block uint j = 0; if (pb->_num_succs != 1) { // More then 1 successor? // Search for successor uint max = pb->number_of_nodes(); assert( max > 1, "" ); uint start = max - pb->_num_succs; // Find which output path belongs to projection for (j = start; j < max; j++) { if( pb->get_node(j) == in0 ) break; } assert( j < max, "must find" ); // Change control to match head of successor basic block j -= start; } n->set_req(0, pb->_succs[j]->head()); } } //------------------------------schedule_pinned_nodes-------------------------- // Set the basic block for Nodes pinned into blocks void PhaseCFG::schedule_pinned_nodes(VectorSet &visited) { // Allocate node stack of size C->unique()+8 to avoid frequent realloc GrowableArray spstack(C->unique() + 8); spstack.push(_root); while (spstack.is_nonempty()) { Node* node = spstack.pop(); if (!visited.test_set(node->_idx)) { // Test node and flag it as visited if (node->pinned() && !has_block(node)) { // Pinned? Nail it down! assert(node->in(0), "pinned Node must have Control"); // Before setting block replace block_proj control edge replace_block_proj_ctrl(node); Node* input = node->in(0); while (!input->is_block_start()) { input = input->in(0); } Block* block = get_block_for_node(input); // Basic block of controlling input schedule_node_into_block(node, block); } // process all inputs that are non NULL for (int i = node->req() - 1; i >= 0; --i) { if (node->in(i) != NULL) { spstack.push(node->in(i)); } } } } } #ifdef ASSERT // Assert that new input b2 is dominated by all previous inputs. // Check this by by seeing that it is dominated by b1, the deepest // input observed until b2. static void assert_dom(Block* b1, Block* b2, Node* n, const PhaseCFG* cfg) { if (b1 == NULL) return; assert(b1->_dom_depth < b2->_dom_depth, "sanity"); Block* tmp = b2; while (tmp != b1 && tmp != NULL) { tmp = tmp->_idom; } if (tmp != b1) { // Detected an unschedulable graph. Print some nice stuff and die. tty->print_cr("!!! Unschedulable graph !!!"); for (uint j=0; jlen(); j++) { // For all inputs Node* inn = n->in(j); // Get input if (inn == NULL) continue; // Ignore NULL, missing inputs Block* inb = cfg->get_block_for_node(inn); tty->print("B%d idom=B%d depth=%2d ",inb->_pre_order, inb->_idom ? inb->_idom->_pre_order : 0, inb->_dom_depth); inn->dump(); } tty->print("Failing node: "); n->dump(); assert(false, "unscheduable graph"); } } #endif static Block* find_deepest_input(Node* n, const PhaseCFG* cfg) { // Find the last input dominated by all other inputs. Block* deepb = NULL; // Deepest block so far int deepb_dom_depth = 0; for (uint k = 0; k < n->len(); k++) { // For all inputs Node* inn = n->in(k); // Get input if (inn == NULL) continue; // Ignore NULL, missing inputs Block* inb = cfg->get_block_for_node(inn); assert(inb != NULL, "must already have scheduled this input"); if (deepb_dom_depth < (int) inb->_dom_depth) { // The new inb must be dominated by the previous deepb. // The various inputs must be linearly ordered in the dom // tree, or else there will not be a unique deepest block. DEBUG_ONLY(assert_dom(deepb, inb, n, cfg)); deepb = inb; // Save deepest block deepb_dom_depth = deepb->_dom_depth; } } assert(deepb != NULL, "must be at least one input to n"); return deepb; } //------------------------------schedule_early--------------------------------- // Find the earliest Block any instruction can be placed in. Some instructions // are pinned into Blocks. Unpinned instructions can appear in last block in // which all their inputs occur. bool PhaseCFG::schedule_early(VectorSet &visited, Node_List &roots) { // Allocate stack with enough space to avoid frequent realloc Node_Stack nstack(roots.Size() + 8); // _root will be processed among C->top() inputs roots.push(C->top()); visited.set(C->top()->_idx); while (roots.size() != 0) { // Use local variables nstack_top_n & nstack_top_i to cache values // on stack's top. Node* parent_node = roots.pop(); uint input_index = 0; while (true) { if (input_index == 0) { // Fixup some control. Constants without control get attached // to root and nodes that use is_block_proj() nodes should be attached // to the region that starts their block. const Node* control_input = parent_node->in(0); if (control_input != NULL) { replace_block_proj_ctrl(parent_node); } else { // Is a constant with NO inputs? if (parent_node->req() == 1) { parent_node->set_req(0, _root); } } } // First, visit all inputs and force them to get a block. If an // input is already in a block we quit following inputs (to avoid // cycles). Instead we put that Node on a worklist to be handled // later (since IT'S inputs may not have a block yet). // Assume all n's inputs will be processed bool done = true; while (input_index < parent_node->len()) { Node* in = parent_node->in(input_index++); if (in == NULL) { continue; } int is_visited = visited.test_set(in->_idx); if (!has_block(in)) { if (is_visited) { return false; } // Save parent node and next input's index. nstack.push(parent_node, input_index); // Process current input now. parent_node = in; input_index = 0; // Not all n's inputs processed. done = false; break; } else if (!is_visited) { // Visit this guy later, using worklist roots.push(in); } } if (done) { // All of n's inputs have been processed, complete post-processing. // Some instructions are pinned into a block. These include Region, // Phi, Start, Return, and other control-dependent instructions and // any projections which depend on them. if (!parent_node->pinned()) { // Set earliest legal block. Block* earliest_block = find_deepest_input(parent_node, this); map_node_to_block(parent_node, earliest_block); } else { assert(get_block_for_node(parent_node) == get_block_for_node(parent_node->in(0)), "Pinned Node should be at the same block as its control edge"); } if (nstack.is_empty()) { // Finished all nodes on stack. // Process next node on the worklist 'roots'. break; } // Get saved parent node and next input's index. parent_node = nstack.node(); input_index = nstack.index(); nstack.pop(); } } } return true; } //------------------------------dom_lca---------------------------------------- // Find least common ancestor in dominator tree // LCA is a current notion of LCA, to be raised above 'this'. // As a convenient boundary condition, return 'this' if LCA is NULL. // Find the LCA of those two nodes. Block* Block::dom_lca(Block* LCA) { if (LCA == NULL || LCA == this) return this; Block* anc = this; while (anc->_dom_depth > LCA->_dom_depth) anc = anc->_idom; // Walk up till anc is as high as LCA while (LCA->_dom_depth > anc->_dom_depth) LCA = LCA->_idom; // Walk up till LCA is as high as anc while (LCA != anc) { // Walk both up till they are the same LCA = LCA->_idom; anc = anc->_idom; } return LCA; } //--------------------------raise_LCA_above_use-------------------------------- // We are placing a definition, and have been given a def->use edge. // The definition must dominate the use, so move the LCA upward in the // dominator tree to dominate the use. If the use is a phi, adjust // the LCA only with the phi input paths which actually use this def. static Block* raise_LCA_above_use(Block* LCA, Node* use, Node* def, const PhaseCFG* cfg) { Block* buse = cfg->get_block_for_node(use); if (buse == NULL) return LCA; // Unused killing Projs have no use block if (!use->is_Phi()) return buse->dom_lca(LCA); uint pmax = use->req(); // Number of Phi inputs // Why does not this loop just break after finding the matching input to // the Phi? Well...it's like this. I do not have true def-use/use-def // chains. Means I cannot distinguish, from the def-use direction, which // of many use-defs lead from the same use to the same