[Backport] [Oracle GraalVM] [GR-69955] Backport to 23.1: Safepoint node: model loop link as guard.

[elkorchi]

What would you like to backport?

Oracle GraalVM backported commits:
(oracle/graal@70eef6c)

Describe the motivation for the backport.

Backported to Oracle GraalVM for JDK 21, fix version: graalvm-23.1.11

[bulasevich]

Merge conflicts reveal a missing change. "Safepoint node: model loop link as guard" can be back ported on top of safepoint elimination: refactorings which is a part of [GR-59001][GR-59002][GR-61452] Safepoint changes.

Merge conflicts (click to expand)

<<<<<<< HEAD:compiler/src/jdk.internal.vm.compiler/src/org/graalvm/compiler/nodes/LoopBeginNode.java
=======
    public List<SafepointNode> loopSafepoints() {
        ArrayList<SafepointNode> safePoints = new ArrayList<>();
        for (LoopExitNode lex : loopExits()) {
            safePoints.addAll(lex.usages().filter(SafepointNode.class).snapshot());
        }
        return safePoints;
    }

>>>>>>> 70eef6c38f7 (express safepoint loop edge as guard to model loop end and exit cases):compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/LoopBeginNode.java
<<<<<<< HEAD:compiler/src/jdk.internal.vm.compiler/src/org/graalvm/compiler/nodes/LoopBeginNode.java
=======
    public void removeSafepoints() {
        this.graph().getDebug().dump(DebugContext.VERY_DETAILED_LEVEL, this.graph(), "Before removing safepoints at %s", this);
        for (SafepointNode loopSafepoint : loopSafepoints()) {
            if (loopSafepoint.isAlive()) {
                if (loopSafepoint.predecessor() != null && loopSafepoint.next() != null) {
                    this.graph().removeFixed(loopSafepoint);
                } else {
                    loopSafepoint.replaceAtPredecessor(null);
                    loopSafepoint.safeDelete();
                }
            }
        }

        this.graph().getDebug().dump(DebugContext.VERY_DETAILED_LEVEL, this.graph(), "After removing safepoints at %s", this);
    }
>>>>>>> 70eef6c38f7 (express safepoint loop edge as guard to model loop end and exit cases):compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/LoopBeginNode.java
<<<<<<< HEAD:compiler/src/jdk.internal.vm.compiler/src/org/graalvm/compiler/nodes/SafepointNode.java
=======
    /**
     * Optional edge that is set when safepoints are added to a graph. If this safepoint is
     * semantically associated with a loop structure links to the loop begin or loop exit it is
     * mapped to. Over the course of optimizations can "degrade" and point to control flow dominated
     * by the original loop (exit).
     */
    @OptionalInput(InputType.Guard) protected GuardingNode loopLink;
>>>>>>> 70eef6c38f7 (express safepoint loop edge as guard to model loop end and exit cases):compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/SafepointNode.java
<<<<<<< HEAD:compiler/src/jdk.internal.vm.compiler/src/org/graalvm/compiler/nodes/SafepointNode.java
=======

    @Override
    public void simplify(SimplifierTool tool) {
        if (next() instanceof SafepointNode) {
            this.graph().removeFixed(this);
        }
    }

    public void setLoopLink(GuardingNode loopLink) {
        updateUsagesInterface(this.loopLink, loopLink);
        this.loopLink = loopLink;
    }

    public GuardingNode getLoopLink() {
        return loopLink;
    }
>>>>>>> 70eef6c38f7 (express safepoint loop edge as guard to model loop end and exit cases):compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/SafepointNode.java
<<<<<<< HEAD:compiler/src/jdk.internal.vm.compiler/src/org/graalvm/compiler/phases/common/LoopSafepointInsertionPhase.java
=======
                            safepointNode.setLoopLink(loopBeginNode);
>>>>>>> 70eef6c38f7 (express safepoint loop edge as guard to model loop end and exit cases):compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/LoopSafepointInsertionPhase.java