--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/opto/block.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,952 @@
+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// Optimization - Graph Style
+
+#include "incls/_precompiled.incl"
+#include "incls/_block.cpp.incl"
+
+
+//-----------------------------------------------------------------------------
+void Block_Array::grow( uint i ) {
+ assert(i >= Max(), "must be an overflow");
+ debug_only(_limit = i+1);
+ if( i < _size ) return;
+ if( !_size ) {
+ _size = 1;
+ _blocks = (Block**)_arena->Amalloc( _size * sizeof(Block*) );
+ _blocks[0] = NULL;
+ }
+ uint old = _size;
+ while( i >= _size ) _size <<= 1; // Double to fit
+ _blocks = (Block**)_arena->Arealloc( _blocks, old*sizeof(Block*),_size*sizeof(Block*));
+ Copy::zero_to_bytes( &_blocks[old], (_size-old)*sizeof(Block*) );
+}
+
+//=============================================================================
+void Block_List::remove(uint i) {
+ assert(i < _cnt, "index out of bounds");
+ Copy::conjoint_words_to_lower((HeapWord*)&_blocks[i+1], (HeapWord*)&_blocks[i], ((_cnt-i-1)*sizeof(Block*)));
+ pop(); // shrink list by one block
+}
+
+void Block_List::insert(uint i, Block *b) {
+ push(b); // grow list by one block
+ Copy::conjoint_words_to_higher((HeapWord*)&_blocks[i], (HeapWord*)&_blocks[i+1], ((_cnt-i-1)*sizeof(Block*)));
+ _blocks[i] = b;
+}
+
+
+//=============================================================================
+
+uint Block::code_alignment() {
+ // Check for Root block
+ if( _pre_order == 0 ) return CodeEntryAlignment;
+ // Check for Start block
+ if( _pre_order == 1 ) return InteriorEntryAlignment;
+ // Check for loop alignment
+ Node *h = head();
+ if( h->is_Loop() && h->as_Loop()->is_inner_loop() ) {
+ // Pre- and post-loops have low trip count so do not bother with
+ // NOPs for align loop head. The constants are hidden from tuning
+ // but only because my "divide by 4" heuristic surely gets nearly
+ // all possible gain (a "do not align at all" heuristic has a
+ // chance of getting a really tiny gain).
+ if( h->is_CountedLoop() && (h->as_CountedLoop()->is_pre_loop() ||
+ h->as_CountedLoop()->is_post_loop()) )
+ return (OptoLoopAlignment > 4) ? (OptoLoopAlignment>>2) : 1;
+ // Loops with low backedge frequency should not be aligned.
+ Node *n = h->in(LoopNode::LoopBackControl)->in(0);
+ if( n->is_MachIf() && n->as_MachIf()->_prob < 0.01 ) {
+ return 1; // Loop does not loop, more often than not!
+ }
+ return OptoLoopAlignment; // Otherwise align loop head
+ }
+ return 1; // no particular alignment
+}
+
+//-----------------------------------------------------------------------------
+// Compute the size of first 'inst_cnt' instructions in this block.
+// Return the number of instructions left to compute if the block has
+// less then 'inst_cnt' instructions.
+uint Block::compute_first_inst_size(uint& sum_size, uint inst_cnt,
+ PhaseRegAlloc* ra) {
+ uint last_inst = _nodes.size();
+ for( uint j = 0; j < last_inst && inst_cnt > 0; j++ ) {
+ uint inst_size = _nodes[j]->size(ra);
+ if( inst_size > 0 ) {
+ inst_cnt--;
+ uint sz = sum_size + inst_size;
+ if( sz <= (uint)OptoLoopAlignment ) {
+ // Compute size of instructions which fit into fetch buffer only
+ // since all inst_cnt instructions will not fit even if we align them.
+ sum_size = sz;
+ } else {
+ return 0;
+ }
+ }
+ }
+ return inst_cnt;
+}
+
+//-----------------------------------------------------------------------------
+uint Block::find_node( const Node *n ) const {
+ for( uint i = 0; i < _nodes.size(); i++ ) {
+ if( _nodes[i] == n )
+ return i;
+ }
+ ShouldNotReachHere();
+ return 0;
+}
+
+// Find and remove n from block list
+void Block::find_remove( const Node *n ) {
+ _nodes.remove(find_node(n));
+}
+
+//------------------------------is_Empty---------------------------------------
+// Return empty status of a block. Empty blocks contain only the head, other
+// ideal nodes, and an optional trailing goto.
