--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/opto/loopTransform.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1729 @@
+/*
+ * 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 );
+}