I've added a `java.lang.invoke.MethodHandle.TRACE_CALLSITE` property to show
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_CALLSITE=true -cp . StrConcat
======== CallSite: StrConcat.main(StrConcat.java:5)
BSM =
java.base/java.lang.invoke.StringConcatFactory.makeConcatWithConstants(StringConcatFactory.java:354)
target class = java.lang.invoke.BoundMethodHandle$Species_L
target = (String,String)String : BMH.reinvoke=Lambda(a0:L/SpeciesData[L =>
Species_L],a1:L,a2:L)=>{
t3:L=Species_L.argL0(a0:L);
t4:L=MethodHandle.invokeBasic(t3:L,a1:L,a2:L);t4:L}
& BMH=[
0: MethodHandle = {(Object,Object)String :
DMH.invokeStatic=Lambda(a0:L,a1:L,a2:L)=>{
t3:L=DirectMethodHandle.internalMemberName(a0:L);
t4:L=MethodHandle.linkToStatic(a1:L,a2:L,t3:L);t4:L}
&
DMH.MN=java.lang.StringConcatHelper.simpleConcat(Object,Object)String/invokeStatic
}
]
HelloWorld
======== CallSite: StrConcat.main(StrConcat.java:6)
BSM =
java.base/java.lang.invoke.StringConcatFactory.makeConcatWithConstants(StringConcatFactory.java:354)
target class = java.lang.invoke.BoundMethodHandle$Species_LL
target = (String)String : invoke=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.invokeStatic=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 )
]
HelloWorld
More complex examples are in the JBS bug report
- https://bugs.openjdk.org/secure/attachment/101170/eclipse-ide-log.txt
- https://bugs.openjdk.org/secure/attachment/101168/lambda-expression.txt
- https://bugs.openjdk.org/secure/attachment/101174/pattern-matching-switch.txt
- https://bugs.openjdk.org/secure/attachment/101169/str-concat.txt
-------------
Commit messages:
- also print the BSM
- cleaned up code; added comments; avoid using indy inside TRACE_CALLSITE;
avoid interleaving output
- 8295537: Debug tracing for resolved dynamic call sites
Changes: https://git.openjdk.org/jdk/pull/10842/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10842&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8295537
Stats: 127 lines in 6 files changed: 114 ins; 0 del; 13 mod
Patch: https://git.openjdk.org/jdk/pull/10842.diff
Fetch: git fetch https://git.openjdk.org/jdk pull/10842/head:pull/10842
PR: https://git.openjdk.org/jdk/pull/10842
