From e994c1c0becddc0d91fd4428f0d673bfac8941a3 Mon Sep 17 00:00:00 2001 From: Jason Zaugg Date: Mon, 26 Sep 2016 09:47:49 +1000 Subject: SD-233 synchronized blocks are JIT-friendly again GenBCode, the new backend in Scala 2.12, subtly changed the way that synchronized blocks are emitted. It used `java/lang/Throwable` as an explicitly named exception type, rather than implying the same by omitting this in bytecode. This appears to confuse HotSpot JIT, which reports a error parsing the bytecode into its IR which leaves the enclosing method stuck in interpreted mode. This commit passes a `null` descriptor to restore the old pattern (the same one used by javac.) I've checked that the JIT warnings are gone and that the method can be compiled again. --- src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala | 4 +++- test/junit/scala/tools/nsc/backend/jvm/BytecodeTest.scala | 8 ++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala index 3e53419573..466793010f 100644 --- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala +++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSyncAndTry.scala @@ -73,9 +73,11 @@ abstract class BCodeSyncAndTry extends BCodeBodyBuilder { /* ------ (4) exception-handler version of monitor-exit code. * Reached upon abrupt termination of (2). * Protected by whatever protects the whole synchronized expression. + * null => "any" exception in bytecode, like we emit for finally. + * Important not to use j/l/Throwable which dooms the method to a life of interpretation! (SD-233) * ------ */ - protect(startProtected, endProtected, currProgramPoint(), jlThrowableRef) + protect(startProtected, endProtected, currProgramPoint(), null) locals.load(monitor) emit(asm.Opcodes.MONITOREXIT) emit(asm.Opcodes.ATHROW) diff --git a/test/junit/scala/tools/nsc/backend/jvm/BytecodeTest.scala b/test/junit/scala/tools/nsc/backend/jvm/BytecodeTest.scala index b09a41969e..00b6d1cc42 100644 --- a/test/junit/scala/tools/nsc/backend/jvm/BytecodeTest.scala +++ b/test/junit/scala/tools/nsc/backend/jvm/BytecodeTest.scala @@ -187,4 +187,12 @@ class BytecodeTest extends BytecodeTesting { List(Label(0), LineNumber(2, Label(0)), VarOp(ALOAD, 0), Invoke(INVOKESPECIAL, "T", "t", "()V", true), Op(RETURN), Label(4)) ) } + + @Test + def sd233(): Unit = { + val code = "def f = { println(1); synchronized(println(2)) }" + val m = compileMethod(code) + val List(ExceptionHandler(_, _, _, desc)) = m.handlers + assert(desc == None, desc) + } } -- cgit v1.2.3