jdk8-mips64-public/hotspot: src/share/vm/opto/gcm.cpp@fd13a567f179 (annotated)

src/share/vm/opto/gcm.cpp@fd13a567f179 (annotated)

src/share/vm/opto/gcm.cpp

Thu, 24 May 2018 19:26:50 +0800

author: aoqi
date: Thu, 24 May 2018 19:26:50 +0800
changeset 8862: fd13a567f179
parent 8604: 04d83ba48607
child 9448: 73d689add964
permissions: -rw-r--r--

#7046 C2 supports long branch
Contributed-by: fujie

 /*
  * Copyright (c) 1997, 2015, 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.
  *
  */
 /*
  * This file has been modified by Loongson Technology in 2015. These
  * modifications are Copyright (c) 2015 Loongson Technology, and are made
  * available on the same license terms set forth above.
  */
 #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"
 #if defined AD_MD_HPP
 # include AD_MD_HPP
 #elif defined TARGET_ARCH_MODEL_x86_32
 # include "adfiles/ad_x86_32.hpp"
 #elif defined TARGET_ARCH_MODEL_x86_64
 # include "adfiles/ad_x86_64.hpp"
 #elif defined TARGET_ARCH_MODEL_sparc
 # include "adfiles/ad_sparc.hpp"
 #elif defined TARGET_ARCH_MODEL_zero
 # include "adfiles/ad_zero.hpp"
 #elif defined TARGET_ARCH_MODEL_ppc_64
 # include "adfiles/ad_ppc_64.hpp"
 #elif defined TARGET_ARCH_MODEL_mips_64
 # include "adfiles/ad_mips_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->live_nodes()+8 to avoid frequent realloc
   GrowableArray <Node *> spstack(C->live_nodes() + 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; j<n->len(); 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; j<pmax; j++) { // For all inputs
     if (use->in(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<uint> 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; j<nlen; j++ ) {
       if (use->in(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->live_nodes() >> 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<uint>(); // 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<int> 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<uint> *)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 = 1.0f;
   for (int i = 0; i < _members.length(); i++) {
     CFGElement* s = _members.at(i);
     float 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();
         float 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.
     float 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, float 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() {
   float loop_freq = _freq * trip_count();
   _freq = loop_freq;
   for (int i = 0; i < _members.length(); i++) {
     CFGElement* s = _members.at(i);
     float 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
 float 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:");
   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();
     float prob = _exits.at(i).get_prob();
     tty->print(" ->%d@%d%%", blk->_pre_order, (int)(prob*100));
   }
   tty->print("\n");
 }
 #endif

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/gcm.cpp@fd13a567f179 (annotated)

src/share/vm/opto/gcm.cpp