ZJIT uses the interpreter to take type profiles of what objects pass through
the code. It stores a compressed record of the history per opcode for the
opcodes we select.
Before this change, we re-used the HIR Type data-structure, a shallow type
lattice, to store historical type information. This was quick for bringup but
is quite lossy as profiles go: we get one bit per built-in type seen, and if we
see a non-built-in type in addition, we end up with BasicObject. Not very
helpful. Additionally, it does not give us any notion of cardinality: how many
of each type did we see?
This change brings with it a much more interesting slice of type history: a
histogram. A Distribution holds a record of the top-N (where N is fixed at Ruby
compile-time) `(Class, ShapeId)` pairs and their counts. It also holds an
*other* count in case we see more than N pairs.
Using this distribution, we can make more informed decisions about when we
should use type information. We can determine if we are strictly monomorphic,
very nearly monomorphic, or something else. Maybe the call-site is polymorphic,
so we should have a polymorphic inline cache. Exciting stuff.
I also plumb this new distribution into the HIR part of the compilation
pipeline.
Fixes `TestZJIT::test_require_rubygems`. It was crashing locally due to
false collection of a live object. See
<https://alanwu.space/post/write-barrier/>.
Co-authored-by: Max Bernstein <max@bernsteinbear.com>
Co-authored-by: Takashi Kokubun <takashi.kokubun@shopify.com>
Co-authored-by: Stan Lo <stan.lo@shopify.com>
This commit allows building YJIT and ZJIT simultaneously, a "combo
build". Previously, `./configure --enable-yjit --enable-zjit` failed. At
runtime, though, only one of the two can be enabled at a time.
Add a root Cargo workspace that contains both the yjit and zjit crate.
The common Rust build integration mechanisms are factored out into
defs/jit.mk.
Combo YJIT+ZJIT dev builds are supported; if either JIT uses
`--enable-*=dev`, both of them are built in dev mode.
The combo build requires Cargo, but building one JIT at a time with only
rustc in release build remains supported.
As well as `RB_OBJ_SHAPE_ID` -> `rb_obj_shape_id`
and `RSHAPE` is now a simple alias for `rb_shape_lookup`.
I tried to turn all these into `static inline` but I'm having
trouble with `RUBY_EXTERN rb_shape_tree_t *rb_shape_tree_ptr;`
not being exposed as I'd expect.
Working towards having YJIT and ZJIT in the same build, we need to
deduplicate some glue code that would otherwise cause name collision.
Add jit.c for this and build it for YJIT and ZJIT builds. Update bindgen
to look at jit.c; some shuffling of functions in the output, but the set
of functions shouldn't have changed.
