From 3e3e0f05d43cf878e3e332814945b0a4a55d9e91 Mon Sep 17 00:00:00 2001
From: David Leopoldseder <david.leopoldseder@oracle.com>
Date: Wed, 13 Mar 2024 13:52:09 +0100
Subject: [PATCH] pi node: guard against deletion in recursion

---
 .../src/jdk/graal/compiler/nodes/PiNode.java  | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/PiNode.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/PiNode.java
index 223e6a3c06a2..3e64a566aec3 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/PiNode.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/PiNode.java
@@ -27,6 +27,8 @@
 import static jdk.graal.compiler.nodeinfo.NodeCycles.CYCLES_0;
 import static jdk.graal.compiler.nodeinfo.NodeSize.SIZE_0;
 
+import java.util.List;
+
 import jdk.graal.compiler.core.common.SuppressFBWarnings;
 import jdk.graal.compiler.core.common.type.AbstractPointerStamp;
 import jdk.graal.compiler.core.common.type.FloatStamp;
@@ -243,7 +245,6 @@ public void virtualize(VirtualizerTool tool) {
 
     @SuppressFBWarnings(value = {"NP"}, justification = "We null check it before")
     public static ValueNode canonical(ValueNode object, Stamp piStamp, GuardingNode guard, ValueNode self) {
-        // GR-52557
         GraalError.guarantee(piStamp != null && object != null, "Invariant piStamp=%s object=%s guard=%s self=%s", piStamp, object, guard, self);
 
         // Use most up to date stamp.
@@ -325,7 +326,9 @@ private static void tryEvacuate(SimplifierTool tool, GuardingNode guard, boolean
         if (guardNode.hasNoUsages()) {
             return;
         }
-        for (PiNode pi : guardNode.usages().filter(PiNode.class).snapshot()) {
+
+        List<PiNode> pis = guardNode.usages().filter(PiNode.class).snapshot();
+        for (PiNode pi : pis) {
             if (!pi.isAlive()) {
                 continue;
             }
@@ -335,6 +338,8 @@ private static void tryEvacuate(SimplifierTool tool, GuardingNode guard, boolean
             }
 
             /*
+             * RECURSE CALL
+             *
              * If there are PiNodes still anchored at this guard then either they must simplify away
              * because they are no longer necessary or this node must be replaced with a
              * ValueAnchorNode because the type injected by the PiNode is only true at this point in
@@ -348,6 +353,16 @@ private static void tryEvacuate(SimplifierTool tool, GuardingNode guard, boolean
                     tryEvacuate(tool, otherGuard, false);
                 }
             }
+            /*
+             * A note on the RECURSE CALL above: When we have pis with input pis on the same guard
+             * (which should actually be combined) it can be that the recurse call (processing the
+             * same pis again) already deletes this node (very special stamp setups necessary).
+             * Thus, it can be that pi is dead at this point already, so we have to check for this
+             * again.
+             */
+            if (!pi.isAlive()) {
+                continue;
+            }
             Node canonical = pi.canonical(tool);
             if (canonical != pi) {
                 if (!canonical.isAlive()) {