truffle: src/share/vm/opto/loopnode.cpp comparison

comparison src/share/vm/opto/loopnode.cpp @ 0:a61af66fc99e jdk7-b24

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author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	ff5961f4c095

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--1:000000000000
+:a61af66fc99e
+/*
+* Copyright 1998-2007 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.
+*
+*/
+#include "incls/_precompiled.incl"
+#include "incls/_loopnode.cpp.incl"
+//=============================================================================
+//------------------------------is_loop_iv-------------------------------------
+// Determine if a node is Counted loop induction variable.
+// The method is declared in node.hpp.
+const Node* Node::is_loop_iv() const {
+if (this->is_Phi() && !this->as_Phi()->is_copy() &&
+this->as_Phi()->region()->is_CountedLoop() &&
+this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
+return this;
+} else {
+return NULL;
+}
+}
+//=============================================================================
+//------------------------------dump_spec--------------------------------------
+// Dump special per-node info
+#ifndef PRODUCT
+void LoopNode::dump_spec(outputStream *st) const {
+if( is_inner_loop () ) st->print( "inner " );
+if( is_partial_peel_loop () ) st->print( "partial_peel " );
+if( partial_peel_has_failed () ) st->print( "partial_peel_failed " );
+}
+#endif
+//------------------------------get_early_ctrl---------------------------------
+// Compute earliest legal control
+Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
+assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
+uint i;
+Node *early;
+if( n->in(0) ) {
+early = n->in(0);
+if( !early->is_CFG() ) // Might be a non-CFG multi-def
+early = get_ctrl(early);        // So treat input as a straight data input
+i = 1;
+} else {
+early = get_ctrl(n->in(1));
+i = 2;
+}
+uint e_d = dom_depth(early);
+assert( early, "" );
+for( ; i < n->req(); i++ ) {
+Node *cin = get_ctrl(n->in(i));
+assert( cin, "" );
+// Keep deepest dominator depth
+uint c_d = dom_depth(cin);
+if( c_d > e_d ) {           // Deeper guy?
+early = cin;              // Keep deepest found so far
+e_d = c_d;
+} else if( c_d == e_d &&    // Same depth?
+early != cin ) { // If not equal, must use slower algorithm
+// If same depth but not equal, one _must_ dominate the other
+// and we want the deeper (i.e., dominated) guy.
+Node *n1 = early;
+Node *n2 = cin;
+while( 1 ) {
+n1 = idom(n1);          // Walk up until break cycle
+n2 = idom(n2);
+if( n1 == cin ||        // Walked early up to cin
+dom_depth(n2) < c_d )
+break;                // early is deeper; keep him
+if( n2 == early ||      // Walked cin up to early
+dom_depth(n1) < c_d ) {
+early = cin;          // cin is deeper; keep him
+break;
+}
+}
+e_d = dom_depth(early);   // Reset depth register cache
+}
+}
+// Return earliest legal location
+assert(early == find_non_split_ctrl(early), "unexpected early control");
+return early;
+}
+//------------------------------set_early_ctrl---------------------------------
+// Set earliest legal control
+void PhaseIdealLoop::set_early_ctrl( Node *n ) {
+Node *early = get_early_ctrl(n);
+// Record earliest legal location
+set_ctrl(n, early);
+}
+//------------------------------set_subtree_ctrl-------------------------------
+// set missing _ctrl entries on new nodes
+void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
+// Already set?  Get out.
+if( _nodes[n->_idx] ) return;
+// Recursively set _nodes array to indicate where the Node goes
+uint i;
+for( i = 0; i < n->req(); ++i ) {
+Node *m = n->in(i);
+if( m && m != C->root() )
+set_subtree_ctrl( m );
+}
+// Fixup self
+set_early_ctrl( n );
+}
+//------------------------------is_counted_loop--------------------------------
+Node *PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
+PhaseGVN *gvn = &_igvn;
+// Counted loop head must be a good RegionNode with only 3 not NULL
+// control input edges: Self, Entry, LoopBack.
+if ( x->in(LoopNode::Self) == NULL || x->req() != 3 )
+return NULL;
+Node *init_control = x->in(LoopNode::EntryControl);
+Node *back_control = x->in(LoopNode::LoopBackControl);
+if( init_control == NULL || back_control == NULL )    // Partially dead
+return NULL;
+// Must also check for TOP when looking for a dead loop
+if( init_control->is_top() || back_control->is_top() )
+return NULL;
+// Allow funny placement of Safepoint
+if( back_control->Opcode() == Op_SafePoint )
+back_control = back_control->in(TypeFunc::Control);
+// Controlling test for loop
+Node *iftrue = back_control;
+uint iftrue_op = iftrue->Opcode();
+if( iftrue_op != Op_IfTrue &&
+iftrue_op != Op_IfFalse )
+// I have a weird back-control.  Probably the loop-exit test is in
+// the middle of the loop and I am looking at some trailing control-flow
+// merge point.  To fix this I would have to partially peel the loop.
+return NULL; // Obscure back-control
+// Get boolean guarding loop-back test
+Node *iff = iftrue->in(0);
+if( get_loop(iff) != loop || !iff->in(1)->is_Bool() ) return NULL;
+BoolNode *test = iff->in(1)->as_Bool();
+BoolTest::mask bt = test->_test._test;
+float cl_prob = iff->as_If()->_prob;
+if( iftrue_op == Op_IfFalse ) {
+bt = BoolTest(bt).negate();
+cl_prob = 1.0 - cl_prob;
+}
+// Get backedge compare
+Node *cmp = test->in(1);
+int cmp_op = cmp->Opcode();
+if( cmp_op != Op_CmpI )
+return NULL;                // Avoid pointer & float compares
+// Find the trip-counter increment & limit.  Limit must be loop invariant.
+Node *incr  = cmp->in(1);
+Node *limit = cmp->in(2);
+// ---------
+// need 'loop()' test to tell if limit is loop invariant
+// ---------
+if( !is_member( loop, get_ctrl(incr) ) ) { // Swapped trip counter and limit?
+Node *tmp = incr;           // Then reverse order into the CmpI
+incr = limit;
+limit = tmp;
+bt = BoolTest(bt).commute(); // And commute the exit test
+}
+if( is_member( loop, get_ctrl(limit) ) ) // Limit must loop-invariant
+return NULL;
+// Trip-counter increment must be commutative & associative.
+uint incr_op = incr->Opcode();
+if( incr_op == Op_Phi && incr->req() == 3 ) {
+incr = incr->in(2);         // Assume incr is on backedge of Phi
+incr_op = incr->Opcode();
+}
+Node* trunc1 = NULL;
+Node* trunc2 = NULL;
+const TypeInt* iv_trunc_t = NULL;
+if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
+return NULL; // Funny increment opcode
+}
+// Get merge point
+Node *xphi = incr->in(1);
+Node *stride = incr->in(2);
+if( !stride->is_Con() ) {     // Oops, swap these
+if( !xphi->is_Con() )       // Is the other guy a constant?
+return NULL;              // Nope, unknown stride, bail out
+Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
+xphi = stride;
+stride = tmp;
+}
+//if( loop(xphi) != l) return NULL;// Merge point is in inner loop??
+if( !xphi->is_Phi() ) return NULL; // Too much math on the trip counter
+PhiNode *phi = xphi->as_Phi();
+// Stride must be constant
+const Type *stride_t = stride->bottom_type();
+int stride_con = stride_t->is_int()->get_con();
+assert( stride_con, "missed some peephole opt" );
+// Phi must be of loop header; backedge must wrap to increment
+if( phi->region() != x ) return NULL;
+if( trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
+trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1 ) {
+return NULL;
+}
+Node *init_trip = phi->in(LoopNode::EntryControl);
+//if (!init_trip->is_Con()) return NULL; // avoid rolling over MAXINT/MININT
+// If iv trunc type is smaller than int, check for possible wrap.
+if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
+assert(trunc1 != NULL, "must have found some truncation");
+// Get a better type for the phi (filtered thru if's)
+const TypeInt* phi_ft = filtered_type(phi);
+// Can iv take on a value that will wrap?
+//
+// Ensure iv's limit is not within "stride" of the wrap value.
+//
+// Example for "short" type
+//    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
+//    If the stride is +10, then the last value of the induction
+//    variable before the increment (phi_ft->_hi) must be
+//    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
+//    ensure no truncation occurs after the increment.
+if (stride_con > 0) {
+if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
+iv_trunc_t->_lo > phi_ft->_lo) {
+return NULL;  // truncation may occur
+}
+} else if (stride_con < 0) {
+if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
+iv_trunc_t->_hi < phi_ft->_hi) {
+return NULL;  // truncation may occur
+}
+}
+// No possibility of wrap so truncation can be discarded
+// Promote iv type to Int
+} else {
+assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
+}
+// =================================================
+// ---- SUCCESS!   Found A Trip-Counted Loop!  -----
+//
+// Canonicalize the condition on the test.  If we can exactly determine
+// the trip-counter exit value, then set limit to that value and use
+// a '!=' test.  Otherwise use conditon '<' for count-up loops and
+// '>' for count-down loops.  If the condition is inverted and we will
+// be rolling through MININT to MAXINT, then bail out.
+C->print_method("Before CountedLoop", 3);
+// Check for SafePoint on backedge and remove
+Node *sfpt = x->in(LoopNode::LoopBackControl);
+if( sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
+lazy_replace( sfpt, iftrue );
+loop->_tail = iftrue;
+}
+// If compare points to incr, we are ok.  Otherwise the compare
+// can directly point to the phi; in this case adjust the compare so that
+// it points to the incr by adusting the limit.
+if( cmp->in(1) == phi || cmp->in(2) == phi )
+limit = gvn->transform(new (C, 3) AddINode(limit,stride));
+// trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
+// Final value for iterator should be: trip_count * stride + init_trip.
+const Type *limit_t = limit->bottom_type();
+const Type *init_t = init_trip->bottom_type();
+Node *one_p = gvn->intcon( 1);
+Node *one_m = gvn->intcon(-1);
+Node *trip_count = NULL;
+Node *hook = new (C, 6) Node(6);
+switch( bt ) {
+case BoolTest::eq:
+return NULL;                // Bail out, but this loop trips at most twice!
+case BoolTest::ne:            // Ahh, the case we desire
+if( stride_con == 1 )
+trip_count = gvn->transform(new (C, 3) SubINode(limit,init_trip));
+else if( stride_con == -1 )
+trip_count = gvn->transform(new (C, 3) SubINode(init_trip,limit));
+else
+return NULL;              // Odd stride; must prove we hit limit exactly
+set_subtree_ctrl( trip_count );
+//_loop.map(trip_count->_idx,loop(limit));
+break;
+case BoolTest::le:            // Maybe convert to '<' case
+limit = gvn->transform(new (C, 3) AddINode(limit,one_p));
+set_subtree_ctrl( limit );
+hook->init_req(4, limit);
+bt = BoolTest::lt;
+// Make the new limit be in the same loop nest as the old limit
+//_loop.map(limit->_idx,limit_loop);
+// Fall into next case
+case BoolTest::lt: {          // Maybe convert to '!=' case
+if( stride_con < 0 ) return NULL; // Count down loop rolls through MAXINT
+Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip));
+set_subtree_ctrl( range );
+hook->init_req(0, range);
+Node *bias  = gvn->transform(new (C, 3) AddINode(range,stride));
+set_subtree_ctrl( bias );
+hook->init_req(1, bias);
+Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_m));
+set_subtree_ctrl( bias1 );
+hook->init_req(2, bias1);
+trip_count  = gvn->transform(new (C, 3) DivINode(0,bias1,stride));
+set_subtree_ctrl( trip_count );
+hook->init_req(3, trip_count);
+break;
+}
+case BoolTest::ge:            // Maybe convert to '>' case
+limit = gvn->transform(new (C, 3) AddINode(limit,one_m));
+set_subtree_ctrl( limit );
+hook->init_req(4 ,limit);
+bt = BoolTest::gt;
+// Make the new limit be in the same loop nest as the old limit
+//_loop.map(limit->_idx,limit_loop);
+// Fall into next case
+case BoolTest::gt: {          // Maybe convert to '!=' case
+if( stride_con > 0 ) return NULL; // count up loop rolls through MININT
+Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip));
+set_subtree_ctrl( range );
+hook->init_req(0, range);
+Node *bias  = gvn->transform(new (C, 3) AddINode(range,stride));
+set_subtree_ctrl( bias );
+hook->init_req(1, bias);
+Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_p));
+set_subtree_ctrl( bias1 );
+hook->init_req(2, bias1);
+trip_count  = gvn->transform(new (C, 3) DivINode(0,bias1,stride));
+set_subtree_ctrl( trip_count );
+hook->init_req(3, trip_count);
+break;
+}
+}
+Node *span = gvn->transform(new (C, 3) MulINode(trip_count,stride));
+set_subtree_ctrl( span );
+hook->init_req(5, span);
+limit = gvn->transform(new (C, 3) AddINode(span,init_trip));
+set_subtree_ctrl( limit );
+// Build a canonical trip test.
