/* * Copyright (c) 1997, 2011, 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. * */ #ifndef SHARE_VM_OPTO_BLOCK_HPP #define SHARE_VM_OPTO_BLOCK_HPP #include "opto/multnode.hpp" #include "opto/node.hpp" #include "opto/phase.hpp" // Optimization - Graph Style class Block; class CFGLoop; class MachCallNode; class Matcher; class RootNode; class VectorSet; struct Tarjan; //------------------------------Block_Array------------------------------------ // Map dense integer indices to Blocks. Uses classic doubling-array trick. // Abstractly provides an infinite array of Block*'s, initialized to NULL. // Note that the constructor just zeros things, and since I use Arena // allocation I do not need a destructor to reclaim storage. class Block_Array : public ResourceObj { friend class VMStructs; uint _size; // allocated size, as opposed to formal limit debug_only(uint _limit;) // limit to formal domain protected: Block **_blocks; void grow( uint i ); // Grow array node to fit public: Arena *_arena; // Arena to allocate in Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) { debug_only(_limit=0); _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize ); for( int i = 0; i < OptoBlockListSize; i++ ) { _blocks[i] = NULL; } } Block *lookup( uint i ) const // Lookup, or NULL for not mapped { return (i=Max() ) grow(i); _blocks[i] = n; } uint Max() const { debug_only(return _limit); return _size; } }; class Block_List : public Block_Array { friend class VMStructs; public: uint _cnt; Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {} void push( Block *b ) { map(_cnt++,b); } Block *pop() { return _blocks[--_cnt]; } Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;} void remove( uint i ); void insert( uint i, Block *n ); uint size() const { return _cnt; } void reset() { _cnt = 0; } void print(); }; class CFGElement : public ResourceObj { friend class VMStructs; public: float _freq; // Execution frequency (estimate) CFGElement() : _freq(0.0f) {} virtual bool is_block() { return false; } virtual bool is_loop() { return false; } Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; } CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; } }; //------------------------------Block------------------------------------------ // This class defines a Basic Block. // Basic blocks are used during the output routines, and are not used during // any optimization pass. They are created late in the game. class Block : public CFGElement { friend class VMStructs; public: // Nodes in this block, in order Node_List _nodes; // Basic blocks have a Node which defines Control for all Nodes pinned in // this block. This Node is a RegionNode. Exception-causing Nodes // (division, subroutines) and Phi functions are always pinned. Later, // every Node will get pinned to some block. Node *head() const { return _nodes[0]; } // CAUTION: num_preds() is ONE based, so that predecessor numbers match // input edges to Regions and Phis. uint num_preds() const { return head()->req(); } Node *pred(uint i) const { return head()->in(i); } // Array of successor blocks, same size as projs array Block_Array _succs; // Basic blocks have some number of Nodes which split control to all // following blocks. These Nodes are always Projections. The field in // the Projection and the block-ending Node determine which Block follows. uint _num_succs; // Basic blocks also carry all sorts of good old fashioned DFS information // used to find loops, loop nesting depth, dominators, etc. uint _pre_order; // Pre-order DFS number // Dominator tree uint _dom_depth; // Depth in dominator tree for fast LCA Block* _idom; // Immediate dominator block CFGLoop *_loop; // Loop to which this block belongs uint _rpo; // Number in reverse post order walk virtual bool is_block() { return true; } float succ_prob(uint i); // return probability of i'th successor int num_fall_throughs(); // How many fall-through candidate this block has void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate Block* lone_fall_through(); // Return lone fall-through Block or null Block* dom_lca(Block* that); // Compute LCA in dominator tree. #ifdef ASSERT bool dominates(Block* that) { int dom_diff = this->_dom_depth - that->_dom_depth; if (dom_diff > 0) return false; for (; dom_diff < 0; dom_diff++) that = that->_idom; return this == that; } #endif // Report the alignment required by this block. Must be a power of 2. // The previous block will