From 293bf83e30d8c643192d70fa01b6375777998299 Mon Sep 17 00:00:00 2001
From: Graham <gpe@openrs2.org>
Date: Fri, 12 Jan 2024 22:03:28 +0000
Subject: [PATCH] Improve initializer extraction in StaticFieldUnscrambler

This commit makes the following improvements:

- Converts the list of instructions in the entry and exit block to a
  set, which makes checking for containment more efficient.

- Removes redundant excluded field filtering, which is already handled
  by the unscramble() method.

- Treats fields written with PUTSTATIC outside the entry or exit block
  as complex, instead of just fields read with GETSTATIC.

- Treats fields with multiple simple initializers as complex.

- Treats fields where we fail to extract a simple initializer as
  complex. This fixes a bug where we accidentally thought those fields
  had no initializer.

Signed-off-by: Graham <gpe@openrs2.org>
---
 .../bytecode/remap/StaticFieldUnscrambler.kt  | 29 ++++++++++++-------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/deob-bytecode/src/main/kotlin/org/openrs2/deob/bytecode/remap/StaticFieldUnscrambler.kt b/deob-bytecode/src/main/kotlin/org/openrs2/deob/bytecode/remap/StaticFieldUnscrambler.kt
index 557c9329..a5c58f0d 100644
--- a/deob-bytecode/src/main/kotlin/org/openrs2/deob/bytecode/remap/StaticFieldUnscrambler.kt
+++ b/deob-bytecode/src/main/kotlin/org/openrs2/deob/bytecode/remap/StaticFieldUnscrambler.kt
@@ -57,7 +57,7 @@ public class StaticFieldUnscrambler(
         return fields
     }
 
-    private fun MethodNode.extractEntryExitBlocks(): List<AbstractInsnNode> {
+    private fun MethodNode.extractEntryExitBlocks(): Set<AbstractInsnNode> {
         /*
          * Most (or all?) of the <clinit> methods have "simple" initializers
          * that we're capable of moving in the first and last basic blocks of
@@ -69,14 +69,14 @@ public class StaticFieldUnscrambler(
 
         val last = instructions.lastOrNull()
         if (last == null || last.opcode != Opcodes.RETURN) {
-            return entry
+            return entry.toSet()
         }
 
         val exit = instructions.toList()
             .dropLast(1)
             .takeLastWhile { it.isSequential }
 
-        return entry.plus(exit)
+        return (entry + exit).toSet()
     }
 
     private fun MethodNode.extractInitializers(
@@ -86,26 +86,35 @@ public class StaticFieldUnscrambler(
 
         val simpleInitializers = mutableMapOf<MemberDesc, List<AbstractInsnNode>>()
         val complexInitializers = instructions.asSequence()
-            .filter { !entryExitBlocks.contains(it) }
+            .filter { it !in entryExitBlocks }
             .filterIsInstance<FieldInsnNode>()
-            .filter { it.opcode == Opcodes.GETSTATIC && it.owner == owner }
-            .filter { !excludedFields.matches(it.owner, it.name, it.desc) }
+            .filter { it.owner == owner }
             .map(::MemberDesc)
-            .toSet()
+            .toMutableSet()
 
         val putstatics = entryExitBlocks
             .filterIsInstance<FieldInsnNode>()
             .filter { it.opcode == Opcodes.PUTSTATIC && it.owner == owner }
-            .filter { !excludedFields.matches(it.owner, it.name, it.desc) }
 
         for (putstatic in putstatics) {
             val desc = MemberDesc(putstatic)
-            if (simpleInitializers.containsKey(desc) || complexInitializers.contains(desc)) {
+            if (desc in complexInitializers) {
+                continue
+            }
+
+            if (desc in simpleInitializers) {
+                simpleInitializers -= desc
+                complexInitializers += desc
                 continue
             }
 
             // TODO(gpe): use a filter here (pure with no *LOADs?)
-            simpleInitializers[desc] = getExpression(putstatic) ?: continue
+            val initializer = getExpression(putstatic)
+            if (initializer != null) {
+                simpleInitializers[desc] = initializer
+            } else {
+                complexInitializers += desc
+            }
         }
 
         return Pair(simpleInitializers, complexInitializers)