Integrated: 8295537: Enhance TRACE_METHOD_LINKAGE to show the target MethodHandle

[Ioi Lam]

On Mon, 24 Oct 2022 22:15:49 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> Improve the handling of the `java.lang.invoke.MethodHandle.TRACE_METHOD_LINKAGE` property to print out the full graph of MethodHandles that are used at a CallSite. This helps us understand how invokedynamic call sites are resolved. For example:
> 
> 
> public class StrConcat {
>     static String hello = "Hello";
>     static String world = "World";
>     public static void main(String args[]) {
>         System.out.println(hello + world);
>         System.out.println(hello + "World");
>     }
> }
> 
> $ java -Djava.lang.invoke.MethodHandle.TRACE_METHOD_LINKAGE=true -cp . StrConcat
> linkCallSite StrConcat.main(StrConcat.java:5) java.lang.invoke.StringConcatFactory.makeConcatWithConstants(Lookup,String,MethodType,String,Object[])CallSite/invokeStatic makeConcatWithConstants(String,String)String/BSA1=
> linkMethod java.lang.invoke.MethodHandle.invokeExact(Lookup,String,MethodType,String,Object[])CallSite/5
> linkMethod => java.lang.invoke.Invokers$Holder.invokeExact_MT(Object,Object,Object,Object,Object,Object,Object)Object/invokeStatic + (Lookup,String,MethodType,String,Object[])CallSite
> linkCallSite target class => java.lang.invoke.BoundMethodHandle$Species_L
> linkCallSite target => (String,String)String : BMH.reinvoke000_LLL_L=Lambda(a0:L/SpeciesData[L => Species_L],a1:L,a2:L)=>{
>     t3:L=Species_L.argL0(a0:L);
>     t4:L=MethodHandle.invokeBasic(t3:L,a1:L,a2:L);t4:L}
> & BMH=[
>   0: MethodHandle = {(Object,Object)String : DMH.invokeStatic000_LLL_L=Lambda(a0:L,a1:L,a2:L)=>{
>         t3:L=DirectMethodHandle.internalMemberName(a0:L);
>         t4:L=MethodHandle.linkToStatic(a1:L,a2:L,t3:L);t4:L}
>     & DMH.MN=java.lang.StringConcatHelper.simpleConcat(Object,Object)String/invokeStatic
>   }
> ]
> linkCallSite linkage => java.lang.invoke.Invokers$Holder.linkToTargetMethod(Object,Object,Object)Object/invokeStatic + MethodHandle(String,String)String
> HelloWorld
> linkCallSite StrConcat.main(StrConcat.java:6) java.lang.invoke.StringConcatFactory.makeConcatWithConstants(Lookup,String,MethodType,String,Object[])CallSite/invokeStatic makeConcatWithConstants(String)String/BSA1=World
> linkCallSite target class => java.lang.invoke.BoundMethodHandle$Species_LL
> linkCallSite target => (String)String : invoke000_LL_L=Lambda(a0:L/SpeciesData[LL => BoundMethodHandle$Species_LL],a1:L)=>{
>     t2:L=BoundMethodHandle$Species_LL.argL1(a0:L);
>     t3:L=BoundMethodHandle$Species_LL.argL0(a0:L);
>     t4:L=MethodHandle.invokeBasic(t3:L,a1:L,t2:L);t4:L}
> & BMH=[
>   0: MethodHandle = {(Object,Object)String : DMH.invokeStatic000_LLL_L=Lambda(a0:L,a1:L,a2:L)=>{
>         t3:L=DirectMethodHandle.internalMemberName(a0:L);
>         t4:L=MethodHandle.linkToStatic(a1:L,a2:L,t3:L);t4:L}
>     & DMH.MN=java.lang.StringConcatHelper.simpleConcat(Object,Object)String/invokeStatic
>   }
>   1: ( World )
> ]
> linkCallSite linkage => java.lang.invoke.Invokers$Holder.linkToTargetMethod(Object,Object)Object/invokeStatic + MethodHandle(String)String
> HelloWorld
> 
> 
> More complex examples are in the JBS bug report
> - https://bugs.openjdk.org/secure/attachment/101202/eclipse-ide-log.txt
> - https://bugs.openjdk.org/secure/attachment/101203/lambda-expression.txt
> - https://bugs.openjdk.org/secure/attachment/101205/pattern-matching-switch.txt
> - https://bugs.openjdk.org/secure/attachment/101204/str-concat.txt

This pull request has now been integrated.

Changeset: fd668dc4
Author:    Ioi Lam <iklam at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fd668dc44f54274518d2bb46c5e22318a872c02e
Stats:     75 lines in 5 files changed: 61 ins; 0 del; 14 mod

8295537: Enhance TRACE_METHOD_LINKAGE to show the target MethodHandle

Reviewed-by: jvernee, redestad, mchung

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PR: https://git.openjdk.org/jdk/pull/10842