+int Block::is_Empty() const {
+
+ // Root or start block is not considered empty
+ if (head()->is_Root() || head()->is_Start()) {
+ return not_empty;
+ }
+
+ int success_result = completely_empty;
+ int end_idx = _nodes.size()-1;
+
+ // Check for ending goto
+ if ((end_idx > 0) && (_nodes[end_idx]->is_Goto())) {
+ success_result = empty_with_goto;
+ end_idx--;
+ }
+
+ // Unreachable blocks are considered empty
+ if (num_preds() <= 1) {
+ return success_result;
+ }
+
+ // Ideal nodes are allowable in empty blocks: skip them Only MachNodes
+ // turn directly into code, because only MachNodes have non-trivial
+ // emit() functions.
+ while ((end_idx > 0) && !_nodes[end_idx]->is_Mach()) {
+ end_idx--;
+ }
+
+ // No room for any interesting instructions?
+ if (end_idx == 0) {
+ return success_result;
+ }
+
+ return not_empty;
+}
+
+//------------------------------has_uncommon_code------------------------------
+// Return true if the block's code implies that it is not likely to be
+// executed infrequently. Check to see if the block ends in a Halt or
+// a low probability call.
+bool Block::has_uncommon_code() const {
+ Node* en = end();
+
+ if (en->is_Goto())
+ en = en->in(0);
+ if (en->is_Catch())
+ en = en->in(0);
+ if (en->is_Proj() && en->in(0)->is_MachCall()) {
+ MachCallNode* call = en->in(0)->as_MachCall();
+ if (call->cnt() != COUNT_UNKNOWN && call->cnt() <= PROB_UNLIKELY_MAG(4)) {
+ // This is true for slow-path stubs like new_{instance,array},
+ // slow_arraycopy, complete_monitor_locking, uncommon_trap.
+ // The magic number corresponds to the probability of an uncommon_trap,
+ // even though it is a count not a probability.
+ return true;
+ }
+ }
+
+ int op = en->is_Mach() ? en->as_Mach()->ideal_Opcode() : en->Opcode();
+ return op == Op_Halt;
+}
+
+//------------------------------is_uncommon------------------------------------
+// True if block is low enough frequency or guarded by a test which
+// mostly does not go here.
+bool Block::is_uncommon( Block_Array &bbs ) const {
+ // Initial blocks must never be moved, so are never uncommon.
+ if (head()->is_Root() || head()->is_Start()) return false;
+
+ // Check for way-low freq
+ if( _freq < BLOCK_FREQUENCY(0.00001f) ) return true;
+
+ // Look for code shape indicating uncommon_trap or slow path
+ if (has_uncommon_code()) return true;
+
+ const float epsilon = 0.05f;
+ const float guard_factor = PROB_UNLIKELY_MAG(4) / (1.f - epsilon);
+ uint uncommon_preds = 0;
+ uint freq_preds = 0;
+ uint uncommon_for_freq_preds = 0;
+
+ for( uint i=1; i<num_preds(); i++ ) {
+ Block* guard = bbs[pred(i)->_idx];
+ // Check to see if this block follows its guard 1 time out of 10000
+ // or less.
+ //
+ // See list of magnitude-4 unlikely probabilities in cfgnode.hpp which
+ // we intend to be "uncommon", such as slow-path TLE allocation,
+ // predicted call failure, and uncommon trap triggers.
+ //
+ // Use an epsilon value of 5% to allow for variability in frequency
+ // predictions and floating point calculations. The net effect is
+ // that guard_factor is set to 9500.
+ //
+ // Ignore low-frequency blocks.
+ // The next check is (guard->_freq < 1.e-5 * 9500.).
+ if(guard->_freq*BLOCK_FREQUENCY(guard_factor) < BLOCK_FREQUENCY(0.00001f)) {
+ uncommon_preds++;
+ } else {
+ freq_preds++;
+ if( _freq < guard->_freq * guard_factor ) {
+ uncommon_for_freq_preds++;
+ }
+ }
+ }
+ if( num_preds() > 1 &&
+ // The block is uncommon if all preds are uncommon or
+ (uncommon_preds == (num_preds()-1) ||
+ // it is uncommon for all frequent preds.