def. That is, this // Phi might have several uses of the same def. Each use appears in a // different predecessor block. But when I enter here, I cannot distinguish // which use-def edge I should find the predecessor block for. So I find // them all. Means I do a little extra work if a Phi uses the same value // more than once. for (uint j=1; jin(j) == def) { // Found matching input? Block* pred = cfg->get_block_for_node(buse->pred(j)); LCA = pred->dom_lca(LCA); } } return LCA; } //----------------------------raise_LCA_above_marks---------------------------- // Return a new LCA that dominates LCA and any of its marked predecessors. // Search all my parents up to 'early' (exclusive), looking for predecessors // which are marked with the given index. Return the LCA (in the dom tree) // of all marked blocks. If there are none marked, return the original // LCA. static Block* raise_LCA_above_marks(Block* LCA, node_idx_t mark, Block* early, const PhaseCFG* cfg) { Block_List worklist; worklist.push(LCA); while (worklist.size() > 0) { Block* mid = worklist.pop(); if (mid == early) continue; // stop searching here // Test and set the visited bit. if (mid->raise_LCA_visited() == mark) continue; // already visited // Don't process the current LCA, otherwise the search may terminate early if (mid != LCA && mid->raise_LCA_mark() == mark) { // Raise the LCA. LCA = mid->dom_lca(LCA); if (LCA == early) break; // stop searching everywhere assert(early->dominates(LCA), "early is high enough"); // Resume searching at that point, skipping intermediate levels. worklist.push(LCA); if (LCA == mid) continue; // Don't mark as visited to avoid early termination. } else { // Keep searching through this block's predecessors. for (uint j = 1, jmax = mid->num_preds(); j < jmax; j++) { Block* mid_parent = cfg->get_block_for_node(mid->pred(j)); worklist.push(mid_parent); } } mid->set_raise_LCA_visited(mark); } return LCA; } //--------------------------memory_early_block-------------------------------- // This is a variation of find_deepest_input, the heart of schedule_early. // Find the "early" block for a load, if we considered only memory and // address inputs, that is, if other data inputs were ignored. // // Because a subset of edges are considered, the resulting block will // be earlier (at a shallower dom_depth) than the true schedule_early // point of the node. We compute this earlier block as a more permissive // site for anti-dependency insertion, but only if subsume_loads is enabled. static Block* memory_early_block(Node* load, Block* early, const PhaseCFG* cfg) { Node* base; Node* index; Node* store = load->in(MemNode::Memory); load->as_Mach()->memory_inputs(base, index); assert(base != NodeSentinel && index != NodeSentinel, "unexpected base/index inputs"); Node* mem_inputs[4]; int mem_inputs_length = 0; if (base != NULL) mem_inputs[mem_inputs_length++] = base; if (index != NULL) mem_inputs[mem_inputs_length++] = index; if (store != NULL) mem_inputs[mem_inputs_length++] = store; // In the comparision below, add one to account for the control input, // which may be null, but always takes up a spot in the in array. if (mem_inputs_length + 1 < (int) load->req()) { // This "load" has more inputs than just the memory, base and index inputs. // For purposes of checking anti-dependences, we need to start // from the early block of only the address portion of the instruction, // and ignore other blocks that may have factored into the wider // schedule_early calculation. if (load->in(0) != NULL) mem_inputs[mem_inputs_length++] = load->in(0); Block* deepb = NULL; // Deepest block so far int deepb_dom_depth = 0; for (int i = 0; i < mem_inputs_length; i++) { Block* inb = cfg->get_block_for_node(mem_inputs[i]); if (deepb_dom_depth < (int) inb->_dom_depth) { // The new inb must be dominated by the previous deepb. // The various inputs must be linearly ordered in the dom // tree, or else there will not be a unique deepest block. DEBUG_ONLY(assert_dom(deepb, inb, load, cfg)); deepb = inb; // Save deepest block deepb_dom_depth = deepb->_dom_depth; } } early = deepb; } return early; } //--------------------------insert_anti_dependences--------------------------- // A load may need to witness memory that nearby stores can overwrite. // For each nearby store, either insert an "anti-dependence" edge // from the load to the store, or else move LCA upward to force the // load to (eventually) be scheduled in a block above the store. // // Do not add edges to stores on distinct control-flow paths; // only add edges to stores which might interfere. // // Return the (updated) LCA. There will not be any possibly interfering // store between the load's "early block" and the updated LCA. // Any stores in the updated LCA will have new precedence edges // back to the load. The caller is expected to schedule the load // in the LCA, in which case the precedence edges will make LCM // preserve anti-dependences. The caller may also hoist the load // above the LCA, if it is not the early block. Block* PhaseCFG::insert_anti_dependences(Block* LCA, Node* load, bool verify) { assert(load->needs_anti_dependence_check(), "must be a load of some sort"); assert(LCA != NULL, ""); DEBUG_ONLY(Block* LCA_orig = LCA); // Compute the alias index. Loads and stores with different alias indices // do not need anti-dependence edges. uint load_alias_idx = C->get_alias_index(load->adr_type()); #ifdef ASSERT if (load_alias_idx == Compile::AliasIdxBot && C->AliasLevel() > 0 && (PrintOpto || VerifyAliases || PrintMiscellaneous && (WizardMode || Verbose))) { // Load nodes should not consume all of memory. // Reporting a bottom type indicates a bug in adlc. // If some particular type of node validly consumes all of memory, // sharpen the preceding "if" to exclude it, so we can catch bugs here. tty->print_cr("*** Possible Anti-Dependence Bug: Load consumes all of memory."); load->dump(2); if (VerifyAliases) assert(load_alias_idx != Compile::AliasIdxBot, ""); } #endif assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrComp), "String compare is only known 'load' that does not conflict with any stores"); assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrEquals), "String equals is a 'load' that does not conflict with any stores"); assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_StrIndexOf), "String indexOf is a 'load' that does not conflict with any stores"); assert(load_alias_idx || (load->is_Mach() && load->as_Mach()->ideal_Opcode() == Op_AryEq), "Arrays equals is a 'load' that do not conflict with any stores"); if (!C->alias_type(load_alias_idx)->is_rewritable()) { // It is impossible to spoil this load by putting stores before it, // because we know that the stores will never update the value // which 'load' must witness. return LCA; } node_idx_t load_index = load->_idx; // Note the earliest legal placement of 'load', as determined by // by the unique point in the dom tree where all memory effects // and other inputs are first available. (Computed by schedule_early.) // For normal loads, 'early' is the shallowest place (dom graph wise) // to look for anti-deps between this load and any store. Block* early = get_block_for_node(load); // If we are subsuming loads, compute an "early" block that only considers // memory or address inputs. This block may be different than the // schedule_early block in that it could be at an even shallower depth in the // dominator tree, and allow for a broader discovery of anti-dependences. if (C->subsume_loads()) { early = memory_early_block(load, early, this); } ResourceArea *area = Thread::current()->resource_area(); Node_List worklist_mem(area); // prior memory state to store