Mercurial > hg > truffle
view src/share/vm/opto/loopTransform.cpp @ 690:d142f1feeed5
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author | acorn |
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date | Sun, 29 Mar 2009 18:19:05 -0400 |
parents | 98cb887364d3 |
children | 273b2358ef1a |
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/* * Copyright 2000-2008 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 reassociate_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 guarantees 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); // Reduce the post-loop trip count. CountedLoopEndNode* post_end = old_new[main_end ->_idx]->as_CountedLoopEnd(); post_end->_prob = PROB_FAIR; // 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(C, 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]; // Reduce the pre-loop trip count. pre_end->_prob = PROB_FAIR; // 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(C, 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 (assume the main-loop is executed always). IfNode *min_iff = new (C, 2) IfNode( new_pre_exit, min_bol, PROB_ALWAYS, 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(C, 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); } loop->record_for_igvn(); } //------------------------------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_StoreIConditional ) || (bol->in(1)->Opcode() == Op_StoreLConditional ) || (bol->in(1)->Opcode() == Op_CompareAndSwapI ) || (bol->in(1)->Opcode() == Op_CompareAndSwapL ) || (bol->in(1)->Opcode() == Op_CompareAndSwapP ) || (bol->in(1)->Opcode() == Op_CompareAndSwapN ))) 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--------------------------- bool 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 true; // 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)) { // Partial peel succeeded so terminate this round of loop opts return false; } 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 true; } CountedLoopNode *cl = _head->as_CountedLoop(); if( !cl->loopexit() ) return true; // Ignore various kinds of broken loops // Do nothing special to pre- and post- loops if( cl->is_pre_loop() || cl->is_post_loop() ) return true; // 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 true; } if (should_unswitch) { phase->do_unswitching(this, old_new); return true; } } // 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); } return true; } //============================================================================= //------------------------------iteration_split-------------------------------- bool IdealLoopTree::iteration_split( PhaseIdealLoop *phase, Node_List &old_new ) { // Recursively iteration split nested loops if( _child && !_child->iteration_split( phase, old_new )) return false; // 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 && _allow_optimizations && !tail()->is_top() ) { // Also ignore the occasional dead backedge if (!_has_call) { if (!iteration_split_impl( phase, old_new )) { return false; } } 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 )) return false; return true; }