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

[Paul Sandoz]

On Mar 14, 2014, at 2:17 PM, Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote:

> Paul,
> 
> You are looking at the other fix (8037210).
> The correct link is [1].
> 

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 PROFILE_LEVEL option, by default set to 0, that results in casts not being emitted:

+                if (VerifyType.isNullConversion(Object.class, pclass, false)) {
+                    if (PROFILE_LEVEL > 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", CLL_SIG, false);
+            if (Object[].class.isAssignableFrom(cls))
+                mv.visitTypeInsn(Opcodes.CHECKCAST, OBJARY);
+            else if (PROFILE_LEVEL > 0)
+                mv.visitTypeInsn(Opcodes.CHECKCAST, OBJ);

Can you explain a bit the rational for that?

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::get_mh_orig (19 bytes)   inline (hot)
                              @ 12   java.lang.invoke.LambdaForm$MH/924874137::invokeExact_MT (15 bytes)   inline (hot)
                                @ 2   java.lang.invoke.Invokers::checkExactType (30 bytes)   inline (hot)
                                  @ 11   java.lang.invoke.MethodHandle::type (5 bytes)   accessor
                                @ 11   java.lang.invoke.LambdaForm$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$BMH/1350345087::reinvoke (26 bytes)   inline (hot)
                                        @ 12   java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8 bytes)   inline (hot)
                                        @ 22   java.lang.invoke.LambdaForm$DMH/1162873666::invokeStatic_LL_L (15 bytes)   inline (hot)
                                          @ 1   java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)   inline (hot)
                                          @ 11   sun.invoke.util.ValueConversions::castReference (20 bytes)   inline (hot)
                                            @ 6   java.lang.Class::isInstance (0 bytes)   (intrinsic)
                                      @ 17   java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes)   inline (hot)
                                        @ 12   java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8 bytes)   inline (hot)
                                        @ 22   java.lang.invoke.LambdaForm$DMH/1162873666::invokeStatic_LL_L (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$BMH/1350345087::reinvoke (26 bytes)   inline (hot)
                                      @ 12   java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8 bytes)   inline (hot)
                                      @ 22   java.lang.invoke.LambdaForm$DMH/1162873666::invokeStatic_LL_L (15 bytes)   inline (hot)
                                        @ 1   java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)   inline (hot)
                                        @ 11   sun.invoke.util.ValueConversions::castReference (20 bytes)   inline (hot)
                                          @ 6   java.lang.Class::isInstance (0 bytes)   (intrinsic)
                                    @ 19   java.lang.invoke.LambdaForm$MH/349834280::identity (10 bytes)   inline (hot)
                                      @ 6   java.lang.invoke.LambdaForm$DMH/1357006072::invokeStatic_L_L (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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