+// Clone code, as old values may be in use.
+incr = incr->clone();
+incr->set_req(1,phi);
+incr->set_req(2,stride);
+incr = _igvn.register_new_node_with_optimizer(incr);
+set_early_ctrl( incr );
+_igvn.hash_delete(phi);
+phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
+// If phi type is more restrictive than Int, raise to
+// Int to prevent (almost) infinite recursion in igvn
+// which can only handle integer types for constants or minint..maxint.
+if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
+Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
+nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
+nphi = _igvn.register_new_node_with_optimizer(nphi);
+set_ctrl(nphi, get_ctrl(phi));
+_igvn.subsume_node(phi, nphi);
+phi = nphi->as_Phi();
+}
+cmp = cmp->clone();
+cmp->set_req(1,incr);
+cmp->set_req(2,limit);
+cmp = _igvn.register_new_node_with_optimizer(cmp);
+set_ctrl(cmp, iff->in(0));
+Node *tmp = test->clone();
+assert( tmp->is_Bool(), "" );
+test = (BoolNode*)tmp;
+(*(BoolTest*)&test->_test)._test = bt; //BoolTest::ne;
+test->set_req(1,cmp);
+_igvn.register_new_node_with_optimizer(test);
+set_ctrl(test, iff->in(0));
+// If the exit test is dead, STOP!
+if( test == NULL ) return NULL;
+_igvn.hash_delete(iff);
+iff->set_req_X( 1, test, &_igvn );
+// Replace the old IfNode with a new LoopEndNode
+Node *lex = _igvn.register_new_node_with_optimizer(new (C, 2) CountedLoopEndNode( iff->in(0), iff->in(1), cl_prob, iff->as_If()->_fcnt ));
+IfNode *le = lex->as_If();
+uint dd = dom_depth(iff);
+set_idom(le, le->in(0), dd); // Update dominance for loop exit
+set_loop(le, loop);
+// Get the loop-exit control
+Node *if_f = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
+// Need to swap loop-exit and loop-back control?
+if( iftrue_op == Op_IfFalse ) {
+Node *ift2=_igvn.register_new_node_with_optimizer(new (C, 1) IfTrueNode (le));
+Node *iff2=_igvn.register_new_node_with_optimizer(new (C, 1) IfFalseNode(le));
+loop->_tail = back_control = ift2;
+set_loop(ift2, loop);
+set_loop(iff2, get_loop(if_f));
+// Lazy update of 'get_ctrl' mechanism.
+lazy_replace_proj( if_f  , iff2 );
+lazy_replace_proj( iftrue, ift2 );
+// Swap names
+if_f   = iff2;
+iftrue = ift2;
+} else {
+_igvn.hash_delete(if_f  );
+_igvn.hash_delete(iftrue);
+if_f  ->set_req_X( 0, le, &_igvn );
+iftrue->set_req_X( 0, le, &_igvn );
+}
+set_idom(iftrue, le, dd+1);
+set_idom(if_f,   le, dd+1);
+// Now setup a new CountedLoopNode to replace the existing LoopNode
+CountedLoopNode *l = new (C, 3) CountedLoopNode(init_control, back_control);
+// The following assert is approximately true, and defines the intention
+// of can_be_counted_loop.  It fails, however, because phase->type
+// is not yet initialized for this loop and its parts.
+//assert(l->can_be_counted_loop(this), "sanity");
+_igvn.register_new_node_with_optimizer(l);
+set_loop(l, loop);
+loop->_head = l;
+// Fix all data nodes placed at the old loop head.
+// Uses the lazy-update mechanism of 'get_ctrl'.
+lazy_replace( x, l );
+set_idom(l, init_control, dom_depth(x));
+// Check for immediately preceeding SafePoint and remove
+Node *sfpt2 = le->in(0);
+if( sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2))
+lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
+// Free up intermediate goo
+_igvn.remove_dead_node(hook);
+C->print_method("After CountedLoop", 3);
+// Return trip counter
+return trip_count;
+}
+//------------------------------Ideal------------------------------------------
+// Return a node which is more "ideal" than the current node.
+// Attempt to convert into a counted-loop.
+Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
+if (!can_be_counted_loop(phase)) {
+phase->C->set_major_progress();
+}
+return RegionNode::Ideal(phase, can_reshape);
+}
+//=============================================================================
+//------------------------------Ideal------------------------------------------
+// Return a node which is more "ideal" than the current node.
+// Attempt to convert into a counted-loop.
+Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
+return RegionNode::Ideal(phase, can_reshape);
+}
+//------------------------------dump_spec--------------------------------------
+// Dump special per-node info
+#ifndef PRODUCT
+void CountedLoopNode::dump_spec(outputStream *st) const {
+LoopNode::dump_spec(st);
+if( stride_is_con() ) {
+st->print("stride: %d ",stride_con());
+} else {
+st->print("stride: not constant ");
+}
+if( is_pre_loop () ) st->print("pre of N%d" , _main_idx );
+if( is_main_loop() ) st->print("main of N%d", _idx );
+if( is_post_loop() ) st->print("post of N%d", _main_idx );
+}
+#endif
+//=============================================================================
+int CountedLoopEndNode::stride_con() const {
+return stride()->bottom_type()->is_int()->get_con();
+}
+//----------------------match_incr_with_optional_truncation--------------------
+// Match increment with optional truncation:
+// CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
+// Return NULL for failure. Success returns the increment node.
+Node* CountedLoopNode::match_incr_with_optional_truncation(
+Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
+// Quick cutouts:
+if (expr == NULL || expr->req() != 3)  return false;
+Node *t1 = NULL;
+Node *t2 = NULL;
+const TypeInt* trunc_t = TypeInt::INT;
+Node* n1 = expr;
+int   n1op = n1->Opcode();
+// Try to strip (n1 & M) or (n1 << N >> N) from n1.
+if (n1op == Op_AndI &&
+n1->in(2)->is_Con() &&
+n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
+// %%% This check should match any mask of 2**K-1.
+t1 = n1;
+n1 = t1->in(1);
+n1op = n1->Opcode();
+trunc_t = TypeInt::CHAR;
+} else if (n1op == Op_RShiftI &&
+n1->in(1) != NULL &&
+n1->in(1)->Opcode() == Op_LShiftI &&
+n1->in(2) == n1->in(1)->in(2) &&
+n1->in(2)->is_Con()) {
+jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
+// %%% This check should match any shift in [1..31].
+if (shift == 16 || shift == 8) {
+t1 = n1;
+t2 = t1->in(1);
+n1 = t2->in(1);
+n1op = n1->Opcode();
+if (shift == 16) {
+trunc_t = TypeInt::SHORT;
+} else if (shift == 8) {
+trunc_t = TypeInt::BYTE;
+}
+}
+}
+// If (maybe after stripping) it is an AddI, we won:
+if (n1op == Op_AddI) {
+*trunc1 = t1;
+*trunc2 = t2;
+*trunc_type = trunc_t;
+return n1;
+}
+// failed
+return NULL;
+}
+//------------------------------filtered_type--------------------------------
+// Return a type based on condition control flow
+// A successful return will be a type that is restricted due
+// to a series of dominating if-tests, such as:
+//    if (i < 10) {
+//       if (i > 0) {
+//          here: "i" type is [1..10)
+//       }
+//    }
+// or a control flow merge
+//    if (i < 10) {
+//       do {
+//          phi( , ) -- at top of loop type is [min_int..10)
+//         i = ?
+//       } while ( i < 10)
+//
+const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
+assert(n && n->bottom_type()->is_int(), "must be int");
+const TypeInt* filtered_t = NULL;
+if (!n->is_Phi()) {
+assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
+filtered_t = filtered_type_from_dominators(n, n_ctrl);
+} else {
+Node* phi    = n->as_Phi();
+Node* region = phi->in(0);
+assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
+if (region && region != C->top()) {
+for (uint i = 1; i < phi->req(); i++) {
+Node* val   = phi->in(i);
+Node* use_c = region->in(i);
+const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
+if (val_t != NULL) {
+if (filtered_t == NULL) {
+filtered_t = val_t;
+} else {
+filtered_t = filtered_t->meet(val_t)->is_int();
+}
+}
+}
+}
+}
+const TypeInt* n_t = _igvn.type(n)->is_int();
+if (filtered_t != NULL) {
+n_t = n_t->join(filtered_t)->is_int();
+}
+return n_t;
+}
+//------------------------------filtered_type_from_dominators--------------------------------
+// Return a possibly more restrictive type for val based on condition control flow of dominators
+const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
+if (val->is_Con()) {
+return val->bottom_type()->is_int();
+}
+uint if_limit = 10; // Max number of dominating if's visited
+const TypeInt* rtn_t = NULL;
+if (use_ctrl && use_ctrl != C->top()) {
+Node* val_ctrl = get_ctrl(val);
+uint val_dom_depth = dom_depth(val_ctrl);
+Node* pred = use_ctrl;
+uint if_cnt = 0;
+while (if_cnt < if_limit) {
+if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
+if_cnt++;
+const TypeInt* if_t = filtered_type_at_if(val, pred);
+if (if_t != NULL) {
+if (rtn_t == NULL) {
+rtn_t = if_t;
+} else {
+rtn_t = rtn_t->join(if_t)->is_int();
+}
+}
+}
+pred = idom(pred);
+if (pred == NULL || pred == C->top()) {
+break;
+}
+// Stop if going beyond definition block of val
+if (dom_depth(pred) < val_dom_depth) {
+break;
+}
+}
+}
+return rtn_t;
+}
+//------------------------------filtered_type_at_if--------------------------------
+// Return a possibly more restrictive type for val based on condition control flow for an if
+const TypeInt* PhaseIdealLoop::filtered_type_at_if( Node* val, Node *if_proj) {
+assert(if_proj &&
+(if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
+if (if_proj->in(0) && if_proj->in(0)->is_If()) {
+IfNode* iff = if_proj->in(0)->as_If();
+if (iff->in(1) && iff->in(1)->is_Bool()) {
+BoolNode* bol = iff->in(1)->as_Bool();
+if (bol->in(1) && bol->in(1)->is_Cmp()) {
+const CmpNode* cmp  = bol->in(1)->as_Cmp();
+if (cmp->in(1) == val) {
+const TypeInt* cmp2_t = _igvn.type(cmp->in(2))->isa_int();
+if (cmp2_t != NULL) {
+jint lo = cmp2_t->_lo;
+jint hi = cmp2_t->_hi;
+BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
+switch (msk) {
+case BoolTest::ne:
+// Can't refine type
+return NULL;
+case BoolTest::eq:
+return cmp2_t;
+case BoolTest::lt:
+lo = TypeInt::INT->_lo;
+if (hi - 1 < hi) {
+hi = hi - 1;
+}
+break;
+case BoolTest::le:
+lo = TypeInt::INT->_lo;
+break;
+case BoolTest::gt:
+if (lo + 1 > lo) {
+lo = lo + 1;
+}
+hi = TypeInt::INT->_hi;
+break;
+case BoolTest::ge:
+// lo unchanged
+hi = TypeInt::INT->_hi;
+break;
+}
+const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
+return rtn_t;
+}
+}
+}
+}
+}
+return NULL;
+}
+//------------------------------dump_spec--------------------------------------
+// Dump special per-node info
+#ifndef PRODUCT
+void CountedLoopEndNode::dump_spec(outputStream *st) const {
+if( in(TestValue)->is_Bool() ) {
+BoolTest bt( test_trip()); // Added this for g++.
+st->print("[");
+bt.dump_on(st);
+st->print("]");
+}
+st->print(" ");
+IfNode::dump_spec(st);
+}
+#endif
+//=============================================================================
+//------------------------------is_member--------------------------------------
+// Is 'l' a member of 'this'?
