graal-compiler: src/share/vm/opto/loopTransform.cpp comparison

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

Initial load

author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	76256d272075

comparison

equal deleted inserted replaced

--1:000000000000
+:a61af66fc99e
+/*
+* Copyright 2000-2007 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/_loopTransform.cpp.incl"
+//------------------------------is_loop_exit-----------------------------------
+// Given an IfNode, return the loop-exiting projection or NULL if both
+// arms remain in the loop.
+Node *IdealLoopTree::is_loop_exit(Node *iff) const {
+if( iff->outcnt() != 2 ) return NULL; // Ignore partially dead tests
+PhaseIdealLoop *phase = _phase;
+// Test is an IfNode, has 2 projections.  If BOTH are in the loop
+// we need loop unswitching instead of peeling.
+if( !is_member(phase->get_loop( iff->raw_out(0) )) )
+return iff->raw_out(0);
+if( !is_member(phase->get_loop( iff->raw_out(1) )) )
+return iff->raw_out(1);
+return NULL;
+}
+//=============================================================================
+//------------------------------record_for_igvn----------------------------
+// Put loop body on igvn work list
+void IdealLoopTree::record_for_igvn() {
+for( uint i = 0; i < _body.size(); i++ ) {
+Node *n = _body.at(i);
+_phase->_igvn._worklist.push(n);
+}
+}
+//------------------------------compute_profile_trip_cnt----------------------------
+// Compute loop trip count from profile data as
+//    (backedge_count + loop_exit_count) / loop_exit_count
+void IdealLoopTree::compute_profile_trip_cnt( PhaseIdealLoop *phase ) {
+if (!_head->is_CountedLoop()) {
+return;
+}
+CountedLoopNode* head = _head->as_CountedLoop();
+if (head->profile_trip_cnt() != COUNT_UNKNOWN) {
+return; // Already computed
+}
+float trip_cnt = (float)max_jint; // default is big
+Node* back = head->in(LoopNode::LoopBackControl);
+while (back != head) {
+if ((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
+back->in(0) &&
+back->in(0)->is_If() &&
+back->in(0)->as_If()->_fcnt != COUNT_UNKNOWN &&
+back->in(0)->as_If()->_prob != PROB_UNKNOWN) {
+break;
+}
+back = phase->idom(back);
+}
+if (back != head) {
+assert((back->Opcode() == Op_IfTrue || back->Opcode() == Op_IfFalse) &&
+back->in(0), "if-projection exists");
+IfNode* back_if = back->in(0)->as_If();
+float loop_back_cnt = back_if->_fcnt * back_if->_prob;
+// Now compute a loop exit count
+float loop_exit_cnt = 0.0f;
+for( uint i = 0; i < _body.size(); i++ ) {
+Node *n = _body[i];
+if( n->is_If() ) {
+IfNode *iff = n->as_If();
+if( iff->_fcnt != COUNT_UNKNOWN && iff->_prob != PROB_UNKNOWN ) {
+Node *exit = is_loop_exit(iff);
+if( exit ) {
+float exit_prob = iff->_prob;
+if (exit->Opcode() == Op_IfFalse) exit_prob = 1.0 - exit_prob;
+if (exit_prob > PROB_MIN) {
+float exit_cnt = iff->_fcnt * exit_prob;
+loop_exit_cnt += exit_cnt;
+}
+}
+}
+}
+}
+if (loop_exit_cnt > 0.0f) {
+trip_cnt = (loop_back_cnt + loop_exit_cnt) / loop_exit_cnt;
+} else {
+// No exit count so use
+trip_cnt = loop_back_cnt;
+}
+}
+#ifndef PRODUCT
+if (TraceProfileTripCount) {
+tty->print_cr("compute_profile_trip_cnt  lp: %d cnt: %f\n", head->_idx, trip_cnt);
+}
+#endif
+head->set_profile_trip_cnt(trip_cnt);
+}
+//---------------------is_invariant_addition-----------------------------
+// Return nonzero index of invariant operand for an Add or Sub
+// of (nonconstant) invariant and variant values. Helper for reassoicate_invariants.
+int IdealLoopTree::is_invariant_addition(Node* n, PhaseIdealLoop *phase) {
+int op = n->Opcode();
+if (op == Op_AddI || op == Op_SubI) {
+bool in1_invar = this->is_invariant(n->in(1));
+bool in2_invar = this->is_invariant(n->in(2));
+if (in1_invar && !in2_invar) return 1;
+if (!in1_invar && in2_invar) return 2;
+}
+return 0;
+}
+//---------------------reassociate_add_sub-----------------------------
+// Reassociate invariant add and subtract expressions:
+//
+// inv1 + (x + inv2)  =>  ( inv1 + inv2) + x
+// (x + inv2) + inv1  =>  ( inv1 + inv2) + x
+// inv1 + (x - inv2)  =>  ( inv1 - inv2) + x
+// inv1 - (inv2 - x)  =>  ( inv1 - inv2) + x
+// (x + inv2) - inv1  =>  (-inv1 + inv2) + x
+// (x - inv2) + inv1  =>  ( inv1 - inv2) + x
+// (x - inv2) - inv1  =>  (-inv1 - inv2) + x
+// inv1 + (inv2 - x)  =>  ( inv1 + inv2) - x
+// inv1 - (x - inv2)  =>  ( inv1 + inv2) - x
+// (inv2 - x) + inv1  =>  ( inv1 + inv2) - x
+// (inv2 - x) - inv1  =>  (-inv1 + inv2) - x
+// inv1 - (x + inv2)  =>  ( inv1 - inv2) - x
+//
+Node* IdealLoopTree::reassociate_add_sub(Node* n1, PhaseIdealLoop *phase) {
+if (!n1->is_Add() && !n1->is_Sub() || n1->outcnt() == 0) return NULL;
+if (is_invariant(n1)) return NULL;
+int inv1_idx = is_invariant_addition(n1, phase);
+if (!inv1_idx) return NULL;
+// Don't mess with add of constant (igvn moves them to expression tree root.)
+if (n1->is_Add() && n1->in(2)->is_Con()) return NULL;
+Node* inv1 = n1->in(inv1_idx);
+Node* n2 = n1->in(3 - inv1_idx);
+int inv2_idx = is_invariant_addition(n2, phase);
+if (!inv2_idx) return NULL;
+Node* x    = n2->in(3 - inv2_idx);
+Node* inv2 = n2->in(inv2_idx);
+bool neg_x    = n2->is_Sub() && inv2_idx == 1;
+bool neg_inv2 = n2->is_Sub() && inv2_idx == 2;
+bool neg_inv1 = n1->is_Sub() && inv1_idx == 2;
+if (n1->is_Sub() && inv1_idx == 1) {
+neg_x    = !neg_x;
+neg_inv2 = !neg_inv2;
+}
+Node* inv1_c = phase->get_ctrl(inv1);
+Node* inv2_c = phase->get_ctrl(inv2);
+Node* n_inv1;
+if (neg_inv1) {
+Node *zero = phase->_igvn.intcon(0);
+phase->set_ctrl(zero, phase->C->root());
+n_inv1 = new (phase->C, 3) SubINode(zero, inv1);
+phase->register_new_node(n_inv1, inv1_c);
+} else {
+n_inv1 = inv1;
+}
+Node* inv;
+if (neg_inv2) {
+inv = new (phase->C, 3) SubINode(n_inv1, inv2);
+} else {
+inv = new (phase->C, 3) AddINode(n_inv1, inv2);
+}
+phase->register_new_node(inv, phase->get_early_ctrl(inv));
+Node* addx;
+if (neg_x) {
+addx = new (phase->C, 3) SubINode(inv, x);
+} else {
+addx = new (phase->C, 3) AddINode(x, inv);
+}
+phase->register_new_node(addx, phase->get_ctrl(x));
+phase->_igvn.hash_delete(n1);
+phase->_igvn.subsume_node(n1, addx);
+return addx;
+}
+//---------------------reassociate_invariants-----------------------------
+// Reassociate invariant expressions:
+void IdealLoopTree::reassociate_invariants(PhaseIdealLoop *phase) {
+for (int i = _body.size() - 1; i >= 0; i--) {
+Node *n = _body.at(i);
+for (int j = 0; j < 5; j++) {
+Node* nn = reassociate_add_sub(n, phase);
+if (nn == NULL) break;
+n = nn; // again
+};
+}
+}
+//------------------------------policy_peeling---------------------------------
+// Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
+// make some loop-invariant test (usually a null-check) happen before the loop.
+bool IdealLoopTree::policy_peeling( PhaseIdealLoop *phase ) const {
+Node *test = ((IdealLoopTree*)this)->tail();
+int  body_size = ((IdealLoopTree*)this)->_body.size();
+int  uniq      = phase->C->unique();
+// Peeling does loop cloning which can result in O(N^2) node construction
+if( body_size > 255 /* Prevent overflow for large body_size */
+|| (body_size * body_size + uniq > MaxNodeLimit) ) {
+return false;           // too large to safely clone
+}
+while( test != _head ) {      // Scan till run off top of loop
+if( test->is_If() ) {       // Test?