Node_List worklist_store(area); // possible-def to explore Node_List worklist_visited(area); // visited mergemem nodes Node_List non_early_stores(area); // all relevant stores outside of early bool must_raise_LCA = false; #ifdef TRACK_PHI_INPUTS // %%% This extra checking fails because MergeMem nodes are not GVNed. // Provide "phi_inputs" to check if every input to a PhiNode is from the // original memory state. This indicates a PhiNode for which should not // prevent the load from sinking. For such a block, set_raise_LCA_mark // may be overly conservative. // Mechanism: count inputs seen for each Phi encountered in worklist_store. DEBUG_ONLY(GrowableArray phi_inputs(area, C->unique(),0,0)); #endif // 'load' uses some memory state; look for users of the same state. // Recurse through MergeMem nodes to the stores that use them. // Each of these stores is a possible definition of memory // that 'load' needs to use. We need to force 'load' // to occur before each such store. When the store is in // the same block as 'load', we insert an anti-dependence // edge load->store. // The relevant stores "nearby" the load consist of a tree rooted // at initial_mem, with internal nodes of type MergeMem. // Therefore, the branches visited by the worklist are of this form: // initial_mem -> (MergeMem ->)* store // The anti-dependence constraints apply only to the fringe of this tree. Node* initial_mem = load->in(MemNode::Memory); worklist_store.push(initial_mem); worklist_visited.push(initial_mem); worklist_mem.push(NULL); while (worklist_store.size() > 0) { // Examine a nearby store to see if it might interfere with our load. Node* mem = worklist_mem.pop(); Node* store = worklist_store.pop(); uint op = store->Opcode(); // MergeMems do not directly have anti-deps. // Treat them as internal nodes in a forward tree of memory states, // the leaves of which are each a 'possible-def'. if (store == initial_mem // root (exclusive) of tree we are searching || op == Op_MergeMem // internal node of tree we are searching ) { mem = store; // It's not a possibly interfering store. if (store == initial_mem) initial_mem = NULL; // only process initial memory once for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) { store = mem->fast_out(i); if (store->is_MergeMem()) { // Be sure we don't get into combinatorial problems. // (Allow phis to be repeated; they can merge two relevant states.) uint j = worklist_visited.size(); for (; j > 0; j--) { if (worklist_visited.at(j-1) == store) break; } if (j > 0) continue; // already on work list; do not repeat worklist_visited.push(store); } worklist_mem.push(mem); worklist_store.push(store); } continue; } if (op == Op_MachProj || op == Op_Catch) continue; if (store->needs_anti_dependence_check()) continue; // not really a store // Compute the alias index. Loads and stores with different alias // indices do not need anti-dependence edges. Wide MemBar's are // anti-dependent on everything (except immutable memories). const TypePtr* adr_type = store->adr_type(); if (!C->can_alias(adr_type, load_alias_idx)) continue; // Most slow-path runtime calls do NOT modify Java memory, but // they can block and so write Raw memory. if (store->is_Mach()) { MachNode* mstore = store->as_Mach(); if (load_alias_idx != Compile::AliasIdxRaw) { // Check for call into the runtime using the Java calling // convention (and from there into a wrapper); it has no // _method. Can't do this optimization for Native calls because // they CAN write to Java memory. if (mstore->ideal_Opcode() == Op_CallStaticJava) { assert(mstore->is_MachSafePoint(), ""); MachSafePointNode* ms = (MachSafePointNode*) mstore; assert(ms->is_MachCallJava(), ""); MachCallJavaNode* mcj = (MachCallJavaNode*) ms; if (mcj->_method == NULL) { // These runtime calls do not write to Java visible memory // (other than Raw) and so do not require anti-dependence edges. continue; } } // Same for SafePoints: they read/write Raw but only read otherwise. // This is basically a workaround for SafePoints only defining control // instead of control + memory. if (mstore->ideal_Opcode() == Op_SafePoint) continue; } else { // Some raw memory, such as the load of "top" at an allocation, // can be control dependent on the previous safepoint. See // comments in GraphKit::allocate_heap() about control input. // Inserting an anti-dep between such a safepoint and a use // creates a cycle, and will cause a subsequent failure in // local scheduling. (BugId 4919904) // (%%% How can a control input be a safepoint and not a projection??) if (mstore->ideal_Opcode() == Op_SafePoint && load->in(0) == mstore) continue; } } // Identify a block that the current load must be above, // or else observe that 'store' is all the way up in the // earliest legal block for 'load'. In the latter case, // immediately insert an anti-dependence edge. Block* store_block = get_block_for_node(store); assert(store_block != NULL, "unused killing projections skipped above"); if (store->is_Phi()) { // 'load' uses memory which is one (or more) of the Phi's inputs. // It must be scheduled not before the Phi, but rather before // each of the relevant Phi inputs. // // Instead of finding the LCA of all inputs to a Phi that match 'mem', // we mark each corresponding predecessor block and do a combined // hoisting operation later (raise_LCA_above_marks). // // Do not assert(store_block != early, "Phi merging memory after access") // PhiNode may be at start of block 'early' with backedge to 'early' DEBUG_ONLY(bool found_match = false); for (uint j = PhiNode::Input, jmax = store->req(); j < jmax; j++) { if (store->in(j) == mem) { // Found matching input? DEBUG_ONLY(found_match = true); Block* pred_block = get_block_for_node(store_block->pred(j)); if (pred_block != early) { // If any predecessor of the Phi matches the load's "early block", // we do not need a precedence edge between the Phi and 'load' // since the load will be forced into a block preceding the Phi. pred_block->set_raise_LCA_mark(load_index); assert(!LCA_orig->dominates(pred_block) || early->dominates(pred_block), "early is high enough"); must_raise_LCA = true; } else { // anti-dependent upon PHI pinned below 'early', no edge needed LCA = early; // but can not schedule below 'early' } } } assert(found_match, "no worklist bug"); #ifdef TRACK_PHI_INPUTS #ifdef ASSERT // This assert asks about correct handling of PhiNodes, which may not // have all input edges directly from 'mem'. See BugId 4621264 int num_mem_inputs = phi_inputs.at_grow(store->_idx,0) + 1; // Increment by exactly one even if there are multiple copies of 'mem' // coming into the phi, because we will run this block several times // if there are several copies of 'mem'. (That's how DU iterators work.) phi_inputs.at_put(store->_idx, num_mem_inputs); assert(PhiNode::Input + num_mem_inputs < store->req(), "Expect at least one phi input will not be from original memory state"); #endif //ASSERT #endif //TRACK_PHI_INPUTS } else if (store_block != early) { // 'store' is between the current LCA and earliest possible block. // Label its block, and decide later on how to raise the LCA // to include the effect on LCA of this store. // If this store's block gets chosen as the raised LCA, we // will find him on the non_early_stores list and stick him // with a precedence edge. // (But, don't bother if LCA is already raised all the way.) if (LCA != early) { store_block->set_raise_LCA_mark(load_index); must_raise_LCA = true; non_early_stores.push(store); } } else { // Found a possibly-interfering store in the load's 'early' block. // This means 'load' cannot sink at all in the dominator tree. // Add an anti-dep edge, and squeeze 'load' into