+int IdealLoopTree::is_member( const IdealLoopTree *l ) const {
+while( l->_nest > _nest ) l = l->_parent;
+return l == this;
+}
+//------------------------------set_nest---------------------------------------
+// Set loop tree nesting depth.  Accumulate _has_call bits.
+int IdealLoopTree::set_nest( uint depth ) {
+_nest = depth;
+int bits = _has_call;
+if( _child ) bits |= _child->set_nest(depth+1);
+if( bits ) _has_call = 1;
+if( _next  ) bits |= _next ->set_nest(depth  );
+return bits;
+}
+//------------------------------split_fall_in----------------------------------
+// Split out multiple fall-in edges from the loop header.  Move them to a
+// private RegionNode before the loop.  This becomes the loop landing pad.
+void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
+PhaseIterGVN &igvn = phase->_igvn;
+uint i;
+// Make a new RegionNode to be the landing pad.
+Node *landing_pad = new (phase->C, fall_in_cnt+1) RegionNode( fall_in_cnt+1 );
+phase->set_loop(landing_pad,_parent);
+// Gather all the fall-in control paths into the landing pad
+uint icnt = fall_in_cnt;
+uint oreq = _head->req();
+for( i = oreq-1; i>0; i-- )
+if( !phase->is_member( this, _head->in(i) ) )
+landing_pad->set_req(icnt--,_head->in(i));
+// Peel off PhiNode edges as well
+for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
+Node *oj = _head->fast_out(j);
+if( oj->is_Phi() ) {
+PhiNode* old_phi = oj->as_Phi();
+assert( old_phi->region() == _head, "" );
+igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
+Node *p = PhiNode::make_blank(landing_pad, old_phi);
+uint icnt = fall_in_cnt;
+for( i = oreq-1; i>0; i-- ) {
+if( !phase->is_member( this, _head->in(i) ) ) {
+p->init_req(icnt--, old_phi->in(i));
+// Go ahead and clean out old edges from old phi
+old_phi->del_req(i);
+}
+}
+// Search for CSE's here, because ZKM.jar does a lot of
+// loop hackery and we need to be a little incremental
+// with the CSE to avoid O(N^2) node blow-up.
+Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
+if( p2 ) {                // Found CSE
+p->destruct();          // Recover useless new node
+p = p2;                 // Use old node
+} else {
+igvn.register_new_node_with_optimizer(p, old_phi);
+}
+// Make old Phi refer to new Phi.
+old_phi->add_req(p);
+// Check for the special case of making the old phi useless and
+// disappear it.  In JavaGrande I have a case where this useless
+// Phi is the loop limit and prevents recognizing a CountedLoop
+// which in turn prevents removing an empty loop.
+Node *id_old_phi = old_phi->Identity( &igvn );
+if( id_old_phi != old_phi ) { // Found a simple identity?
+// Note that I cannot call 'subsume_node' here, because
+// that will yank the edge from old_phi to the Region and
+// I'm mid-iteration over the Region's uses.
+for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
+Node* use = old_phi->last_out(i);
+igvn.hash_delete(use);
+igvn._worklist.push(use);
+uint uses_found = 0;
+for (uint j = 0; j < use->len(); j++) {
+if (use->in(j) == old_phi) {
+if (j < use->req()) use->set_req (j, id_old_phi);
+else                use->set_prec(j, id_old_phi);
+uses_found++;
+}
+}
+i -= uses_found;    // we deleted 1 or more copies of this edge
+}
+}
+igvn._worklist.push(old_phi);
+}
+}
+// Finally clean out the fall-in edges from the RegionNode
+for( i = oreq-1; i>0; i-- ) {
+if( !phase->is_member( this, _head->in(i) ) ) {
+_head->del_req(i);
+}
+}
+// Transform landing pad
+igvn.register_new_node_with_optimizer(landing_pad, _head);
+// Insert landing pad into the header
+_head->add_req(landing_pad);
+}
+//------------------------------split_outer_loop-------------------------------
+// Split out the outermost loop from this shared header.
+void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
+PhaseIterGVN &igvn = phase->_igvn;
+// Find index of outermost loop; it should also be my tail.
+uint outer_idx = 1;
+while( _head->in(outer_idx) != _tail ) outer_idx++;
+// Make a LoopNode for the outermost loop.
+Node *ctl = _head->in(LoopNode::EntryControl);
+Node *outer = new (phase->C, 3) LoopNode( ctl, _head->in(outer_idx) );
+outer = igvn.register_new_node_with_optimizer(outer, _head);
+phase->set_created_loop_node();
+// Outermost loop falls into '_head' loop
+_head->set_req(LoopNode::EntryControl, outer);
+_head->del_req(outer_idx);
+// Split all the Phis up between '_head' loop and 'outer' loop.
+for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
+Node *out = _head->fast_out(j);
+if( out->is_Phi() ) {
+PhiNode *old_phi = out->as_Phi();
+assert( old_phi->region() == _head, "" );
+Node *phi = PhiNode::make_blank(outer, old_phi);
+phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
+phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
+phi = igvn.register_new_node_with_optimizer(phi, old_phi);
+// Make old Phi point to new Phi on the fall-in path
+igvn.hash_delete(old_phi);
+old_phi->set_req(LoopNode::EntryControl, phi);
+old_phi->del_req(outer_idx);
+igvn._worklist.push(old_phi);
+}
+}
+// Use the new loop head instead of the old shared one
+_head = outer;
+phase->set_loop(_head, this);
+}
+//------------------------------fix_parent-------------------------------------
+static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
+loop->_parent = parent;
+if( loop->_child ) fix_parent( loop->_child, loop   );
+if( loop->_next  ) fix_parent( loop->_next , parent );
+}
+//------------------------------estimate_path_freq-----------------------------
+static float estimate_path_freq( Node *n ) {
+// Try to extract some path frequency info
+IfNode *iff;
+for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
+uint nop = n->Opcode();
+if( nop == Op_SafePoint ) {   // Skip any safepoint
+n = n->in(0);
+continue;
+}
+if( nop == Op_CatchProj ) {   // Get count from a prior call
+// Assume call does not always throw exceptions: means the call-site
+// count is also the frequency of the fall-through path.
+assert( n->is_CatchProj(), "" );
+if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
+return 0.0f;            // Assume call exception path is rare
+Node *call = n->in(0)->in(0)->in(0);
+assert( call->is_Call(), "expect a call here" );
+const JVMState *jvms = ((CallNode*)call)->jvms();
+ciMethodData* methodData = jvms->method()->method_data();
+if (!methodData->is_mature())  return 0.0f; // No call-site data
+ciProfileData* data = methodData->bci_to_data(jvms->bci());
+if ((data == NULL) || !data->is_CounterData()) {
+// no call profile available, try call's control input
+n = n->in(0);
+continue;
+}
+return data->as_CounterData()->count()/FreqCountInvocations;
+}
+// See if there's a gating IF test
+Node *n_c = n->in(0);
+if( !n_c->is_If() ) break;       // No estimate available
+iff = n_c->as_If();
+if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
+// Compute how much count comes on this path
+return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
+// Have no count info.  Skip dull uncommon-trap like branches.
+if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
+(nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
+break;
+// Skip through never-taken branch; look for a real loop exit.
+n = iff->in(0);
+}
+return 0.0f;                  // No estimate available
+}
+//------------------------------merge_many_backedges---------------------------
+// Merge all the backedges from the shared header into a private Region.
+// Feed that region as the one backedge to this loop.
+void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
+uint i;
+// Scan for the top 2 hottest backedges
+float hotcnt = 0.0f;
+float warmcnt = 0.0f;
+uint hot_idx = 0;
+// Loop starts at 2 because slot 1 is the fall-in path
+for( i = 2; i < _head->req(); i++ ) {
+float cnt = estimate_path_freq(_head->in(i));
+if( cnt > hotcnt ) {       // Grab hottest path
+warmcnt = hotcnt;
+hotcnt = cnt;
+hot_idx = i;
+} else if( cnt > warmcnt ) { // And 2nd hottest path
+warmcnt = cnt;
+}
+}
+// See if the hottest backedge is worthy of being an inner loop
+// by being much hotter than the next hottest backedge.
+if( hotcnt <= 0.0001 ||
+hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
+// Peel out the backedges into a private merge point; peel
+// them all except optionally hot_idx.
+PhaseIterGVN &igvn = phase->_igvn;
+Node *hot_tail = NULL;
+// Make a Region for the merge point
+Node *r = new (phase->C, 1) RegionNode(1);
+for( i = 2; i < _head->req(); i++ ) {
+if( i != hot_idx )
+r->add_req( _head->in(i) );
+else hot_tail = _head->in(i);
+}
+igvn.register_new_node_with_optimizer(r, _head);
+// Plug region into end of loop _head, followed by hot_tail
+while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
+_head->set_req(2, r);
+if( hot_idx ) _head->add_req(hot_tail);
+// Split all the Phis up between '_head' loop and the Region 'r'
+for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
+Node *out = _head->fast_out(j);
+if( out->is_Phi() ) {
+PhiNode* n = out->as_Phi();
+igvn.hash_delete(n);      // Delete from hash before hacking edges
+Node *hot_phi = NULL;
+Node *phi = new (phase->C, r->req()) PhiNode(r, n->type(), n->adr_type());
+// Check all inputs for the ones to peel out
+uint j = 1;
+for( uint i = 2; i < n->req(); i++ ) {
+if( i != hot_idx )
+phi->set_req( j++, n->in(i) );
+else hot_phi = n->in(i);
+}
+// Register the phi but do not transform until whole place transforms
+igvn.register_new_node_with_optimizer(phi, n);
+// Add the merge phi to the old Phi
+while( n->req() > 3 ) n->del_req( n->req()-1 );
+n->set_req(2, phi);
+if( hot_idx ) n->add_req(hot_phi);
+}
+}
+// Insert a new IdealLoopTree inserted below me.  Turn it into a clone
+// of self loop tree.  Turn self into a loop headed by _head and with
+// tail being the new merge point.
+IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
+phase->set_loop(_tail,ilt);   // Adjust tail
+_tail = r;                    // Self's tail is new merge point
+phase->set_loop(r,this);
+ilt->_child = _child;         // New guy has my children
+_child = ilt;                 // Self has new guy as only child
+ilt->_parent = this;          // new guy has self for parent
+ilt->_nest = _nest;           // Same nesting depth (for now)
+// Starting with 'ilt', look for child loop trees using the same shared
+// header.  Flatten these out; they will no longer be loops in the end.
+IdealLoopTree **pilt = &_child;
+while( ilt ) {
+if( ilt->_head == _head ) {
+uint i;
+for( i = 2; i < _head->req(); i++ )
+if( _head->in(i) == ilt->_tail )
+break;                // Still a loop
+if( i == _head->req() ) { // No longer a loop
+// Flatten ilt.  Hang ilt's "_next" list from the end of
+// ilt's '_child' list.  Move the ilt's _child up to replace ilt.
+IdealLoopTree **cp = &ilt->_child;
+while( *cp ) cp = &(*cp)->_next;   // Find end of child list
+*cp = ilt->_next;       // Hang next list at end of child list
+*pilt = ilt->_child;    // Move child up to replace ilt
+ilt->_head = NULL;      // Flag as a loop UNIONED into parent
+ilt = ilt->_child;      // Repeat using new ilt
+continue;               // do not advance over ilt->_child
+}
+assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
+phase->set_loop(_head,ilt);
+}
+pilt = &ilt->_child;        // Advance to next
+ilt = *pilt;
+}
+if( _child ) fix_parent( _child, this );
+}
+//------------------------------beautify_loops---------------------------------
+// Split shared headers and insert loop landing pads.
+// Insert a LoopNode to replace the RegionNode.
+// Return TRUE if loop tree is structurally changed.
+bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
+bool result = false;
+// Cache parts in locals for easy
+PhaseIterGVN &igvn = phase->_igvn;
+phase->C->print_method("Before beautify loops", 3);
+igvn.hash_delete(_head);      // Yank from hash before hacking edges
+// Check for multiple fall-in paths.  Peel off a landing pad if need be.
+int fall_in_cnt = 0;
+for( uint i = 1; i < _head->req(); i++ )
+if( !phase->is_member( this, _head->in(i) ) )
+fall_in_cnt++;
+assert( fall_in_cnt, "at least 1 fall-in path" );
+if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
+split_fall_in( phase, fall_in_cnt );
+// Swap inputs to the _head and all Phis to move the fall-in edge to
+// the left.