+ uncommon_for_freq_preds == freq_preds) ) {
+ return true;
+ }
+ return false;
+}
+
+//------------------------------dump-------------------------------------------
+#ifndef PRODUCT
+void Block::dump_bidx(const Block* orig) const {
+ if (_pre_order) tty->print("B%d",_pre_order);
+ else tty->print("N%d", head()->_idx);
+
+ if (Verbose && orig != this) {
+ // Dump the original block's idx
+ tty->print(" (");
+ orig->dump_bidx(orig);
+ tty->print(")");
+ }
+}
+
+void Block::dump_pred(const Block_Array *bbs, Block* orig) const {
+ if (is_connector()) {
+ for (uint i=1; i<num_preds(); i++) {
+ Block *p = ((*bbs)[pred(i)->_idx]);
+ p->dump_pred(bbs, orig);
+ }
+ } else {
+ dump_bidx(orig);
+ tty->print(" ");
+ }
+}
+
+void Block::dump_head( const Block_Array *bbs ) const {
+ // Print the basic block
+ dump_bidx(this);
+ tty->print(": #\t");
+
+ // Print the incoming CFG edges and the outgoing CFG edges
+ for( uint i=0; i<_num_succs; i++ ) {
+ non_connector_successor(i)->dump_bidx(_succs[i]);
+ tty->print(" ");
+ }
+ tty->print("<- ");
+ if( head()->is_block_start() ) {
+ for (uint i=1; i<num_preds(); i++) {
+ Node *s = pred(i);
+ if (bbs) {
+ Block *p = (*bbs)[s->_idx];
+ p->dump_pred(bbs, p);
+ } else {
+ while (!s->is_block_start())
+ s = s->in(0);
+ tty->print("N%d ", s->_idx );
+ }
+ }
+ } else
+ tty->print("BLOCK HEAD IS JUNK ");
+
+ // Print loop, if any
+ const Block *bhead = this; // Head of self-loop
+ Node *bh = bhead->head();
+ if( bbs && bh->is_Loop() && !head()->is_Root() ) {
+ LoopNode *loop = bh->as_Loop();
+ const Block *bx = (*bbs)[loop->in(LoopNode::LoopBackControl)->_idx];
+ while (bx->is_connector()) {
+ bx = (*bbs)[bx->pred(1)->_idx];
+ }
+ tty->print("\tLoop: B%d-B%d ", bhead->_pre_order, bx->_pre_order);
+ // Dump any loop-specific bits, especially for CountedLoops.
+ loop->dump_spec(tty);
+ }
+ tty->print(" Freq: %g",_freq);
+ if( Verbose || WizardMode ) {
+ tty->print(" IDom: %d/#%d", _idom ? _idom->_pre_order : 0, _dom_depth);
+ tty->print(" RegPressure: %d",_reg_pressure);
+ tty->print(" IHRP Index: %d",_ihrp_index);
+ tty->print(" FRegPressure: %d",_freg_pressure);
+ tty->print(" FHRP Index: %d",_fhrp_index);
+ }
+ tty->print_cr("");
+}
+
+void Block::dump() const { dump(0); }
+
+void Block::dump( const Block_Array *bbs ) const {
+ dump_head(bbs);
+ uint cnt = _nodes.size();
+ for( uint i=0; i<cnt; i++ )
+ _nodes[i]->dump();
+ tty->print("\n");
+}
+#endif
+
+//=============================================================================
+//------------------------------PhaseCFG---------------------------------------
+PhaseCFG::PhaseCFG( Arena *a, RootNode *r, Matcher &m ) :
+ Phase(CFG),
+ _bbs(a),
+ _root(r)
+#ifndef PRODUCT
+ , _trace_opto_pipelining(TraceOptoPipelining || C->method_has_option("TraceOptoPipelining"))
+#endif
+{
+ ResourceMark rm;
+ // I'll need a few machine-specific GotoNodes. Make an Ideal GotoNode,
+ // then Match it into a machine-specific Node. Then clone the machine
+ // Node on demand.
+ Node *x = new (C, 1) GotoNode(NULL);
+ x->init_req(0, x);
+ _goto = m.match_tree(x);
+ assert(_goto != NULL, "");
+ _goto->set_req(0,_goto);
+
+ // Build the CFG in Reverse Post Order
+ _num_blocks = build_cfg();
+ _broot = _bbs[_root->_idx];
+}
+
+//------------------------------build_cfg--------------------------------------
+// Build a proper looking CFG. Make every block begin with either a StartNode
+// or a RegionNode. Make every block end with either a Goto, If or Return.
+// The RootNode both starts and ends it's own block. Do this with a recursive
+// backwards walk over the control edges.
+uint PhaseCFG::build_cfg() {
+ Arena *a = Thread::current()->resource_area();
+ VectorSet visited(a);
+
+ // Allocate stack with enough space to avoid frequent realloc
+ Node_Stack nstack(a, C->unique() >> 1);
+ nstack.push(_root, 0);
+ uint sum = 0; // Counter for blocks
+
+ while (nstack.is_nonempty()) {
+ // node and in's index from stack's top
+ // 'np' is _root (see above) or RegionNode, StartNode: we push on stack
+ // only nodes which point to the start of basic block (see below).
