Introduce BOP_CMP for optimized comparison

Prior to this commit the `OPTIMIZED_CMP` macro relied on a method lookup
to determine whether `<=>` was overridden. The result of the lookup was
cached, but only for the duration of the specific method that
initialized the cmp_opt_data cache structure.

With this method lookup, `[x,y].max` is slower than doing `x > y ?
x : y` even though there's an optimized instruction for "new array max".
(John noticed somebody a proposed micro-optimization based on this fact
in https://github.com/mastodon/mastodon/pull/19903.)

```rb
a, b = 1, 2
Benchmark.ips do |bm|
  bm.report('conditional') { a > b ? a : b }
  bm.report('method') { [a, b].max }
  bm.compare!
end
```

Before:

```
Comparison:
         conditional: 22603733.2 i/s
              method: 19820412.7 i/s - 1.14x  (± 0.00) slower
```

This commit replaces the method lookup with a new CMP basic op, which
gives the examples above equivalent performance.

After:

```
Comparison:
              method: 24022466.5 i/s
         conditional: 23851094.2 i/s - same-ish: difference falls within
error
```

Relevant benchmarks show an improvement to Array#max and Array#min when
not using the optimized newarray_max instruction as well. They are
noticeably faster for small arrays with the relevant types, and the same
or maybe a touch faster on larger arrays.

```
$ make benchmark COMPARE_RUBY=<master@5958c305> ITEM=array_min
$ make benchmark COMPARE_RUBY=<master@5958c305> ITEM=array_max
```

The benchmarks added in this commit also look generally improved.

Co-authored-by: John Hawthorn <jhawthorn@github.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/vm.c b/vm.c
index 0f0383b9b8..b2fca12b74 100644
--- a/vm.c
+++ b/vm.c
@@ -2035,6 +2035,7 @@ vm_init_redefined_flag(void)
     OP(And, AND), (C(Integer));
     OP(Or, OR), (C(Integer));
     OP(NilP, NIL_P), (C(NilClass));
+    OP(Cmp, CMP), (C(Integer), C(Float), C(String));
 #undef C
 #undef OP
 }