+fall_in_cnt = 1;
+while( phase->is_member( this, _head->in(fall_in_cnt) ) )
+fall_in_cnt++;
+if( fall_in_cnt > 1 ) {
+// Since I am just swapping inputs I do not need to update def-use info
+Node *tmp = _head->in(1);
+_head->set_req( 1, _head->in(fall_in_cnt) );
+_head->set_req( fall_in_cnt, tmp );
+// Swap also all Phis
+for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
+Node* phi = _head->fast_out(i);
+if( phi->is_Phi() ) {
+igvn.hash_delete(phi); // Yank from hash before hacking edges
+tmp = phi->in(1);
+phi->set_req( 1, phi->in(fall_in_cnt) );
+phi->set_req( fall_in_cnt, tmp );
+}
+}
+}
+assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
+assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
+// If I am a shared header (multiple backedges), peel off the many
+// backedges into a private merge point and use the merge point as
+// the one true backedge.
+if( _head->req() > 3 ) {
+// Merge the many backedges into a single backedge.
+merge_many_backedges( phase );
+result = true;
+}
+// If I am a shared header (multiple backedges), peel off myself loop.
+// I better be the outermost loop.
+if( _head->req() > 3 ) {
+split_outer_loop( phase );
+result = true;
+} else if( !_head->is_Loop() && !_irreducible ) {
+// Make a new LoopNode to replace the old loop head
+Node *l = new (phase->C, 3) LoopNode( _head->in(1), _head->in(2) );
+l = igvn.register_new_node_with_optimizer(l, _head);
+phase->set_created_loop_node();
+// Go ahead and replace _head
+phase->_igvn.subsume_node( _head, l );
+_head = l;
+phase->set_loop(_head, this);
+for (DUIterator_Fast imax, i = l->fast_outs(imax); i < imax; i++)
+phase->_igvn.add_users_to_worklist(l->fast_out(i));
+}
+phase->C->print_method("After beautify loops", 3);
+// Now recursively beautify nested loops
+if( _child ) result |= _child->beautify_loops( phase );
+if( _next  ) result |= _next ->beautify_loops( phase );
+return result;
+}
+//------------------------------allpaths_check_safepts----------------------------
+// Allpaths backwards scan from loop tail, terminating each path at first safepoint
+// encountered.  Helper for check_safepts.
+void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
+assert(stack.size() == 0, "empty stack");
+stack.push(_tail);
+visited.Clear();
+visited.set(_tail->_idx);
+while (stack.size() > 0) {
+Node* n = stack.pop();
+if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
+// Terminate this path
+} else if (n->Opcode() == Op_SafePoint) {
+if (_phase->get_loop(n) != this) {
+if (_required_safept == NULL) _required_safept = new Node_List();
+_required_safept->push(n);  // save the one closest to the tail
+}
+// Terminate this path
+} else {
+uint start = n->is_Region() ? 1 : 0;
+uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
+for (uint i = start; i < end; i++) {
+Node* in = n->in(i);
+assert(in->is_CFG(), "must be");
+if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
+stack.push(in);
+}
+}
+}
+}
+}
+//------------------------------check_safepts----------------------------
+// Given dominators, try to find loops with calls that must always be
+// executed (call dominates loop tail).  These loops do not need non-call
+// safepoints (ncsfpt).
+//
+// A complication is that a safepoint in a inner loop may be needed
+// by an outer loop. In the following, the inner loop sees it has a
+// call (block 3) on every path from the head (block 2) to the
+// backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
+// in block 2, _but_ this leaves the outer loop without a safepoint.
+//
+//          entry  0
+//                 |
+//                 v
+// outer 1,2    +->1
+//              |  |
+//              |  v
+//              |  2<---+  ncsfpt in 2
+//              |_/|\   |
+//                 | v  |
+// inner 2,3      /  3  |  call in 3
+//               /   |  |
+//              v    +--+
+//        exit  4
+//
+//
+// This method creates a list (_required_safept) of ncsfpt nodes that must
+// be protected is created for each loop. When a ncsfpt maybe deleted, it
+// is first looked for in the lists for the outer loops of the current loop.
+//
+// The insights into the problem:
+//  A) counted loops are okay
+//  B) innermost loops are okay (only an inner loop can delete
+//     a ncsfpt needed by an outer loop)
+//  C) a loop is immune from an inner loop deleting a safepoint
+//     if the loop has a call on the idom-path
+//  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
+//     idom-path that is not in a nested loop
+//  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
+//     loop needs to be prevented from deletion by an inner loop
+//
+// There are two analyses:
+//  1) The first, and cheaper one, scans the loop body from
+//     tail to head following the idom (immediate dominator)
+//     chain, looking for the cases (C,D,E) above.
+//     Since inner loops are scanned before outer loops, there is summary
+//     information about inner loops.  Inner loops can be skipped over
+//     when the tail of an inner loop is encountered.
+//
+//  2) The second, invoked if the first fails to find a call or ncsfpt on
+//     the idom path (which is rare), scans all predecessor control paths
+//     from the tail to the head, terminating a path when a call or sfpt
+//     is encountered, to find the ncsfpt's that are closest to the tail.
+//
+void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
+// Bottom up traversal
+IdealLoopTree* ch = _child;
+while (ch != NULL) {
+ch->check_safepts(visited, stack);
+ch = ch->_next;
+}
+if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
+bool  has_call         = false; // call on dom-path
+bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
+Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
+// Scan the dom-path nodes from tail to head
+for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
+if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
+has_call = true;
+_has_sfpt = 1;          // Then no need for a safept!
+break;
+} else if (n->Opcode() == Op_SafePoint) {
+if (_phase->get_loop(n) == this) {
+has_local_ncsfpt = true;
+break;
+}
+if (nonlocal_ncsfpt == NULL) {
+nonlocal_ncsfpt = n; // save the one closest to the tail
+}
+} else {
+IdealLoopTree* nlpt = _phase->get_loop(n);
+if (this != nlpt) {
+// If at an inner loop tail, see if the inner loop has already
+// recorded seeing a call on the dom-path (and stop.)  If not,
+// jump to the head of the inner loop.
+assert(is_member(nlpt), "nested loop");
+Node* tail = nlpt->_tail;
+if (tail->in(0)->is_If()) tail = tail->in(0);
+if (n == tail) {
+// If inner loop has call on dom-path, so does outer loop
+if (nlpt->_has_sfpt) {
+has_call = true;
+_has_sfpt = 1;
+break;
+}
+// Skip to head of inner loop
+assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
+n = nlpt->_head;
+}
+}
+}
+}
+// Record safept's that this loop needs preserved when an
+// inner loop attempts to delete it's safepoints.
+if (_child != NULL && !has_call && !has_local_ncsfpt) {
+if (nonlocal_ncsfpt != NULL) {
+if (_required_safept == NULL) _required_safept = new Node_List();
+_required_safept->push(nonlocal_ncsfpt);
+} else {
+// Failed to find a suitable safept on the dom-path.  Now use
+// an all paths walk from tail to head, looking for safepoints to preserve.
+allpaths_check_safepts(visited, stack);
+}
+}
+}
+}
+//---------------------------is_deleteable_safept----------------------------
+// Is safept not required by an outer loop?
+bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
+assert(sfpt->Opcode() == Op_SafePoint, "");
+IdealLoopTree* lp = get_loop(sfpt)->_parent;
+while (lp != NULL) {
+Node_List* sfpts = lp->_required_safept;
+if (sfpts != NULL) {
+for (uint i = 0; i < sfpts->size(); i++) {
+if (sfpt == sfpts->at(i))
+return false;
+}
+}
+lp = lp->_parent;
+}
+return true;
+}
+//------------------------------counted_loop-----------------------------------
+// Convert to counted loops where possible
+void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
+// For grins, set the inner-loop flag here
+if( !_child ) {
+if( _head->is_Loop() ) _head->as_Loop()->set_inner_loop();
+}
+if( _head->is_CountedLoop() ||
+phase->is_counted_loop( _head, this ) ) {
+_has_sfpt = 1;              // Indicate we do not need a safepoint here
+// Look for a safepoint to remove
+for (Node* n = tail(); n != _head; n = phase->idom(n))
+if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this &&
+phase->is_deleteable_safept(n))
+phase->lazy_replace(n,n->in(TypeFunc::Control));
+CountedLoopNode *cl = _head->as_CountedLoop();
+Node *incr = cl->incr();
+if( !incr ) return;         // Dead loop?
+Node *init = cl->init_trip();
+Node *phi  = cl->phi();
+// protect against stride not being a constant
+if( !cl->stride_is_con() ) return;
+int stride_con = cl->stride_con();
+// Look for induction variables
+// Visit all children, looking for Phis
+for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
+Node *out = cl->out(i);
+if (!out->is_Phi())  continue; // Looking for phis
+PhiNode* phi2 = out->as_Phi();
+Node *incr2 = phi2->in( LoopNode::LoopBackControl );
+// Look for induction variables of the form:  X += constant
+if( phi2->region() != _head ||
+incr2->req() != 3 ||
+incr2->in(1) != phi2 ||
+incr2 == incr ||
+incr2->Opcode() != Op_AddI ||
+!incr2->in(2)->is_Con() )
+continue;
+// Check for parallel induction variable (parallel to trip counter)
+// via an affine function.  In particular, count-down loops with
+// count-up array indices are common. We only RCE references off
+// the trip-counter, so we need to convert all these to trip-counter
+// expressions.
+Node *init2 = phi2->in( LoopNode::EntryControl );
+int stride_con2 = incr2->in(2)->get_int();
+// The general case here gets a little tricky.  We want to find the
+// GCD of all possible parallel IV's and make a new IV using this
+// GCD for the loop.  Then all possible IVs are simple multiples of
+// the GCD.  In practice, this will cover very few extra loops.
+// Instead we require 'stride_con2' to be a multiple of 'stride_con',
+// where +/-1 is the common case, but other integer multiples are
+// also easy to handle.
+int ratio_con = stride_con2/stride_con;
+if( ratio_con * stride_con == stride_con2 ) { // Check for exact
+// Convert to using the trip counter.  The parallel induction
+// variable differs from the trip counter by a loop-invariant
+// amount, the difference between their respective initial values.
+// It is scaled by the 'ratio_con'.
+Compile* C = phase->C;
+Node* ratio = phase->_igvn.intcon(ratio_con);
+phase->set_ctrl(ratio, C->root());
+Node* ratio_init = new (C, 3) MulINode(init, ratio);
+phase->_igvn.register_new_node_with_optimizer(ratio_init, init);
+phase->set_early_ctrl(ratio_init);
+Node* diff = new (C, 3) SubINode(init2, ratio_init);
+phase->_igvn.register_new_node_with_optimizer(diff, init2);
+phase->set_early_ctrl(diff);
+Node* ratio_idx = new (C, 3) MulINode(phi, ratio);
+phase->_igvn.register_new_node_with_optimizer(ratio_idx, phi);
+phase->set_ctrl(ratio_idx, cl);
+Node* add  = new (C, 3) AddINode(ratio_idx, diff);
+phase->_igvn.register_new_node_with_optimizer(add);
+phase->set_ctrl(add, cl);
+phase->_igvn.hash_delete( phi2 );
+phase->_igvn.subsume_node( phi2, add );
+// Sometimes an induction variable is unused
+if (add->outcnt() == 0) {
+phase->_igvn.remove_dead_node(add);
+}
+--i; // deleted this phi; rescan starting with next position
+continue;
+}
+}
+} else if (_parent != NULL && !_irreducible) {
+// Not a counted loop.