+Node *ctrl = phase->get_ctrl(test->in(1));
+if (ctrl->is_top())
+return false;           // Found dead test on live IF?  No peeling!
+// Standard IF only has one input value to check for loop invariance
+assert( test->Opcode() == Op_If || test->Opcode() == Op_CountedLoopEnd, "Check this code when new subtype is added");
+// Condition is not a member of this loop?
+if( !is_member(phase->get_loop(ctrl)) &&
+is_loop_exit(test) )
+return true;            // Found reason to peel!
+}
+// Walk up dominators to loop _head looking for test which is
+// executed on every path thru loop.
+test = phase->idom(test);
+}
+return false;
+}
+//------------------------------peeled_dom_test_elim---------------------------
+// If we got the effect of peeling, either by actually peeling or by making
+// a pre-loop which must execute at least once, we can remove all
+// loop-invariant dominated tests in the main body.
+void PhaseIdealLoop::peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new ) {
+bool progress = true;
+while( progress ) {
+progress = false;           // Reset for next iteration
+Node *prev = loop->_head->in(LoopNode::LoopBackControl);//loop->tail();
+Node *test = prev->in(0);
+while( test != loop->_head ) { // Scan till run off top of loop
+int p_op = prev->Opcode();
+if( (p_op == Op_IfFalse || p_op == Op_IfTrue) &&
+test->is_If() &&      // Test?
+!test->in(1)->is_Con() && // And not already obvious?
+// Condition is not a member of this loop?
+!loop->is_member(get_loop(get_ctrl(test->in(1))))){
+// Walk loop body looking for instances of this test
+for( uint i = 0; i < loop->_body.size(); i++ ) {
+Node *n = loop->_body.at(i);
+if( n->is_If() && n->in(1) == test->in(1) /*&& n != loop->tail()->in(0)*/ ) {
+// IfNode was dominated by version in peeled loop body
+progress = true;
+dominated_by( old_new[prev->_idx], n );
+}
+}
+}
+prev = test;
+test = idom(test);
+} // End of scan tests in loop
+} // End of while( progress )
+}
+//------------------------------do_peeling-------------------------------------
+// Peel the first iteration of the given loop.
+// Step 1: Clone the loop body.  The clone becomes the peeled iteration.
+//         The pre-loop illegally has 2 control users (old & new loops).
+// Step 2: Make the old-loop fall-in edges point to the peeled iteration.
+//         Do this by making the old-loop fall-in edges act as if they came
+//         around the loopback from the prior iteration (follow the old-loop
+//         backedges) and then map to the new peeled iteration.  This leaves
+//         the pre-loop with only 1 user (the new peeled iteration), but the
+//         peeled-loop backedge has 2 users.
+// Step 3: Cut the backedge on the clone (so its not a loop) and remove the
+//         extra backedge user.
+void PhaseIdealLoop::do_peeling( IdealLoopTree *loop, Node_List &old_new ) {
+C->set_major_progress();
+// Peeling a 'main' loop in a pre/main/post situation obfuscates the
+// 'pre' loop from the main and the 'pre' can no longer have it's
+// iterations adjusted.  Therefore, we need to declare this loop as
+// no longer a 'main' loop; it will need new pre and post loops before
+// we can do further RCE.
+Node *h = loop->_head;
+if( h->is_CountedLoop() ) {
+CountedLoopNode *cl = h->as_CountedLoop();
+assert(cl->trip_count() > 0, "peeling a fully unrolled loop");
+cl->set_trip_count(cl->trip_count() - 1);
+if( cl->is_main_loop() ) {
+cl->set_normal_loop();
+#ifndef PRODUCT
+if( PrintOpto && VerifyLoopOptimizations ) {
+tty->print("Peeling a 'main' loop; resetting to 'normal' ");
+loop->dump_head();
+}
+#endif
+}
+}
+// Step 1: Clone the loop body.  The clone becomes the peeled iteration.
+//         The pre-loop illegally has 2 control users (old & new loops).
+clone_loop( loop, old_new, dom_depth(loop->_head) );
+// Step 2: Make the old-loop fall-in edges point to the peeled iteration.
+//         Do this by making the old-loop fall-in edges act as if they came
+//         around the loopback from the prior iteration (follow the old-loop
+//         backedges) and then map to the new peeled iteration.  This leaves
+//         the pre-loop with only 1 user (the new peeled iteration), but the
+//         peeled-loop backedge has 2 users.
+for (DUIterator_Fast jmax, j = loop->_head->fast_outs(jmax); j < jmax; j++) {
+Node* old = loop->_head->fast_out(j);
+if( old->in(0) == loop->_head && old->req() == 3 &&
+(old->is_Loop() || old->is_Phi()) ) {
+Node *new_exit_value = old_new[old->in(LoopNode::LoopBackControl)->_idx];
+if( !new_exit_value )     // Backedge value is ALSO loop invariant?
+// Then loop body backedge value remains the same.
+new_exit_value = old->in(LoopNode::LoopBackControl);
+_igvn.hash_delete(old);
+old->set_req(LoopNode::EntryControl, new_exit_value);
+}
+}
+// Step 3: Cut the backedge on the clone (so its not a loop) and remove the
+//         extra backedge user.
+Node *nnn = old_new[loop->_head->_idx];
+_igvn.hash_delete(nnn);
+nnn->set_req(LoopNode::LoopBackControl, C->top());
+for (DUIterator_Fast j2max, j2 = nnn->fast_outs(j2max); j2 < j2max; j2++) {
+Node* use = nnn->fast_out(j2);
+if( use->in(0) == nnn && use->req() == 3 && use->is_Phi() ) {
+_igvn.hash_delete(use);
+use->set_req(LoopNode::LoopBackControl, C->top());
+}
+}
+// Step 4: Correct dom-depth info.  Set to loop-head depth.
+int dd = dom_depth(loop->_head);
+set_idom(loop->_head, loop->_head->in(1), dd);
+for (uint j3 = 0; j3 < loop->_body.size(); j3++) {
+Node *old = loop->_body.at(j3);
+Node *nnn = old_new[old->_idx];
+if (!has_ctrl(nnn))
+set_idom(nnn, idom(nnn), dd-1);
+// While we're at it, remove any SafePoints from the peeled code
+if( old->Opcode() == Op_SafePoint ) {
+Node *nnn = old_new[old->_idx];
+lazy_replace(nnn,nnn->in(TypeFunc::Control));
+}
+}
+// Now force out all loop-invariant dominating tests.  The optimizer
+// finds some, but we _know_ they are all useless.
+peeled_dom_test_elim(loop,old_new);
+loop->record_for_igvn();
+}
+//------------------------------policy_maximally_unroll------------------------
+// Return exact loop trip count, or 0 if not maximally unrolling
+bool IdealLoopTree::policy_maximally_unroll( PhaseIdealLoop *phase ) const {
+CountedLoopNode *cl = _head->as_CountedLoop();
+assert( cl->is_normal_loop(), "" );
+Node *init_n = cl->init_trip();
+Node *limit_n = cl->limit();
+// Non-constant bounds
+if( init_n   == NULL || !init_n->is_Con()  ||
+limit_n  == NULL || !limit_n->is_Con() ||
+// protect against stride not being a constant
+!cl->stride_is_con() ) {
+return false;
+}
+int init   = init_n->get_int();
+int limit  = limit_n->get_int();
+int span   = limit - init;
+int stride = cl->stride_con();
+if (init >= limit || stride > span) {
+// return a false (no maximally unroll) and the regular unroll/peel
+// route will make a small mess which CCP will fold away.
+return false;
+}
+uint trip_count = span/stride;   // trip_count can be greater than 2 Gig.
+assert( (int)trip_count*stride == span, "must divide evenly" );
+// Real policy: if we maximally unroll, does it get too big?
+// Allow the unrolled mess to get larger than standard loop
+// size.  After all, it will no longer be a loop.
+uint body_size    = _body.size();
+uint unroll_limit = (uint)LoopUnrollLimit * 4;
+assert( (intx)unroll_limit == LoopUnrollLimit * 4, "LoopUnrollLimit must fit in 32bits");
+cl->set_trip_count(trip_count);
+if( trip_count <= unroll_limit && body_size <= unroll_limit ) {
+uint new_body_size = body_size * trip_count;
+if (new_body_size <= unroll_limit &&
+body_size == new_body_size / trip_count &&
+// Unrolling can result in a large amount of node construction
+new_body_size < MaxNodeLimit - phase->C->unique()) {
+return true;    // maximally unroll
+}
+}
+return false;               // Do not maximally unroll
+}
+//------------------------------policy_unroll----------------------------------
+// Return TRUE or FALSE if the loop should be unrolled or not.  Unroll if
+// the loop is a CountedLoop and the body is small enough.
+bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
+CountedLoopNode *cl = _head->as_CountedLoop();
+assert( cl->is_normal_loop() || cl->is_main_loop(), "" );
+// protect against stride not being a constant
+if( !cl->stride_is_con() ) return false;
+// protect against over-unrolling
+if( cl->trip_count() <= 1 ) return false;
+int future_unroll_ct = cl->unrolled_count() * 2;
+// Don't unroll if the next round of unrolling would push us
+// over the expected trip count of the loop.  One is subtracted
+// from the expected trip count because the pre-loop normally
+// executes 1 iteration.
