diff -r fd16c54261b3 -r 489c9b5090e2 hotspot/src/share/vm/opto/loopTransform.cpp --- /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 ); +}