+// Look for a safepoint on the idom-path to remove, preserving the first one
+bool found = false;
+Node* n = tail();
+for (; n != _head && !found; n = phase->idom(n)) {
+if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this)
+found = true; // Found one
+}
+// Skip past it and delete the others
+for (; n != _head; n = phase->idom(n)) {
+if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this &&
+phase->is_deleteable_safept(n))
+phase->lazy_replace(n,n->in(TypeFunc::Control));
+}
+}
+// Recursively
+if( _child ) _child->counted_loop( phase );
+if( _next  ) _next ->counted_loop( phase );
+}
+#ifndef PRODUCT
+//------------------------------dump_head--------------------------------------
+// Dump 1 liner for loop header info
+void IdealLoopTree::dump_head( ) const {
+for( uint i=0; i<_nest; i++ )
+tty->print("  ");
+tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
+if( _irreducible ) tty->print(" IRREDUCIBLE");
+if( _head->is_CountedLoop() ) {
+CountedLoopNode *cl = _head->as_CountedLoop();
+tty->print(" counted");
+if( cl->is_pre_loop () ) tty->print(" pre" );
+if( cl->is_main_loop() ) tty->print(" main");
+if( cl->is_post_loop() ) tty->print(" post");
+}
+tty->cr();
+}
+//------------------------------dump-------------------------------------------
+// Dump loops by loop tree
+void IdealLoopTree::dump( ) const {
+dump_head();
+if( _child ) _child->dump();
+if( _next  ) _next ->dump();
+}
+#endif
+//=============================================================================
+//------------------------------PhaseIdealLoop---------------------------------
+// Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
+// its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
+PhaseIdealLoop::PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me, bool do_split_ifs )
+: PhaseTransform(Ideal_Loop),
+_igvn(igvn),
+_dom_lca_tags(C->comp_arena()) {
+// Reset major-progress flag for the driver's heuristics
+C->clear_major_progress();
+#ifndef PRODUCT
+// Capture for later assert
+uint unique = C->unique();
+_loop_invokes++;
+_loop_work += unique;
+#endif
+// True if the method has at least 1 irreducible loop
+_has_irreducible_loops = false;
+_created_loop_node = false;
+Arena *a = Thread::current()->resource_area();
+VectorSet visited(a);
+// Pre-grow the mapping from Nodes to IdealLoopTrees.
+_nodes.map(C->unique(), NULL);
+memset(_nodes.adr(), 0, wordSize * C->unique());
+// Pre-build the top-level outermost loop tree entry
+_ltree_root = new IdealLoopTree( this, C->root(), C->root() );
+// Do not need a safepoint at the top level
+_ltree_root->_has_sfpt = 1;
+// Empty pre-order array
+allocate_preorders();
+// Build a loop tree on the fly.  Build a mapping from CFG nodes to
+// IdealLoopTree entries.  Data nodes are NOT walked.
+build_loop_tree();
+// Check for bailout, and return
+if (C->failing()) {
+return;
+}
+// No loops after all
+if( !_ltree_root->_child ) C->set_has_loops(false);
+// There should always be an outer loop containing the Root and Return nodes.
+// If not, we have a degenerate empty program.  Bail out in this case.
+if (!has_node(C->root())) {
+C->clear_major_progress();
+C->record_method_not_compilable("empty program detected during loop optimization");
+return;
+}
+// Nothing to do, so get out
+if( !C->has_loops() && !do_split_ifs && !verify_me) {
+_igvn.optimize();           // Cleanup NeverBranches
+return;
+}
+// Set loop nesting depth
+_ltree_root->set_nest( 0 );
+// Split shared headers and insert loop landing pads.
+// Do not bother doing this on the Root loop of course.
+if( !verify_me && _ltree_root->_child ) {
+if( _ltree_root->_child->beautify_loops( this ) ) {
+// Re-build loop tree!
+_ltree_root->_child = NULL;
+_nodes.clear();
+reallocate_preorders();
+build_loop_tree();
+// Check for bailout, and return
+if (C->failing()) {
+return;
+}
+// Reset loop nesting depth
+_ltree_root->set_nest( 0 );
+}
+}
+// Build Dominators for elision of NULL checks & loop finding.
+// Since nodes do not have a slot for immediate dominator, make
+// a persistant side array for that info indexed on node->_idx.
+_idom_size = C->unique();
+_idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
+_dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
+_dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
+memset( _dom_depth, 0, _idom_size * sizeof(uint) );
+Dominators();
+// As a side effect, Dominators removed any unreachable CFG paths
+// into RegionNodes.  It doesn't do this test against Root, so
+// we do it here.
+for( uint i = 1; i < C->root()->req(); i++ ) {
+if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
+_igvn.hash_delete(C->root());
+C->root()->del_req(i);
+_igvn._worklist.push(C->root());
+i--;                      // Rerun same iteration on compressed edges
+}
+}
+// Given dominators, try to find inner loops with calls that must
+// always be executed (call dominates loop tail).  These loops do
+// not need a seperate safepoint.
+Node_List cisstack(a);
+_ltree_root->check_safepts(visited, cisstack);
+// Walk the DATA nodes and place into loops.  Find earliest control
+// node.  For CFG nodes, the _nodes array starts out and remains
+// holding the associated IdealLoopTree pointer.  For DATA nodes, the
+// _nodes array holds the earliest legal controlling CFG node.
+// Allocate stack with enough space to avoid frequent realloc
+int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats
+Node_Stack nstack( a, stack_size );
+visited.Clear();
+Node_List worklist(a);
+// Don't need C->root() on worklist since
+// it will be processed among C->top() inputs
+worklist.push( C->top() );
+visited.set( C->top()->_idx ); // Set C->top() as visited now
+build_loop_early( visited, worklist, nstack, verify_me );
+// Given early legal placement, try finding counted loops.  This placement
+// is good enough to discover most loop invariants.
+if( !verify_me )
+_ltree_root->counted_loop( this );
+// Find latest loop placement.  Find ideal loop placement.
+visited.Clear();
+init_dom_lca_tags();
+// Need C->root() on worklist when processing outs
+worklist.push( C->root() );
+NOT_PRODUCT( C->verify_graph_edges(); )
+worklist.push( C->top() );
+build_loop_late( visited, worklist, nstack, verify_me );
+// clear out the dead code
+while(_deadlist.size()) {
+igvn.remove_globally_dead_node(_deadlist.pop());
+}
+#ifndef PRODUCT
+C->verify_graph_edges();
+if( verify_me ) {             // Nested verify pass?
+// Check to see if the verify mode is broken
+assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
+return;
+}
+if( VerifyLoopOptimizations ) verify();
+#endif
+if (ReassociateInvariants) {
+// Reassociate invariants and prep for split_thru_phi
+for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
+IdealLoopTree* lpt = iter.current();
+if (!lpt->is_counted() || !lpt->is_inner()) continue;
+lpt->reassociate_invariants(this);
+// Because RCE opportunities can be masked by split_thru_phi,
+// look for RCE candidates and inhibit split_thru_phi
+// on just their loop-phi's for this pass of loop opts
+if( SplitIfBlocks && do_split_ifs ) {
+if (lpt->policy_range_check(this)) {
+lpt->_rce_candidate = true;
+}
+}
+}
+}
+// Check for aggressive application of split-if and other transforms
+// that require basic-block info (like cloning through Phi's)
+if( SplitIfBlocks && do_split_ifs ) {
+visited.Clear();
+split_if_with_blocks( visited, nstack );
+NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
+}
+// Perform iteration-splitting on inner loops.  Split iterations to avoid
+// range checks or one-shot null checks.
+// If split-if's didn't hack the graph too bad (no CFG changes)
+// then do loop opts.
+if( C->has_loops() && !C->major_progress() ) {
+memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
+_ltree_root->_child->iteration_split( this, worklist );
+// No verify after peeling!  GCM has hoisted code out of the loop.
+// After peeling, the hoisted code could sink inside the peeled area.
+// The peeling code does not try to recompute the best location for
+// all the code before the peeled area, so the verify pass will always
+// complain about it.
+}
+// Do verify graph edges in any case
+NOT_PRODUCT( C->verify_graph_edges(); );
+if( !do_split_ifs ) {
+// We saw major progress in Split-If to get here.  We forced a
+// pass with unrolling and not split-if, however more split-if's
+// might make progress.  If the unrolling didn't make progress
+// then the major-progress flag got cleared and we won't try
+// another round of Split-If.  In particular the ever-common
+// instance-of/check-cast pattern requires at least 2 rounds of
+// Split-If to clear out.
+C->set_major_progress();
+}
+// Repeat loop optimizations if new loops were seen
+if (created_loop_node()) {
+C->set_major_progress();
+}
+// Convert scalar to superword operations
+if (UseSuperWord && C->has_loops() && !C->major_progress()) {
+// SuperWord transform
+SuperWord sw(this);
+for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
+IdealLoopTree* lpt = iter.current();
+if (lpt->is_counted()) {
+sw.transform_loop(lpt);
+}
+}
+}
+// Cleanup any modified bits
+_igvn.optimize();
+// Do not repeat loop optimizations if irreducible loops are present
+// by claiming no-progress.
+if( _has_irreducible_loops )
+C->clear_major_progress();
+}
+#ifndef PRODUCT
+//------------------------------print_statistics-------------------------------
+int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
+int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
+void PhaseIdealLoop::print_statistics() {
+tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
+}
+//------------------------------verify-----------------------------------------
+// Build a verify-only PhaseIdealLoop, and see that it agrees with me.
+static int fail;                // debug only, so its multi-thread dont care
+void PhaseIdealLoop::verify() const {
+int old_progress = C->major_progress();
+ResourceMark rm;
+PhaseIdealLoop loop_verify( _igvn, this, false );
+VectorSet visited(Thread::current()->resource_area());
+fail = 0;
+verify_compare( C->root(), &loop_verify, visited );
+assert( fail == 0, "verify loops failed" );
+// Verify loop structure is the same
+_ltree_root->verify_tree(loop_verify._ltree_root, NULL);
+// Reset major-progress.  It was cleared by creating a verify version of
+// PhaseIdealLoop.
+for( int i=0; i<old_progress; i++ )
+C->set_major_progress();
+}
+//------------------------------verify_compare---------------------------------
+// Make sure me and the given PhaseIdealLoop agree on key data structures
+void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
+if( !n ) return;
+if( visited.test_set( n->_idx ) ) return;
+if( !_nodes[n->_idx] ) {      // Unreachable
+assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
+return;
+}
+uint i;
+for( i = 0; i < n->req(); i++ )
+verify_compare( n->in(i), loop_verify, visited );
+// Check the '_nodes' block/loop structure
+i = n->_idx;
+if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
+if( _nodes[i] != loop_verify->_nodes[i] &&
+get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
+tty->print("Mismatched control setting for: ");
+n->dump();
+if( fail++ > 10 ) return;
+Node *c = get_ctrl_no_update(n);
+tty->print("We have it as: ");
+if( c->in(0) ) c->dump();
+else tty->print_cr("N%d",c->_idx);
+tty->print("Verify thinks: ");
+if( loop_verify->has_ctrl(n) )
+loop_verify->get_ctrl_no_update(n)->dump();
+else
+loop_verify->get_loop_idx(n)->dump();
+tty->cr();
+}
+} else {                    // We have a loop
+IdealLoopTree *us = get_loop_idx(n);
+if( loop_verify->has_ctrl(n) ) {
+tty->print("Mismatched loop setting for: ");
+n->dump();
+if( fail++ > 10 ) return;
+tty->print("We have it as: ");
+us->dump();
+tty->print("Verify thinks: ");
+loop_verify->get_ctrl_no_update(n)->dump();
+tty->cr();
+} else if (!C->major_progress()) {
+// Loop selection can be messed up if we did a major progress
+// operation, like split-if.  Do not verify in that case.
+IdealLoopTree *them = loop_verify->get_loop_idx(n);
+if( us->_head != them->_head ||  us->_tail != them->_tail ) {
+tty->print("Unequals loops for: ");
+n->dump();
+if( fail++ > 10 ) return;
+tty->print("We have it as: ");
+us->dump();
+tty->print("Verify thinks: ");
+them->dump();
+tty->cr();
+}
+}
+}
+// Check for immediate dominators being equal
+if( i >= _idom_size ) {
+if( !n->is_CFG() ) return;
+tty->print("CFG Node with no idom: ");
+n->dump();
+return;
+}
+if( !n->is_CFG() ) return;
+if( n == C->root() ) return; // No IDOM here
+assert(n->_idx == i, "sanity");
+Node *id = idom_no_update(n);
+if( id != loop_verify->idom_no_update(n) ) {
+tty->print("Unequals idoms for: ");
+n->dump();
+if( fail++ > 10 ) return;
+tty->print("We have it as: ");
+id->dump();
+tty->print("Verify thinks: ");
+loop_verify->idom_no_update(n)->dump();
+tty->cr();
+}
+}
+//------------------------------verify_tree------------------------------------
+// Verify that tree structures match.  Because the CFG can change, siblings
+// within the loop tree can be reordered.  We attempt to deal with that by
+// reordering the verify's loop tree if possible.
+void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
+assert( _parent == parent, "Badly formed loop tree" );
+// Siblings not in same order?  Attempt to re-order.