+if (UnrollLimitForProfileCheck > 0 &&
+cl->profile_trip_cnt() != COUNT_UNKNOWN &&
+future_unroll_ct        > UnrollLimitForProfileCheck &&
+(float)future_unroll_ct > cl->profile_trip_cnt() - 1.0) {
+return false;
+}
+// When unroll count is greater than LoopUnrollMin, don't unroll if:
+//   the residual iterations are more than 10% of the trip count
+//   and rounds of "unroll,optimize" are not making significant progress
+//   Progress defined as current size less than 20% larger than previous size.
+if (UseSuperWord && cl->node_count_before_unroll() > 0 &&
+future_unroll_ct > LoopUnrollMin &&
+(future_unroll_ct - 1) * 10.0 > cl->profile_trip_cnt() &&
+1.2 * cl->node_count_before_unroll() < (double)_body.size()) {
+return false;
+}
+Node *init_n = cl->init_trip();
+Node *limit_n = cl->limit();
+// Non-constant bounds.
+// Protect against over-unrolling when init or/and limit are not constant
+// (so that trip_count's init value is maxint) but iv range is known.
+if( init_n   == NULL || !init_n->is_Con()  ||
+limit_n  == NULL || !limit_n->is_Con() ) {
+Node* phi = cl->phi();
+if( phi != NULL ) {
+assert(phi->is_Phi() && phi->in(0) == _head, "Counted loop should have iv phi.");
+const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
+int next_stride = cl->stride_con() * 2; // stride after this unroll
+if( next_stride > 0 ) {
+if( iv_type->_lo + next_stride <= iv_type->_lo || // overflow
+iv_type->_lo + next_stride >  iv_type->_hi ) {
+return false;  // over-unrolling
+}
+} else if( next_stride < 0 ) {
+if( iv_type->_hi + next_stride >= iv_type->_hi || // overflow
+iv_type->_hi + next_stride <  iv_type->_lo ) {
+return false;  // over-unrolling
+}
+}
+}
+}
+// Adjust body_size to determine if we unroll or not
+uint body_size = _body.size();
+// Key test to unroll CaffeineMark's Logic test
+int xors_in_loop = 0;
+// Also count ModL, DivL and MulL which expand mightly
+for( uint k = 0; k < _body.size(); k++ ) {
+switch( _body.at(k)->Opcode() ) {
+case Op_XorI: xors_in_loop++; break; // CaffeineMark's Logic test
+case Op_ModL: body_size += 30; break;
+case Op_DivL: body_size += 30; break;
+case Op_MulL: body_size += 10; break;
+}
+}
+// Check for being too big
+if( body_size > (uint)LoopUnrollLimit ) {
+if( xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
+// Normal case: loop too big
+return false;
+}
+// Check for stride being a small enough constant
+if( abs(cl->stride_con()) > (1<<3) ) return false;
+// Unroll once!  (Each trip will soon do double iterations)
+return true;
+}
+//------------------------------policy_align-----------------------------------
+// Return TRUE or FALSE if the loop should be cache-line aligned.  Gather the
+// expression that does the alignment.  Note that only one array base can be
+// aligned in a loop (unless the VM guarentees mutual alignment).  Note that
+// if we vectorize short memory ops into longer memory ops, we may want to
+// increase alignment.
+bool IdealLoopTree::policy_align( PhaseIdealLoop *phase ) const {
+return false;
+}
+//------------------------------policy_range_check-----------------------------
+// Return TRUE or FALSE if the loop should be range-check-eliminated.
+// Actually we do iteration-splitting, a more powerful form of RCE.
+bool IdealLoopTree::policy_range_check( PhaseIdealLoop *phase ) const {
+if( !RangeCheckElimination ) return false;
+CountedLoopNode *cl = _head->as_CountedLoop();
+// If we unrolled with no intention of doing RCE and we later
+// changed our minds, we got no pre-loop.  Either we need to
+// make a new pre-loop, or we gotta disallow RCE.
+if( cl->is_main_no_pre_loop() ) return false; // Disallowed for now.
+Node *trip_counter = cl->phi();
+// Check loop body for tests of trip-counter plus loop-invariant vs
+// loop-invariant.
+for( uint i = 0; i < _body.size(); i++ ) {
+Node *iff = _body[i];
+if( iff->Opcode() == Op_If ) { // Test?
+// Comparing trip+off vs limit
+Node *bol = iff->in(1);
+if( bol->req() != 2 ) continue; // dead constant test
+Node *cmp = bol->in(1);
+Node *rc_exp = cmp->in(1);
+Node *limit = cmp->in(2);
+Node *limit_c = phase->get_ctrl(limit);
+if( limit_c == phase->C->top() )
+return false;           // Found dead test on live IF?  No RCE!
+if( is_member(phase->get_loop(limit_c) ) ) {
+// Compare might have operands swapped; commute them
+rc_exp = cmp->in(2);
+limit  = cmp->in(1);
+limit_c = phase->get_ctrl(limit);
+if( is_member(phase->get_loop(limit_c) ) )
+continue;             // Both inputs are loop varying; cannot RCE
+}
+if (!phase->is_scaled_iv_plus_offset(rc_exp, trip_counter, NULL, NULL)) {
+continue;
+}
+// Yeah!  Found a test like 'trip+off vs limit'
+// Test is an IfNode, has 2 projections.  If BOTH are in the loop
+// we need loop unswitching instead of iteration splitting.
+if( is_loop_exit(iff) )
+return true;            // Found reason to split iterations
+} // End of is IF
+}
+return false;
+}
+//------------------------------policy_peel_only-------------------------------
+// Return TRUE or FALSE if the loop should NEVER be RCE'd or aligned.  Useful
+// for unrolling loops with NO array accesses.
+bool IdealLoopTree::policy_peel_only( PhaseIdealLoop *phase ) const {
+for( uint i = 0; i < _body.size(); i++ )
+if( _body[i]->is_Mem() )
+return false;
+// No memory accesses at all!
+return true;
+}
+//------------------------------clone_up_backedge_goo--------------------------
+// If Node n lives in the back_ctrl block and cannot float, we clone a private
+// version of n in preheader_ctrl block and return that, otherwise return n.
+Node *PhaseIdealLoop::clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n ) {
+if( get_ctrl(n) != back_ctrl ) return n;
+Node *x = NULL;               // If required, a clone of 'n'
+// Check for 'n' being pinned in the backedge.
+if( n->in(0) && n->in(0) == back_ctrl ) {
+x = n->clone();             // Clone a copy of 'n' to preheader
+x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader
+}
+// Recursive fixup any other input edges into x.
+// If there are no changes we can just return 'n', otherwise
+// we need to clone a private copy and change it.
+for( uint i = 1; i < n->req(); i++ ) {
+Node *g = clone_up_backedge_goo( back_ctrl, preheader_ctrl, n->in(i) );
+if( g != n->in(i) ) {
+if( !x )
+x = n->clone();
+x->set_req(i, g);
+}
+}
+if( x ) {                     // x can legally float to pre-header location
+register_new_node( x, preheader_ctrl );
+return x;
+} else {                      // raise n to cover LCA of uses
+set_ctrl( n, find_non_split_ctrl(back_ctrl->in(0)) );
+}
+return n;
+}
+//------------------------------insert_pre_post_loops--------------------------
+// Insert pre and post loops.  If peel_only is set, the pre-loop can not have
+// more iterations added.  It acts as a 'peel' only, no lower-bound RCE, no
+// alignment.  Useful to unroll loops that do no array accesses.
+void PhaseIdealLoop::insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only ) {
+C->set_major_progress();
+// Find common pieces of the loop being guarded with pre & post loops
+CountedLoopNode *main_head = loop->_head->as_CountedLoop();
+assert( main_head->is_normal_loop(), "" );
+CountedLoopEndNode *main_end = main_head->loopexit();
+assert( main_end->outcnt() == 2, "1 true, 1 false path only" );
+uint dd_main_head = dom_depth(main_head);
+uint max = main_head->outcnt();
+Node *pre_header= main_head->in(LoopNode::EntryControl);
+Node *init      = main_head->init_trip();
+Node *incr      = main_end ->incr();
+Node *limit     = main_end ->limit();
+Node *stride    = main_end ->stride();
+Node *cmp       = main_end ->cmp_node();
+BoolTest::mask b_test = main_end->test_trip();
+// Need only 1 user of 'bol' because I will be hacking the loop bounds.
+Node *bol = main_end->in(CountedLoopEndNode::TestValue);
+if( bol->outcnt() != 1 ) {
+bol = bol->clone();
+register_new_node(bol,main_end->in(CountedLoopEndNode::TestControl));
+_igvn.hash_delete(main_end);
+main_end->set_req(CountedLoopEndNode::TestValue, bol);
+}
+// Need only 1 user of 'cmp' because I will be hacking the loop bounds.