+ Node *np = nstack.node();
+ // idx > 0, except for the first node (_root) pushed on stack
+ // at the beginning when idx == 0.
+ // We will use the condition (idx == 0) later to end the build.
+ uint idx = nstack.index();
+ Node *proj = np->in(idx);
+ const Node *x = proj->is_block_proj();
+ // Does the block end with a proper block-ending Node? One of Return,
+ // If or Goto? (This check should be done for visited nodes also).
+ if (x == NULL) { // Does not end right...
+ Node *g = _goto->clone(); // Force it to end in a Goto
+ g->set_req(0, proj);
+ np->set_req(idx, g);
+ x = proj = g;
+ }
+ if (!visited.test_set(x->_idx)) { // Visit this block once
+ // Skip any control-pinned middle'in stuff
+ Node *p = proj;
+ do {
+ proj = p; // Update pointer to last Control
+ p = p->in(0); // Move control forward
+ } while( !p->is_block_proj() &&
+ !p->is_block_start() );
+ // Make the block begin with one of Region or StartNode.
+ if( !p->is_block_start() ) {
+ RegionNode *r = new (C, 2) RegionNode( 2 );
+ r->init_req(1, p); // Insert RegionNode in the way
+ proj->set_req(0, r); // Insert RegionNode in the way
+ p = r;
+ }
+ // 'p' now points to the start of this basic block
+
+ // Put self in array of basic blocks
+ Block *bb = new (_bbs._arena) Block(_bbs._arena,p);
+ _bbs.map(p->_idx,bb);
+ _bbs.map(x->_idx,bb);
+ if( x != p ) // Only for root is x == p
+ bb->_nodes.push((Node*)x);
+
+ // Now handle predecessors
+ ++sum; // Count 1 for self block
+ uint cnt = bb->num_preds();
+ for (int i = (cnt - 1); i > 0; i-- ) { // For all predecessors
+ Node *prevproj = p->in(i); // Get prior input
+ assert( !prevproj->is_Con(), "dead input not removed" );
+ // Check to see if p->in(i) is a "control-dependent" CFG edge -
+ // i.e., it splits at the source (via an IF or SWITCH) and merges
+ // at the destination (via a many-input Region).
+ // This breaks critical edges. The RegionNode to start the block
+ // will be added when <p,i> is pulled off the node stack
+ if ( cnt > 2 ) { // Merging many things?
+ assert( prevproj== bb->pred(i),"");
+ if(prevproj->is_block_proj() != prevproj) { // Control-dependent edge?
+ // Force a block on the control-dependent edge
+ Node *g = _goto->clone(); // Force it to end in a Goto
+ g->set_req(0,prevproj);
+ p->set_req(i,g);
+ }
+ }
+ nstack.push(p, i); // 'p' is RegionNode or StartNode
+ }
+ } else { // Post-processing visited nodes
+ nstack.pop(); // remove node from stack
+ // Check if it the fist node pushed on stack at the beginning.
+ if (idx == 0) break; // end of the build
+ // Find predecessor basic block
+ Block *pb = _bbs[x->_idx];
+ // Insert into nodes array, if not already there
+ if( !_bbs.lookup(proj->_idx) ) {
+ assert( x != proj, "" );
+ // Map basic block of projection
+ _bbs.map(proj->_idx,pb);
+ pb->_nodes.push(proj);
+ }
+ // Insert self as a child of my predecessor block
+ pb->_succs.map(pb->_num_succs++, _bbs[np->_idx]);
+ assert( pb->_nodes[ pb->_nodes.size() - pb->_num_succs ]->is_block_proj(),
+ "too many control users, not a CFG?" );
+ }
+ }
+ // Return number of basic blocks for all children and self
+ return sum;
+}
+
+//------------------------------insert_goto_at---------------------------------
+// Inserts a goto & corresponding basic block between
+// block[block_no] and its succ_no'th successor block
+void PhaseCFG::insert_goto_at(uint block_no, uint succ_no) {
+ // get block with block_no
+ assert(block_no < _num_blocks, "illegal block number");
+ Block* in = _blocks[block_no];
+ // get successor block succ_no
+ assert(succ_no < in->_num_succs, "illegal successor number");
+ Block* out = in->_succs[succ_no];
+ // get ProjNode corresponding to the succ_no'th successor of the in block
+ ProjNode* proj = in->_nodes[in->_nodes.size() - in->_num_succs + succ_no]->as_Proj();
+ // create region for basic block
+ RegionNode* region = new (C, 2) RegionNode(2);
+ region->init_req(1, proj);
+ // setup corresponding basic block
+ Block* block = new (_bbs._arena) Block(_bbs._arena, region);
+ _bbs.map(region->_idx, block);
+ C->regalloc()->set_bad(region->_idx);
+ // add a goto node
+ Node* gto = _goto->clone(); // get a new goto node
+ gto->set_req(0, region);
+ // add it to the basic block
+ block->_nodes.push(gto);
+ _bbs.map(gto->_idx, block);
+ C->regalloc()->set_bad(gto->_idx);
+ // hook up successor block
+ block->_succs.map(block->_num_succs++, out);
+ // remap successor's predecessors if necessary
+ for (uint i = 1; i < out->num_preds(); i++) {
+ if (out->pred(i) == proj) out->head()->set_req(i, gto);
+ }
+ // remap predecessor's successor to new block
+ in->_succs.map(succ_no, block);
+ // add new basic block to basic block list
+ _blocks.insert(block_no + 1, block);
+ _num_blocks++;
+}
+
+//------------------------------no_flip_branch---------------------------------
+// Does this block end in a multiway branch that cannot have the default case
+// flipped for another case?
