From 10c3276674cbed384a4739f1a4b94f5441e7b8db Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Mon, 4 May 2020 12:41:57 +0700
Subject: [PATCH] DefUseUtil: make the traversal non-recursive to avoid
 possible SOE for huge methods (EA-144050)

GitOrigin-RevId: 02df88e041af9be7a4259a734bbfe3b7b0e3cd93
---
 .../intellij/psi/controlFlow/DefUseUtil.java  | 89 ++++++++++---------
 1 file changed, 47 insertions(+), 42 deletions(-)

diff --git a/java/java-psi-impl/src/com/intellij/psi/controlFlow/DefUseUtil.java b/java/java-psi-impl/src/com/intellij/psi/controlFlow/DefUseUtil.java
index b5a003224594..1a1019ca19ec 100644
--- a/java/java-psi-impl/src/com/intellij/psi/controlFlow/DefUseUtil.java
+++ b/java/java-psi-impl/src/com/intellij/psi/controlFlow/DefUseUtil.java
@@ -13,6 +13,7 @@ import com.intellij.util.containers.Queue;
 import com.intellij.util.containers.Stack;
 import gnu.trove.THashMap;
 import gnu.trove.THashSet;
+import gnu.trove.TIntArrayList;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -391,7 +392,8 @@ public class DefUseUtil {
 
       final boolean [] visited = new boolean[instructions.size() + 1];
       visited [visited.length-1] = true; // stop on the code end
-      int elem = defs() ? flow.getStartOffset(refOrDef) : flow.getEndOffset(refOrDef);
+      final boolean defs = defs();
+      int elem = defs ? flow.getStartOffset(refOrDef) : flow.getEndOffset(refOrDef);
 
       // hack: ControlFlow doesn't contains parameters initialization
       if (elem == -1 && def instanceof PsiParameter) {
@@ -399,62 +401,65 @@ public class DefUseUtil {
       }
 
       if (elem != -1) {
-        if (!defs () && instructions.get(elem) instanceof ReadVariableInstruction) {
+        if (!defs && instructions.get(elem) instanceof ReadVariableInstruction) {
           LOG.assertTrue(nNext(elem) == 1);
           LOG.assertTrue(getNext(elem,0) == elem+1);
           elem += 1;
         }
 
         final Set<@NotNull PsiElement> res = new THashSet<>();
-        class Inner {
-          private void traverse(int index) {
-            if (visited[index]) {
-              return;
-            }
-            visited [index] = true;
+        // hack: ControlFlow doesn't contains parameters initialization
+        int startIndex = elem;
 
-            if (defs ()) {
-              final Instruction instruction = instructions.get(index);
-              processInstruction(res, instruction, index);
-              if (instruction instanceof WriteVariableInstruction) {
-                WriteVariableInstruction instructionW = (WriteVariableInstruction)instruction;
-                if (instructionW.variable == def) {
-                  return;
-                }
-              }
+        TIntArrayList workQueue = new TIntArrayList();
+        workQueue.add(startIndex);
 
-              // hack: ControlFlow doesn't contains parameters initialization
-              if (index == 0 && def instanceof PsiParameter) {
-                PsiIdentifier identifier = def.getNameIdentifier();
-                if (identifier != null) {
-                  res.add(identifier);
-                }
+        while (!workQueue.isEmpty()) {
+          int index = workQueue.remove(workQueue.size() - 1);
+          if (visited[index]) {
+            continue;
+          }
+          visited [index] = true;
+
+          if (defs) {
+            final Instruction instruction = instructions.get(index);
+            processInstruction(res, instruction, index);
+            if (instruction instanceof WriteVariableInstruction) {
+              WriteVariableInstruction instructionW = (WriteVariableInstruction)instruction;
+              if (instructionW.variable == def) {
+                continue;
               }
             }
 
-            final int nNext = nNext (index);
-            for (int i = 0; i < nNext; i++) {
-              final int prev = getNext(index, i);
-              if (!visited [prev]) {
-                if (!defs ()) {
-                  final Instruction instruction = instructions.get(prev);
-                  if (instruction instanceof WriteVariableInstruction) {
-                    WriteVariableInstruction instructionW = (WriteVariableInstruction)instruction;
-                    if (instructionW.variable == def) {
-                      continue;
-                    }
-                  }
-                  else {
-                    processInstruction(res, instruction, prev);
-                  }
-                }
-                traverse (prev);
-
+            // hack: ControlFlow doesn't contains parameters initialization
+            if (index == 0 && def instanceof PsiParameter) {
+              PsiIdentifier identifier = def.getNameIdentifier();
+              if (identifier != null) {
+                res.add(identifier);
               }
             }
           }
+
+          final int nNext = nNext (index);
+          for (int i = 0; i < nNext; i++) {
+            final int prev = getNext(index, i);
+            if (!visited [prev]) {
+              if (!defs) {
+                final Instruction instruction = instructions.get(prev);
+                if (instruction instanceof WriteVariableInstruction) {
+                  WriteVariableInstruction instructionW = (WriteVariableInstruction)instruction;
+                  if (instructionW.variable == def) {
+                    continue;
+                  }
+                }
+                else {
+                  processInstruction(res, instruction, prev);
+                }
+              }
+              workQueue.add(prev);
+            }
+          }
         }
-        new Inner ().traverse(elem);
         return PsiUtilCore.toPsiElementArray(res);
       }
       return PsiElement.EMPTY_ARRAY;