RFR: 8271461: CompileCommand support for hidden class methods [v2]

[Ioi Lam]

On Fri, 30 Jul 2021 02:01:55 GMT, Jie Fu <jiefu at openjdk.org> wrote:

>> Hi all,
>> 
>> We'd like to improve the CompileCommand to support hidden class methods, which is helpful for debugging and perfmance analysis.
>> 
>> Current implementation of CompileCommand doesn't work for hidden class methods.
>> For example, if you run with `java -Xcomp -Xbatch -XX:+PrintCompilation`
>> The following hidden class methods were compiled:
>> 
>>    5317 1573    b  3       java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run (8 bytes)
>>    5318 1574    b  4       java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run (8 bytes)
>>    6735 1938    b  3       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$2/0x0000000801041e80::run (12 bytes)
>>    6736 1939    b  4       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$2/0x0000000801041e80::run (12 bytes)
>>    7060 2029    b  3       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$58/0x800000060::run (8 bytes)
>>    7061 2030    b  4       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$58/0x800000060::run (8 bytes)
>>    7688 2153    b  3       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$4/0x0000000801043218::run (16 bytes)
>>    7688 2154    b  4       java.util.ResourceBundle$ResourceBundleProviderHelper$$Lambda$4/0x0000000801043218::run (16 bytes)
>> 
>> 
>> Then people may want to exclude the compilation of `java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run` like this
>> 
>> -XX:CompileCommand=exclude,'java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run'
>> 
>> 
>> But unfortunately, it doesn't work.
>> 
>> CompileCommand: An error occurred during parsing
>> Error: Method pattern uses '/' together with '::'
>> Line: 'exclude,java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run'
>> 
>> Usage: '-XX:CompileCommand=<option>,<method pattern>' - to set boolean option to true
>> Usage: '-XX:CompileCommand=<option>,<method pattern>,<value>'
>> Use:   '-XX:CompileCommand=help' for more information and to list all option.
>> 
>> 
>> The failing reason is that the name of `java.util.ResourceBundle$$Lambda$1/0x00000008010413c8::run` is actually `java.util.ResourceBundle$$Lambda$1+0x00000008010413c8::run` in the VM.
>> But "+" had been replaced with "/" when it was printed by PrintCompilation [1].
>> 
>> So for a hidden class method, "/" should be replaced with "+" to make CompileCommand work.
>> 
>> Thanks.
>> Best regards,
>> Jie
>> 
>> 
>> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/oops/klass.cpp#L685
>
> Jie Fu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use isdigit

There's no guarantee that the same class names will be used. Here's an example that prints out the name of the auto-generated Lambda proxy class which invokes the Lambda expression inside the `test1()` function:


$ java Lambda.java 1
Lambda$$Lambda$233/0x0000000800d4c1f0.run
$ java Lambda.java 2
Lambda$$Lambda$234/0x0000000800d4c3f8.run



import java.lang.StackWalker.StackFrame;
import java.util.List;
import java.util.stream.Collectors;
import java.util.Set;

public class Lambda {
    public static void main(String args[]) {
        if (args.length > 0 && args[0].equals("1")) {
            test1(); test0();
        } else {
            test0(); test1();
        }
    }

    static void test0() { doit(() -> {}); }
    static void test1() { doit(() -> { System.out.println(getCaller(1)); });  }
    static void doit(Runnable r) { r.run(); }

    // depth==0 returns the immediate caller of getCaller
    static String getCaller(int depth) {
        StackWalker walker = StackWalker.getInstance(
            Set.of(StackWalker.Option.RETAIN_CLASS_REFERENCE,
                   StackWalker.Option.SHOW_HIDDEN_FRAMES));
        List<StackFrame> stack = walker.walk(s -> s.limit(depth+2).collect(Collectors.toList()));
        StackFrame sf = stack.get(depth+1);
        return sf.getDeclaringClass().getName() + "." + sf.getMethodName();
    }
}

-------------

PR: https://git.openjdk.java.net/jdk/pull/4926