+static bool no_flip_branch( Block *b ) {
+ int branch_idx = b->_nodes.size() - b->_num_succs-1;
+ if( branch_idx < 1 ) return false;
+ Node *bra = b->_nodes[branch_idx];
+ if( bra->is_Catch() ) return true;
+ if( bra->is_Mach() ) {
+ if( bra->is_MachNullCheck() ) return true;
+ int iop = bra->as_Mach()->ideal_Opcode();
+ if( iop == Op_FastLock || iop == Op_FastUnlock )
+ return true;
+ }
+ return false;
+}
+
+//------------------------------convert_NeverBranch_to_Goto--------------------
+// 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 PhaseCFG::convert_NeverBranch_to_Goto(Block *b) {
+ // Find true target
+ int end_idx = b->end_idx();
+ int idx = b->_nodes[end_idx+1]->as_Proj()->_con;
+ Block *succ = b->_succs[idx];
+ Node* gto = _goto->clone(); // get a new goto node
+ gto->set_req(0, b->head());
+ Node *bp = b->_nodes[end_idx];
+ b->_nodes.map(end_idx,gto); // Slam over NeverBranch
+ _bbs.map(gto->_idx, b);
+ C->regalloc()->set_bad(gto->_idx);
+ b->_nodes.pop(); // Yank projections
+ b->_nodes.pop(); // Yank projections
+ b->_succs.map(0,succ); // Map only successor
+ b->_num_succs = 1;
+ // remap successor's predecessors if necessary
+ uint j;
+ for( j = 1; j < succ->num_preds(); j++)
+ if( succ->pred(j)->in(0) == bp )
+ succ->head()->set_req(j, gto);
+ // Kill alternate exit path
+ Block *dead = b->_succs[1-idx];
+ for( j = 1; j < dead->num_preds(); j++)
+ if( dead->pred(j)->in(0) == bp )
+ break;
+ // Scan through block, yanking dead path from
+ // all regions and phis.
+ dead->head()->del_req(j);
+ for( int k = 1; dead->_nodes[k]->is_Phi(); k++ )
+ dead->_nodes[k]->del_req(j);
+}
+
+//------------------------------MoveToNext-------------------------------------
+// Helper function to move block bx to the slot following b_index. Return
+// true if the move is successful, otherwise false
+bool PhaseCFG::MoveToNext(Block* bx, uint b_index) {
+ if (bx == NULL) return false;
+
+ // Return false if bx is already scheduled.
+ uint bx_index = bx->_pre_order;
+ if ((bx_index <= b_index) && (_blocks[bx_index] == bx)) {
+ return false;
+ }
+
+ // Find the current index of block bx on the block list
+ bx_index = b_index + 1;
+ while( bx_index < _num_blocks && _blocks[bx_index] != bx ) bx_index++;
+ assert(_blocks[bx_index] == bx, "block not found");
+
+ // If the previous block conditionally falls into bx, return false,
+ // because moving bx will create an extra jump.
+ for(uint k = 1; k < bx->num_preds(); k++ ) {
+ Block* pred = _bbs[bx->pred(k)->_idx];
+ if (pred == _blocks[bx_index-1]) {
+ if (pred->_num_succs != 1) {
+ return false;
+ }
+ }
+ }
+
+ // Reinsert bx just past block 'b'
+ _blocks.remove(bx_index);
+ _blocks.insert(b_index + 1, bx);
+ return true;
+}
+
+//------------------------------MoveToEnd--------------------------------------
+// Move empty and uncommon blocks to the end.
