Current behavior - caches depend on a global counter. All constant mutations cause caches to be invalidated.
```ruby
class A
B = 1
end
def foo
A::B # inline cache depends on global counter
end
foo # populate inline cache
foo # hit inline cache
C = 1 # global counter increments, all caches are invalidated
foo # misses inline cache due to `C = 1`
```
Proposed behavior - caches depend on name components. Only constant mutations with corresponding names will invalidate the cache.
```ruby
class A
B = 1
end
def foo
A::B # inline cache depends constants named "A" and "B"
end
foo # populate inline cache
foo # hit inline cache
C = 1 # caches that depend on the name "C" are invalidated
foo # hits inline cache because IC only depends on "A" and "B"
```
Examples of breaking the new cache:
```ruby
module C
# Breaks `foo` cache because "A" constant is set and the cache in foo depends
# on "A" and "B"
class A; end
end
B = 1
```
We expect the new cache scheme to be invalidated less often because names aren't frequently reused. With the cache being invalidated less, we can rely on its stability more to keep our constant references fast and reduce the need to throw away generated code in YJIT.
This commit implements arrays on Variable Width Allocation. This allows
longer arrays to be embedded (i.e. contents directly follow the object
header) which improves performance through better cache locality.
Header file include/ruby/internal/abi.h contains RUBY_ABI_VERSION which
is the ABI version. This value should be bumped whenever an ABI
incompatible change is introduced.
When loading dynamic libraries, Ruby will compare its own
`ruby_abi_version` and the `ruby_abi_version` of the loaded library. If
these two values don't match it will raise a `LoadError`. This feature
can also be turned off by setting the environment variable
`RUBY_RUBY_ABI_CHECK=0`.
This feature will prevent cases where previously installed native gems
fail in unexpected ways due to incompatibility of changes in header
files. This will force the developer to recompile their gems to use the
same header files as the built Ruby.
In Ruby, the ABI version is exposed through
`RbConfig::CONFIG["ruby_abi_version"]`.
Configuration for mingw32 can't detect 'shutdown' due to wrong -l
option even though it's available (this has been going on for a while,
and it needs to be fixed).
In this situation, include/ruby/missing.h declares a stub shutdown
function since 7ee786388a, and another shutdown decl is came from
system header. They are incompatible at stdcall attribute, so it
causes compilation failure.
This change defines a HAVE_SHUTDOWN to guard a newly introduced stub
decl in include/ruby/missing.h
At least OpenBSD/sparc64 doesn't appear to define them, and possibly
some other OpenBSD GCC platforms don't (most OpenBSD platforms have
already switched to clang).
- prerequisite of supporting YJIT with VC++.
- note that now can specfily `--yjit` on mswin64, but not enabled
YJIT'ed code because of YJIT requires `OPT_DIRECT_THREADED_CODE`
or `OPT_CALL_THREADED_CODE` in `rb_yjit_compile_iseq`.
