Allow tracing methods and classes in GenBCode

5 files changed, 75 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/AsmUtils.scala b/src/compiler/scala/tools/nsc/backend/jvm/AsmUtils.scala
new file mode 100644
index 0000000000..856f85d9e3
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/backend/jvm/AsmUtils.scala
@@ -0,0 +1,53 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2014 LAMP/EPFL
+ * @author  Martin Odersky
+ */
+
+package scala.tools.nsc.backend.jvm
+
+import scala.tools.asm.tree.{ClassNode, MethodNode}
+import java.io.PrintWriter
+import scala.tools.asm.util.{TraceClassVisitor, TraceMethodVisitor, Textifier}
+
+object AsmUtils {
+
+  /**
+   * Print the bytecode of methods generated by GenBCode to the standard output. Only methods
+   * whose name contains `traceMethodPattern` are traced.
+   */
+  final val traceMethodEnabled = false
+  final val traceMethodPattern = ""
+
+  /**
+   * Print the bytecode of classes generated by GenBCode to the standard output.
+   */
+  final val traceClassEnabled = false
+  final val traceClassPattern = ""
+
+  /**
+   * Print the bytedcode of classes as they are serialized by the ASM library. The serialization
+   * performed by `asm.ClassWriter` can change the code generated by GenBCode. For example, it
+   * introduces stack map frames, it computes the maximal stack sizes, and it replaces dead
+   * code by NOPs (see also https://github.com/scala/scala/pull/3726#issuecomment-42861780).
+   */
+  final val traceSerializedClassEnabled = false
+  final val traceSerializedClassPattern = ""
+
+  def traceMethod(mnode: MethodNode): Unit = {
+    println(s"Bytecode for method ${mnode.name}")
+    val p = new Textifier
+    val tracer = new TraceMethodVisitor(p)
+    mnode.accept(tracer)
+    val w = new PrintWriter(System.out)
+    p.print(w)
+    w.flush()
+  }
+
+  def traceClass(cnode: ClassNode): Unit = {
+    println(s"Bytecode for class ${cnode.name}")
+    val w = new PrintWriter(System.out)
+    cnode.accept(new TraceClassVisitor(w))
+    w.flush()
+  }
+
+}
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
index 92ebe5027a..3d1b646069 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
@@ -808,7 +808,7 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
         emit(asm.Opcodes.ATHROW) // ICode enters here into enterIgnoreMode, we'll rely instead on DCE at ClassNode level.
       } else if (from.isNullType) {
         bc drop from
-        mnode.visitInsn(asm.Opcodes.ACONST_NULL)
+        emit(asm.Opcodes.ACONST_NULL)
       }
       else (from, to) match  {
         case (BYTE, LONG) | (SHORT, LONG) | (CHAR, LONG) | (INT, LONG) => bc.emitT2T(INT, LONG)
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala
index 360ce58ecc..dae53bc0e5 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala
@@ -14,6 +14,8 @@ import scala.tools.nsc.symtab._
 import scala.annotation.switch
 
 import scala.tools.asm
+import scala.tools.asm.util.{TraceMethodVisitor, ASMifier}
+import java.io.PrintWriter
 
 /*
  *
@@ -117,6 +119,9 @@ abstract class BCodeSkelBuilder extends BCodeHelpers {
 
       gen(cd.impl)
 
+      if (AsmUtils.traceClassEnabled && cnode.name.contains(AsmUtils.traceClassPattern))
+        AsmUtils.traceClass(cnode)
+
       assert(cd.symbol == claszSymbol, "Someone messed up BCodePhase.claszSymbol during genPlainClass().")
 
     } // end of method genPlainClass()
@@ -639,6 +644,10 @@ abstract class BCodeSkelBuilder extends BCodeHelpers {
         // Note we don't invoke visitMax, thus there are no FrameNode among mnode.instructions.
         // The only non-instruction nodes to be found are LabelNode and LineNumberNode.
       }
+
+      if (AsmUtils.traceMethodEnabled && mnode.name.contains(AsmUtils.traceMethodPattern))
+        AsmUtils.traceMethod(mnode)
+
       mnode = null
     } // end of method genDefDef()
 
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
index 8e6c09213f..1d29fdee10 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
@@ -1,6 +1,6 @@
 /* NSC -- new Scala compiler
  * Copyright 2005-2013 LAMP/EPFL
- * @author  Paul Phillips
+ * @author  Martin Odersky
  */
 
 package scala.tools.nsc
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
index 193100474c..61cf76f524 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
@@ -243,6 +243,17 @@ abstract class GenBCode extends BCodeSyncAndTry {
         val plainC  = SubItem3(plain.name, getByteArray(plain))
         val beanC   = if (bean == null)   null else SubItem3(bean.name, getByteArray(bean))
 
+        if (AsmUtils.traceSerializedClassEnabled && plain.name.contains(AsmUtils.traceSerializedClassPattern)) {
+          def readClass(bytes: Array[Byte]): asm.tree.ClassNode = {
+            val node = new asm.tree.ClassNode()
+            new asm.ClassReader(bytes).accept(node, 0)
+            node
+          }
+          if (mirrorC != null) AsmUtils.traceClass(readClass(mirrorC.jclassBytes))
+          AsmUtils.traceClass(readClass(plainC.jclassBytes))
+          if (beanC != null) AsmUtils.traceClass(readClass(beanC.jclassBytes))
+        }
+
         q3 add Item3(arrivalPos, mirrorC, plainC, beanC, outFolder)
 
       }