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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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.
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package org.graalvm.compiler.phases.common;

import static org.graalvm.compiler.core.common.GraalOptions.OptEliminateGuards;
import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_IGNORED;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_IGNORED;
import static org.graalvm.compiler.phases.common.LoweringPhase.ProcessBlockState.ST_ENTER;
import static org.graalvm.compiler.phases.common.LoweringPhase.ProcessBlockState.ST_ENTER_ALWAYS_REACHED;
import static org.graalvm.compiler.phases.common.LoweringPhase.ProcessBlockState.ST_LEAVE;
import static org.graalvm.compiler.phases.common.LoweringPhase.ProcessBlockState.ST_PROCESS;
import static org.graalvm.compiler.phases.common.LoweringPhase.ProcessBlockState.ST_PROCESS_ALWAYS_REACHED;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

import org.graalvm.compiler.core.common.spi.ConstantFieldProvider;
import org.graalvm.compiler.core.common.type.StampFactory;
import org.graalvm.compiler.debug.DebugCloseable;
import org.graalvm.compiler.debug.GraalError;
import org.graalvm.compiler.graph.Graph.Mark;
import org.graalvm.compiler.graph.Node;
import org.graalvm.compiler.graph.NodeBitMap;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.iterators.NodeIterable;
import org.graalvm.compiler.nodeinfo.InputType;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.BeginNode;
import org.graalvm.compiler.nodes.FixedGuardNode;
import org.graalvm.compiler.nodes.FixedNode;
import org.graalvm.compiler.nodes.FixedWithNextNode;
import org.graalvm.compiler.nodes.GuardNode;
import org.graalvm.compiler.nodes.LogicNode;
import org.graalvm.compiler.nodes.StructuredGraph;
import org.graalvm.compiler.nodes.StructuredGraph.ScheduleResult;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.calc.FloatingNode;
import org.graalvm.compiler.nodes.cfg.Block;
import org.graalvm.compiler.nodes.extended.AnchoringNode;
import org.graalvm.compiler.nodes.extended.GuardedNode;
import org.graalvm.compiler.nodes.extended.GuardingNode;
import org.graalvm.compiler.nodes.spi.Lowerable;
import org.graalvm.compiler.nodes.spi.LoweringProvider;
import org.graalvm.compiler.nodes.spi.LoweringTool;
import org.graalvm.compiler.nodes.spi.NodeCostProvider;
import org.graalvm.compiler.nodes.spi.Replacements;
import org.graalvm.compiler.nodes.spi.StampProvider;
import org.graalvm.compiler.phases.BasePhase;
import org.graalvm.compiler.phases.Phase;
import org.graalvm.compiler.phases.schedule.SchedulePhase;
import org.graalvm.compiler.phases.tiers.PhaseContext;

import jdk.vm.ci.meta.ConstantReflectionProvider;
import jdk.vm.ci.meta.DeoptimizationAction;
import jdk.vm.ci.meta.DeoptimizationReason;
import jdk.vm.ci.meta.JavaConstant;
import jdk.vm.ci.meta.MetaAccessProvider;

Processes all Lowerable nodes to do their lowering.