+if( cmp->outcnt() != 1 ) {
+cmp = cmp->clone();
+register_new_node(cmp,main_end->in(CountedLoopEndNode::TestControl));
+_igvn.hash_delete(bol);
+bol->set_req(1, cmp);
+}
+//------------------------------
+// Step A: Create Post-Loop.
+Node* main_exit = main_end->proj_out(false);
+assert( main_exit->Opcode() == Op_IfFalse, "" );
+int dd_main_exit = dom_depth(main_exit);
+// Step A1: Clone the loop body.  The clone becomes the post-loop.  The main
+// loop pre-header illegally has 2 control users (old & new loops).
+clone_loop( loop, old_new, dd_main_exit );
+assert( old_new[main_end ->_idx]->Opcode() == Op_CountedLoopEnd, "" );
+CountedLoopNode *post_head = old_new[main_head->_idx]->as_CountedLoop();
+post_head->set_post_loop(main_head);
+// Build the main-loop normal exit.
+IfFalseNode *new_main_exit = new (C, 1) IfFalseNode(main_end);
+_igvn.register_new_node_with_optimizer( new_main_exit );
+set_idom(new_main_exit, main_end, dd_main_exit );
+set_loop(new_main_exit, loop->_parent);
+// Step A2: Build a zero-trip guard for the post-loop.  After leaving the
+// main-loop, the post-loop may not execute at all.  We 'opaque' the incr
+// (the main-loop trip-counter exit value) because we will be changing
+// the exit value (via unrolling) so we cannot constant-fold away the zero
+// trip guard until all unrolling is done.
+Node *zer_opaq = new (C, 2) Opaque1Node(incr);
+Node *zer_cmp  = new (C, 3) CmpINode( zer_opaq, limit );
+Node *zer_bol  = new (C, 2) BoolNode( zer_cmp, b_test );
+register_new_node( zer_opaq, new_main_exit );
+register_new_node( zer_cmp , new_main_exit );
+register_new_node( zer_bol , new_main_exit );
+// Build the IfNode
+IfNode *zer_iff = new (C, 2) IfNode( new_main_exit, zer_bol, PROB_FAIR, COUNT_UNKNOWN );
+_igvn.register_new_node_with_optimizer( zer_iff );
+set_idom(zer_iff, new_main_exit, dd_main_exit);
+set_loop(zer_iff, loop->_parent);
+// Plug in the false-path, taken if we need to skip post-loop
+_igvn.hash_delete( main_exit );
+main_exit->set_req(0, zer_iff);
+_igvn._worklist.push(main_exit);
+set_idom(main_exit, zer_iff, dd_main_exit);
+set_idom(main_exit->unique_out(), zer_iff, dd_main_exit);
+// Make the true-path, must enter the post loop
+Node *zer_taken = new (C, 1) IfTrueNode( zer_iff );
+_igvn.register_new_node_with_optimizer( zer_taken );
+set_idom(zer_taken, zer_iff, dd_main_exit);
+set_loop(zer_taken, loop->_parent);
+// Plug in the true path
+_igvn.hash_delete( post_head );
+post_head->set_req(LoopNode::EntryControl, zer_taken);
+set_idom(post_head, zer_taken, dd_main_exit);
+// Step A3: Make the fall-in values to the post-loop come from the
+// fall-out values of the main-loop.
+for (DUIterator_Fast imax, i = main_head->fast_outs(imax); i < imax; i++) {
+Node* main_phi = main_head->fast_out(i);
+if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() >0 ) {
+Node *post_phi = old_new[main_phi->_idx];
+Node *fallmain  = clone_up_backedge_goo(main_head->back_control(),
+post_head->init_control(),
+main_phi->in(LoopNode::LoopBackControl));
+_igvn.hash_delete(post_phi);
+post_phi->set_req( LoopNode::EntryControl, fallmain );
+}
+}
+// Update local caches for next stanza
+main_exit = new_main_exit;
+//------------------------------
+// Step B: Create Pre-Loop.
+// Step B1: Clone the loop body.  The clone becomes the pre-loop.  The main
+// loop pre-header illegally has 2 control users (old & new loops).
+clone_loop( loop, old_new, dd_main_head );
+CountedLoopNode*    pre_head = old_new[main_head->_idx]->as_CountedLoop();
+CountedLoopEndNode* pre_end  = old_new[main_end ->_idx]->as_CountedLoopEnd();
+pre_head->set_pre_loop(main_head);
+Node *pre_incr = old_new[incr->_idx];
+// Find the pre-loop normal exit.
+Node* pre_exit = pre_end->proj_out(false);
+assert( pre_exit->Opcode() == Op_IfFalse, "" );
+IfFalseNode *new_pre_exit = new (C, 1) IfFalseNode(pre_end);
+_igvn.register_new_node_with_optimizer( new_pre_exit );
+set_idom(new_pre_exit, pre_end, dd_main_head);
+set_loop(new_pre_exit, loop->_parent);
+// Step B2: Build a zero-trip guard for the main-loop.  After leaving the
+// pre-loop, the main-loop may not execute at all.  Later in life this
+// zero-trip guard will become the minimum-trip guard when we unroll
+// the main-loop.
+Node *min_opaq = new (C, 2) Opaque1Node(limit);
+Node *min_cmp  = new (C, 3) CmpINode( pre_incr, min_opaq );
+Node *min_bol  = new (C, 2) BoolNode( min_cmp, b_test );
+register_new_node( min_opaq, new_pre_exit );
+register_new_node( min_cmp , new_pre_exit );
+register_new_node( min_bol , new_pre_exit );
+// Build the IfNode
+IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_FAIR, COUNT_UNKNOWN );
+_igvn.register_new_node_with_optimizer( min_iff );
+set_idom(min_iff, new_pre_exit, dd_main_head);
+set_loop(min_iff, loop->_parent);
+// Plug in the false-path, taken if we need to skip main-loop
+_igvn.hash_delete( pre_exit );
+pre_exit->set_req(0, min_iff);
+set_idom(pre_exit, min_iff, dd_main_head);
+set_idom(pre_exit->unique_out(), min_iff, dd_main_head);
+// Make the true-path, must enter the main loop
+Node *min_taken = new (C, 1) IfTrueNode( min_iff );
+_igvn.register_new_node_with_optimizer( min_taken );
+set_idom(min_taken, min_iff, dd_main_head);
+set_loop(min_taken, loop->_parent);
+// Plug in the true path
+_igvn.hash_delete( main_head );
+main_head->set_req(LoopNode::EntryControl, min_taken);
+set_idom(main_head, min_taken, dd_main_head);
+// Step B3: Make the fall-in values to the main-loop come from the
+// fall-out values of the pre-loop.
+for (DUIterator_Fast i2max, i2 = main_head->fast_outs(i2max); i2 < i2max; i2++) {
+Node* main_phi = main_head->fast_out(i2);
+if( main_phi->is_Phi() && main_phi->in(0) == main_head && main_phi->outcnt() > 0 ) {
+Node *pre_phi = old_new[main_phi->_idx];
+Node *fallpre  = clone_up_backedge_goo(pre_head->back_control(),
+main_head->init_control(),
+pre_phi->in(LoopNode::LoopBackControl));
+_igvn.hash_delete(main_phi);
+main_phi->set_req( LoopNode::EntryControl, fallpre );
+}
+}
+// Step B4: Shorten the pre-loop to run only 1 iteration (for now).
+// RCE and alignment may change this later.
+Node *cmp_end = pre_end->cmp_node();
+assert( cmp_end->in(2) == limit, "" );
+Node *pre_limit = new (C, 3) AddINode( init, stride );
+// Save the original loop limit in this Opaque1 node for
+// use by range check elimination.
+Node *pre_opaq  = new (C, 3) Opaque1Node(pre_limit, limit);
+register_new_node( pre_limit, pre_head->in(0) );
+register_new_node( pre_opaq , pre_head->in(0) );
+// Since no other users of pre-loop compare, I can hack limit directly
+assert( cmp_end->outcnt() == 1, "no other users" );
+_igvn.hash_delete(cmp_end);
+cmp_end->set_req(2, peel_only ? pre_limit : pre_opaq);
+// Special case for not-equal loop bounds:
+// Change pre loop test, main loop test, and the
+// main loop guard test to use lt or gt depending on stride
+// direction:
+// positive stride use <
+// negative stride use >
+if (pre_end->in(CountedLoopEndNode::TestValue)->as_Bool()->_test._test == BoolTest::ne) {
+BoolTest::mask new_test = (main_end->stride_con() > 0) ? BoolTest::lt : BoolTest::gt;
+// Modify pre loop end condition
+Node* pre_bol = pre_end->in(CountedLoopEndNode::TestValue)->as_Bool();
+BoolNode* new_bol0 = new (C, 2) BoolNode(pre_bol->in(1), new_test);
+register_new_node( new_bol0, pre_head->in(0) );
+_igvn.hash_delete(pre_end);
+pre_end->set_req(CountedLoopEndNode::TestValue, new_bol0);
+// Modify main loop guard condition
+assert(min_iff->in(CountedLoopEndNode::TestValue) == min_bol, "guard okay");
+BoolNode* new_bol1 = new (C, 2) BoolNode(min_bol->in(1), new_test);
+register_new_node( new_bol1, new_pre_exit );
+_igvn.hash_delete(min_iff);
+min_iff->set_req(CountedLoopEndNode::TestValue, new_bol1);
+// Modify main loop end condition
+BoolNode* main_bol = main_end->in(CountedLoopEndNode::TestValue)->as_Bool();
+BoolNode* new_bol2 = new (C, 2) BoolNode(main_bol->in(1), new_test);
+register_new_node( new_bol2, main_end->in(CountedLoopEndNode::TestControl) );
+_igvn.hash_delete(main_end);
+main_end->set_req(CountedLoopEndNode::TestValue, new_bol2);
+}
+// Flag main loop
+main_head->set_main_loop();
+if( peel_only ) main_head->set_main_no_pre_loop();
+// It's difficult to be precise about the trip-counts
+// for the pre/post loops.  They are usually very short,
+// so guess that 4 trips is a reasonable value.
