[9] RFR (M): 8037209: Improvements and cleanups to bytecode assembly for lambda forms (original) (raw)

Vladimir Ivanov vladimir.x.ivanov at oracle.com
Tue Jul 8 10:09:04 UTC 2014

I'd like to revive this review thread.

Updated version: http://cr.openjdk.java.net/~vlivanov/8037209/webrev.04/

Paul, I'd like to address your case (if possible) separately. Right now, I don't see any way to avoid null check you see with your tests.

Best regards, Vladimir Ivanov

On 3/24/14 8:33 PM, Vladimir Ivanov wrote:

Updated version: http://cr.openjdk.java.net/~vlivanov/8037209/webrev.01/

Changes: - rebased to enum-based BasicType; - decided to integrate changes for typed array getters/setters separately; Best regards, Vladimir Ivanov On 3/14/14 8:36 PM, Vladimir Ivanov wrote:

Doh! crossed webrevs, thanks.

Just had a quick look, this looks like a really nice improvement to the array setter/getter support, definitely simplified. IIUC the mh.viewAsType will now handle the appropriate casting. I believe it might reduce the "ceremony" for array setter/getter MHs [1]. I see there is a PROFILELEVEL option, by default set to 0, that results in casts not being emitted: + if (VerifyType.isNullConversion(Object.class, pclass, false)) { + if (PROFILELEVEL > 0) + emitReferenceCast(Object.class, arg); + return; + } ... + mv.visitLdcInsn(constantPlaceholder(cls)); + mv.visitTypeInsn(Opcodes.CHECKCAST, CLS); + mv.visitInsn(Opcodes.SWAP); + mv.visitMethodInsn(Opcodes.INVOKESTATIC, MHI, "castReference", CLLSIG, false); + if (Object[].class.isAssignableFrom(cls)) + mv.visitTypeInsn(Opcodes.CHECKCAST, OBJARY); + else if (PROFILELEVEL > 0) + mv.visitTypeInsn(Opcodes.CHECKCAST, OBJ); Can you explain a bit the rational for that? These casts are redundant - they aren't required for bytecode correctness. The idea behind PROFILELEVEL is to provide more type information to JIT-compiler. Right now, type profiling occurs on every checkcast instruction. So, having these additional instructions we can feed C2 with more accurate information about types. Consider this as a hack to overcome some of the limitations of current profiling implementation in VM. Best regards, Vladimir Ivanov Paul. [1] Below is an inlining trace for an array getter MH in the current code i obtained a few weeks ago when investigating CAS-based MHs for arrays: Inlining isInstance on constant Class java/lang/Class Inlining isInstance on constant Class [Ljava/lang/Object; Inlining isInstance on constant Class [Ljava/lang/String; Inlining isInstance on constant Class java/lang/String @ 12 unsafe.ArrayMHTest::getmhorig (19 bytes) inline (hot) @ 12 java.lang.invoke.LambdaForm$MH/924874137::invokeExactMT (15 bytes) inline (hot) @ 2 java.lang.invoke.Invokers::checkExactType (30 bytes) inline (hot) @ 11 java.lang.invoke.MethodHandle::type (5 bytes) accessor @ 11 java.lang.invoke.LambdaForm$MH/1980556943::convert (21 bytes) inline (hot) @ 7 java.lang.invoke.LambdaForm$MH/1892887290::getElement (20 bytes) inline (hot) @ 16 java.lang.invoke.LambdaForm$MH/816943783::convert (37 bytes) inline (hot) @ 6 java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes) inline (hot) @ 12 java.lang.invoke.BoundMethodHandle$SpeciesLL::reinvokerTarget (8 bytes) inline (hot) @ 22 java.lang.invoke.LambdaForm$DMH/1162873666::invokeStaticLLL (15 bytes) inline (hot) @ 1 java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes) inline (hot) @ 11 sun.invoke.util.ValueConversions::castReference (20 bytes) inline (hot) @ 6 java.lang.Class::isInstance (0 bytes) (intrinsic) @ 17 java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes) inline (hot) @ 12 java.lang.invoke.BoundMethodHandle$SpeciesLL::reinvokerTarget (8 bytes) inline (hot) @ 22 java.lang.invoke.LambdaForm$DMH/1162873666::invokeStaticLLL (15 bytes) inline (hot) @ 1 java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes) inline (hot) @ 11 sun.invoke.util.ValueConversions::castReference (20 bytes) inline (hot) @ 6 java.lang.Class::isInstance (0 bytes) (intrinsic) @ 33 java.lang.invoke.MethodHandleImpl$ArrayAccessor::getElementL (10 bytes) inline (hot) @ 2 java.lang.Class::cast (27 bytes) inline (hot) @ 6 java.lang.Class::isInstance (0 bytes) (intrinsic) @ 17 java.lang.invoke.LambdaForm$MH/91466391::convert (23 bytes) inline (hot) @ 6 java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes) inline (hot) @ 12 java.lang.invoke.BoundMethodHandle$SpeciesLL::reinvokerTarget (8 bytes) inline (hot) @ 22 java.lang.invoke.LambdaForm$DMH/1162873666::invokeStaticLLL (15 bytes) inline (hot) @ 1 java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes) inline (hot) @ 11 sun.invoke.util.ValueConversions::castReference (20 bytes) inline (hot) @ 6 java.lang.Class::isInstance (0 bytes) (intrinsic) @ 19 java.lang.invoke.LambdaForm$MH/349834280::identity (10 bytes) inline (hot) @ 6 java.lang.invoke.LambdaForm$DMH/1357006072::invokeStaticLL (14 bytes) inline (hot) @ 1 java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes) inline (hot) @ 10 sun.invoke.util.ValueConversions::identity (2 bytes) inline (hot)

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