/** * Processes all {@link Lowerable} nodes to do their lowering. */
public class LoweringPhase extends BasePhase<PhaseContext> { @NodeInfo(cycles = CYCLES_IGNORED, size = SIZE_IGNORED) static final class DummyGuardHandle extends ValueNode implements GuardedNode { public static final NodeClass<DummyGuardHandle> TYPE = NodeClass.create(DummyGuardHandle.class); @Input(InputType.Guard) GuardingNode guard; protected DummyGuardHandle(GuardingNode guard) { super(TYPE, StampFactory.forVoid()); this.guard = guard; } @Override public GuardingNode getGuard() { return guard; } @Override public void setGuard(GuardingNode guard) { updateUsagesInterface(this.guard, guard); this.guard = guard; } @Override public ValueNode asNode() { return this; } } @Override public boolean checkContract() { return false; } final class LoweringToolImpl implements LoweringTool { private final PhaseContext context; private final NodeBitMap activeGuards; private AnchoringNode guardAnchor; private FixedWithNextNode lastFixedNode; LoweringToolImpl(PhaseContext context, AnchoringNode guardAnchor, NodeBitMap activeGuards, FixedWithNextNode lastFixedNode) { this.context = context; this.guardAnchor = guardAnchor; this.activeGuards = activeGuards; this.lastFixedNode = lastFixedNode; } @Override public LoweringStage getLoweringStage() { return loweringStage; } @Override public ConstantReflectionProvider getConstantReflection() { return context.getConstantReflection(); } @Override public ConstantFieldProvider getConstantFieldProvider() { return context.getConstantFieldProvider(); } @Override public MetaAccessProvider getMetaAccess() { return context.getMetaAccess(); } @Override public LoweringProvider getLowerer() { return context.getLowerer(); } @Override public Replacements getReplacements() { return context.getReplacements(); } @Override public AnchoringNode getCurrentGuardAnchor() { return guardAnchor; } @Override public GuardingNode createGuard(FixedNode before, LogicNode condition, DeoptimizationReason deoptReason, DeoptimizationAction action) { return createGuard(before, condition, deoptReason, action, JavaConstant.NULL_POINTER, false); } @Override public StampProvider getStampProvider() { return context.getStampProvider(); } @Override public GuardingNode createGuard(FixedNode before, LogicNode condition, DeoptimizationReason deoptReason, DeoptimizationAction action, JavaConstant speculation, boolean negated) { if (OptEliminateGuards.getValue()) { for (Node usage : condition.usages()) { if (!activeGuards.isNew(usage) && activeGuards.isMarked(usage) && ((GuardNode) usage).isNegated() == negated) { return (GuardNode) usage; } } } StructuredGraph graph = before.graph(); if (!condition.graph().getGuardsStage().allowsFloatingGuards()) { FixedGuardNode fixedGuard = graph.add(new FixedGuardNode(condition, deoptReason, action, speculation, negated)); graph.addBeforeFixed(before, fixedGuard); DummyGuardHandle handle = graph.add(new DummyGuardHandle(fixedGuard)); fixedGuard.lower(this); GuardingNode result = handle.getGuard(); handle.safeDelete(); return result; } else { GuardNode newGuard = graph.unique(new GuardNode(condition, guardAnchor, deoptReason, action, negated, speculation)); if (OptEliminateGuards.getValue()) { activeGuards.markAndGrow(newGuard); } return newGuard; } } @Override public FixedWithNextNode lastFixedNode() { return lastFixedNode; } @Override public NodeCostProvider getNodeCostProvider() { return context.getNodeCostProvider(); } private void setLastFixedNode(FixedWithNextNode n) { assert n.isAlive() : n; lastFixedNode = n; } } private final CanonicalizerPhase canonicalizer; private final LoweringTool.LoweringStage loweringStage; public LoweringPhase(CanonicalizerPhase canonicalizer, LoweringTool.LoweringStage loweringStage) { this.canonicalizer = canonicalizer; this.loweringStage = loweringStage; }
Checks that second lowering of a given graph did not introduce any new nodes.
Params:
  • graph – a graph that was just lowered
Throws:
/** * Checks that second lowering of a given graph did not introduce any new nodes. * * @param graph a graph that was just {@linkplain #lower lowered} * @throws AssertionError if the check fails */
private boolean checkPostLowering(StructuredGraph graph, PhaseContext context) { Mark expectedMark = graph.getMark(); lower(graph, context, LoweringMode.VERIFY_LOWERING); Mark mark = graph.getMark(); assert mark.equals(expectedMark) : graph + ": a second round in the current lowering phase introduced these new nodes: " + graph.getNewNodes(expectedMark).snapshot(); return true; } @Override protected void run(final StructuredGraph graph, PhaseContext context) { lower(graph, context, LoweringMode.LOWERING); assert checkPostLowering(graph, context); } private void lower(StructuredGraph graph, PhaseContext context, LoweringMode mode) { IncrementalCanonicalizerPhase<PhaseContext> incrementalCanonicalizer = new IncrementalCanonicalizerPhase<>(canonicalizer); incrementalCanonicalizer.appendPhase(new Round(context, mode)); incrementalCanonicalizer.apply(graph, context); assert graph.verify(); }
Checks that lowering of a given node did not introduce any new Lowerable nodes that could be lowered in the current LoweringPhase. Such nodes must be recursively lowered as part of lowering node.