+post_head->set_profile_trip_cnt(4.0);
+pre_head->set_profile_trip_cnt(4.0);
+// Now force out all loop-invariant dominating tests.  The optimizer
+// finds some, but we _know_ they are all useless.
+peeled_dom_test_elim(loop,old_new);
+}
+//------------------------------is_invariant-----------------------------
+// Return true if n is invariant
+bool IdealLoopTree::is_invariant(Node* n) const {
+Node *n_c = _phase->get_ctrl(n);
+if (n_c->is_top()) return false;
+return !is_member(_phase->get_loop(n_c));
+}
+//------------------------------do_unroll--------------------------------------
+// Unroll the loop body one step - make each trip do 2 iterations.
+void PhaseIdealLoop::do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip ) {
+assert( LoopUnrollLimit, "" );
+#ifndef PRODUCT
+if( PrintOpto && VerifyLoopOptimizations ) {
+tty->print("Unrolling ");
+loop->dump_head();
+}
+#endif
+CountedLoopNode *loop_head = loop->_head->as_CountedLoop();
+CountedLoopEndNode *loop_end = loop_head->loopexit();
+assert( loop_end, "" );
+// Remember loop node count before unrolling to detect
+// if rounds of unroll,optimize are making progress
+loop_head->set_node_count_before_unroll(loop->_body.size());
+Node *ctrl  = loop_head->in(LoopNode::EntryControl);
+Node *limit = loop_head->limit();
+Node *init  = loop_head->init_trip();
+Node *strid = loop_head->stride();
+Node *opaq = NULL;
+if( adjust_min_trip ) {       // If not maximally unrolling, need adjustment
+assert( loop_head->is_main_loop(), "" );
+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, "" );
+opaq = cmp->in(2);
+// Occasionally it's possible for a pre-loop Opaque1 node to be
+// optimized away and then another round of loop opts attempted.
+// We can not optimize this particular loop in that case.
+if( opaq->Opcode() != Op_Opaque1 )
+return;                   // Cannot find pre-loop!  Bail out!
+}
+C->set_major_progress();
+// Adjust max trip count. The trip count is intentionally rounded
+// down here (e.g. 15-> 7-> 3-> 1) because if we unwittingly over-unroll,
+// the main, unrolled, part of the loop will never execute as it is protected
+// by the min-trip test.  See bug 4834191 for a case where we over-unrolled
+// and later determined that part of the unrolled loop was dead.
+loop_head->set_trip_count(loop_head->trip_count() / 2);
+// Double the count of original iterations in the unrolled loop body.
+loop_head->double_unrolled_count();
+// -----------
+// Step 2: Cut back the trip counter for an unroll amount of 2.
+// Loop will normally trip (limit - init)/stride_con.  Since it's a
+// CountedLoop this is exact (stride divides limit-init exactly).
+// We are going to double the loop body, so we want to knock off any
+// odd iteration: (trip_cnt & ~1).  Then back compute a new limit.
+Node *span = new (C, 3) SubINode( limit, init );
+register_new_node( span, ctrl );
+Node *trip = new (C, 3) DivINode( 0, span, strid );
+register_new_node( trip, ctrl );
+Node *mtwo = _igvn.intcon(-2);
+set_ctrl(mtwo, C->root());
+Node *rond = new (C, 3) AndINode( trip, mtwo );
+register_new_node( rond, ctrl );
+Node *spn2 = new (C, 3) MulINode( rond, strid );
+register_new_node( spn2, ctrl );
+Node *lim2 = new (C, 3) AddINode( spn2, init );
+register_new_node( lim2, ctrl );
+// Hammer in the new limit
+Node *ctrl2 = loop_end->in(0);
+Node *cmp2 = new (C, 3) CmpINode( loop_head->incr(), lim2 );
+register_new_node( cmp2, ctrl2 );
+Node *bol2 = new (C, 2) BoolNode( cmp2, loop_end->test_trip() );
+register_new_node( bol2, ctrl2 );
+_igvn.hash_delete(loop_end);
+loop_end->set_req(CountedLoopEndNode::TestValue, bol2);
+// Step 3: Find the min-trip test guaranteed before a 'main' loop.
+// Make it a 1-trip test (means at least 2 trips).
+if( adjust_min_trip ) {
+// Guard test uses an 'opaque' node which is not shared.  Hence I
+// can edit it's inputs directly.  Hammer in the new limit for the
+// minimum-trip guard.
+assert( opaq->outcnt() == 1, "" );
+_igvn.hash_delete(opaq);
+opaq->set_req(1, lim2);
+}
+// ---------
+// Step 4: Clone the loop body.  Move it inside the loop.  This loop body
+// represents the odd iterations; since the loop trips an even number of
+// times its backedge is never taken.  Kill the backedge.
+uint dd = dom_depth(loop_head);
+clone_loop( loop, old_new, dd );
+// Make backedges of the clone equal to backedges of the original.
+// Make the fall-in from the original come from the fall-out of the clone.
+for (DUIterator_Fast jmax, j = loop_head->fast_outs(jmax); j < jmax; j++) {
+Node* phi = loop_head->fast_out(j);
+if( phi->is_Phi() && phi->in(0) == loop_head && phi->outcnt() > 0 ) {
+Node *newphi = old_new[phi->_idx];
+_igvn.hash_delete( phi );
+_igvn.hash_delete( newphi );
+phi   ->set_req(LoopNode::   EntryControl, newphi->in(LoopNode::LoopBackControl));
+newphi->set_req(LoopNode::LoopBackControl, phi   ->in(LoopNode::LoopBackControl));
+phi   ->set_req(LoopNode::LoopBackControl, C->top());
+}
+}
+Node *clone_head = old_new[loop_head->_idx];
+_igvn.hash_delete( clone_head );
+loop_head ->set_req(LoopNode::   EntryControl, clone_head->in(LoopNode::LoopBackControl));
+clone_head->set_req(LoopNode::LoopBackControl, loop_head ->in(LoopNode::LoopBackControl));
+loop_head ->set_req(LoopNode::LoopBackControl, C->top());
+loop->_head = clone_head;     // New loop header
+set_idom(loop_head,  loop_head ->in(LoopNode::EntryControl), dd);
+set_idom(clone_head, clone_head->in(LoopNode::EntryControl), dd);
+// Kill the clone's backedge
+Node *newcle = old_new[loop_end->_idx];
+_igvn.hash_delete( newcle );
+Node *one = _igvn.intcon(1);
+set_ctrl(one, C->root());
+newcle->set_req(1, one);
+// Force clone into same loop body
+uint max = loop->_body.size();
+for( uint k = 0; k < max; k++ ) {
+Node *old = loop->_body.at(k);
+Node *nnn = old_new[old->_idx];
+loop->_body.push(nnn);
+if (!has_ctrl(old))
+set_loop(nnn, loop);
+}
+}
+//------------------------------do_maximally_unroll----------------------------
+void PhaseIdealLoop::do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new ) {
+CountedLoopNode *cl = loop->_head->as_CountedLoop();
+assert( cl->trip_count() > 0, "");
+// If loop is tripping an odd number of times, peel odd iteration
+if( (cl->trip_count() & 1) == 1 ) {
+do_peeling( loop, old_new );
+}
+// Now its tripping an even number of times remaining.  Double loop body.
+// Do not adjust pre-guards; they are not needed and do not exist.
+if( cl->trip_count() > 0 ) {
+do_unroll( loop, old_new, false );
+}
+}
+//------------------------------dominates_backedge---------------------------------
+// Returns true if ctrl is executed on every complete iteration
+bool IdealLoopTree::dominates_backedge(Node* ctrl) {
+assert(ctrl->is_CFG(), "must be control");
+Node* backedge = _head->as_Loop()->in(LoopNode::LoopBackControl);
+return _phase->dom_lca_internal(ctrl, backedge) == ctrl;
+}
+//------------------------------add_constraint---------------------------------
+// Constrain the main loop iterations so the condition:
+//    scale_con * I + offset  <  limit
+// always holds true.  That is, either increase the number of iterations in
+// the pre-loop or the post-loop until the condition holds true in the main
+// loop.  Stride, scale, offset and limit are all loop invariant.  Further,
+// stride and scale are constants (offset and limit often are).
