Revert "Simplify static field scrambling"

This reverts commit b6bba95435.

Although this code is more complicated, it allows us to control the
destination class for fields individually (rather than an entire set at
a time). This is a requirement for name mapping.

deob/src/main/java/dev/openrs2/deob/transform/StaticScramblingTransformer.kt

@@ -2,20 +2,22 @@ package dev.openrs2.deob.transform
 
 import com.github.michaelbull.logging.InlineLogger
 import dev.openrs2.asm.ClassVersionUtils
+import dev.openrs2.asm.MemberDesc
 import dev.openrs2.asm.MemberRef
 import dev.openrs2.asm.classpath.ClassPath
 import dev.openrs2.asm.classpath.Library
+import dev.openrs2.asm.getExpression
+import dev.openrs2.asm.isSequential
 import dev.openrs2.asm.transform.Transformer
 import dev.openrs2.deob.Profile
 import dev.openrs2.util.collect.DisjointSet
 import org.objectweb.asm.Opcodes
+import org.objectweb.asm.tree.AbstractInsnNode
 import org.objectweb.asm.tree.ClassNode
 import org.objectweb.asm.tree.FieldInsnNode
 import org.objectweb.asm.tree.FieldNode
 import org.objectweb.asm.tree.InsnList
 import org.objectweb.asm.tree.InsnNode
-import org.objectweb.asm.tree.JumpInsnNode
-import org.objectweb.asm.tree.LabelNode
 import org.objectweb.asm.tree.MethodInsnNode
 import org.objectweb.asm.tree.MethodNode
 import javax.inject.Inject
@@ -24,16 +26,17 @@ import kotlin.math.max
 
 @Singleton
 class StaticScramblingTransformer @Inject constructor(private val profile: Profile) : Transformer() {
-    private class FieldSet(val owner: ClassNode, val fields: List<FieldNode>, val clinit: MethodNode?) {
-        val dependencies = clinit?.instructions
-            ?.filterIsInstance<FieldInsnNode>()
-            ?.filter { it.opcode == Opcodes.GETSTATIC && it.owner != owner.name }
-            ?.mapTo(mutableSetOf(), ::MemberRef) ?: emptySet<MemberRef>()
+    private data class Field(val node: FieldNode, val initializer: InsnList, val version: Int, val maxStack: Int) {
+        val dependencies = initializer.asSequence()
+            .filterIsInstance<FieldInsnNode>()
+            .filter { it.opcode == Opcodes.GETSTATIC }
+            .map(::MemberRef)
+            .toSet()
     }
 
     private lateinit var inheritedFieldSets: DisjointSet<MemberRef>
     private lateinit var inheritedMethodSets: DisjointSet<MemberRef>
-    private val fieldSets = mutableMapOf<MemberRef, FieldSet>()
+    private val fields = mutableMapOf<DisjointSet.Partition<MemberRef>, Field>()
     private val fieldClasses = mutableMapOf<DisjointSet.Partition<MemberRef>, String>()
     private val methodClasses = mutableMapOf<DisjointSet.Partition<MemberRef>, String>()
     private var nextStaticClass: ClassNode? = null
@@ -73,63 +76,103 @@ class StaticScramblingTransformer @Inject constructor(private val profile: Profi
         return Pair(clazz, clinit)
     }
 
-    private fun spliceFields() {
-        val done = mutableSetOf<FieldSet>()
-        for (fieldSet in fieldSets.values) {
-            spliceFields(done, fieldSet)
-        }
+    private fun MethodNode.extractEntryExitBlocks(): List<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
+         * the method. The last basic block is always at the end of the code
+         * and ends in a RETURN. This allows us to avoid worrying about making
+         * a full basic block control flow graph here.
+         */
+        val entry = instructions.takeWhile { it.isSequential }
+
+        val last = instructions.lastOrNull()
+        if (last == null || last.opcode != Opcodes.RETURN) {
+            return entry
         }
 
-    private fun spliceFields(done: MutableSet<FieldSet>, fieldSet: FieldSet) {
-        if (!done.add(fieldSet)) {
-            return
+        val exit = instructions.toList()
+            .dropLast(1)
+            .takeLastWhile { it.isSequential }
+
+        return entry.plus(exit)
     }
 
-        for (dependency in fieldSet.dependencies) {
-            val dependencyFieldSet = fieldSets[dependency] ?: continue
-            spliceFields(done, dependencyFieldSet)
+    private fun MethodNode.extractInitializers(owner: String): Pair<Map<MemberDesc, InsnList>, Set<MemberDesc>> {
+        val entryExitBlocks = extractEntryExitBlocks()
+
+        val simpleInitializers = mutableMapOf<MemberDesc, InsnList>()
+        val complexInitializers = instructions.asSequence()
+            .filter { !entryExitBlocks.contains(it) }
+            .filterIsInstance<FieldInsnNode>()
+            .filter { it.opcode == Opcodes.GETSTATIC && it.owner == owner }
+            .filter { !profile.excludedFields.matches(it.owner, it.name, it.desc) }
+            .map(::MemberDesc)
+            .toSet()
+
+        val putstatics = entryExitBlocks
+            .filterIsInstance<FieldInsnNode>()
+            .filter { it.opcode == Opcodes.PUTSTATIC && it.owner == owner }
+            .filter { !profile.excludedFields.matches(it.owner, it.name, it.desc) }
+
+        for (putstatic in putstatics) {
+            val desc = MemberDesc(putstatic)
+            if (simpleInitializers.containsKey(desc) || complexInitializers.contains(desc)) {
+                continue
             }
 
