YJIT: Support nil and blockparamproxy as blockarg in send

[matthewd]

Here, @jhawthorn and I have implemented support for the simple but common cases of supplying a block to send via a blockparamproxy (or a nil). Because the blockparamproxy only appears in controlled circumstances, we are able to rely entirely on the type system to recognise this case, without runtime checks.

To support that, we've added a new Type::BlockParamProxy. It mostly fits in there with the other singleton types like Type::True, though it's unique in that it's not accessible from Ruby code (despite being a real VALUE object).

We've also moved some logic into gen_push_frame, turning CurrentFrame into a parameterized BlockISeq(IseqPtr). In the process, we've folded in PrevEP, renaming the enum from BlockHandler to SpecVal. They're mutually exclusive (they both end up storing their value in the same place), so this allows the type system to enforce that.

[jhawthorn]

This reduces total exits by 9%, from 2509837 to 2275480

Before:

method call exit reasons: 
                block_arg     299619 (40.8%)
    optimized_method_call     177089 (24.1%)
...

After:

method call exit reasons: 
    optimized_method_call     177089 (33.4%)
      iseq_complex_callee     143880 (27.1%)
              iseq_zsuper      46021 ( 8.7%)
    optimized_method_send      39761 ( 7.5%)
      args_splat_non_iseq      36747 ( 6.9%)
                block_arg      33595 ( 6.3%)

[maximecb]

Would also like a comment explaining what SpecVal is generally used for. In general, it's best not to assume that people are familiar with all the details of the CRuby codebase and send imo.

[maximecb]

Looks good over all with some minor comments and one test failure.

[maximecb]

This reduces total exits by 9%, from 2509837 to 2275480

Before:

method call exit reasons: 
                block_arg     299619 (40.8%)
    optimized_method_call     177089 (24.1%)
...

After:

method call exit reasons: 
    optimized_method_call     177089 (33.4%)
      iseq_complex_callee     143880 (27.1%)
              iseq_zsuper      46021 ( 8.7%)
    optimized_method_send      39761 ( 7.5%)
      args_splat_non_iseq      36747 ( 6.9%)
                block_arg      33595 ( 6.3%)

Nice 👌

[XrXr]

Looks nice!

[k0kubun]

FYI for the Arm CI failure:

$ cat /tmp/a.rb
define_method(:foo) do |&block|
  block.call
end

def bar(&block)
  foo(&block)
end

bar { 1 }
bar { 2 }

$ RUST_BACKTRACE=1 ruby --disable-gems --yjit-verify-ctx --yjit-call-threshold=1 /tmp/a.rb
thread '<unnamed>' panicked at 'verify_ctx: ctx type (BlockParamProxy) incompatible with actual value on stack: T_OBJECT', src/codegen.rs:352:13
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: yjit::codegen::verify_ctx
             at ./yjit/src/codegen.rs:352:13
   3: yjit::codegen::gen_single_block
             at ./yjit/src/codegen.rs:778:13
   4: yjit::core::gen_block_series_body
             at ./yjit/src/core.rs:1440:23
   5: yjit::core::gen_block_series
             at ./yjit/src/core.rs:1418:18
   6: yjit::core::branch_stub_hit_body
             at ./yjit/src/core.rs:1774:17
   7: yjit::core::branch_stub_hit::{{closure}}
             at ./yjit/src/core.rs:1678:13
   8: std::panicking::try::do_call
             at /private/tmp/rust-20220719-52938-vitvrw/rustc-1.62.1-src/library/std/src/panicking.rs:492:40
   9: ___rust_try
  10: std::panicking::try
             at /private/tmp/rust-20220719-52938-vitvrw/rustc-1.62.1-src/library/std/src/panicking.rs:456:19
  11: std::panic::catch_unwind
             at /private/tmp/rust-20220719-52938-vitvrw/rustc-1.62.1-src/library/std/src/panic.rs:137:14
  12: yjit::cruby::with_vm_lock
             at ./yjit/src/cruby.rs:577:21
  13: yjit::core::branch_stub_hit
             at ./yjit/src/core.rs:1677:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
YJIT panicked while holding VM lock acquired at src/core.rs:1677. Aborting...
zsh: abort      RUST_BACKTRACE=1 ruby --disable-gems --yjit-verify-ctx --yjit-call-threshold=

[k0kubun]

ratio_in_yjit: 88.3% (https://github.com/ruby/ruby/actions/runs/3330379311/jobs/5508791316) → 89.7% (https://github.com/ruby/ruby/actions/runs/3331130072/jobs/5510507239)

Nice 🙂

[maximecb]

Good work! :)