+if( _head != loop->_head ) {
+// Find _next pointer to update
+IdealLoopTree **pp = &loop->_parent->_child;
+while( *pp != loop )
+pp = &((*pp)->_next);
+// Find proper sibling to be next
+IdealLoopTree **nn = &loop->_next;
+while( (*nn) && (*nn)->_head != _head )
+nn = &((*nn)->_next);
+// Check for no match.
+if( !(*nn) ) {
+// Annoyingly, irreducible loops can pick different headers
+// after a major_progress operation, so the rest of the loop
+// tree cannot be matched.
+if (_irreducible && Compile::current()->major_progress())  return;
+assert( 0, "failed to match loop tree" );
+}
+// Move (*nn) to (*pp)
+IdealLoopTree *hit = *nn;
+*nn = hit->_next;
+hit->_next = loop;
+*pp = loop;
+loop = hit;
+// Now try again to verify
+}
+assert( _head  == loop->_head , "mismatched loop head" );
+Node *tail = _tail;           // Inline a non-updating version of
+while( !tail->in(0) )         // the 'tail()' call.
+tail = tail->in(1);
+assert( tail == loop->_tail, "mismatched loop tail" );
+// Counted loops that are guarded should be able to find their guards
+if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
+CountedLoopNode *cl = _head->as_CountedLoop();
+Node *init = cl->init_trip();
+Node *ctrl = cl->in(LoopNode::EntryControl);
+assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
+Node *iff  = ctrl->in(0);
+assert( iff->Opcode() == Op_If, "" );
+Node *bol  = iff->in(1);
+assert( bol->Opcode() == Op_Bool, "" );
+Node *cmp  = bol->in(1);
+assert( cmp->Opcode() == Op_CmpI, "" );
+Node *add  = cmp->in(1);
+Node *opaq;
+if( add->Opcode() == Op_Opaque1 ) {
+opaq = add;
+} else {
+assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
+assert( add == init, "" );
+opaq = cmp->in(2);
+}
+assert( opaq->Opcode() == Op_Opaque1, "" );
+}
+if (_child != NULL)  _child->verify_tree(loop->_child, this);
+if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
+// Innermost loops need to verify loop bodies,
+// but only if no 'major_progress'
+int fail = 0;
+if (!Compile::current()->major_progress() && _child == NULL) {
+for( uint i = 0; i < _body.size(); i++ ) {
+Node *n = _body.at(i);
+if (n->outcnt() == 0)  continue; // Ignore dead
+uint j;
+for( j = 0; j < loop->_body.size(); j++ )
+if( loop->_body.at(j) == n )
+break;
+if( j == loop->_body.size() ) { // Not found in loop body
+// Last ditch effort to avoid assertion: Its possible that we
+// have some users (so outcnt not zero) but are still dead.
+// Try to find from root.
+if (Compile::current()->root()->find(n->_idx)) {
+fail++;
+tty->print("We have that verify does not: ");
+n->dump();
+}
+}
+}
+for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
+Node *n = loop->_body.at(i2);
+if (n->outcnt() == 0)  continue; // Ignore dead
+uint j;
+for( j = 0; j < _body.size(); j++ )
+if( _body.at(j) == n )
+break;
+if( j == _body.size() ) { // Not found in loop body
+// Last ditch effort to avoid assertion: Its possible that we
+// have some users (so outcnt not zero) but are still dead.
+// Try to find from root.
+if (Compile::current()->root()->find(n->_idx)) {
+fail++;
+tty->print("Verify has that we do not: ");
+n->dump();
+}
+}
+}
+assert( !fail, "loop body mismatch" );
+}
+}
+#endif
+//------------------------------set_idom---------------------------------------
+void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
+uint idx = d->_idx;
+if (idx >= _idom_size) {
+uint newsize = _idom_size<<1;
+while( idx >= newsize ) {
+newsize <<= 1;
+}
+_idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
+_dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
+memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
+_idom_size = newsize;
+}
+_idom[idx] = n;
+_dom_depth[idx] = dom_depth;
+}
+//------------------------------recompute_dom_depth---------------------------------------
+// The dominator tree is constructed with only parent pointers.
+// This recomputes the depth in the tree by first tagging all
+// nodes as "no depth yet" marker.  The next pass then runs up
+// the dom tree from each node marked "no depth yet", and computes
+// the depth on the way back down.
+void PhaseIdealLoop::recompute_dom_depth() {
+uint no_depth_marker = C->unique();
+uint i;
+// Initialize depth to "no depth yet"
+for (i = 0; i < _idom_size; i++) {
+if (_dom_depth[i] > 0 && _idom[i] != NULL) {
+_dom_depth[i] = no_depth_marker;
+}
+}
+if (_dom_stk == NULL) {
+uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size.
+if (init_size < 10) init_size = 10;
+_dom_stk = new (C->node_arena()) GrowableArray<uint>(C->node_arena(), init_size, 0, 0);
+}
+// Compute new depth for each node.
+for (i = 0; i < _idom_size; i++) {
+uint j = i;
+// Run up the dom tree to find a node with a depth
+while (_dom_depth[j] == no_depth_marker) {
+_dom_stk->push(j);
+j = _idom[j]->_idx;
+}
+// Compute the depth on the way back down this tree branch
+uint dd = _dom_depth[j] + 1;
+while (_dom_stk->length() > 0) {
+uint j = _dom_stk->pop();
+_dom_depth[j] = dd;
+dd++;
+}
+}
+}
+//------------------------------sort-------------------------------------------
+// Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
+// loop tree, not the root.
+IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
+if( !innermost ) return loop; // New innermost loop
+int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
+assert( loop_preorder, "not yet post-walked loop" );
+IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
+IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
+// Insert at start of list
+while( l ) {                  // Insertion sort based on pre-order
+if( l == loop ) return innermost; // Already on list!
+int l_preorder = get_preorder(l->_head); // Cache pre-order number
+assert( l_preorder, "not yet post-walked l" );
+// Check header pre-order number to figure proper nesting
+if( loop_preorder > l_preorder )
+break;                    // End of insertion
+// If headers tie (e.g., shared headers) check tail pre-order numbers.
+// Since I split shared headers, you'd think this could not happen.
+// BUT: I must first do the preorder numbering before I can discover I
+// have shared headers, so the split headers all get the same preorder
+// number as the RegionNode they split from.
+if( loop_preorder == l_preorder &&
+get_preorder(loop->_tail) < get_preorder(l->_tail) )
+break;                    // Also check for shared headers (same pre#)
+pp = &l->_parent;           // Chain up list
+l = *pp;
+}
+// Link into list
+// Point predecessor to me
+*pp = loop;
+// Point me to successor
+IdealLoopTree *p = loop->_parent;
+loop->_parent = l;            // Point me to successor
+if( p ) sort( p, innermost ); // Insert my parents into list as well
+return innermost;
+}
+//------------------------------build_loop_tree--------------------------------
+// I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
+// bits.  The _nodes[] array is mapped by Node index and holds a NULL for
+// not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
+// tightest enclosing IdealLoopTree for post-walked.
+//
+// During my forward walk I do a short 1-layer lookahead to see if I can find
+// a loop backedge with that doesn't have any work on the backedge.  This
+// helps me construct nested loops with shared headers better.
+//
+// Once I've done the forward recursion, I do the post-work.  For each child
+// I check to see if there is a backedge.  Backedges define a loop!  I
+// insert an IdealLoopTree at the target of the backedge.
+//
+// During the post-work I also check to see if I have several children
+// belonging to different loops.  If so, then this Node is a decision point
+// where control flow can choose to change loop nests.  It is at this
+// decision point where I can figure out how loops are nested.  At this
+// time I can properly order the different loop nests from my children.
+// Note that there may not be any backedges at the decision point!
+//
+// Since the decision point can be far removed from the backedges, I can't
+// order my loops at the time I discover them.  Thus at the decision point
+// I need to inspect loop header pre-order numbers to properly nest my
+// loops.  This means I need to sort my childrens' loops by pre-order.
+// The sort is of size number-of-control-children, which generally limits
+// it to size 2 (i.e., I just choose between my 2 target loops).
+void PhaseIdealLoop::build_loop_tree() {
+// Allocate stack of size C->unique()/2 to avoid frequent realloc
+GrowableArray <Node *> bltstack(C->unique() >> 1);
+Node *n = C->root();
+bltstack.push(n);
+int pre_order = 1;
+int stack_size;
+while ( ( stack_size = bltstack.length() ) != 0 ) {
+n = bltstack.top(); // Leave node on stack
+if ( !is_visited(n) ) {
+// ---- Pre-pass Work ----
+// Pre-walked but not post-walked nodes need a pre_order number.
+set_preorder_visited( n, pre_order ); // set as visited
+// ---- Scan over children ----
+// Scan first over control projections that lead to loop headers.
+// This helps us find inner-to-outer loops with shared headers better.
+// Scan children's children for loop headers.
+for ( int i = n->outcnt() - 1; i >= 0; --i ) {
+Node* m = n->raw_out(i);       // Child
+if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
+// Scan over children's children to find loop
+for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
+Node* l = m->fast_out(j);
+if( is_visited(l) &&       // Been visited?
+!is_postvisited(l) &&  // But not post-visited
+get_preorder(l) < pre_order ) { // And smaller pre-order
+// Found!  Scan the DFS down this path before doing other paths
+bltstack.push(m);
+break;
+}
+}
+}
+}
+pre_order++;
+}
+else if ( !is_postvisited(n) ) {
+// Note: build_loop_tree_impl() adds out edges on rare occasions,
+// such as com.sun.rsasign.am::a.
+// For non-recursive version, first, process current children.
+// On next iteration, check if additional children were added.
+for ( int k = n->outcnt() - 1; k >= 0; --k ) {
+Node* u = n->raw_out(k);
+if ( u->is_CFG() && !is_visited(u) ) {
+bltstack.push(u);
+}
+}
+if ( bltstack.length() == stack_size ) {
+// There were no additional children, post visit node now
+(void)bltstack.pop(); // Remove node from stack
+pre_order = build_loop_tree_impl( n, pre_order );
+// Check for bailout
+if (C->failing()) {
+return;
+}
+// Check to grow _preorders[] array for the case when
+// build_loop_tree_impl() adds new nodes.
+check_grow_preorders();
+}
+}
+else {
+(void)bltstack.pop(); // Remove post-visited node from stack
+}
+}
+}
+//------------------------------build_loop_tree_impl---------------------------
+int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
+// ---- Post-pass Work ----
+// Pre-walked but not post-walked nodes need a pre_order number.
+// Tightest enclosing loop for this Node
+IdealLoopTree *innermost = NULL;
+// For all children, see if any edge is a backedge.  If so, make a loop
+// for it.  Then find the tightest enclosing loop for the self Node.
+for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
+Node* m = n->fast_out(i);   // Child
+if( n == m ) continue;      // Ignore control self-cycles
+if( !m->is_CFG() ) continue;// Ignore non-CFG edges
+IdealLoopTree *l;           // Child's loop
+if( !is_postvisited(m) ) {  // Child visited but not post-visited?
+// Found a backedge
+assert( get_preorder(m) < pre_order, "should be backedge" );
+// Check for the RootNode, which is already a LoopNode and is allowed
+// to have multiple "backedges".
+if( m == C->root()) {     // Found the root?
+l = _ltree_root;        // Root is the outermost LoopNode
+} else {                  // Else found a nested loop
+// Insert a LoopNode to mark this loop.
+l = new IdealLoopTree(this, m, n);
+} // End of Else found a nested loop
+if( !has_loop(m) )        // If 'm' does not already have a loop set
+set_loop(m, l);         // Set loop header to loop now
+} else {                    // Else not a nested loop
+if( !_nodes[m->_idx] ) continue; // Dead code has no loop
+l = get_loop(m);          // Get previously determined loop
+// If successor is header of a loop (nest), move up-loop till it
+// is a member of some outer enclosing loop.  Since there are no
+// shared headers (I've split them already) I only need to go up
+// at most 1 level.
+while( l && l->_head == m ) // Successor heads loop?
+l = l->_parent;         // Move up 1 for me
+// If this loop is not properly parented, then this loop
+// has no exit path out, i.e. its an infinite loop.
+if( !l ) {
+// Make loop "reachable" from root so the CFG is reachable.  Basically
+// insert a bogus loop exit that is never taken.  'm', the loop head,
+// points to 'n', one (of possibly many) fall-in paths.  There may be
+// many backedges as well.