+void PhaseCFG::MoveToEnd(Block *b, uint i) {
+ int e = b->is_Empty();
+ if (e != Block::not_empty) {
+ if (e == Block::empty_with_goto) {
+ // Remove the goto, but leave the block.
+ b->_nodes.pop();
+ }
+ // Mark this block as a connector block, which will cause it to be
+ // ignored in certain functions such as non_connector_successor().
+ b->set_connector();
+ }
+ // Move the empty block to the end, and don't recheck.
+ _blocks.remove(i);
+ _blocks.push(b);
+}
+
+//------------------------------RemoveEmpty------------------------------------
+// Remove empty basic blocks and useless branches.
+void PhaseCFG::RemoveEmpty() {
+ // Move uncommon blocks to the end
+ uint last = _num_blocks;
+ uint i;
+ assert( _blocks[0] == _broot, "" );
+ for( i = 1; i < last; i++ ) {
+ Block *b = _blocks[i];
+
+ // 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.
+ if( b->_nodes[b->end_idx()]->Opcode() == Op_NeverBranch )
+ convert_NeverBranch_to_Goto(b);
+
+ // Look for uncommon blocks and move to end.
+ if( b->is_uncommon(_bbs) ) {
+ MoveToEnd(b, i);
+ last--; // No longer check for being uncommon!
+ if( no_flip_branch(b) ) { // Fall-thru case must follow?
+ b = _blocks[i]; // Find the fall-thru block
+ MoveToEnd(b, i);
+ last--;
+ }
+ i--; // backup block counter post-increment
+ }
+ }
+
+ // Remove empty blocks
+ uint j1;
+ last = _num_blocks;
+ for( i=0; i < last; i++ ) {
+ Block *b = _blocks[i];
+ if (i > 0) {
+ if (b->is_Empty() != Block::not_empty) {
+ MoveToEnd(b, i);
+ last--;
+ i--;
+ }
+ }
+ } // End of for all blocks
+
+ // Fixup final control flow for the blocks. Remove jump-to-next
+ // block. If neither arm of a IF follows the conditional branch, we
+ // have to add a second jump after the conditional. We place the
+ // TRUE branch target in succs[0] for both GOTOs and IFs.
+ for( i=0; i < _num_blocks; i++ ) {
+ Block *b = _blocks[i];
+ b->_pre_order = i; // turn pre-order into block-index
+
+ // Connector blocks need no further processing.
+ if (b->is_connector()) {
+ assert((i+1) == _num_blocks || _blocks[i+1]->is_connector(),
+ "All connector blocks should sink to the end");
+ continue;
+ }
+ assert(b->is_Empty() != Block::completely_empty,
+ "Empty blocks should be connectors");
+
+ Block *bnext = (i < _num_blocks-1) ? _blocks[i+1] : NULL;
+ Block *bs0 = b->non_connector_successor(0);
+
+ // Check for multi-way branches where I cannot negate the test to
+ // exchange the true and false targets.
+ if( no_flip_branch( b ) ) {
+ // Find fall through case - if must fall into its target
+ int branch_idx = b->_nodes.size() - b->_num_succs;
+ for (uint j2 = 0; j2 < b->_num_succs; j2++) {
+ const ProjNode* p = b->_nodes[branch_idx + j2]->as_Proj();
+ if (p->_con == 0) {
+ // successor j2 is fall through case
+ if (b->non_connector_successor(j2) != bnext) {
+ // but it is not the next block => insert a goto
+ insert_goto_at(i, j2);
+ }
+ // Put taken branch in slot 0
+ if( j2 == 0 && b->_num_succs == 2) {
+ // Flip targets in succs map
+ Block *tbs0 = b->_succs[0];
+ Block *tbs1 = b->_succs[1];
+ b->_succs.map( 0, tbs1 );
+ b->_succs.map( 1, tbs0 );
+ }
+ break;
+ }
+ }
+ // Remove all CatchProjs
+ for (j1 = 0; j1 < b->_num_succs; j1++) b->_nodes.pop();
+
+ } else if (b->_num_succs == 1) {
+ // Block ends in a Goto?
+ if (bnext == bs0) {
+ // We fall into next block; remove the Goto
+ b->_nodes.pop();
+ }
+
+ } else if( b->_num_succs == 2 ) { // Block ends in a If?
+ // Get opcode of 1st projection (matches _succs[0])
+ // Note: Since this basic block has 2 exits, the last 2 nodes must
+ // be projections (in any order), the 3rd last node must be
+ // the IfNode (we have excluded other 2-way exits such as
+ // CatchNodes already).