Params:
  • node – a node that was just lowered
  • preLoweringMark – the graph mark before node was lowered
  • unscheduledUsages – set of node's usages that were unscheduled before it was lowered
Throws:
/** * Checks that lowering of a given node did not introduce any new {@link Lowerable} nodes that * could be lowered in the current {@link LoweringPhase}. Such nodes must be recursively lowered * as part of lowering {@code node}. * * @param node a node that was just lowered * @param preLoweringMark the graph mark before {@code node} was lowered * @param unscheduledUsages set of {@code node}'s usages that were unscheduled before it was * lowered * @throws AssertionError if the check fails */
private static boolean checkPostNodeLowering(Node node, LoweringToolImpl loweringTool, Mark preLoweringMark, Collection<Node> unscheduledUsages) { StructuredGraph graph = (StructuredGraph) node.graph(); Mark postLoweringMark = graph.getMark(); NodeIterable<Node> newNodesAfterLowering = graph.getNewNodes(preLoweringMark); if (node instanceof FloatingNode) { if (!unscheduledUsages.isEmpty()) { for (Node n : newNodesAfterLowering) { assert !(n instanceof FixedNode) : node.graph() + ": cannot lower floatable node " + node + " as it introduces fixed node(s) but has the following unscheduled usages: " + unscheduledUsages; } } } for (Node n : newNodesAfterLowering) { if (n instanceof Lowerable) { ((Lowerable) n).lower(loweringTool); Mark mark = graph.getMark(); assert postLoweringMark.equals(mark) : graph + ": lowering of " + node + " produced lowerable " + n + " that should have been recursively lowered as it introduces these new nodes: " + graph.getNewNodes(postLoweringMark).snapshot(); } } return true; } private enum LoweringMode { LOWERING, VERIFY_LOWERING } private final class Round extends Phase { private final PhaseContext context; private final LoweringMode mode; private ScheduleResult schedule; private final SchedulePhase schedulePhase; private Round(PhaseContext context, LoweringMode mode) { this.context = context; this.mode = mode; /* * In VERIFY_LOWERING, we want to verify whether the lowering itself changes the graph. * Make sure we're not detecting spurious changes because the SchedulePhase modifies the * graph. */ boolean immutableSchedule = mode == LoweringMode.VERIFY_LOWERING; this.schedulePhase = new SchedulePhase(immutableSchedule); } @Override protected CharSequence getName() { switch (mode) { case LOWERING: return "LoweringRound"; case VERIFY_LOWERING: return "VerifyLoweringRound"; default: throw GraalError.shouldNotReachHere(); } } @Override public boolean checkContract() { /* * lowering with snippets cannot be fully built in the node costs of all high level * nodes */ return false; } @Override public void run(StructuredGraph graph) { schedulePhase.apply(graph, false); schedule = graph.getLastSchedule(); schedule.getCFG().computePostdominators(); Block startBlock = schedule.getCFG().getStartBlock(); ProcessFrame rootFrame = new ProcessFrame(startBlock, graph.createNodeBitMap(), startBlock.getBeginNode(), null); LoweringPhase.processBlock(rootFrame); } private class ProcessFrame extends Frame<ProcessFrame> { private final NodeBitMap activeGuards; private AnchoringNode anchor; ProcessFrame(Block block, NodeBitMap activeGuards, AnchoringNode anchor, ProcessFrame parent) { super(block, parent); this.activeGuards = activeGuards; this.anchor = anchor; } @Override public void preprocess() { this.anchor = Round.this.process(block, activeGuards, anchor); } @Override public ProcessFrame enter(Block b) { return new ProcessFrame(b, activeGuards, b.getBeginNode(), this); } @Override public Frame<?