bytecode diffing support in ByteCodeTest

use sameByteCode(methodNode1, methodNode2) to check methods
compile to identical bytecode (line number info is not taken into account)

src/partest/scala/tools/partest/BytecodeTest.scala

@@ -8,11 +8,11 @@ import asm.tree.{ClassNode, MethodNode, InsnList}
 import java.io.InputStream
 
 /**
- * Providies utilities for inspecting bytecode using ASM library.
+ * Provides utilities for inspecting bytecode using ASM library.
  *
  * HOW TO USE
  * 1. Create subdirectory in test/files/jvm for your test. Let's name it $TESTDIR.
- * 2. Create $TESTDIR/BytecodeSrc_1.scala that contains Scala source file which you
+ * 2. Create $TESTDIR/BytecodeSrc_1.scala that contains Scala source file that you
  *    want to inspect the bytecode for. The '_1' suffix signals to partest that it
  *    should compile this file first.
  * 3. Create $TESTDIR/Test.scala:
@@ -35,19 +35,31 @@ abstract class BytecodeTest {
 
   def main(args: Array[String]): Unit = show
 
+// asserts
+  def sameBytecode(methA: MethodNode, methB: MethodNode) = {
+    val isa = instructions.fromMethod(methA)
+    val isb = instructions.fromMethod(methB)
+    if (isa == isb) println("bytecode identical")
+    else (isa, isb).zipped.foreach { case (a, b) =>
+      if (a == b) println("OK  : "+ a)
+      else println("DIFF: "+ a +" <=> "+ b)
+    }
+  }
+
+// loading
   protected def getMethod(classNode: ClassNode, name: String): MethodNode =
     classNode.methods.asScala.find(_.name == name) getOrElse
       sys.error(s"Didn't find method '$name' in class '${classNode.name}'")
 
-  protected def loadClassNode(name: String): ClassNode = {
+  protected def loadClassNode(name: String, skipDebugInfo: Boolean = true): ClassNode = {
     val classBytes: InputStream = (for {
       classRep <- classpath.findClass(name)
       binary <- classRep.binary
     } yield binary.input) getOrElse sys.error(s"failed to load class '$name'; classpath = $classpath")
 
     val cr = new ClassReader(classBytes)
     val cn = new ClassNode()
-    cr.accept(cn, 0)
+    cr.accept(cn, if (skipDebugInfo) ClassReader.SKIP_DEBUG else 0)
     cn
   }
 
@@ -58,4 +70,61 @@ abstract class BytecodeTest {
     val containers = DefaultJavaContext.classesInExpandedPath(Defaults.javaUserClassPath)
     new JavaClassPath(containers, DefaultJavaContext)
   }
+
+  // wrap ASM's instructions so we get case class-style `equals` and `toString`
+  object instructions {
+    def fromMethod(meth: MethodNode): List[instructions.Instruction] = {
+      val insns = meth.instructions
+      val asmToScala = new AsmToScala{ def labelIndex(l: asm.tree.AbstractInsnNode) = insns.indexOf(l) }
+
+      asmToScala.mapOver(insns.iterator.asScala.toList).asInstanceOf[List[instructions.Instruction]]
+    }
+
+    sealed abstract class Instruction { def opcode: Int }
+    case class Field         (opcode: Int, desc: String, name: String, owner: String)              extends Instruction
+    case class Incr          (opcode: Int, incr: Int, `var`: Int)                                  extends Instruction
+    case class Op            (opcode: Int)                                                         extends Instruction
+    case class IntOp         (opcode: Int, operand: Int)                                           extends Instruction
+    case class Jump          (opcode: Int, label: Label)                                           extends Instruction
+    case class Ldc           (opcode: Int, cst: Any)                                               extends Instruction
+    case class LookupSwitch  (opcode: Int, dflt: Label, keys: List[Integer], labels: List[Label])  extends Instruction
+    case class TableSwitch   (opcode: Int, dflt: Label, max: Int, min: Int, labels: List[Label])   extends Instruction
+    case class Method        (opcode: Int, desc: String, name: String, owner: String)              extends Instruction
+    case class NewArray      (opcode: Int, desc: String, dims: Int)                                extends Instruction
+    case class TypeOp        (opcode: Int, desc: String)                                           extends Instruction
+    case class VarOp         (opcode: Int, `var`: Int)                                             extends Instruction
+    case class Label         (opcode: Int, offset: Int)                                            extends Instruction
+    case class FrameEntry    (opcode: Int, local: List[Any], stack: List[Any])                     extends Instruction
+    case class LineNumber    (opcode: Int, line: Int, start: Label)                                extends Instruction
+  }
+
+  abstract class AsmToScala {
+    import instructions._
+    def labelIndex(l: asm.tree.AbstractInsnNode): Int
+
+    def mapOver(is: List[Any]): List[Any] = is map {
+      case i: asm.tree.AbstractInsnNode => apply(i)
+      case x => x
+    }
+
+   def lst[T](xs: java.util.List[T]): List[T] = if (xs == null) Nil else xs.asScala.toList
+   def apply(l: asm.tree.LabelNode): Label = this(l: asm.tree.AbstractInsnNode).asInstanceOf[Label]
+   def apply(x: asm.tree.AbstractInsnNode): Instruction = x match {
+      case i: asm.tree.FieldInsnNode          => Field        (i.getOpcode: Int, i.desc: String, i.name: String, i.owner: String)
+      case i: asm.tree.IincInsnNode           => Incr         (i.getOpcode: Int, i.incr: Int, i.`var`: Int)
+      case i: asm.tree.InsnNode               => Op           (i.getOpcode: Int)
+      case i: asm.tree.IntInsnNode            => IntOp        (i.getOpcode: Int, i.operand: Int)
+      case i: asm.tree.JumpInsnNode           => Jump         (i.getOpcode: Int, this(i.label))
+      case i: asm.tree.LdcInsnNode            => Ldc          (i.getOpcode: Int, i.cst: Any)
+      case i: asm.tree.LookupSwitchInsnNode   => LookupSwitch (i.getOpcode: Int, this(i.dflt), lst(i.keys), mapOver(lst(i.labels)).asInstanceOf[List[Label]])
+      case i: asm.tree.TableSwitchInsnNode    => TableSwitch  (i.getOpcode: Int, this(i.dflt), i.max: Int, i.min: Int, mapOver(lst(i.labels)).asInstanceOf[List[Label]])
+      case i: asm.tree.MethodInsnNode         => Method       (i.getOpcode: Int, i.desc: String, i.name: String, i.owner: String)
+      case i: asm.tree.MultiANewArrayInsnNode => NewArray     (i.getOpcode: Int, i.desc: String, i.dims: Int)
+      case i: asm.tree.TypeInsnNode           => TypeOp       (i.getOpcode: Int, i.desc: String)
+      case i: asm.tree.VarInsnNode            => VarOp        (i.getOpcode: Int, i.`var`: Int)
+      case i: asm.tree.LabelNode              => Label        (i.getOpcode: Int, labelIndex(x))
+      case i: asm.tree.FrameNode              => FrameEntry   (i.getOpcode: Int, mapOver(lst(i.local)), mapOver(lst(i.stack)))
+      case i: asm.tree.LineNumberNode         => LineNumber   (i.getOpcode: Int, i.line: Int, this(i.start): Label)
+    }
+  }
 }