+void PhaseIdealLoop::add_constraint( int stride_con, int scale_con, Node *offset, Node *limit, Node *pre_ctrl, Node **pre_limit, Node **main_limit ) {
+// Compute "I :: (limit-offset)/scale_con"
+Node *con = new (C, 3) SubINode( limit, offset );
+register_new_node( con, pre_ctrl );
+Node *scale = _igvn.intcon(scale_con);
+set_ctrl(scale, C->root());
+Node *X = new (C, 3) DivINode( 0, con, scale );
+register_new_node( X, pre_ctrl );
+// For positive stride, the pre-loop limit always uses a MAX function
+// and the main loop a MIN function.  For negative stride these are
+// reversed.
+// Also for positive stride*scale the affine function is increasing, so the
+// pre-loop must check for underflow and the post-loop for overflow.
+// Negative stride*scale reverses this; pre-loop checks for overflow and
+// post-loop for underflow.
+if( stride_con*scale_con > 0 ) {
+// Compute I < (limit-offset)/scale_con
+// Adjust main-loop last iteration to be MIN/MAX(main_loop,X)
+*main_limit = (stride_con > 0)
+? (Node*)(new (C, 3) MinINode( *main_limit, X ))
+: (Node*)(new (C, 3) MaxINode( *main_limit, X ));
+register_new_node( *main_limit, pre_ctrl );
+} else {
+// Compute (limit-offset)/scale_con + SGN(-scale_con) <= I
+// Add the negation of the main-loop constraint to the pre-loop.
+// See footnote [++] below for a derivation of the limit expression.
+Node *incr = _igvn.intcon(scale_con > 0 ? -1 : 1);
+set_ctrl(incr, C->root());
+Node *adj = new (C, 3) AddINode( X, incr );
+register_new_node( adj, pre_ctrl );
+*pre_limit = (scale_con > 0)
+? (Node*)new (C, 3) MinINode( *pre_limit, adj )
+: (Node*)new (C, 3) MaxINode( *pre_limit, adj );
+register_new_node( *pre_limit, pre_ctrl );
+//   [++] Here's the algebra that justifies the pre-loop limit expression:
+//
+//   NOT( scale_con * I + offset  <  limit )
+//      ==
+//   scale_con * I + offset  >=  limit
+//      ==
+//   SGN(scale_con) * I  >=  (limit-offset)/|scale_con|
+//      ==
+//   (limit-offset)/|scale_con|   <=  I * SGN(scale_con)
+//      ==
+//   (limit-offset)/|scale_con|-1  <  I * SGN(scale_con)
+//      ==
+//   ( if (scale_con > 0) /*common case*/
+//       (limit-offset)/scale_con - 1  <  I
+//     else
+//       (limit-offset)/scale_con + 1  >  I
+//    )
+//   ( if (scale_con > 0) /*common case*/
+//       (limit-offset)/scale_con + SGN(-scale_con)  <  I
+//     else
+//       (limit-offset)/scale_con + SGN(-scale_con)  >  I
+}
+}
+//------------------------------is_scaled_iv---------------------------------
+// Return true if exp is a constant times an induction var
+bool PhaseIdealLoop::is_scaled_iv(Node* exp, Node* iv, int* p_scale) {
+if (exp == iv) {
+if (p_scale != NULL) {
+*p_scale = 1;
+}
+return true;
+}
+int opc = exp->Opcode();
+if (opc == Op_MulI) {
+if (exp->in(1) == iv && exp->in(2)->is_Con()) {
+if (p_scale != NULL) {
+*p_scale = exp->in(2)->get_int();
+}
+return true;
+}
+if (exp->in(2) == iv && exp->in(1)->is_Con()) {
+if (p_scale != NULL) {
+*p_scale = exp->in(1)->get_int();
+}
+return true;
+}
+} else if (opc == Op_LShiftI) {
+if (exp->in(1) == iv && exp->in(2)->is_Con()) {
+if (p_scale != NULL) {
+*p_scale = 1 << exp->in(2)->get_int();
+}
+return true;
+}
+}
+return false;
+}
+//-----------------------------is_scaled_iv_plus_offset------------------------------
+// Return true if exp is a simple induction variable expression: k1*iv + (invar + k2)
+bool PhaseIdealLoop::is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth) {
+if (is_scaled_iv(exp, iv, p_scale)) {
+if (p_offset != NULL) {
+Node *zero = _igvn.intcon(0);
+set_ctrl(zero, C->root());
+*p_offset = zero;
+}
+return true;
+}
+int opc = exp->Opcode();
+if (opc == Op_AddI) {
+if (is_scaled_iv(exp->in(1), iv, p_scale)) {
+if (p_offset != NULL) {
+*p_offset = exp->in(2);
+}
+return true;
+}
+if (exp->in(2)->is_Con()) {
+Node* offset2 = NULL;
+if (depth < 2 &&
+is_scaled_iv_plus_offset(exp->in(1), iv, p_scale,
+p_offset != NULL ? &offset2 : NULL, depth+1)) {
+if (p_offset != NULL) {
+Node *ctrl_off2 = get_ctrl(offset2);
+Node* offset = new (C, 3) AddINode(offset2, exp->in(2));
+register_new_node(offset, ctrl_off2);
+*p_offset = offset;
+}
+return true;
+}
+}
+} else if (opc == Op_SubI) {
+if (is_scaled_iv(exp->in(1), iv, p_scale)) {
+if (p_offset != NULL) {
+Node *zero = _igvn.intcon(0);
+set_ctrl(zero, C->root());
+Node *ctrl_off = get_ctrl(exp->in(2));
+Node* offset = new (C, 3) SubINode(zero, exp->in(2));
+register_new_node(offset, ctrl_off);
+*p_offset = offset;
+}
+return true;
+}
+if (is_scaled_iv(exp->in(2), iv, p_scale)) {
+if (p_offset != NULL) {
+*p_scale *= -1;
+*p_offset = exp->in(1);
+}
+return true;
+}
+}
+return false;
+}
+//------------------------------do_range_check---------------------------------
+// Eliminate range-checks and other trip-counter vs loop-invariant tests.
+void PhaseIdealLoop::do_range_check( IdealLoopTree *loop, Node_List &old_new ) {
+#ifndef PRODUCT
+if( PrintOpto && VerifyLoopOptimizations ) {
+tty->print("Range Check Elimination ");
+loop->dump_head();
+}
+#endif
+assert( RangeCheckElimination, "" );
+CountedLoopNode *cl = loop->_head->as_CountedLoop();
+assert( cl->is_main_loop(), "" );
+// Find the trip counter; we are iteration splitting based on it
+Node *trip_counter = cl->phi();
+// Find the main loop limit; we will trim it's iterations
+// to not ever trip end tests
+Node *main_limit = cl->limit();
+// Find the pre-loop limit; we will expand it's iterations to
+// not ever trip low tests.
+Node *ctrl  = cl->in(LoopNode::EntryControl);
+assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
+Node *iffm = ctrl->in(0);
+assert( iffm->Opcode() == Op_If, "" );
+Node *p_f = iffm->in(0);
+assert( p_f->Opcode() == Op_IfFalse, "" );
+CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();
+assert( pre_end->loopnode()->is_pre_loop(), "" );
+Node *pre_opaq1 = pre_end->limit();
+// Occasionally it's possible for a pre-loop Opaque1 node to be
+// optimized away and then another round of loop opts attempted.
+// We can not optimize this particular loop in that case.
+if( pre_opaq1->Opcode() != Op_Opaque1 )
+return;
+Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;
+Node *pre_limit = pre_opaq->in(1);
+// Where do we put new limit calculations
+Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);
+// Ensure the original loop limit is available from the
+// pre-loop Opaque1 node.
+Node *orig_limit = pre_opaq->original_loop_limit();
+if( orig_limit == NULL || _igvn.type(orig_limit) == Type::TOP )
+return;
+// Need to find the main-loop zero-trip guard
+Node *bolzm = iffm->in(1);
+assert( bolzm->Opcode() == Op_Bool, "" );
+Node *cmpzm = bolzm->in(1);
+assert( cmpzm->is_Cmp(), "" );
+Node *opqzm = cmpzm->in(2);
+if( opqzm->Opcode() != Op_Opaque1 )
+return;
+assert( opqzm->in(1) == main_limit, "do not understand situation" );
+// Must know if its a count-up or count-down loop
+// protect against stride not being a constant
+if ( !cl->stride_is_con() ) {
+return;
+}
+int stride_con = cl->stride_con();
+Node *zero = _igvn.intcon(0);
+Node *one  = _igvn.intcon(1);
+set_ctrl(zero, C->root());
+set_ctrl(one,  C->root());
+// Range checks that do not dominate the loop backedge (ie.
+// conditionally executed) can lengthen the pre loop limit beyond
+// the original loop limit. To prevent this, the pre limit is
+// (for stride > 0) MINed with the original loop limit (MAXed
+// stride < 0) when some range_check (rc) is conditionally
+// executed.