+// Here I set the loop to be the root loop.  I could have, after
+// inserting a bogus loop exit, restarted the recursion and found my
+// new loop exit.  This would make the infinite loop a first-class
+// loop and it would then get properly optimized.  What's the use of
+// optimizing an infinite loop?
+l = _ltree_root;        // Oops, found infinite loop
+// Insert the NeverBranch between 'm' and it's control user.
+NeverBranchNode *iff = new (C, 1) NeverBranchNode( m );
+_igvn.register_new_node_with_optimizer(iff);
+set_loop(iff, l);
+Node *if_t = new (C, 1) CProjNode( iff, 0 );
+_igvn.register_new_node_with_optimizer(if_t);
+set_loop(if_t, l);
+Node* cfg = NULL;       // Find the One True Control User of m
+for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
+Node* x = m->fast_out(j);
+if (x->is_CFG() && x != m && x != iff)
+{ cfg = x; break; }
+}
+assert(cfg != NULL, "must find the control user of m");
+uint k = 0;             // Probably cfg->in(0)
+while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
+cfg->set_req( k, if_t ); // Now point to NeverBranch
+// Now create the never-taken loop exit
+Node *if_f = new (C, 1) CProjNode( iff, 1 );
+_igvn.register_new_node_with_optimizer(if_f);
+set_loop(if_f, l);
+// Find frame ptr for Halt.  Relies on the optimizer
+// V-N'ing.  Easier and quicker than searching through
+// the program structure.
+Node *frame = new (C, 1) ParmNode( C->start(), TypeFunc::FramePtr );
+_igvn.register_new_node_with_optimizer(frame);
+// Halt & Catch Fire
+Node *halt = new (C, TypeFunc::Parms) HaltNode( if_f, frame );
+_igvn.register_new_node_with_optimizer(halt);
+set_loop(halt, l);
+C->root()->add_req(halt);
+set_loop(C->root(), _ltree_root);
+}
+}
+// Weeny check for irreducible.  This child was already visited (this
+// IS the post-work phase).  Is this child's loop header post-visited
+// as well?  If so, then I found another entry into the loop.
+while( is_postvisited(l->_head) ) {
+// found irreducible
+l->_irreducible = true;
+l = l->_parent;
+_has_irreducible_loops = true;
+// Check for bad CFG here to prevent crash, and bailout of compile
+if (l == NULL) {
+C->record_method_not_compilable("unhandled CFG detected during loop optimization");
+return pre_order;
+}
+}
+// This Node might be a decision point for loops.  It is only if
+// it's children belong to several different loops.  The sort call
+// does a trivial amount of work if there is only 1 child or all
+// children belong to the same loop.  If however, the children
+// belong to different loops, the sort call will properly set the
+// _parent pointers to show how the loops nest.
+//
+// In any case, it returns the tightest enclosing loop.
+innermost = sort( l, innermost );
+}
+// Def-use info will have some dead stuff; dead stuff will have no
+// loop decided on.
+// Am I a loop header?  If so fix up my parent's child and next ptrs.
+if( innermost && innermost->_head == n ) {
+assert( get_loop(n) == innermost, "" );
+IdealLoopTree *p = innermost->_parent;
+IdealLoopTree *l = innermost;
+while( p && l->_head == n ) {
+l->_next = p->_child;     // Put self on parents 'next child'
+p->_child = l;            // Make self as first child of parent
+l = p;                    // Now walk up the parent chain
+p = l->_parent;
+}
+} else {
+// Note that it is possible for a LoopNode to reach here, if the
+// backedge has been made unreachable (hence the LoopNode no longer
+// denotes a Loop, and will eventually be removed).
+// Record tightest enclosing loop for self.  Mark as post-visited.
+set_loop(n, innermost);
+// Also record has_call flag early on
+if( innermost ) {
+if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
+// Do not count uncommon calls
+if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
+Node *iff = n->in(0)->in(0);
+if( !iff->is_If() ||
+(n->in(0)->Opcode() == Op_IfFalse &&
+(1.0 - iff->as_If()->_prob) >= 0.01) ||
+(iff->as_If()->_prob >= 0.01) )
+innermost->_has_call = 1;
+}
+}
+}
+}
+// Flag as post-visited now
+set_postvisited(n);
+return pre_order;
+}
+//------------------------------build_loop_early-------------------------------
+// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
+// First pass computes the earliest controlling node possible.  This is the
+// controlling input with the deepest dominating depth.
+void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me ) {
+while (worklist.size() != 0) {
+// Use local variables nstack_top_n & nstack_top_i to cache values
+// on nstack's top.
+Node *nstack_top_n = worklist.pop();
+uint  nstack_top_i = 0;
+//while_nstack_nonempty:
+while (true) {
+// Get parent node and next input's index from stack's top.
+Node  *n = nstack_top_n;
+uint   i = nstack_top_i;
+uint cnt = n->req(); // Count of inputs
+if (i == 0) {        // Pre-process the node.
+if( has_node(n) &&            // Have either loop or control already?
+!has_ctrl(n) ) {          // Have loop picked out already?
+// During "merge_many_backedges" we fold up several nested loops
+// into a single loop.  This makes the members of the original
+// loop bodies pointing to dead loops; they need to move up
+// to the new UNION'd larger loop.  I set the _head field of these
+// dead loops to NULL and the _parent field points to the owning
+// loop.  Shades of UNION-FIND algorithm.
+IdealLoopTree *ilt;
+while( !(ilt = get_loop(n))->_head ) {
+// Normally I would use a set_loop here.  But in this one special
+// case, it is legal (and expected) to change what loop a Node
+// belongs to.
+_nodes.map(n->_idx, (Node*)(ilt->_parent) );
+}
+// Remove safepoints ONLY if I've already seen I don't need one.
+// (the old code here would yank a 2nd safepoint after seeing a
+// first one, even though the 1st did not dominate in the loop body
+// and thus could be avoided indefinitely)
+if( !verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
+is_deleteable_safept(n)) {
+Node *in = n->in(TypeFunc::Control);
+lazy_replace(n,in);       // Pull safepoint now
+// Carry on with the recursion "as if" we are walking
+// only the control input
+if( !visited.test_set( in->_idx ) ) {
+worklist.push(in);      // Visit this guy later, using worklist
+}
+// Get next node from nstack:
+// - skip n's inputs processing by setting i > cnt;
+// - we also will not call set_early_ctrl(n) since
+//   has_node(n) == true (see the condition above).
+i = cnt + 1;
+}
+}
+} // if (i == 0)
+// Visit all inputs
+bool done = true;       // Assume all n's inputs will be processed
+while (i < cnt) {
+Node *in = n->in(i);
+++i;
+if (in == NULL) continue;
+if (in->pinned() && !in->is_CFG())
+set_ctrl(in, in->in(0));
+int is_visited = visited.test_set( in->_idx );
+if (!has_node(in)) {  // No controlling input yet?
+assert( !in->is_CFG(), "CFG Node with no controlling input?" );
+assert( !is_visited, "visit only once" );
+nstack.push(n, i);  // Save parent node and next input's index.
+nstack_top_n = in;  // Process current input now.
+nstack_top_i = 0;
+done = false;       // Not all n's inputs processed.
+break; // continue while_nstack_nonempty;
+} else if (!is_visited) {
+// This guy has a location picked out for him, but has not yet
+// been visited.  Happens to all CFG nodes, for instance.
+// Visit him using the worklist instead of recursion, to break
+// cycles.  Since he has a location already we do not need to
+// find his location before proceeding with the current Node.
+worklist.push(in);  // Visit this guy later, using worklist
+}
+}
+if (done) {
+// All of n's inputs have been processed, complete post-processing.
+// Compute earilest point this Node can go.
+// CFG, Phi, pinned nodes already know their controlling input.
+if (!has_node(n)) {
+// Record earliest legal location
+set_early_ctrl( n );
+}
+if (nstack.is_empty()) {
+// Finished all nodes on stack.
+// Process next node on the worklist.
+break;
+}
+// Get saved parent node and next input's index.
+nstack_top_n = nstack.node();
+nstack_top_i = nstack.index();
+nstack.pop();
+}
+} // while (true)
+}
+}
+//------------------------------dom_lca_internal--------------------------------
+// Pair-wise LCA
+Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
+if( !n1 ) return n2;          // Handle NULL original LCA
+assert( n1->is_CFG(), "" );
+assert( n2->is_CFG(), "" );
+// find LCA of all uses
+uint d1 = dom_depth(n1);
+uint d2 = dom_depth(n2);
+while (n1 != n2) {
+if (d1 > d2) {
+n1 =      idom(n1);
+d1 = dom_depth(n1);
+} else if (d1 < d2) {
+n2 =      idom(n2);
+d2 = dom_depth(n2);
+} else {
+// Here d1 == d2.  Due to edits of the dominator-tree, sections
+// of the tree might have the same depth.  These sections have
+// to be searched more carefully.
+// Scan up all the n1's with equal depth, looking for n2.
+Node *t1 = idom(n1);
+while (dom_depth(t1) == d1) {
+if (t1 == n2)  return n2;
+t1 = idom(t1);
+}
+// Scan up all the n2's with equal depth, looking for n1.
+Node *t2 = idom(n2);
+while (dom_depth(t2) == d2) {
+if (t2 == n1)  return n1;
+t2 = idom(t2);
+}
+// Move up to a new dominator-depth value as well as up the dom-tree.
+n1 = t1;
+n2 = t2;
+d1 = dom_depth(n1);
+d2 = dom_depth(n2);
+}
+}
+return n1;
+}
+//------------------------------compute_idom-----------------------------------
+// Locally compute IDOM using dom_lca call.  Correct only if the incoming
+// IDOMs are correct.
+Node *PhaseIdealLoop::compute_idom( Node *region ) const {
+assert( region->is_Region(), "" );
+Node *LCA = NULL;
+for( uint i = 1; i < region->req(); i++ ) {
+if( region->in(i) != C->top() )
+LCA = dom_lca( LCA, region->in(i) );
+}
+return LCA;
+}
+//------------------------------get_late_ctrl----------------------------------
+// Compute latest legal control.
+Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
+assert(early != NULL, "early control should not be NULL");
+// Compute LCA over list of uses
+Node *LCA = NULL;
+for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
+Node* c = n->fast_out(i);
+if (_nodes[c->_idx] == NULL)
+continue;                 // Skip the occasional dead node
+if( c->is_Phi() ) {         // For Phis, we must land above on the path
+for( uint j=1; j<c->req(); j++ ) {// For all inputs
+if( c->in(j) == n ) {   // Found matching input?
+Node *use = c->in(0)->in(j);
+LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
+}
+}
+} else {
+// For CFG data-users, use is in the block just prior
+Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
+LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
+}
+}
+// if this is a load, check for anti-dependent stores
+// We use a conservative algorithm to identify potential interfering
+// instructions and for rescheduling the load.  The users of the memory
+// input of this load are examined.  Any use which is not a load and is
+// dominated by early is considered a potentially interfering store.
+// This can produce false positives.
+if (n->is_Load() && LCA != early) {
+Node_List worklist;
+Node *mem = n->in(MemNode::Memory);
+for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
+Node* s = mem->fast_out(i);
+worklist.push(s);
+}
+while(worklist.size() != 0 && LCA != early) {
+Node* s = worklist.pop();
+if (s->is_Load()) {
+continue;
+} else if (s->is_MergeMem()) {
+for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
+Node* s1 = s->fast_out(i);
+worklist.push(s1);
+}
+} else {
+Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
+assert(sctrl != NULL || s->outcnt() == 0, "must have control");
+if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
+LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
+}
+}
+}
+}
+assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
+return LCA;
+}
+// true if CFG node d dominates CFG node n
+bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
+if (d == n)
+return true;
+assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
+uint dd = dom_depth(d);
+while (dom_depth(n) >= dd) {
+if (n == d)
+return true;
+n = idom(n);
+}
+return false;
+}
+//------------------------------dom_lca_for_get_late_ctrl_internal-------------
+// Pair-wise LCA with tags.
+// Tag each index with the node 'tag' currently being processed
+// before advancing up the dominator chain using idom().
+// Later calls that find a match to 'tag' know that this path has already
+// been considered in the current LCA (which is input 'n1' by convention).
+// Since get_late_ctrl() is only called once for each node, the tag array
+// does not need to be cleared between calls to get_late_ctrl().