> enterAlwaysReached(Block b) { AnchoringNode newAnchor = anchor; if (parent != null && b.getLoop() != parent.block.getLoop() && !b.isLoopHeader()) { // We are exiting a loop => cannot reuse the anchor without inserting loop // proxies. newAnchor = b.getBeginNode(); } return new ProcessFrame(b, activeGuards, newAnchor, this); } @Override public void postprocess() { if (anchor != null && OptEliminateGuards.getValue()) { for (GuardNode guard : anchor.asNode().usages().filter(GuardNode.class)) { if (activeGuards.isMarkedAndGrow(guard)) { activeGuards.clear(guard); } } } } } @SuppressWarnings("try") private AnchoringNode process(final Block b, final NodeBitMap activeGuards, final AnchoringNode startAnchor) { final LoweringToolImpl loweringTool = new LoweringToolImpl(context, startAnchor, activeGuards, b.getBeginNode()); // Lower the instructions of this block. List<Node> nodes = schedule.nodesFor(b); for (Node node : nodes) { if (node.isDeleted()) { // This case can happen when previous lowerings deleted nodes. continue; } // Cache the next node to be able to reconstruct the previous of the next node // after lowering. FixedNode nextNode = null; if (node instanceof FixedWithNextNode) { nextNode = ((FixedWithNextNode) node).next(); } else { nextNode = loweringTool.lastFixedNode().next(); } if (node instanceof Lowerable) { Collection<Node> unscheduledUsages = null; assert (unscheduledUsages = getUnscheduledUsages(node)) != null; Mark preLoweringMark = node.graph().getMark(); try (DebugCloseable s = node.graph().withNodeSourcePosition(node)) { ((Lowerable) node).lower(loweringTool); } if (loweringTool.guardAnchor.asNode().isDeleted()) { // TODO nextNode could be deleted but this is not currently supported assert nextNode.isAlive(); loweringTool.guardAnchor = AbstractBeginNode.prevBegin(nextNode); } assert checkPostNodeLowering(node, loweringTool, preLoweringMark, unscheduledUsages); } if (!nextNode.isAlive()) { // can happen when the rest of the block is killed by lowering // (e.g. by an unconditional deopt) break; } else { Node nextLastFixed = nextNode.predecessor(); if (!(nextLastFixed instanceof FixedWithNextNode)) { // insert begin node, to have a valid last fixed for next lowerable node. // This is about lowering a FixedWithNextNode to a control split while this // FixedWithNextNode is followed by some kind of BeginNode. // For example the when a FixedGuard followed by a loop exit is lowered to a // control-split + deopt. AbstractBeginNode begin = node.graph().add(new BeginNode()); nextLastFixed.replaceFirstSuccessor(nextNode, begin); begin.setNext(nextNode); nextLastFixed = begin; } loweringTool.setLastFixedNode((FixedWithNextNode) nextLastFixed); } } return loweringTool.getCurrentGuardAnchor(); }
Gets all usages of a floating, lowerable node that are unscheduled.

Given that the lowering of such nodes may introduce fixed nodes, they must be lowered in the context of a usage that dominates all other usages. The fixed nodes resulting from lowering are attached to the fixed node context of the dominating usage. This ensures the post-lowering graph still has a valid schedule.

Params:
/** * Gets all usages of a floating, lowerable node that are unscheduled. * <p> * Given that the lowering of such nodes may introduce fixed nodes, they must be lowered in * the context of a usage that dominates all other usages. The fixed nodes resulting from * lowering are attached to the fixed node context of the dominating usage. This ensures the * post-lowering graph still has a valid schedule. * * @param node a {@link Lowerable} node */
private Collection<Node> getUnscheduledUsages(Node node) { List<Node> unscheduledUsages = new ArrayList<>(); if (node instanceof FloatingNode) { for (Node usage : node.usages()) { if (usage instanceof ValueNode) { if (schedule.getCFG().getNodeToBlock().isNew(usage) || schedule.getCFG().blockFor(usage) == null) { unscheduledUsages.add(usage); } } } } return unscheduledUsages; } } enum ProcessBlockState { ST_ENTER, ST_PROCESS, ST_ENTER_ALWAYS_REACHED, ST_LEAVE, ST_PROCESS_ALWAYS_REACHED; }
This state-machine resembles the following recursion:
void processBlock(Block block) {
    preprocess();
    // Process always reached block first.
    Block alwaysReachedBlock = block.getPostdominator();
    if (alwaysReachedBlock != null && alwaysReachedBlock.getDominator() == block) {
        processBlock(alwaysReachedBlock);
    }
    // Now go for the other dominators.
    for (Block dominated : block.getDominated()) {
        if (dominated != alwaysReachedBlock) {
            assert dominated.getDominator() == block;
            processBlock(dominated);
        }
    }
    postprocess();
}
This is necessary, as the recursive implementation quickly exceed the stack depth on SPARC.
Params:
  • rootFrame – contains the starting block.
