RFR: 8274983: Pattern.matcher performance regression after JDK-8238358

[Dean Long]

On Sat, 20 Nov 2021 04:40:51 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> It looks like this does what we want for private interface methods, but I'm wondering if we handle all combinations of private/final and invokevirtual/invokeinterface, or are we missing some cases where can_be_statically_bound() would return true?
>
> hi, @dean-long,
> 
> I think C1 covers all cases as long as the target method is loaded. I have seen cases which target methods haven't been loaded in startup time, but they are rare. 
> 
> ciMethod::can_be_statically_bound() return true if the method is private or final. The matrix shows the modifiers of target methods.
> 
> |                 | final | private | 
> |-----------------|-------|---------|
> | invokevirtual   | 1     | 2       | 
> | invokespecial   | N/A1    | 3       |
> | invokeinterface | N/A2    | 4       | 
> 
> 1. generates the optimized virtual call because [x->target_is_final()](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/c1/c1_LIRGenerator.cpp#L2799) is true.
> 2. transforms to `invokespecial` [here](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/c1/c1_GraphBuilder.cpp#L1885) ,  then it will be case 3. 
> 3. generates the optimize virtual call because `x->code() == Bytecodes::_invokespecial` is true.
> 4. is what this patch covers. 
> 
> NA-1. I think it's impossible for javac.  it would be an optimized virtual call like case 3 even it existed.
> NA-2: it's an illegal modifier for an interface method.
>  https://docs.oracle.com/javase/specs/jls/se17/html/jls-9.html#jls-InterfaceMethodModifier

Thanks @navyxliu.  I wonder if we can do 2) and 3) for invokeinterface, simplying the patch.  Something like:

  // Some methods are obviously bindable without any type checks so
  // convert them directly to an invokespecial or invokestatic.
  if (target->is_loaded() && !target->is_abstract() && target->can_be_statically_bound()) {
    switch (bc_raw) {
    case Bytecodes::_invokevirtual:
    case Bytecodes::_invokeinterface::
      code = Bytecodes::_invokespecial;
      break;
[...]
  // invoke-special-super
  if (code == Bytecodes::_invokespecial && !target->is_object_initializer()) {
    ciInstanceKlass* sender_klass = calling_klass;
    if (sender_klass->is_interface()) {
[...]

What do you think?

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

PR: https://git.openjdk.java.net/jdk/pull/6445