+bool conditional_rc = false;
+// Check loop body for tests of trip-counter plus loop-invariant vs
+// loop-invariant.
+for( uint i = 0; i < loop->_body.size(); i++ ) {
+Node *iff = loop->_body[i];
+if( iff->Opcode() == Op_If ) { // Test?
+// Test is an IfNode, has 2 projections.  If BOTH are in the loop
+// we need loop unswitching instead of iteration splitting.
+Node *exit = loop->is_loop_exit(iff);
+if( !exit ) continue;
+int flip = (exit->Opcode() == Op_IfTrue) ? 1 : 0;
+// Get boolean condition to test
+Node *i1 = iff->in(1);
+if( !i1->is_Bool() ) continue;
+BoolNode *bol = i1->as_Bool();
+BoolTest b_test = bol->_test;
+// Flip sense of test if exit condition is flipped
+if( flip )
+b_test = b_test.negate();
+// Get compare
+Node *cmp = bol->in(1);
+// Look for trip_counter + offset vs limit
+Node *rc_exp = cmp->in(1);
+Node *limit  = cmp->in(2);
+jint scale_con= 1;        // Assume trip counter not scaled
+Node *limit_c = get_ctrl(limit);
+if( loop->is_member(get_loop(limit_c) ) ) {
+// Compare might have operands swapped; commute them
+b_test = b_test.commute();
+rc_exp = cmp->in(2);
+limit  = cmp->in(1);
+limit_c = get_ctrl(limit);
+if( loop->is_member(get_loop(limit_c) ) )
+continue;             // Both inputs are loop varying; cannot RCE
+}
+// Here we know 'limit' is loop invariant
+// 'limit' maybe pinned below the zero trip test (probably from a
+// previous round of rce), in which case, it can't be used in the
+// zero trip test expression which must occur before the zero test's if.
+if( limit_c == ctrl ) {
+continue;  // Don't rce this check but continue looking for other candidates.
+}
+// Check for scaled induction variable plus an offset
+Node *offset = NULL;
+if (!is_scaled_iv_plus_offset(rc_exp, trip_counter, &scale_con, &offset)) {
+continue;
+}
+Node *offset_c = get_ctrl(offset);
+if( loop->is_member( get_loop(offset_c) ) )
+continue;               // Offset is not really loop invariant
+// Here we know 'offset' is loop invariant.
+// As above for the 'limit', the 'offset' maybe pinned below the
+// zero trip test.
+if( offset_c == ctrl ) {
+continue; // Don't rce this check but continue looking for other candidates.
+}
+// At this point we have the expression as:
+//   scale_con * trip_counter + offset :: limit
+// where scale_con, offset and limit are loop invariant.  Trip_counter
+// monotonically increases by stride_con, a constant.  Both (or either)
+// stride_con and scale_con can be negative which will flip about the
+// sense of the test.
+// Adjust pre and main loop limits to guard the correct iteration set
+if( cmp->Opcode() == Op_CmpU ) {// Unsigned compare is really 2 tests
+if( b_test._test == BoolTest::lt ) { // Range checks always use lt
+// The overflow limit: scale*I+offset < limit
+add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
+// The underflow limit: 0 <= scale*I+offset.
+// Some math yields: -scale*I-(offset+1) < 0
+Node *plus_one = new (C, 3) AddINode( offset, one );
+register_new_node( plus_one, pre_ctrl );
+Node *neg_offset = new (C, 3) SubINode( zero, plus_one );
+register_new_node( neg_offset, pre_ctrl );
+add_constraint( stride_con, -scale_con, neg_offset, zero, pre_ctrl, &pre_limit, &main_limit );
+if (!conditional_rc) {
+conditional_rc = !loop->dominates_backedge(iff);
+}
+} else {
+#ifndef PRODUCT
+if( PrintOpto )
+tty->print_cr("missed RCE opportunity");
+#endif
+continue;             // In release mode, ignore it
+}
+} else {                  // Otherwise work on normal compares
+switch( b_test._test ) {
+case BoolTest::ge:      // Convert X >= Y to -X <= -Y
+scale_con = -scale_con;
+offset = new (C, 3) SubINode( zero, offset );
+register_new_node( offset, pre_ctrl );
+limit  = new (C, 3) SubINode( zero, limit  );
+register_new_node( limit, pre_ctrl );
+// Fall into LE case
+case BoolTest::le:      // Convert X <= Y to X < Y+1
+limit = new (C, 3) AddINode( limit, one );
+register_new_node( limit, pre_ctrl );
+// Fall into LT case
+case BoolTest::lt:
+add_constraint( stride_con, scale_con, offset, limit, pre_ctrl, &pre_limit, &main_limit );
+if (!conditional_rc) {
+conditional_rc = !loop->dominates_backedge(iff);
+}
+break;
+default:
+#ifndef PRODUCT
+if( PrintOpto )
+tty->print_cr("missed RCE opportunity");
+#endif
+continue;             // Unhandled case
+}
+}
+// Kill the eliminated test
+C->set_major_progress();
+Node *kill_con = _igvn.intcon( 1-flip );
+set_ctrl(kill_con, C->root());
+_igvn.hash_delete(iff);
+iff->set_req(1, kill_con);
+_igvn._worklist.push(iff);
+// Find surviving projection
+assert(iff->is_If(), "");
+ProjNode* dp = ((IfNode*)iff)->proj_out(1-flip);
+// Find loads off the surviving projection; remove their control edge
+for (DUIterator_Fast imax, i = dp->fast_outs(imax); i < imax; i++) {
+Node* cd = dp->fast_out(i); // Control-dependent node
+if( cd->is_Load() ) {   // Loads can now float around in the loop
+_igvn.hash_delete(cd);
+// Allow the load to float around in the loop, or before it
+// but NOT before the pre-loop.
+cd->set_req(0, ctrl);   // ctrl, not NULL
+_igvn._worklist.push(cd);
+--i;
+--imax;
+}
+}
+} // End of is IF
+}
+// Update loop limits
+if (conditional_rc) {
+pre_limit = (stride_con > 0) ? (Node*)new (C,3) MinINode(pre_limit, orig_limit)
+: (Node*)new (C,3) MaxINode(pre_limit, orig_limit);
+register_new_node(pre_limit, pre_ctrl);
+}
+_igvn.hash_delete(pre_opaq);
+pre_opaq->set_req(1, pre_limit);
+// Note:: we are making the main loop limit no longer precise;
+// need to round up based on stride.
+if( stride_con != 1 && stride_con != -1 ) { // Cutout for common case
+// "Standard" round-up logic:  ([main_limit-init+(y-1)]/y)*y+init
+// Hopefully, compiler will optimize for powers of 2.
+Node *ctrl = get_ctrl(main_limit);
+Node *stride = cl->stride();
+Node *init = cl->init_trip();
+Node *span = new (C, 3) SubINode(main_limit,init);
+register_new_node(span,ctrl);
+Node *rndup = _igvn.intcon(stride_con + ((stride_con>0)?-1:1));
+Node *add = new (C, 3) AddINode(span,rndup);
+register_new_node(add,ctrl);
+Node *div = new (C, 3) DivINode(0,add,stride);
+register_new_node(div,ctrl);
+Node *mul = new (C, 3) MulINode(div,stride);
+register_new_node(mul,ctrl);
+Node *newlim = new (C, 3) AddINode(mul,init);
+register_new_node(newlim,ctrl);
+main_limit = newlim;
+}
+Node *main_cle = cl->loopexit();
+Node *main_bol = main_cle->in(1);
+// Hacking loop bounds; need private copies of exit test
+if( main_bol->outcnt() > 1 ) {// BoolNode shared?
+_igvn.hash_delete(main_cle);
+main_bol = main_bol->clone();// Clone a private BoolNode
+register_new_node( main_bol, main_cle->in(0) );
+main_cle->set_req(1,main_bol);
+}
+Node *main_cmp = main_bol->in(1);
+if( main_cmp->outcnt() > 1 ) { // CmpNode shared?
+_igvn.hash_delete(main_bol);
+main_cmp = main_cmp->clone();// Clone a private CmpNode
+register_new_node( main_cmp, main_cle->in(0) );
+main_bol->set_req(1,main_cmp);
+}
+// Hack the now-private loop bounds
+_igvn.hash_delete(main_cmp);
+main_cmp->set_req(2, main_limit);
+_igvn._worklist.push(main_cmp);
+// The OpaqueNode is unshared by design
+_igvn.hash_delete(opqzm);
+assert( opqzm->outcnt() == 1, "cannot hack shared node" );
+opqzm->set_req(1,main_limit);
+_igvn._worklist.push(opqzm);
+}
+//------------------------------DCE_loop_body----------------------------------
+// Remove simplistic dead code from loop body
+void IdealLoopTree::DCE_loop_body() {
+for( uint i = 0; i < _body.size(); i++ )
+if( _body.at(i)->outcnt() == 0 )
+_body.map( i--, _body.pop() );
+}
+//------------------------------adjust_loop_exit_prob--------------------------
+// Look for loop-exit tests with the 50/50 (or worse) guesses from the parsing stage.