+// Algorithm trades a larger constant factor for better asymptotic behavior
+//
+Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
+uint d1 = dom_depth(n1);
+uint d2 = dom_depth(n2);
+do {
+if (d1 > d2) {
+// current lca is deeper than n2
+_dom_lca_tags.map(n1->_idx, tag);
+n1 =      idom(n1);
+d1 = dom_depth(n1);
+} else if (d1 < d2) {
+// n2 is deeper than current lca
+Node *memo = _dom_lca_tags[n2->_idx];
+if( memo == tag ) {
+return n1;    // Return the current LCA
+}
+_dom_lca_tags.map(n2->_idx, tag);
+n2 =      idom(n2);
+d2 = dom_depth(n2);
+} else {
+// Here d1 == d2.  Due to edits of the dominator-tree, sections
+// of the tree might have the same depth.  These sections have
+// to be searched more carefully.
+// Scan up all the n1's with equal depth, looking for n2.
+_dom_lca_tags.map(n1->_idx, tag);
+Node *t1 = idom(n1);
+while (dom_depth(t1) == d1) {
+if (t1 == n2)  return n2;
+_dom_lca_tags.map(t1->_idx, tag);
+t1 = idom(t1);
+}
+// Scan up all the n2's with equal depth, looking for n1.
+_dom_lca_tags.map(n2->_idx, tag);
+Node *t2 = idom(n2);
+while (dom_depth(t2) == d2) {
+if (t2 == n1)  return n1;
+_dom_lca_tags.map(t2->_idx, tag);
+t2 = idom(t2);
+}
+// Move up to a new dominator-depth value as well as up the dom-tree.
+n1 = t1;
+n2 = t2;
+d1 = dom_depth(n1);
+d2 = dom_depth(n2);
+}
+} while (n1 != n2);
+return n1;
+}
+//------------------------------init_dom_lca_tags------------------------------
+// Tag could be a node's integer index, 32bits instead of 64bits in some cases
+// Intended use does not involve any growth for the array, so it could
+// be of fixed size.
+void PhaseIdealLoop::init_dom_lca_tags() {
+uint limit = C->unique() + 1;
+_dom_lca_tags.map( limit, NULL );
+#ifdef ASSERT
+for( uint i = 0; i < limit; ++i ) {
+assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
+}
+#endif // ASSERT
+}
+//------------------------------clear_dom_lca_tags------------------------------
+// Tag could be a node's integer index, 32bits instead of 64bits in some cases
+// Intended use does not involve any growth for the array, so it could
+// be of fixed size.
+void PhaseIdealLoop::clear_dom_lca_tags() {
+uint limit = C->unique() + 1;
+_dom_lca_tags.map( limit, NULL );
+_dom_lca_tags.clear();
+#ifdef ASSERT
+for( uint i = 0; i < limit; ++i ) {
+assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
+}
+#endif // ASSERT
+}
+//------------------------------build_loop_late--------------------------------
+// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
+// Second pass finds latest legal placement, and ideal loop placement.
+void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack, const PhaseIdealLoop *verify_me ) {
+while (worklist.size() != 0) {
+Node *n = worklist.pop();
+// Only visit once
+if (visited.test_set(n->_idx)) continue;
+uint cnt = n->outcnt();
+uint   i = 0;
+while (true) {
+assert( _nodes[n->_idx], "no dead nodes" );
+// Visit all children
+if (i < cnt) {
+Node* use = n->raw_out(i);
+++i;
+// Check for dead uses.  Aggressively prune such junk.  It might be
+// dead in the global sense, but still have local uses so I cannot
+// easily call 'remove_dead_node'.
+if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
+// Due to cycles, we might not hit the same fixed point in the verify
+// pass as we do in the regular pass.  Instead, visit such phis as
+// simple uses of the loop head.
+if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
+if( !visited.test(use->_idx) )
+worklist.push(use);
+} else if( !visited.test_set(use->_idx) ) {
+nstack.push(n, i); // Save parent and next use's index.
+n   = use;         // Process all children of current use.
+cnt = use->outcnt();
+i   = 0;
+}
+} else {
+// Do not visit around the backedge of loops via data edges.
+// push dead code onto a worklist
+_deadlist.push(use);
+}
+} else {
+// All of n's children have been processed, complete post-processing.
+build_loop_late_post(n, verify_me);
+if (nstack.is_empty()) {
+// Finished all nodes on stack.
+// Process next node on the worklist.
+break;
+}
+// Get saved parent node and next use's index. Visit the rest of uses.
+n   = nstack.node();
+cnt = n->outcnt();
+i   = nstack.index();
+nstack.pop();
+}
+}
+}
+}
+//------------------------------build_loop_late_post---------------------------
+// Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
+// Second pass finds latest legal placement, and ideal loop placement.
+void PhaseIdealLoop::build_loop_late_post( Node *n, const PhaseIdealLoop *verify_me ) {
+if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress()) {
+_igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
+}
+// CFG and pinned nodes already handled
+if( n->in(0) ) {
+if( n->in(0)->is_top() ) return; // Dead?
+// We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
+// _must_ be pinned (they have to observe their control edge of course).
+// Unlike Stores (which modify an unallocable resource, the memory
+// state), Mods/Loads can float around.  So free them up.
+bool pinned = true;
+switch( n->Opcode() ) {
+case Op_DivI:
+case Op_DivF:
+case Op_DivD:
+case Op_ModI:
+case Op_ModF:
+case Op_ModD:
+case Op_LoadB:              // Same with Loads; they can sink
+case Op_LoadC:              // during loop optimizations.
+case Op_LoadD:
+case Op_LoadF:
+case Op_LoadI:
+case Op_LoadKlass:
+case Op_LoadL:
+case Op_LoadS:
+case Op_LoadP:
+case Op_LoadRange:
+case Op_LoadD_unaligned:
+case Op_LoadL_unaligned:
+case Op_StrComp:            // Does a bunch of load-like effects
+pinned = false;
+}
+if( pinned ) {
+IdealLoopTree *choosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
+if( !choosen_loop->_child )       // Inner loop?
+choosen_loop->_body.push(n); // Collect inner loops
+return;
+}
+} else {                      // No slot zero
+if( n->is_CFG() ) {         // CFG with no slot 0 is dead
+_nodes.map(n->_idx,0);    // No block setting, it's globally dead
+return;
+}
+assert(!n->is_CFG() || n->outcnt() == 0, "");
+}
+// Do I have a "safe range" I can select over?
+Node *early = get_ctrl(n);// Early location already computed
+// Compute latest point this Node can go
+Node *LCA = get_late_ctrl( n, early );
+// LCA is NULL due to uses being dead
+if( LCA == NULL ) {
+#ifdef ASSERT
+for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
+assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
+}
+#endif
+_nodes.map(n->_idx, 0);     // This node is useless
+_deadlist.push(n);
+return;
+}
+assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
+Node *legal = LCA;            // Walk 'legal' up the IDOM chain
+Node *least = legal;          // Best legal position so far
+while( early != legal ) {     // While not at earliest legal
+// Find least loop nesting depth
+legal = idom(legal);        // Bump up the IDOM tree
+// Check for lower nesting depth
+if( get_loop(legal)->_nest < get_loop(least)->_nest )
+least = legal;
+}
+// Try not to place code on a loop entry projection
+// which can inhibit range check elimination.
+if (least != early) {
+Node* ctrl_out = least->unique_ctrl_out();
+if (ctrl_out && ctrl_out->is_CountedLoop() &&
+least == ctrl_out->in(LoopNode::EntryControl)) {
+Node* least_dom = idom(least);
+if (get_loop(least_dom)->is_member(get_loop(least))) {
+least = least_dom;
+}
+}
+}
+#ifdef ASSERT
+// If verifying, verify that 'verify_me' has a legal location
+// and choose it as our location.
+if( verify_me ) {
+Node *v_ctrl = verify_me->get_ctrl_no_update(n);
+Node *legal = LCA;
+while( early != legal ) {   // While not at earliest legal
+if( legal == v_ctrl ) break;  // Check for prior good location
+legal = idom(legal)      ;// Bump up the IDOM tree
+}
+// Check for prior good location
+if( legal == v_ctrl ) least = legal; // Keep prior if found
+}
+#endif
+// Assign discovered "here or above" point
+least = find_non_split_ctrl(least);
+set_ctrl(n, least);
+// Collect inner loop bodies
+IdealLoopTree *choosen_loop = get_loop(least);
+if( !choosen_loop->_child )   // Inner loop?
+choosen_loop->_body.push(n);// Collect inner loops
+}
+#ifndef PRODUCT
+//------------------------------dump-------------------------------------------
+void PhaseIdealLoop::dump( ) const {
+ResourceMark rm;
+Arena* arena = Thread::current()->resource_area();
+Node_Stack stack(arena, C->unique() >> 2);
+Node_List rpo_list;
+VectorSet visited(arena);
+visited.set(C->top()->_idx);
+rpo( C->root(), stack, visited, rpo_list );
+// Dump root loop indexed by last element in PO order
+dump( _ltree_root, rpo_list.size(), rpo_list );
+}
+void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
+// Indent by loop nesting depth
+for( uint x = 0; x < loop->_nest; x++ )
+tty->print("  ");
+tty->print_cr("---- Loop N%d-N%d ----", loop->_head->_idx,loop->_tail->_idx);
+// Now scan for CFG nodes in the same loop
+for( uint j=idx; j > 0;  j-- ) {
+Node *n = rpo_list[j-1];
+if( !_nodes[n->_idx] )      // Skip dead nodes
+continue;
+if( get_loop(n) != loop ) { // Wrong loop nest
+if( get_loop(n)->_head == n &&    // Found nested loop?
+get_loop(n)->_parent == loop )
+dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
+continue;
+}
+// Dump controlling node
+for( uint x = 0; x < loop->_nest; x++ )
+tty->print("  ");
+tty->print("C");
+if( n == C->root() ) {
+n->dump();
+} else {
+Node* cached_idom   = idom_no_update(n);
+Node *computed_idom = n->in(0);
+if( n->is_Region() ) {
+computed_idom = compute_idom(n);
+// computed_idom() will return n->in(0) when idom(n) is an IfNode (or
+// any MultiBranch ctrl node), so apply a similar transform to
+// the cached idom returned from idom_no_update.
+cached_idom = find_non_split_ctrl(cached_idom);
+}
+tty->print(" ID:%d",computed_idom->_idx);
+n->dump();
+if( cached_idom != computed_idom ) {
+tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
+computed_idom->_idx, cached_idom->_idx);
+}
+}
+// Dump nodes it controls
+for( uint k = 0; k < _nodes.Size(); k++ ) {
+// (k < C->unique() && get_ctrl(find(k)) == n)
+if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
+Node *m = C->root()->find(k);
+if( m && m->outcnt() > 0 ) {
+if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
+tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
+_nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
+}
+for( uint j = 0; j < loop->_nest; j++ )
+tty->print("  ");
+tty->print(" ");
+m->dump();
+}
+}
+}
+}
+}
+// Collect a R-P-O for the whole CFG.
+// Result list is in post-order (scan backwards for RPO)
+void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
+stk.push(start, 0);
+visited.set(start->_idx);
+while (stk.is_nonempty()) {
+Node* m   = stk.node();
+uint  idx = stk.index();
+if (idx < m->outcnt()) {
+stk.set_index(idx + 1);
+Node* n = m->raw_out(idx);
+if (n->is_CFG() && !visited.test_set(n->_idx)) {
+stk.push(n, 0);
+}
+} else {
+rpo_list.push(m);
+stk.pop();
+}
+}
+}
+#endif
+//=============================================================================
+//------------------------------LoopTreeIterator-----------------------------------
+// Advance to next loop tree using a preorder, left-to-right traversal.
+void LoopTreeIterator::next() {
+assert(!done(), "must not be done.");
+if (_curnt->_child != NULL) {
+_curnt = _curnt->_child;
+} else if (_curnt->_next != NULL) {
+_curnt = _curnt->_next;
+} else {
+while (_curnt != _root && _curnt->_next == NULL) {
+_curnt = _curnt->_parent;
+}
+if (_curnt == _root) {
+_curnt = NULL;
+assert(done(), "must be done.");
+} else {
+assert(_curnt->_next != NULL, "must be more to do");
+_curnt = _curnt->_next;
+}
+}
+}

Mercurial > hg > truffle

comparison src/share/vm/opto/loopnode.cpp @ 0:a61af66fc99e jdk7-b24