+ MachNode *iff = b->_nodes[b->_nodes.size()-3]->as_Mach();
+ ProjNode *proj0 = b->_nodes[b->_nodes.size()-2]->as_Proj();
+ ProjNode *proj1 = b->_nodes[b->_nodes.size()-1]->as_Proj();
+
+ // Assert that proj0 and succs[0] match up. Similarly for proj1 and succs[1].
+ assert(proj0->raw_out(0) == b->_succs[0]->head(), "Mismatch successor 0");
+ assert(proj1->raw_out(0) == b->_succs[1]->head(), "Mismatch successor 1");
+
+ Block *bs1 = b->non_connector_successor(1);
+
+ // Check for neither successor block following the current
+ // block ending in a conditional. If so, move one of the
+ // successors after the current one, provided that the
+ // successor was previously unscheduled, but moveable
+ // (i.e., all paths to it involve a branch).
+ if( bnext != bs0 && bnext != bs1 ) {
+
+ // Choose the more common successor based on the probability
+ // of the conditional branch.
+ Block *bx = bs0;
+ Block *by = bs1;
+
+ // _prob is the probability of taking the true path. Make
+ // p the probability of taking successor #1.
+ float p = iff->as_MachIf()->_prob;
+ if( proj0->Opcode() == Op_IfTrue ) {
+ p = 1.0 - p;
+ }
+
+ // Prefer successor #1 if p > 0.5
+ if (p > PROB_FAIR) {
+ bx = bs1;
+ by = bs0;
+ }
+
+ // Attempt the more common successor first
+ if (MoveToNext(bx, i)) {
+ bnext = bx;
+ } else if (MoveToNext(by, i)) {
+ bnext = by;
+ }
+ }
+
+ // Check for conditional branching the wrong way. Negate
+ // conditional, if needed, so it falls into the following block
+ // and branches to the not-following block.
+
+ // Check for the next block being in succs[0]. We are going to branch
+ // to succs[0], so we want the fall-thru case as the next block in
+ // succs[1].
+ if (bnext == bs0) {
+ // Fall-thru case in succs[0], so flip targets in succs map
+ Block *tbs0 = b->_succs[0];
+ Block *tbs1 = b->_succs[1];
+ b->_succs.map( 0, tbs1 );
+ b->_succs.map( 1, tbs0 );
+ // Flip projection for each target
+ { ProjNode *tmp = proj0; proj0 = proj1; proj1 = tmp; }
+
+ } else if( bnext == bs1 ) { // Fall-thru is already in succs[1]
+
+ } else { // Else need a double-branch
+
+ // The existing conditional branch need not change.
+ // Add a unconditional branch to the false target.
+ // Alas, it must appear in its own block and adding a
+ // block this late in the game is complicated. Sigh.
+ insert_goto_at(i, 1);
+ }
+
+ // Make sure we TRUE branch to the target
+ if( proj0->Opcode() == Op_IfFalse )
+ iff->negate();
+
+ b->_nodes.pop(); // Remove IfFalse & IfTrue projections
+ b->_nodes.pop();
+
+ } else {
+ // Multi-exit block, e.g. a switch statement
+ // But we don't need to do anything here
+ }
+
+ } // End of for all blocks
+
+}
+
+
+//------------------------------dump-------------------------------------------
+#ifndef PRODUCT
+void PhaseCFG::_dump_cfg( const Node *end, VectorSet &visited ) const {
+ const Node *x = end->is_block_proj();
+ assert( x, "not a CFG" );
+
+ // Do not visit this block again
+ if( visited.test_set(x->_idx) ) return;
+
+ // Skip through this block
+ const Node *p = x;
+ do {
+ p = p->in(0); // Move control forward
+ assert( !p->is_block_proj() || p->is_Root(), "not a CFG" );
+ } while( !p->is_block_start() );
+
+ // Recursively visit
+ for( uint i=1; i<p->req(); i++ )
+ _dump_cfg(p->in(i),visited);
+
+ // Dump the block
+ _bbs[p->_idx]->dump(&_bbs);
+}
+
+void PhaseCFG::dump( ) const {
+ tty->print("\n--- CFG --- %d BBs\n",_num_blocks);
+ if( _blocks.size() ) { // Did we do basic-block layout?