+// Replace with a 1-in-10 exit guess.
+void IdealLoopTree::adjust_loop_exit_prob( PhaseIdealLoop *phase ) {
+Node *test = tail();
+while( test != _head ) {
+uint top = test->Opcode();
+if( top == Op_IfTrue || top == Op_IfFalse ) {
+int test_con = ((ProjNode*)test)->_con;
+assert(top == (uint)(test_con? Op_IfTrue: Op_IfFalse), "sanity");
+IfNode *iff = test->in(0)->as_If();
+if( iff->outcnt() == 2 ) {        // Ignore dead tests
+Node *bol = iff->in(1);
+if( bol && bol->req() > 1 && bol->in(1) &&
+((bol->in(1)->Opcode() == Op_StorePConditional ) ||
+(bol->in(1)->Opcode() == Op_StoreLConditional ) ||
+(bol->in(1)->Opcode() == Op_CompareAndSwapI ) ||
+(bol->in(1)->Opcode() == Op_CompareAndSwapL ) ||
+(bol->in(1)->Opcode() == Op_CompareAndSwapP )))
+return;               // Allocation loops RARELY take backedge
+// Find the OTHER exit path from the IF
+Node* ex = iff->proj_out(1-test_con);
+float p = iff->_prob;
+if( !phase->is_member( this, ex ) && iff->_fcnt == COUNT_UNKNOWN ) {
+if( top == Op_IfTrue ) {
+if( p < (PROB_FAIR + PROB_UNLIKELY_MAG(3))) {
+iff->_prob = PROB_STATIC_FREQUENT;
+}
+} else {
+if( p > (PROB_FAIR - PROB_UNLIKELY_MAG(3))) {
+iff->_prob = PROB_STATIC_INFREQUENT;
+}
+}
+}
+}
+}
+test = phase->idom(test);
+}
+}
+//------------------------------policy_do_remove_empty_loop--------------------
+// Micro-benchmark spamming.  Policy is to always remove empty loops.
+// The 'DO' part is to replace the trip counter with the value it will
+// have on the last iteration.  This will break the loop.
+bool IdealLoopTree::policy_do_remove_empty_loop( PhaseIdealLoop *phase ) {
+// Minimum size must be empty loop
+if( _body.size() > 7/*number of nodes in an empty loop*/ ) return false;
+if( !_head->is_CountedLoop() ) return false;     // Dead loop
+CountedLoopNode *cl = _head->as_CountedLoop();
+if( !cl->loopexit() ) return false; // Malformed loop
+if( !phase->is_member(this,phase->get_ctrl(cl->loopexit()->in(CountedLoopEndNode::TestValue)) ) )
+return false;             // Infinite loop
+#ifndef PRODUCT
+if( PrintOpto )
+tty->print_cr("Removing empty loop");
+#endif
+#ifdef ASSERT
+// Ensure only one phi which is the iv.
+Node* iv = NULL;
+for (DUIterator_Fast imax, i = cl->fast_outs(imax); i < imax; i++) {
+Node* n = cl->fast_out(i);
+if (n->Opcode() == Op_Phi) {
+assert(iv == NULL, "Too many phis" );
+iv = n;
+}
+}
+assert(iv == cl->phi(), "Wrong phi" );
+#endif
+// Replace the phi at loop head with the final value of the last
+// iteration.  Then the CountedLoopEnd will collapse (backedge never
+// taken) and all loop-invariant uses of the exit values will be correct.
+Node *phi = cl->phi();
+Node *final = new (phase->C, 3) SubINode( cl->limit(), cl->stride() );
+phase->register_new_node(final,cl->in(LoopNode::EntryControl));
+phase->_igvn.hash_delete(phi);
+phase->_igvn.subsume_node(phi,final);
+phase->C->set_major_progress();
+return true;
+}
+//=============================================================================
+//------------------------------iteration_split_impl---------------------------
+void IdealLoopTree::iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new ) {
+// Check and remove empty loops (spam micro-benchmarks)
+if( policy_do_remove_empty_loop(phase) )
+return;                     // Here we removed an empty loop
+bool should_peel = policy_peeling(phase); // Should we peel?
+bool should_unswitch = policy_unswitching(phase);
+// Non-counted loops may be peeled; exactly 1 iteration is peeled.
+// This removes loop-invariant tests (usually null checks).
+if( !_head->is_CountedLoop() ) { // Non-counted loop
+if (PartialPeelLoop && phase->partial_peel(this, old_new)) {
+return;
+}
+if( should_peel ) {            // Should we peel?
+#ifndef PRODUCT
+if (PrintOpto) tty->print_cr("should_peel");
+#endif
+phase->do_peeling(this,old_new);
+} else if( should_unswitch ) {
+phase->do_unswitching(this, old_new);
+}
+return;
+}
+CountedLoopNode *cl = _head->as_CountedLoop();
+if( !cl->loopexit() ) return; // Ignore various kinds of broken loops
+// Do nothing special to pre- and post- loops
+if( cl->is_pre_loop() || cl->is_post_loop() ) return;
+// Compute loop trip count from profile data
+compute_profile_trip_cnt(phase);
+// Before attempting fancy unrolling, RCE or alignment, see if we want
+// to completely unroll this loop or do loop unswitching.
+if( cl->is_normal_loop() ) {
+bool should_maximally_unroll =  policy_maximally_unroll(phase);
+if( should_maximally_unroll ) {
+// Here we did some unrolling and peeling.  Eventually we will
+// completely unroll this loop and it will no longer be a loop.
+phase->do_maximally_unroll(this,old_new);
+return;
+}
+if (should_unswitch) {
+phase->do_unswitching(this, old_new);
+return;
+}
+}
+// Counted loops may be peeled, may need some iterations run up
+// front for RCE, and may want to align loop refs to a cache
+// line.  Thus we clone a full loop up front whose trip count is
+// at least 1 (if peeling), but may be several more.
+// The main loop will start cache-line aligned with at least 1
+// iteration of the unrolled body (zero-trip test required) and
+// will have some range checks removed.
+// A post-loop will finish any odd iterations (leftover after
+// unrolling), plus any needed for RCE purposes.
+bool should_unroll = policy_unroll(phase);
+bool should_rce = policy_range_check(phase);
+bool should_align = policy_align(phase);
+// If not RCE'ing (iteration splitting) or Aligning, then we do not
+// need a pre-loop.  We may still need to peel an initial iteration but
+// we will not be needing an unknown number of pre-iterations.
+//
+// Basically, if may_rce_align reports FALSE first time through,
+// we will not be able to later do RCE or Aligning on this loop.
+bool may_rce_align = !policy_peel_only(phase) || should_rce || should_align;
+// If we have any of these conditions (RCE, alignment, unrolling) met, then
+// we switch to the pre-/main-/post-loop model.  This model also covers
+// peeling.
+if( should_rce || should_align || should_unroll ) {
+if( cl->is_normal_loop() )  // Convert to 'pre/main/post' loops
+phase->insert_pre_post_loops(this,old_new, !may_rce_align);
+// Adjust the pre- and main-loop limits to let the pre and post loops run
+// with full checks, but the main-loop with no checks.  Remove said
+// checks from the main body.
+if( should_rce )
+phase->do_range_check(this,old_new);
+// Double loop body for unrolling.  Adjust the minimum-trip test (will do
+// twice as many iterations as before) and the main body limit (only do
+// an even number of trips).  If we are peeling, we might enable some RCE
+// and we'd rather unroll the post-RCE'd loop SO... do not unroll if
+// peeling.
+if( should_unroll && !should_peel )
+phase->do_unroll(this,old_new, true);
+// Adjust the pre-loop limits to align the main body
+// iterations.
+if( should_align )
+Unimplemented();
+} else {                      // Else we have an unchanged counted loop
+if( should_peel )           // Might want to peel but do nothing else
+phase->do_peeling(this,old_new);
+}
+}
+//=============================================================================
+//------------------------------iteration_split--------------------------------
+void IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) {
+// Recursively iteration split nested loops
+if( _child ) _child->iteration_split( phase, old_new );
+// Clean out prior deadwood
+DCE_loop_body();
+// Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
+// Replace with a 1-in-10 exit guess.
+if( _parent /*not the root loop*/ &&
+!_irreducible &&
+// Also ignore the occasional dead backedge
+!tail()->is_top() ) {
+adjust_loop_exit_prob(phase);
+}
+// Gate unrolling, RCE and peeling efforts.
+if( !_child &&                // If not an inner loop, do not split
+!_irreducible &&
+!tail()->is_top() ) {     // Also ignore the occasional dead backedge
+if (!_has_call) {
+iteration_split_impl( phase, old_new );
+} else if (policy_unswitching(phase)) {
+phase->do_unswitching(this, old_new);
+}
+}
+// Minor offset re-organization to remove loop-fallout uses of
+// trip counter.
+if( _head->is_CountedLoop() ) phase->reorg_offsets( this );
+if( _next ) _next->iteration_split( phase, old_new );
+}

Mercurial > hg > graal-compiler

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