| /* |
| * 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 ); |
| } |