insert nops to get this alignment. uint code_alignment(); uint compute_loop_alignment(); // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies. // It is currently also used to scale such frequencies relative to // FreqCountInvocations relative to the old value of 1500. #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations) // Register Pressure (estimate) for Splitting heuristic uint _reg_pressure; uint _ihrp_index; uint _freg_pressure; uint _fhrp_index; // Mark and visited bits for an LCA calculation in insert_anti_dependences. // Since they hold unique node indexes, they do not need reinitialization. node_idx_t _raise_LCA_mark; void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; } node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; } node_idx_t _raise_LCA_visited; void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; } node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; } // Estimated size in bytes of first instructions in a loop. uint _first_inst_size; uint first_inst_size() const { return _first_inst_size; } void set_first_inst_size(uint s) { _first_inst_size = s; } // Compute the size of first instructions in this block. uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra); // Compute alignment padding if the block needs it. // Align a loop if loop's padding is less or equal to padding limit // or the size of first instructions in the loop > padding. uint alignment_padding(int current_offset) { int block_alignment = code_alignment(); int max_pad = block_alignment-relocInfo::addr_unit(); if( max_pad > 0 ) { assert(is_power_of_2(max_pad+relocInfo::addr_unit()), ""); int current_alignment = current_offset & max_pad; if( current_alignment != 0 ) { uint padding = (block_alignment-current_alignment) & max_pad; if( has_loop_alignment() && padding > (uint)MaxLoopPad && first_inst_size() <= padding ) { return 0; } return padding; } } return 0; } // Connector blocks. Connector blocks are basic blocks devoid of // instructions, but may have relevant non-instruction Nodes, such as // Phis or MergeMems. Such blocks are discovered and marked during the // RemoveEmpty phase, and elided during Output. bool _connector; void set_connector() { _connector = true; } bool is_connector() const { return _connector; }; // Loop_alignment will be set for blocks which are at the top of loops. // The block layout pass may rotate loops such that the loop head may not // be the sequentially first block of the loop encountered in the linear // list of blocks. If the layout pass is not run, loop alignment is set // for each block which is the head of a loop. uint _loop_alignment; void set_loop_alignment(Block *loop_top) { uint new_alignment = loop_top->compute_loop_alignment(); if (new_alignment > _loop_alignment) { _loop_alignment = new_alignment; } } uint loop_alignment() const { return _loop_alignment; } bool has_loop_alignment() const { return loop_alignment() > 0; } // Create a new Block with given head Node. // Creates the (empty) predecessor arrays. Block( Arena *a, Node *headnode ) : CFGElement(), _nodes(a), _succs(a), _num_succs(0), _pre_order(0), _idom(0), _loop(NULL), _reg_pressure(0), _ihrp_index(1), _freg_pressure(0), _fhrp_index(1), _raise_LCA_mark(0), _raise_LCA_visited(0), _first_inst_size(999999), _connector(false), _loop_alignment(0) { _nodes.push(headnode); } // Index of 'end' Node uint end_idx() const { // %%%%% add a proj after every goto // so (last->is_block_proj() != last) always, then simplify this code // This will not give correct end_idx for block 0 when it only contains root. int last_idx = _nodes.size() - 1; Node *last = _nodes[last_idx]; assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], ""); return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs); } // Basic blocks have a Node which ends them. This Node determines which // basic block follows this one in the program flow. This Node is either an // IfNode, a GotoNode, a JmpNode, or a ReturnNode. Node *end() const { return _nodes[end_idx()]; } // Add an instruction to an existing block. It must go after the head // instruction and before the end instruction. void add_inst( Node *n ) { _nodes.insert(end_idx(),n); } // Find node in block uint find_node( const Node *n ) const; // Find and remove n from block list void find_remove( const Node *n ); // helper function that adds caller save registers to MachProjNode void add_call_kills(MachProjNode *proj, RegMask& regs, const char* save_policy, bool exclude_soe); // Schedule a call next in the block uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, GrowableArray &ready_cnt, MachCallNode *mcall, VectorSet &next_call); // Perform basic-block local scheduling Node *select(PhaseCFG *cfg, Node_List &worklist, GrowableArray &ready_cnt, VectorSet &next_call, uint sched_slot); void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs ); void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs); bool schedule_local(PhaseCFG *cfg, Matcher &m, GrowableArray &ready_cnt, VectorSet &next_call); // Cleanup if any code lands between a Call and his Catch void call_catch_cleanup(Block_Array &bbs); // 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. void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons); // Return the empty status of a block enum { not_empty, empty_with_goto, completely_empty }; int is_Empty() const; // Forward through connectors Block* non_connector() { Block* s = this; while (s->is_connector()) { s = s->_succs[0]; } return s; } // Return true if b is a successor of this block bool has_successor(Block* b) const { for (uint i = 0; i < _num_succs; i++ ) { if (non_connector_successor(i) == b) { return true; } } return false; } // Successor block, after forwarding through connectors Block* non_connector_successor(int i) const { return _succs[i]->non_connector(); } // Examine block's code shape to predict if it is not commonly executed. bool has_uncommon_code() const; // Use frequency calculations and code shape to predict if the block // is uncommon. bool is_uncommon( Block_Array &bbs ) const; #ifndef PRODUCT // Debugging print of basic block void dump_bidx(const Block* orig, outputStream* st = tty) const; void dump_pred(const Block_Array *bbs, Block* orig, outputStream* st = tty) const; void dump_head( const Block_Array *bbs, outputStream* st = tty ) const; void dump() const; void dump( const Block_Array *bbs ) const; #endif }; //------------------------------PhaseCFG--------------------------------------- // Build an array of Basic Block pointers, one per Node. class PhaseCFG : public Phase { friend class VMStructs; private: // Build a proper looking cfg. Return count of basic blocks uint build_cfg(); // Perform DFS search. // Setup 'vertex' as DFS to vertex mapping. // Setup 'semi' as vertex to DFS mapping. // Set 'parent' to DFS parent. uint DFS( Tarjan *tarjan ); // Helper function to insert a node into a block void schedule_node_into_block( Node *n, Block *b ); void replace_block_proj_ctrl( Node *n ); // Set the basic block for pinned Nodes void schedule_pinned_nodes( VectorSet &visited ); // I'll need a few machine-specific GotoNodes. Clone from this one. MachNode *_goto; Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false); void verify_anti_dependences(Block* LCA, Node* load) { assert(LCA == _bbs[load->_idx], "should already be scheduled"); insert_anti_dependences(LCA, load, true); } public: PhaseCFG( Arena *a, RootNode *r, Matcher &m ); uint _num_blocks; // Count of basic blocks Block_List _blocks; // List of basic blocks RootNode *_root; // Root of whole program Block_Array _bbs; // Map Nodes to owning Basic Block Block *_broot; // Basic block of root uint _rpo_ctr; CFGLoop* _root_loop; float _outer_loop_freq; // Outmost loop frequency // Per node latency estimation, valid only during GCM GrowableArray *_node_latency; #ifndef PRODUCT bool _trace_opto_pipelining; // tracing flag #endif #ifdef ASSERT Unique_Node_List _raw_oops; #endif // Build dominators void Dominators(); // Estimate block frequencies based on IfNode probabilities void Estimate_Block_Frequency(); // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block. void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list ); // Compute the (backwards) latency of a node from the uses void latency_from_uses(Node *n); // Compute the (backwards) latency of a node from a single use int latency_from_use(Node *n, const Node *def, Node *use); // Compute the (backwards) latency of a node from the uses of this instruction void partial_latency_of_defs(Node *n); // Schedule Nodes early in their basic blocks. bool schedule_early(VectorSet &visited, Node_List &roots); // For each node, find the latest block it can be scheduled into // and then select the cheapest block between the latest and earliest // block to place the node. void schedule_late(VectorSet &visited, Node_List &stack); // Pick a block between early and late that is a cheaper alternative // to late. Helper for schedule_late. Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self); // Compute the instruction global latency with a backwards walk void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack); // Set loop alignment void set_loop_alignment(); // Remove empty basic blocks void remove_empty(); void fixup_flow(); bool move_to_next(Block* bx, uint b_index); void move_to_end(Block* bx, uint b_index); void insert_goto_at(uint block_no, uint succ_no); // Check for NeverBranch at block end. This needs to become a GOTO to the // true target. NeverBranch are treated as a conditional branch that always // goes the same direction for most of the optimizer and are used to give a // fake exit path to infinite loops. At this late stage they need to turn // into Goto's so that when you enter the infinite loop you indeed hang. void convert_NeverBranch_to_Goto(Block *b); CFGLoop* create_loop_tree(); // Insert a node into a block, and update the _bbs void insert( Block *b, uint idx, Node *n ) { b->_nodes.insert( idx, n ); _bbs.map( n->_idx, b ); } #ifndef PRODUCT bool trace_opto_pipelining() const { return _trace_opto_pipelining; } // Debugging print of CFG void dump( ) const; // CFG only void _dump_cfg( const Node *end, VectorSet &visited ) const; void verify() const; void dump_headers(); #else bool trace_opto_pipelining() const { return false; } #endif }; //------------------------------UnionFind-------------------------------------- // Map Block indices to a block-index for a cfg-cover. // Array lookup in the optimized case. class UnionFind : public ResourceObj { uint _cnt, _max; uint* _indices; ReallocMark _nesting; // assertion check for reallocations public: UnionFind( uint max ); void reset( uint max ); // Reset to identity map for [0..max] uint lookup( uint nidx ) const { return _indices[nidx]; } uint operator[] (uint nidx) const { return lookup(nidx); } void map( uint from_idx, uint to_idx ) { assert( from_idx < _cnt, "oob" ); _indices[from_idx] = to_idx; } void extend( uint from_idx, uint to_idx ); uint Size() const { return _cnt; } uint Find( uint idx ) { assert( idx < 65536, "Must fit into uint"); uint uf_idx = lookup(idx); return (uf_idx == idx) ? uf_idx : Find_compress(idx); } uint Find_compress( uint idx ); uint Find_const( uint idx ) const; void Union( uint idx1, uint idx2 ); }; //----------------------------BlockProbPair--------------------------- // Ordered pair of Node*. class BlockProbPair VALUE_OBJ_CLASS_SPEC { protected: Block* _target; // block target float _prob; // probability of edge to block public: BlockProbPair() : _target(NULL), _prob(0.0) {} BlockProbPair(Block* b, float p) : _target(b), _prob(p) {} Block* get_target() const { return _target; } float get_prob() const { return _prob; } }; //------------------------------CFGLoop------------------------------------------- class CFGLoop : public CFGElement { friend class VMStructs; int _id; int _depth; CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null CFGLoop *_sibling; // null terminated list CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops GrowableArray _members; // list of members of loop GrowableArray _exits; // list of successor blocks and their probabilities float _exit_prob; // probability any loop exit is taken on a single loop iteration void update_succ_freq(Block* b, float freq); public: CFGLoop(int id) : CFGElement(), _id(id), _depth(0), _parent(NULL), _sibling(NULL), _child(NULL), _exit_prob(1.0f) {} CFGLoop* parent() { return _parent; } void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk); void add_member(CFGElement *s) { _members.push(s); } void add_nested_loop(CFGLoop* cl); Block* head() { assert(_members.at(0)->is_block(), "head must be a block"); Block* hd = _members.at(0)->as_Block(); assert(hd->_loop == this, "just checking"); assert(hd->head()->is_Loop(), "must begin with loop head node"); return hd; } Block* backedge_block(); // Return the block on the backedge of the loop (else NULL) void compute_loop_depth(int depth); void compute_freq(); // compute frequency with loop assuming head freq 1.0f void scale_freq(); // scale frequency by loop trip count (including outer loops) float outer_loop_freq() const; // frequency of outer loop bool in_loop_nest(Block* b); float trip_count() const { return 1.0f / _exit_prob; } virtual bool is_loop() { return