the highest block. assert(store != load->in(0), "dependence cycle found"); if (verify) { assert(store->find_edge(load) != -1, "missing precedence edge"); } else { store->add_prec(load); } LCA = early; // This turns off the process of gathering non_early_stores. } } // (Worklist is now empty; all nearby stores have been visited.) // Finished if 'load' must be scheduled in its 'early' block. // If we found any stores there, they have already been given // precedence edges. if (LCA == early) return LCA; // We get here only if there are no possibly-interfering stores // in the load's 'early' block. Move LCA up above all predecessors // which contain stores we have noted. // // The raised LCA block can be a home to such interfering stores, // but its predecessors must not contain any such stores. // // The raised LCA will be a lower bound for placing the load, // preventing the load from sinking past any block containing // a store that may invalidate the memory state required by 'load'. if (must_raise_LCA) LCA = raise_LCA_above_marks(LCA, load->_idx, early, this); if (LCA == early) return LCA; // Insert anti-dependence edges from 'load' to each store // in the non-early LCA block. // Mine the non_early_stores list for such stores. if (LCA->raise_LCA_mark() == load_index) { while (non_early_stores.size() > 0) { Node* store = non_early_stores.pop(); Block* store_block = get_block_for_node(store); if (store_block == LCA) { // add anti_dependence from store to load in its own block assert(store != load->in(0), "dependence cycle found"); if (verify) { assert(store->find_edge(load) != -1, "missing precedence edge"); } else { store->add_prec(load); } } else { assert(store_block->raise_LCA_mark() == load_index, "block was marked"); // Any other stores we found must be either inside the new LCA // or else outside the original LCA. In the latter case, they // did not interfere with any use of 'load'. assert(LCA->dominates(store_block) || !LCA_orig->dominates(store_block), "no stray stores"); } } } // Return the highest block containing stores; any stores // within that block have been given anti-dependence edges. return LCA; } // This class is used to iterate backwards over the nodes in the graph. class Node_Backward_Iterator { private: Node_Backward_Iterator(); public: // Constructor for the iterator Node_Backward_Iterator(Node *root, VectorSet &visited, Node_List &stack, PhaseCFG &cfg); // Postincrement operator to iterate over the nodes Node *next(); private: VectorSet &_visited; Node_List &_stack; PhaseCFG &_cfg; }; // Constructor for the Node_Backward_Iterator Node_Backward_Iterator::Node_Backward_Iterator( Node *root, VectorSet &visited, Node_List &stack, PhaseCFG &cfg) : _visited(visited), _stack(stack), _cfg(cfg) { // The stack should contain exactly the root stack.clear(); stack.push(root); // Clear the visited bits visited.Clear(); } // Iterator for the Node_Backward_Iterator Node *Node_Backward_Iterator::next() { // If the _stack is empty, then just return NULL: finished. if ( !_stack.size() ) return NULL; // '_stack' is emulating a real _stack. The 'visit-all-users' loop has been // made stateless, so I do not need to record the index 'i' on my _stack. // Instead I visit all users each time, scanning for unvisited users. // I visit unvisited not-anti-dependence users first, then anti-dependent // children next. Node *self = _stack.pop(); // I cycle here when I am entering a deeper level of recursion. // The key variable 'self' was set prior to jumping here. while( 1 ) { _visited.set(self->_idx); // Now schedule all uses as late as possible. const Node* src = self->is_Proj() ? self->in(0) : self; uint src_rpo = _cfg.get_block_for_node(src)->_rpo; // Schedule all nodes in a post-order visit Node *unvisited = NULL; // Unvisited anti-dependent Node, if any // Scan for unvisited nodes for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) { // For all uses, schedule late Node* n = self->fast_out(i); // Use // Skip already visited children if ( _visited.test(n->_idx) ) continue; // do not traverse backward control edges Node *use = n->is_Proj() ? n->in(0) : n; uint use_rpo = _cfg.get_block_for_node(use)->_rpo; if ( use_rpo < src_rpo ) continue; // Phi nodes always precede uses in a basic block if ( use_rpo == src_rpo && use->is_Phi() ) continue; unvisited = n; // Found unvisited // Check for possible-anti-dependent if( !n->needs_anti_dependence_check() ) break; // Not visited, not anti-dep; schedule it NOW } // Did I find an unvisited not-anti-dependent Node? if ( !unvisited ) break; // All done with children; post-visit 'self' // Visit the unvisited Node. Contains the obvious push to // indicate I'm entering a deeper level of recursion. I push the // old state onto the _stack and set a new state and loop (recurse). _stack.push(self); self = unvisited; } // End recursion loop return self; } //------------------------------ComputeLatenciesBackwards---------------------- // Compute the latency of all the instructions. void PhaseCFG::compute_latencies_backwards(VectorSet &visited, Node_List &stack) { #ifndef PRODUCT if (trace_opto_pipelining()) tty->print("\n#---- ComputeLatenciesBackwards ----\n"); #endif Node_Backward_Iterator iter((Node *)_root, visited, stack, *this); Node *n; // Walk over all the nodes from last to first while (n = iter.next()) { // Set the latency for the definitions of this instruction partial_latency_of_defs(n); } } // end ComputeLatenciesBackwards //------------------------------partial_latency_of_defs------------------------ // Compute the latency impact of this node on all defs. This computes // a number that increases as we approach the beginning of the routine. void PhaseCFG::partial_latency_of_defs(Node *n) { // Set the latency for this instruction #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("# latency_to_inputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n)); dump(); } #endif if (n->is_Proj()) { n = n->in(0); } if (n->is_Root()) { return; } uint nlen = n->len(); uint use_latency = get_latency_for_node(n); uint use_pre_order = get_block_for_node(n)->_pre_order; for (uint j = 0; j < nlen; j++) { Node *def = n->in(j); if (!def || def == n) { continue; } // Walk backwards thru projections if (def->is_Proj()) { def = def->in(0); } #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("# in(%2d): ", j); def->dump(); } #endif // If the defining block is not known, assume it is ok Block *def_block = get_block_for_node(def); uint def_pre_order = def_block ? def_block->_pre_order : 0; if ((use_pre_order < def_pre_order) || (use_pre_order == def_pre_order && n->is_Phi())) { continue; } uint delta_latency = n->latency(j); uint current_latency = delta_latency + use_latency; if (get_latency_for_node(def) < current_latency) { set_latency_for_node(def, current_latency); } #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print_cr("# %d + edge_latency(%d) == %d -> %d, node_latency[%d] = %d", use_latency, j, delta_latency, current_latency, def->_idx, get_latency_for_node(def)); } #endif } } //------------------------------latency_from_use------------------------------- // Compute the latency of a specific use int PhaseCFG::latency_from_use(Node *n, const Node *def, Node *use) { // If self-reference, return no latency if (use == n || use->is_Root()) { return 0; } uint def_pre_order = get_block_for_node(def)->_pre_order; uint latency = 0; // If the use is not a projection, then it is simple... if (!use->is_Proj()) { #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("# out(): "); use->dump(); } #endif uint use_pre_order = get_block_for_node(use)->_pre_order; if (use_pre_order < def_pre_order) return 0; if (use_pre_order == def_pre_order && use->is_Phi()) return 0; uint nlen = use->len(); uint nl = get_latency_for_node(use); for ( uint j=0; jin(j) == n) { // Change this if we want local latencies uint ul = use->latency(j); uint l = ul + nl; if (latency < l) latency = l; #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print_cr("# %d + edge_latency(%d) == %d -> %d, latency = %d", nl, j, ul, l, latency); } #endif } } } else { // This is a projection, just grab the latency of the use(s) for (DUIterator_Fast jmax, j = use->fast_outs(jmax); j < jmax; j++) { uint l = latency_from_use(use, def, use->fast_out(j)); if (latency < l) latency = l; } } return latency; } //------------------------------latency_from_uses------------------------------ // Compute the latency of this instruction relative to all of it's uses. // This computes a number that increases as we approach the beginning of the // routine. void PhaseCFG::latency_from_uses(Node *n) { // Set the latency for this instruction #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("# latency_from_outputs: node_latency[%d] = %d for node", n->_idx, get_latency_for_node(n)); dump(); } #endif uint latency=0; const Node *def = n->is_Proj() ? n->in(0): n; for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) { uint l = latency_from_use(n, def, n->fast_out(i)); if (latency < l) latency = l; } set_latency_for_node(n, latency); } //------------------------------hoist_to_cheaper_block------------------------- // Pick a block for node self, between early and LCA, that is a cheaper // alternative to LCA. Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) { const double delta = 1+PROB_UNLIKELY_MAG(4); Block* least = LCA; double least_freq = least->_freq; uint target = get_latency_for_node(self); uint start_latency = get_latency_for_node(LCA->head()); uint end_latency = get_latency_for_node(LCA->get_node(LCA->end_idx())); bool in_latency = (target <= start_latency); const Block* root_block = get_block_for_node(_root); // Turn off latency scheduling if scheduling is just plain off if (!C->do_scheduling()) in_latency = true; // Do not hoist (to cover latency) instructions which target a // single register. Hoisting stretches the live range of the // single register and may force spilling. MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL; if (mach && mach->out_RegMask().is_bound1() && mach->out_RegMask().is_NotEmpty()) in_latency = true; #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("# Find cheaper block for latency %d: ", get_latency_for_node(self)); self->dump(); tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g", LCA->_pre_order, LCA->head()->_idx, start_latency, LCA->get_node(LCA->end_idx())->_idx, end_latency, least_freq); } #endif int cand_cnt = 0; // number of candidates tried // Walk up the dominator tree from LCA (Lowest common ancestor) to // the earliest legal location. Capture the least execution frequency. while (LCA != early) { LCA = LCA->_idom; // Follow up the dominator tree if (LCA == NULL) { // Bailout without retry C->record_method_not_compilable("late schedule failed: LCA == NULL"); return least; } // Don't hoist machine instructions to the root basic block if (mach && LCA == root_block) break; uint start_lat = get_latency_for_node(LCA->head()); uint end_idx = LCA->end_idx(); uint end_lat = get_latency_for_node(LCA->get_node(end_idx)); double LCA_freq = LCA->_freq; #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print_cr("# B%d: start latency for [%4d]=%d, end latency for [%4d]=%d, freq=%g", LCA->_pre_order, LCA->head()->_idx, start_lat, end_idx, end_lat, LCA_freq); } #endif cand_cnt++; if (LCA_freq < least_freq || // Better Frequency (StressGCM && Compile::randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode (!StressGCM && // Otherwise, choose with latency !in_latency && // No block containing latency LCA_freq < least_freq * delta && // No worse frequency target >= end_lat && // within latency range !self->is_iteratively_computed() ) // But don't hoist IV increments // because they may end up above other uses of their phi forcing // their result register to be different from their input. ) { least = LCA; // Found cheaper block least_freq = LCA_freq; start_latency = start_lat; end_latency = end_lat; if (target <= start_lat) in_latency = true; } } #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print_cr("# Choose block B%d with start latency=%d and freq=%g", least->_pre_order, start_latency, least_freq); } #endif // See if the latency needs to be updated if (target < end_latency) { #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print_cr("# Change latency for [%4d] from %d to %d", self->_idx, target, end_latency); } #endif set_latency_for_node(self, end_latency); partial_latency_of_defs(self); } return least; } //------------------------------schedule_late----------------------------------- // Now schedule all codes as LATE as possible. This is the LCA in the // dominator tree of all USES of a value. Pick the block with the least // loop nesting depth that is lowest in the dominator tree. extern const char must_clone[]; void PhaseCFG::schedule_late(VectorSet &visited, Node_List &stack) { #ifndef PRODUCT if (trace_opto_pipelining()) tty->print("\n#---- schedule_late ----\n"); #endif Node_Backward_Iterator iter((Node *)_root, visited, stack, *this); Node *self; // Walk over all the nodes from last to first while (self = iter.next()) { Block* early = get_block_for_node(self); // Earliest legal placement if (self->is_top()) { // Top node goes in bb #2 with other constants. // It must be special-cased, because it has no out edges. early->add_inst(self); continue; } // No uses, just terminate if (self->outcnt() == 0) { assert(self->is_MachProj(), "sanity"); continue; // Must be a dead machine projection } // If node is pinned in the block, then no scheduling can be done. if( self->pinned() ) // Pinned in block? continue; MachNode* mach = self->is_Mach() ? self->as_Mach() : NULL; if (mach) { switch (mach->ideal_Opcode()) { case Op_CreateEx: // Don't move exception creation early->add_inst(self); continue; break; case Op_CheckCastPP: // Don't move CheckCastPP nodes away from their input, if the input // is a rawptr (5071820). Node *def = self->in(1); if (def != NULL && def->bottom_type()->base() == Type::RawPtr) { early->add_inst(self); #ifdef ASSERT _raw_oops.push(def); #endif continue; } break; } } // Gather LCA of all uses Block *LCA = NULL; { for (DUIterator_Fast imax, i = self->fast_outs(imax); i < imax; i++) { // For all uses, find LCA Node* use = self->fast_out(i); LCA = raise_LCA_above_use(LCA, use, self, this); } } // (Hide defs of imax, i from rest of block.) // Place temps in the block of their use. This isn't a // requirement for correctness but it reduces useless // interference between temps and other nodes. if (mach != NULL && mach->is_MachTemp()) { map_node_to_block(self, LCA); LCA->add_inst(self); continue; } // Check if 'self' could be anti-dependent on memory if (self->needs_anti_dependence_check()) { // Hoist LCA above possible-defs and insert anti-dependences to // defs in new LCA block. LCA = insert_anti_dependences(LCA, self); } if (early->_dom_depth > LCA->_dom_depth) { // Somehow the LCA has moved above the earliest legal point. // (One way this can happen is via memory_early_block.) if (C->subsume_loads() == true && !C->failing()) { // Retry with subsume_loads == false // If this is the first failure, the sentinel string will "stick" // to the Compile object, and the C2Compiler will see it and retry. C->record_failure(C2Compiler::retry_no_subsuming_loads()); } else { // Bailout without retry when (early->_dom_depth > LCA->_dom_depth) C->record_method_not_compilable("late schedule failed: incorrect graph"); } return; } // If there is no opportunity to hoist, then we're done. // In stress mode, try to hoist even the single operations. bool try_to_hoist = StressGCM || (LCA != early); // Must clone guys stay next to use; no hoisting allowed. // Also cannot hoist guys that alter memory or are otherwise not // allocatable (hoisting can make a value live longer, leading to // anti and output dependency problems which are normally resolved // by the register allocator giving everyone a different register). if (mach != NULL && must_clone[mach->ideal_Opcode()]) try_to_hoist = false; Block* late = NULL; if (try_to_hoist) { // Now find the block with the least execution frequency. // Start at the latest schedule and work up to the earliest schedule // in the dominator tree. Thus the Node will dominate all its uses. late = hoist_to_cheaper_block(LCA, early, self); } else { // Just use the LCA of the uses. late = LCA; } // Put the node into target block schedule_node_into_block(self, late); #ifdef ASSERT if (self->needs_anti_dependence_check()) { // since precedence edges are only inserted when we're sure they // are needed make sure that after placement in a block we don't // need any new precedence edges. verify_anti_dependences(late, self); } #endif } // Loop until all nodes have been visited } // end ScheduleLate //------------------------------GlobalCodeMotion------------------------------- void PhaseCFG::global_code_motion() { ResourceMark rm; #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("\n---- Start GlobalCodeMotion ----\n"); } #endif // Initialize the node to block mapping for things on the proj_list for (uint i = 0; i < _matcher.number_of_projections(); i++) { unmap_node_from_block(_matcher.get_projection(i)); } // Set the basic block for Nodes pinned into blocks Arena* arena = Thread::current()->resource_area(); VectorSet visited(arena); schedule_pinned_nodes(visited); // Find the earliest Block any instruction can be placed in. Some // instructions are pinned into Blocks. Unpinned instructions can // appear in last block in which all their inputs occur. visited.Clear(); Node_List stack(arena); // Pre-grow the list stack.map((C->unique() >> 1) + 16, NULL); if (!schedule_early(visited, stack)) { // Bailout without retry C->record_method_not_compilable("early schedule failed"); return; } // Build Def-Use edges. // Compute the latency information (via backwards walk) for all the // instructions in the graph _node_latency = new GrowableArray(); // resource_area allocation if (C->do_scheduling()) { compute_latencies_backwards(visited, stack); } // Now schedule all codes as LATE as possible. This is the LCA in the // dominator tree of all USES of a value. Pick the block with the least // loop nesting depth that is lowest in the dominator tree. // ( visited.Clear() called in schedule_late()->Node_Backward_Iterator() ) schedule_late(visited, stack); if (C->failing()) { // schedule_late fails only when graph is incorrect. assert(!VerifyGraphEdges, "verification should have failed"); return; } #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("\n---- Detect implicit null checks ----\n"); } #endif // Detect implicit-null-check opportunities. Basically, find NULL checks // with suitable memory ops nearby. Use the memory op to do the NULL check. // I can generate a memory op if there is not one nearby. if (C->is_method_compilation()) { // By reversing the loop direction we get a very minor gain on mpegaudio. // Feel free to revert to a forward loop for clarity. // for( int i=0; i < (int)matcher._null_check_tests.size(); i+=2 ) { for (int i = _matcher._null_check_tests.size() - 2; i >= 0; i -= 2) { Node* proj = _matcher._null_check_tests[i]; Node* val = _matcher._null_check_tests[i + 1]; Block* block = get_block_for_node(proj); implicit_null_check(block, proj, val, C->allowed_deopt_reasons()); // The implicit_null_check will only perform the transformation // if the null branch is truly uncommon, *and* it leads to an // uncommon trap. Combined with the too_many_traps guards // above, this prevents SEGV storms reported in 6366351, // by recompiling offending methods without this optimization. } } #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("\n---- Start Local Scheduling ----\n"); } #endif // Schedule locally. Right now a simple topological sort. // Later, do a real latency aware scheduler. GrowableArray ready_cnt(C->unique(), C->unique(), -1); visited.Clear(); for (uint i = 0; i < number_of_blocks(); i++) { Block* block = get_block(i); if (!schedule_local(block, ready_cnt, visited)) { if (!C->failure_reason_is(C2Compiler::retry_no_subsuming_loads())) { C->record_method_not_compilable("local schedule failed"); } return; } } // If we inserted any instructions between a Call and his CatchNode, // clone the instructions on all paths below the Catch. for (uint i = 0; i < number_of_blocks(); i++) { Block* block = get_block(i); call_catch_cleanup(block); } #ifndef PRODUCT if (trace_opto_pipelining()) { tty->print("\n---- After GlobalCodeMotion ----\n"); for (uint i = 0; i < number_of_blocks(); i++) { Block* block = get_block(i); block->dump(); } } #endif // Dead. _node_latency = (GrowableArray *)0xdeadbeef; } bool PhaseCFG::do_global_code_motion() { build_dominator_tree(); if (C->failing()) { return false; } NOT_PRODUCT( C->verify_graph_edges(); ) estimate_block_frequency(); global_code_motion(); if (C->failing()) { return false; } return true; } //------------------------------Estimate_Block_Frequency----------------------- // Estimate block frequencies based on IfNode probabilities. void PhaseCFG::estimate_block_frequency() { // Force conditional branches leading to uncommon traps to be unlikely, // not because we get to the uncommon_trap with less relative frequency, // but because an uncommon_trap typically causes a deopt, so we only get // there once. if (C->do_freq_based_layout()) { Block_List worklist; Block* root_blk = get_block(0); for (uint i = 1; i < root_blk->num_preds(); i++) { Block *pb = get_block_for_node(root_blk->pred(i)); if (pb->has_uncommon_code()) { worklist.push(pb); } } while (worklist.size() > 0) { Block* uct = worklist.pop(); if (uct == get_root_block()) { continue; } for (uint i = 1; i < uct->num_preds(); i++) { Block *pb = get_block_for_node(uct->pred(i)); if (pb->_num_succs == 1) { worklist.push(pb); } else if (pb->num_fall_throughs() == 2) { pb->update_uncommon_branch(uct); } } } } // Create the loop tree and calculate loop depth. _root_loop = create_loop_tree(); _root_loop->compute_loop_depth(0); // Compute block frequency of each block, relative to a single loop entry. _root_loop->compute_freq(); // Adjust all frequencies to be relative to a single method entry _root_loop->_freq = 1.0; _root_loop->scale_freq(); // Save outmost loop frequency for LRG frequency threshold _outer_loop_frequency = _root_loop->outer_loop_freq(); // force paths ending at uncommon traps to be infrequent if (!C->do_freq_based_layout()) { Block_List worklist; Block* root_blk = get_block(0); for (uint i = 1; i < root_blk->num_preds(); i++) { Block *pb = get_block_for_node(root_blk->pred(i)); if (pb->has_uncommon_code()) { worklist.push(pb); } } while (worklist.size() > 0) { Block* uct = worklist.pop(); uct->_freq = PROB_MIN; for (uint i = 1; i < uct->num_preds(); i++) { Block *pb = get_block_for_node(uct->pred(i)); if (pb->_num_succs == 1 && pb->_freq > PROB_MIN) { worklist.push(pb); } } } } #ifdef ASSERT for (uint i = 0; i < number_of_blocks(); i++) { Block* b = get_block(i); assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requires meaningful block frequency"); } #endif #ifndef PRODUCT if (PrintCFGBlockFreq) { tty->print_cr("CFG Block Frequencies"); _root_loop->dump_tree(); if (Verbose) { tty->print_cr("PhaseCFG dump"); dump(); tty->print_cr("Node dump"); _root->dump(99999); } } #endif } //----------------------------create_loop_tree-------------------------------- // Create a loop tree from the CFG CFGLoop* PhaseCFG::create_loop_tree() { #ifdef ASSERT assert(get_block(0) == get_root_block(), "first block should be root block"); for (uint i = 0; i < number_of_blocks(); i++) { Block* block = get_block(i); // Check that _loop field are clear...we could clear them if not. assert(block->_loop == NULL, "clear _loop expected"); // Sanity check that the RPO numbering is reflected in the _blocks array. // It doesn't have to be for the loop tree to be built, but if it is not, // then the blocks have been reordered since dom graph building...which // may question the RPO numbering assert(block->_rpo == i, "unexpected reverse post order number"); } #endif int idct = 0; CFGLoop* root_loop = new CFGLoop(idct++); Block_List worklist; // Assign blocks to loops for(uint i = number_of_blocks() - 1; i > 0; i-- ) { // skip Root block Block* block = get_block(i); if (block->head()->is_Loop()) { Block* loop_head = block; assert(loop_head->num_preds() - 1 == 2, "loop must have 2 predecessors"); Node* tail_n = loop_head->pred(LoopNode::LoopBackControl); Block* tail = get_block_for_node(tail_n); // Defensively filter out Loop nodes for non-single-entry loops. // For all reasonable loops, the head occurs before the tail in RPO. if (i <= tail->_rpo) { // The tail and (recursive) predecessors of the tail // are made members of a new loop. assert(worklist.size() == 0, "nonempty worklist"); CFGLoop* nloop = new CFGLoop(idct++); assert(loop_head->_loop == NULL, "just checking"); loop_head->_loop = nloop; // Add to nloop so push_pred() will skip over inner loops nloop->add_member(loop_head); nloop->push_pred(loop_head, LoopNode::LoopBackControl, worklist, this); while (worklist.size() > 0) { Block* member = worklist.pop(); if (member != loop_head) { for (uint j = 1; j < member->num_preds(); j++) { nloop->push_pred(member, j, worklist, this); } } } } } } // Create a member list for each loop consisting // of both blocks and (immediate child) loops. for (uint i = 0; i < number_of_blocks(); i++) { Block* block = get_block(i); CFGLoop* lp = block->_loop; if (lp == NULL) { // Not assigned to a loop. Add it to the method's pseudo loop. block->_loop = root_loop; lp = root_loop; } if (lp == root_loop || block != lp->head()) { // loop heads are already members lp->add_member(block); } if (lp != root_loop) { if (lp->parent() == NULL) { // Not a nested loop. Make it a child of the method's pseudo loop. root_loop->add_nested_loop(lp); } if (block == lp->head()) { // Add nested loop to member list of parent loop. lp->parent()->add_member(lp); } } } return root_loop; } //------------------------------push_pred-------------------------------------- void CFGLoop::push_pred(Block* blk, int i, Block_List& worklist, PhaseCFG* cfg) { Node* pred_n = blk->pred(i); Block* pred = cfg->get_block_for_node(pred_n); CFGLoop *pred_loop = pred->_loop; if (pred_loop == NULL) { // Filter out blocks for non-single-entry loops. // For all reasonable loops, the head occurs before the tail in RPO. if (pred->_rpo > head()->_rpo) { pred->_loop = this; worklist.push(pred); } } else if (pred_loop != this) { // Nested loop. while (pred_loop->_parent != NULL && pred_loop->_parent != this) { pred_loop = pred_loop->_parent; } // Make pred's loop be a child if (pred_loop->_parent == NULL) { add_nested_loop(pred_loop); // Continue with loop entry predecessor. Block* pred_head = pred_loop->head(); assert(pred_head->num_preds() - 1 == 2, "loop must have 2 predecessors"); assert(pred_head != head(), "loop head in only one loop"); push_pred(pred_head, LoopNode::EntryControl, worklist, cfg); } else { assert(pred_loop->_parent == this && _parent == NULL, "just checking"); } } } //------------------------------add_nested_loop-------------------------------- // Make cl a child of the current loop in the loop tree. void CFGLoop::add_nested_loop(CFGLoop* cl) { assert(_parent == NULL, "no parent yet"); assert(cl != this, "not my own parent"); cl->_parent = this; CFGLoop* ch = _child; if (ch == NULL) { _child = cl; } else { while (ch->_sibling != NULL) { ch = ch->_sibling; } ch->_sibling = cl; } } //------------------------------compute_loop_depth----------------------------- // Store the loop depth in each CFGLoop object. // Recursively walk the children to do the same for them. void CFGLoop::compute_loop_depth(int depth) { _depth = depth; CFGLoop* ch = _child; while (ch != NULL) { ch->compute_loop_depth(depth + 1); ch = ch->_sibling; } } //------------------------------compute_freq----------------------------------- // Compute the frequency of each block and loop, relative to a single entry // into the dominating loop head. void CFGLoop::compute_freq() { // Bottom up traversal of loop tree (visit inner loops first.) // Set loop head frequency to 1.0, then transitively // compute frequency for all successors in the loop, // as well as for each exit edge. Inner loops are // treated as single blocks with loop exit targets // as the successor blocks. // Nested loops first CFGLoop* ch = _child; while (ch != NULL) { ch->compute_freq(); ch = ch->_sibling; } assert (_members.length() > 0, "no empty loops"); Block* hd = head(); hd->_freq = 1.0; for (int i = 0; i < _members.length(); i++) { CFGElement* s = _members.at(i); double freq = s->_freq; if (s->is_block()) { Block* b = s->as_Block(); for (uint j = 0; j < b->_num_succs; j++) { Block* sb = b->_succs[j]; update_succ_freq(sb, freq * b->succ_prob(j)); } } else { CFGLoop* lp = s->as_CFGLoop(); assert(lp->_parent == this, "immediate child"); for (int k = 0; k < lp->_exits.length(); k++) { Block* eb = lp->_exits.at(k).get_target(); double prob = lp->_exits.at(k).get_prob(); update_succ_freq(eb, freq * prob); } } } // For all loops other than the outer, "method" loop, // sum and normalize the exit probability. The "method" loop // should keep the initial exit probability of 1, so that // inner blocks do not get erroneously scaled. if (_depth != 0) { // Total the exit probabilities for this loop. double exits_sum = 0.0f; for (int i = 0; i < _exits.length(); i++) { exits_sum += _exits.at(i).get_prob(); } // Normalize the exit probabilities. Until now, the // probabilities estimate the possibility of exit per // a single loop iteration; afterward, they estimate // the probability of exit per loop entry. for (int i = 0; i < _exits.length(); i++) { Block* et = _exits.at(i).get_target(); float new_prob = 0.0f; if (_exits.at(i).get_prob() > 0.0f) { new_prob = _exits.at(i).get_prob() / exits_sum; } BlockProbPair bpp(et, new_prob); _exits.at_put(i, bpp); } // Save the total, but guard against unreasonable probability, // as the value is used to estimate the loop trip count. // An infinite trip count would blur relative block // frequencies. if (exits_sum > 1.0f) exits_sum = 1.0; if (exits_sum < PROB_MIN) exits_sum = PROB_MIN; _exit_prob = exits_sum; } } //------------------------------succ_prob------------------------------------- // Determine the probability of reaching successor 'i' from the receiver block. float Block::succ_prob(uint i) { int eidx = end_idx(); Node *n = get_node(eidx); // Get ending Node int op = n->Opcode(); if (n->is_Mach()) { if (n->is_MachNullCheck()) { // Can only reach here if called after lcm. The original Op_If is gone, // so we attempt to infer the probability from one or both of the // successor blocks. assert(_num_succs == 