/** * This state-machine resembles the following recursion: * * <pre> * void processBlock(Block block) { * preprocess(); * // Process always reached block first. * Block alwaysReachedBlock = block.getPostdominator(); * if (alwaysReachedBlock != null &amp;&amp; alwaysReachedBlock.getDominator() == block) { * processBlock(alwaysReachedBlock); * } * * // Now go for the other dominators. * for (Block dominated : block.getDominated()) { * if (dominated != alwaysReachedBlock) { * assert dominated.getDominator() == block; * processBlock(dominated); * } * } * postprocess(); * } * </pre> * * This is necessary, as the recursive implementation quickly exceed the stack depth on SPARC. * * @param rootFrame contains the starting block. */
public static void processBlock(final Frame<?> rootFrame) { ProcessBlockState state = ST_PROCESS; Frame<?> f = rootFrame; while (f != null) { ProcessBlockState nextState; if (state == ST_PROCESS || state == ST_PROCESS_ALWAYS_REACHED) { f.preprocess(); nextState = state == ST_PROCESS_ALWAYS_REACHED ? ST_ENTER : ST_ENTER_ALWAYS_REACHED; } else if (state == ST_ENTER_ALWAYS_REACHED) { if (f.alwaysReachedBlock != null && f.alwaysReachedBlock.getDominator() == f.block) { f = f.enterAlwaysReached(f.alwaysReachedBlock); nextState = ST_PROCESS; } else { nextState = ST_ENTER; } } else if (state == ST_ENTER) { if (f.dominated.hasNext()) { Block n = f.dominated.next(); if (n == f.alwaysReachedBlock) { if (f.dominated.hasNext()) { n = f.dominated.next(); } else { n = null; } } if (n == null) { nextState = ST_LEAVE; } else { f = f.enter(n); assert f.block.getDominator() == f.parent.block; nextState = ST_PROCESS; } } else { nextState = ST_LEAVE; } } else if (state == ST_LEAVE) { f.postprocess(); f = f.parent; nextState = ST_ENTER; } else { throw GraalError.shouldNotReachHere(); } state = nextState; } } public static void processBlockBounded(final Frame<?> rootFrame) { ProcessBlockState state = ST_PROCESS; Frame<?> f = rootFrame; while (f != null) { ProcessBlockState nextState; if (state == ST_PROCESS || state == ST_PROCESS_ALWAYS_REACHED) { f.preprocess(); nextState = state == ST_PROCESS_ALWAYS_REACHED ? ST_ENTER : ST_ENTER_ALWAYS_REACHED; } else if (state == ST_ENTER_ALWAYS_REACHED) { if (f.alwaysReachedBlock != null && f.alwaysReachedBlock.getDominator() == f.block) { Frame<?> continueRecur = f.enterAlwaysReached(f.alwaysReachedBlock); if (continueRecur == null) { // stop recursion here f.postprocess(); f = f.parent; state = ST_ENTER; continue; } f = continueRecur; nextState = ST_PROCESS; } else { nextState = ST_ENTER; } } else if (state == ST_ENTER) { if (f.dominated.hasNext()) { Block n = f.dominated.next(); if (n == f.alwaysReachedBlock) { if (f.dominated.hasNext()) { n = f.dominated.next(); } else { n = null; } } if (n == null) { nextState = ST_LEAVE; } else { Frame<?> continueRecur = f.enter(n); if (continueRecur == null) { // stop recursion here f.postprocess(); f = f.parent; state = ST_ENTER; continue; } f = continueRecur; nextState = ST_PROCESS; } } else { nextState = ST_LEAVE; } } else if (state == ST_LEAVE) { f.postprocess(); f = f.parent; nextState = ST_ENTER; } else { throw GraalError.shouldNotReachHere(); } state = nextState; } } public abstract static class Frame<T extends Frame<?>> { protected final Block block; final T parent; Iterator<Block> dominated; final Block alwaysReachedBlock; public Frame(Block block, T parent) { super(); this.block = block; this.alwaysReachedBlock = block.getPostdominator(); this.dominated = block.getDominated().iterator(); this.parent = parent; } public Frame<?> enterAlwaysReached(Block b) { return enter(b); } public abstract Frame<?> enter(Block b); public abstract void preprocess(); public abstract void postprocess(); } }