true; } int id() { return _id; } #ifndef PRODUCT void dump( ) const; void dump_tree() const; #endif }; //----------------------------------CFGEdge------------------------------------ // A edge between two basic blocks that will be embodied by a branch or a // fall-through. class CFGEdge : public ResourceObj { friend class VMStructs; private: Block * _from; // Source basic block Block * _to; // Destination basic block float _freq; // Execution frequency (estimate) int _state; bool _infrequent; int _from_pct; int _to_pct; // Private accessors int from_pct() const { return _from_pct; } int to_pct() const { return _to_pct; } int from_infrequent() const { return from_pct() < BlockLayoutMinDiamondPercentage; } int to_infrequent() const { return to_pct() < BlockLayoutMinDiamondPercentage; } public: enum { open, // initial edge state; unprocessed connected, // edge used to connect two traces together interior // edge is interior to trace (could be backedge) }; CFGEdge(Block *from, Block *to, float freq, int from_pct, int to_pct) : _from(from), _to(to), _freq(freq), _from_pct(from_pct), _to_pct(to_pct), _state(open) { _infrequent = from_infrequent() || to_infrequent(); } float freq() const { return _freq; } Block* from() const { return _from; } Block* to () const { return _to; } int infrequent() const { return _infrequent; } int state() const { return _state; } void set_state(int state) { _state = state; } #ifndef PRODUCT void dump( ) const; #endif }; //-----------------------------------Trace------------------------------------- // An ordered list of basic blocks. class Trace : public ResourceObj { private: uint _id; // Unique Trace id (derived from initial block) Block ** _next_list; // Array mapping index to next block Block ** _prev_list; // Array mapping index to previous block Block * _first; // First block in the trace Block * _last; // Last block in the trace // Return the block that follows "b" in the trace. Block * next(Block *b) const { return _next_list[b->_pre_order]; } void set_next(Block *b, Block *n) const { _next_list[b->_pre_order] = n; } // Return the block that precedes "b" in the trace. Block * prev(Block *b) const { return _prev_list[b->_pre_order]; } void set_prev(Block *b, Block *p) const { _prev_list[b->_pre_order] = p; } // We've discovered a loop in this trace. Reset last to be "b", and first as // the block following "b void break_loop_after(Block *b) { _last = b; _first = next(b); set_prev(_first, NULL); set_next(_last, NULL); } public: Trace(Block *b, Block **next_list, Block **prev_list) : _first(b), _last(b), _next_list(next_list), _prev_list(prev_list), _id(b->_pre_order) { set_next(b, NULL); set_prev(b, NULL); }; // Return the id number uint id() const { return _id; } void set_id(uint id) { _id = id; } // Return the first block in the trace Block * first_block() const { return _first; } // Return the last block in the trace Block * last_block() const { return _last; } // Insert a trace in the middle of this one after b void insert_after(Block *b, Trace *tr) { set_next(tr->last_block(), next(b)); if (next(b) != NULL) { set_prev(next(b), tr->last_block()); } set_next(b, tr->first_block()); set_prev(tr->first_block(), b); if (b == _last) { _last = tr->last_block(); } } void insert_before(Block *b, Trace *tr) { Block *p = prev(b); assert(p != NULL, "use append instead"); insert_after(p, tr); } // Append another trace to this one. void append(Trace *tr) { insert_after(_last, tr); } // Append a block at the end of this trace void append(Block *b) { set_next(_last, b); set_prev(b, _last); _last = b; } // Adjust the the blocks in this trace void fixup_blocks(PhaseCFG &cfg); bool backedge(CFGEdge *e); #ifndef PRODUCT void dump( ) const; #endif }; //------------------------------PhaseBlockLayout------------------------------- // Rearrange blocks into some canonical order, based on edges and their frequencies class PhaseBlockLayout : public Phase { friend class VMStructs; PhaseCFG &_cfg; // Control flow graph GrowableArray *edges; Trace **traces; Block **next; Block **prev; UnionFind *uf; // Given a block, find its encompassing Trace Trace * trace(Block *b) { return traces[uf->Find_compress(b->_pre_order)]; } public: PhaseBlockLayout(PhaseCFG &cfg); void find_edges(); void grow_traces(); void merge_traces(bool loose_connections); void reorder_traces(int count); void union_traces(Trace* from, Trace* to); }; #endif // SHARE_VM_OPTO_BLOCK_HPP