-        val (staticClass, staticClinit) = nextClass()
-        staticClass.fields.addAll(fieldSet.fields)
-        staticClass.version = ClassVersionUtils.max(staticClass.version, fieldSet.owner.version)
+            // TODO(gpe): use a filter here (pure with no *LOADs?)
+            val expr = getExpression(putstatic) ?: continue
+
+            val initializer = InsnList()
+            for (insn in expr) {
+                instructions.remove(insn)
+                initializer.add(insn)
+            }
+            instructions.remove(putstatic)
+            initializer.add(putstatic)
 
-        if (fieldSet.clinit != null) {
-            // remove tail RETURN
-            val insns = fieldSet.clinit.instructions
-            val last = insns.lastOrNull()
-            if (last != null && last.opcode == Opcodes.RETURN) {
-                insns.remove(last)
+            simpleInitializers[desc] = initializer
         }
 
-            // replace any remaining RETURNs with a GOTO to the end of the method
-            val end = LabelNode()
-            insns.add(end)
+        return Pair(simpleInitializers, complexInitializers)
+    }
 
-            for (insn in insns) {
-                if (insn.opcode == Opcodes.RETURN) {
-                    insns.set(insn, JumpInsnNode(Opcodes.GOTO, end))
+    private fun spliceInitializers() {
+        val done = mutableSetOf<DisjointSet.Partition<MemberRef>>()
+        for ((partition, field) in fields) {
+            spliceInitializers(done, partition, field)
         }
     }
 
-            // append just before the end of the static <clinit> RETURN
-            staticClinit.instructions.insertBefore(staticClinit.instructions.last, insns)
+    private fun spliceInitializers(
+        done: MutableSet<DisjointSet.Partition<MemberRef>>,
+        partition: DisjointSet.Partition<MemberRef>,
+        field: Field
+    ) {
+        if (!done.add(partition)) {
+            return
+        }
 
-            staticClinit.tryCatchBlocks.addAll(fieldSet.clinit.tryCatchBlocks)
-            staticClinit.maxStack = max(staticClinit.maxStack, fieldSet.clinit.maxStack)
-            staticClinit.maxLocals = max(staticClinit.maxLocals, fieldSet.clinit.maxLocals)
+        for (dependency in field.dependencies) {
+            val dependencyPartition = inheritedFieldSets[dependency]!!
+            val dependencyField = fields[dependencyPartition] ?: continue
+            spliceInitializers(done, partition, dependencyField)
         }
 
-        for (field in fieldSet.fields) {
-            val partition = inheritedFieldSets[MemberRef(fieldSet.owner, field)]!!
+        val (staticClass, clinit) = nextClass()
+        staticClass.fields.add(field.node)
+        staticClass.version = ClassVersionUtils.max(staticClass.version, field.version)
+        clinit.instructions.insertBefore(clinit.instructions.last, field.initializer)
+        clinit.maxStack = max(clinit.maxStack, field.maxStack)
+
         fieldClasses[partition] = staticClass.name
     }
-    }
 
     override fun preTransform(classPath: ClassPath) {
         inheritedFieldSets = classPath.createInheritedFieldSets()
         inheritedMethodSets = classPath.createInheritedMethodSets()
-        fieldSets.clear()
+        fields.clear()
         fieldClasses.clear()
         methodClasses.clear()
         nextStaticClass = null
@@ -143,22 +186,29 @@ class StaticScramblingTransformer @Inject constructor(private val profile: Profi
 
             for (clazz in library) {
                 // TODO(gpe): exclude the JSObject class
-                if (clazz.name == "jagex3/jagmisc/jagmisc") {
-                    continue
-                }
-
-                val fields = clazz.fields.filter { it.access and Opcodes.ACC_STATIC != 0 }
-                clazz.fields.removeAll(fields)
 
                 val clinit = clazz.methods.find { it.name == "<clinit>" }
-                if (clinit != null) {
-                    clazz.methods.remove(clinit)
+                val (simpleInitializers, complexInitializers) = clinit?.extractInitializers(clazz.name)
+                    ?: Pair(emptyMap(), emptySet())
+
+                clazz.fields.removeIf { field ->
+                    if (field.access and Opcodes.ACC_STATIC == 0) {
+                        return@removeIf false
+                    } else if (profile.excludedFields.matches(clazz.name, field.name, field.desc)) {
+                        return@removeIf false
+                    }
+
+                    val desc = MemberDesc(field)
+                    if (complexInitializers.contains(desc)) {
+                        return@removeIf false
                     }
 
-                val fieldSet = FieldSet(clazz, fields, clinit)
-                for (field in fields) {
-                    val ref = MemberRef(clazz, field)
-                    fieldSets[ref] = fieldSet
+                    val initializer = simpleInitializers[desc] ?: InsnList()
+                    val maxStack = clinit?.maxStack ?: 0
+
+                    val partition = inheritedFieldSets[MemberRef(clazz, field)]!!
+                    fields[partition] = Field(field, initializer, clazz.version, maxStack)
+                    return@removeIf true
                 }
 
                 clazz.methods.removeIf { method ->
@@ -180,7 +230,7 @@ class StaticScramblingTransformer @Inject constructor(private val profile: Profi
                 }
             }
 
-            spliceFields()
+            spliceInitializers()
 
             for (clazz in staticClasses) {
                 library.add(clazz)