+ for( uint i=0; i<_num_blocks; i++ )
+ _blocks[i]->dump(&_bbs);
+ } else { // Else do it with a DFS
+ VectorSet visited(_bbs._arena);
+ _dump_cfg(_root,visited);
+ }
+}
+
+void PhaseCFG::dump_headers() {
+ for( uint i = 0; i < _num_blocks; i++ ) {
+ if( _blocks[i] == NULL ) continue;
+ _blocks[i]->dump_head(&_bbs);
+ }
+}
+
+void PhaseCFG::verify( ) const {
+ // Verify sane CFG
+ for( uint i = 0; i < _num_blocks; i++ ) {
+ Block *b = _blocks[i];
+ uint cnt = b->_nodes.size();
+ uint j;
+ for( j = 0; j < cnt; j++ ) {
+ Node *n = b->_nodes[j];
+ assert( _bbs[n->_idx] == b, "" );
+ if( j >= 1 && n->is_Mach() &&
+ n->as_Mach()->ideal_Opcode() == Op_CreateEx ) {
+ assert( j == 1 || b->_nodes[j-1]->is_Phi(),
+ "CreateEx must be first instruction in block" );
+ }
+ for( uint k = 0; k < n->req(); k++ ) {
+ Node *use = n->in(k);
+ if( use && use != n ) {
+ assert( _bbs[use->_idx] || use->is_Con(),
+ "must have block; constants for debug info ok" );
+ }
+ }
+ }
+
+ j = b->end_idx();
+ Node *bp = (Node*)b->_nodes[b->_nodes.size()-1]->is_block_proj();
+ assert( bp, "last instruction must be a block proj" );
+ assert( bp == b->_nodes[j], "wrong number of successors for this block" );
+ if( bp->is_Catch() ) {
+ while( b->_nodes[--j]->Opcode() == Op_MachProj ) ;
+ assert( b->_nodes[j]->is_Call(), "CatchProj must follow call" );
+ }
+ else if( bp->is_Mach() && bp->as_Mach()->ideal_Opcode() == Op_If ) {
+ assert( b->_num_succs == 2, "Conditional branch must have two targets");
+ }
+ }
+}
+#endif
+
+//=============================================================================
+//------------------------------UnionFind--------------------------------------
+UnionFind::UnionFind( uint max ) : _cnt(max), _max(max), _indices(NEW_RESOURCE_ARRAY(uint,max)) {
+ Copy::zero_to_bytes( _indices, sizeof(uint)*max );
+}
+
+void UnionFind::extend( uint from_idx, uint to_idx ) {
+ _nesting.check();
+ if( from_idx >= _max ) {
+ uint size = 16;
+ while( size <= from_idx ) size <<=1;
+ _indices = REALLOC_RESOURCE_ARRAY( uint, _indices, _max, size );
+ _max = size;
+ }
+ while( _cnt <= from_idx ) _indices[_cnt++] = 0;
+ _indices[from_idx] = to_idx;
+}
+
+void UnionFind::reset( uint max ) {
+ assert( max <= max_uint, "Must fit within uint" );
+ // Force the Union-Find mapping to be at least this large
+ extend(max,0);
+ // Initialize to be the ID mapping.
+ for( uint i=0; i<_max; i++ ) map(i,i);
+}
+
+//------------------------------Find_compress----------------------------------
+// Straight out of Tarjan's union-find algorithm
+uint UnionFind::Find_compress( uint idx ) {
+ uint cur = idx;
+ uint next = lookup(cur);
+ while( next != cur ) { // Scan chain of equivalences
+ assert( next < cur, "always union smaller" );
+ cur = next; // until find a fixed-point
+ next = lookup(cur);
+ }
+ // Core of union-find algorithm: update chain of
+ // equivalences to be equal to the root.
+ while( idx != next ) {
+ uint tmp = lookup(idx);
+ map(idx, next);
+ idx = tmp;
+ }
+ return idx;
+}
+
+//------------------------------Find_const-------------------------------------
+// Like Find above, but no path compress, so bad asymptotic behavior
+uint UnionFind::Find_const( uint idx ) const {
+ if( idx == 0 ) return idx; // Ignore the zero idx
+ // Off the end? This can happen during debugging dumps
+ // when data structures have not finished being updated.
+ if( idx >= _max ) return idx;
+ uint next = lookup(idx);
+ while( next != idx ) { // Scan chain of equivalences
+ assert( next < idx, "always union smaller" );
+ idx = next; // until find a fixed-point
+ next = lookup(idx);
+ }
+ return next;
+}
+
+//------------------------------Union------------------------------------------
+// union 2 sets together.
+void UnionFind::Union( uint idx1, uint idx2 ) {
+ uint src = Find(idx1);
+ uint dst = Find(idx2);
+ assert( src, "" );
+ assert( dst, "" );
+ assert( src < _max, "oob" );
+ assert( dst < _max, "oob" );
+ assert( src < dst, "always union smaller" );
+ map(dst,src);
+}