2, "expecting 2 successors of a null check"); // If either successor has only one predecessor, then the // probability estimate can be derived using the // relative frequency of the successor and this block. if (_succs[i]->num_preds() == 2) { return _succs[i]->_freq / _freq; } else if (_succs[1-i]->num_preds() == 2) { return 1 - (_succs[1-i]->_freq / _freq); } else { // Estimate using both successor frequencies float freq = _succs[i]->_freq; return freq / (freq + _succs[1-i]->_freq); } } op = n->as_Mach()->ideal_Opcode(); } // Switch on branch type switch( op ) { case Op_CountedLoopEnd: case Op_If: { assert (i < 2, "just checking"); // Conditionals pass on only part of their frequency float prob = n->as_MachIf()->_prob; assert(prob >= 0.0 && prob <= 1.0, "out of range probability"); // If succ[i] is the FALSE branch, invert path info if( get_node(i + eidx + 1)->Opcode() == Op_IfFalse ) { return 1.0f - prob; // not taken } else { return prob; // taken } } case Op_Jump: // Divide the frequency between all successors evenly return 1.0f/_num_succs; case Op_Catch: { const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj(); if (ci->_con == CatchProjNode::fall_through_index) { // Fall-thru path gets the lion's share. return 1.0f - PROB_UNLIKELY_MAG(5)*_num_succs; } else { // Presume exceptional paths are equally unlikely return PROB_UNLIKELY_MAG(5); } } case Op_Root: case Op_Goto: // Pass frequency straight thru to target return 1.0f; case Op_NeverBranch: return 0.0f; case Op_TailCall: case Op_TailJump: case Op_Return: case Op_Halt: case Op_Rethrow: // Do not push out freq to root block return 0.0f; default: ShouldNotReachHere(); } return 0.0f; } //------------------------------num_fall_throughs----------------------------- // Return the number of fall-through candidates for a block int Block::num_fall_throughs() { int eidx = end_idx(); Node *n = get_node(eidx); // Get ending Node int op = n->Opcode(); if (n->is_Mach()) { if (n->is_MachNullCheck()) { // In theory, either side can fall-thru, for simplicity sake, // let's say only the false branch can now. return 1; } op = n->as_Mach()->ideal_Opcode(); } // Switch on branch type switch( op ) { case Op_CountedLoopEnd: case Op_If: return 2; case Op_Root: case Op_Goto: return 1; case Op_Catch: { for (uint i = 0; i < _num_succs; i++) { const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj(); if (ci->_con == CatchProjNode::fall_through_index) { return 1; } } return 0; } case Op_Jump: case Op_NeverBranch: case Op_TailCall: case Op_TailJump: case Op_Return: case Op_Halt: case Op_Rethrow: return 0; default: ShouldNotReachHere(); } return 0; } //------------------------------succ_fall_through----------------------------- // Return true if a specific successor could be fall-through target. bool Block::succ_fall_through(uint i) { int eidx = end_idx(); Node *n = get_node(eidx); // Get ending Node int op = n->Opcode(); if (n->is_Mach()) { if (n->is_MachNullCheck()) { // In theory, either side can fall-thru, for simplicity sake, // let's say only the false branch can now. return get_node(i + eidx + 1)->Opcode() == Op_IfFalse; } op = n->as_Mach()->ideal_Opcode(); } // Switch on branch type switch( op ) { case Op_CountedLoopEnd: case Op_If: case Op_Root: case Op_Goto: return true; case Op_Catch: { const CatchProjNode *ci = get_node(i + eidx + 1)->as_CatchProj(); return ci->_con == CatchProjNode::fall_through_index; } case Op_Jump: case Op_NeverBranch: case Op_TailCall: case Op_TailJump: case Op_Return: case Op_Halt: case Op_Rethrow: return false; default: ShouldNotReachHere(); } return false; } //------------------------------update_uncommon_branch------------------------ // Update the probability of a two-branch to be uncommon void Block::update_uncommon_branch(Block* ub) { int eidx = end_idx(); Node *n = get_node(eidx); // Get ending Node int op = n->as_Mach()->ideal_Opcode(); assert(op == Op_CountedLoopEnd || op == Op_If, "must be a If"); assert(num_fall_throughs() == 2, "must be a two way branch block"); // Which successor is ub? uint s; for (s = 0; s <_num_succs; s++) { if (_succs[s] == ub) break; } assert(s < 2, "uncommon successor must be found"); // If ub is the true path, make the proability small, else // ub is the false path, and make the probability large bool invert = (get_node(s + eidx + 1)->Opcode() == Op_IfFalse); // Get existing probability float p = n->as_MachIf()->_prob; if (invert) p = 1.0 - p; if (p > PROB_MIN) { p = PROB_MIN; } if (invert) p = 1.0 - p; n->as_MachIf()->_prob = p; } //------------------------------update_succ_freq------------------------------- // Update the appropriate frequency associated with block 'b', a successor of // a block in this loop. void CFGLoop::update_succ_freq(Block* b, double freq) { if (b->_loop == this) { if (b == head()) { // back branch within the loop // Do nothing now, the loop carried frequency will be // adjust later in scale_freq(). } else { // simple branch within the loop b->_freq += freq; } } else if (!in_loop_nest(b)) { // branch is exit from this loop BlockProbPair bpp(b, freq); _exits.append(bpp); } else { // branch into nested loop CFGLoop* ch = b->_loop; ch->_freq += freq; } } //------------------------------in_loop_nest----------------------------------- // Determine if block b is in the receiver's loop nest. bool CFGLoop::in_loop_nest(Block* b) { int depth = _depth; CFGLoop* b_loop = b->_loop; int b_depth = b_loop->_depth; if (depth == b_depth) { return true; } while (b_depth > depth) { b_loop = b_loop->_parent; b_depth = b_loop->_depth; } return b_loop == this; } //------------------------------scale_freq------------------------------------- // Scale frequency of loops and blocks by trip counts from outer loops // Do a top down traversal of loop tree (visit outer loops first.) void CFGLoop::scale_freq() { double loop_freq = _freq * trip_count(); _freq = loop_freq; for (int i = 0; i < _members.length(); i++) { CFGElement* s = _members.at(i); double block_freq = s->_freq * loop_freq; if (g_isnan(block_freq) || block_freq < MIN_BLOCK_FREQUENCY) block_freq = MIN_BLOCK_FREQUENCY; s->_freq = block_freq; } CFGLoop* ch = _child; while (ch != NULL) { ch->scale_freq(); ch = ch->_sibling; } } // Frequency of outer loop double CFGLoop::outer_loop_freq() const { if (_child != NULL) { return _child->_freq; } return _freq; } #ifndef PRODUCT //------------------------------dump_tree-------------------------------------- void CFGLoop::dump_tree() const { dump(); if (_child != NULL) _child->dump_tree(); if (_sibling != NULL) _sibling->dump_tree(); } //------------------------------dump------------------------------------------- void CFGLoop::dump() const { for (int i = 0; i < _depth; i++) tty->print(" "); tty->print("%s: %d trip_count: %6.0f freq: %6.0f\n", _depth == 0 ? "Method" : "Loop", _id, trip_count(), _freq); for (int i = 0; i < _depth; i++) tty->print(" "); tty->print(" members:", _id); int k = 0; for (int i = 0; i < _members.length(); i++) { if (k++ >= 6) { tty->print("\n "); for (int j = 0; j < _depth+1; j++) tty->print(" "); k = 0; } CFGElement *s = _members.at(i); if (s->is_block()) { Block *b = s->as_Block(); tty->print(" B%d(%6.3f)", b->_pre_order, b->_freq); } else { CFGLoop* lp = s->as_CFGLoop(); tty->print(" L%d(%6.3f)", lp->_id, lp->_freq); } } tty->print("\n"); for (int i = 0; i < _depth; i++) tty->print(" "); tty->print(" exits: "); k = 0; for (int i = 0; i < _exits.length(); i++) { if (k++ >= 7) { tty->print("\n "); for (int j = 0; j < _depth+1; j++) tty->print(" "); k = 0; } Block *blk = _exits.at(i).get_target(); double prob = _exits.at(i).get_prob(); tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100)); } tty->print("\n"); } #endif