* Rename --jit to --mjit
[Feature #18349]
* Fix a few more --jit references
* Fix MJIT Actions
* More s/jit/mjit/ and re-introduce --disable-jit
* Update NEWS.md
* Fix test_bug_reporter_add
As part of YJIT's strategy for promoting Ruby constant expressions into
constants in the output native code, the interpreter calls
rb_yjit_constant_ic_update() from opt_setinlinecache.
The block invalidation loop indirectly calls rb_darray_remove_unordered(),
which does a shuffle remove. Because of this, looping with an
incrementing counter like done previously can miss some elements in the
array. Repeatedly invalidate the first element instead.
The bug this commit resolves does not seem to cause crashes or divergent
behaviors.
Co-authored-by: Jemma Issroff <jemmaissroff@gmail.com>
Previously, YJIT assumed that basic blocks never consume more than
1 KiB of memory. This assumption does not hold for long Ruby methods
such as the one in the following:
```ruby
eval(<<RUBY)
def set_local_a_lot
#{'_=0;'*0x40000}
end
RUBY
set_local_a_lot
```
For low `--yjit-exec-mem-size` values, one basic block could exhaust the
entire buffer.
Introduce a new field `codeblock_t::dropped_bytes` that the assembler
sets whenever it runs out of space. Check this field in
gen_single_block() to respond to out of memory situations and other
error conditions. This design avoids making the control flow graph of
existing code generation functions more complex.
Use POSIX shell in misc/test_yjit_asm.sh since bash is expanding
`0%/*/*` differently.
Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>
If YJIT isn't enabled, or hasn't finished booting, cb / ocb could be
null. This commit just checks to make sure they're available before
marking as executable
Co-Authored-By: Maxime Chevalier-Boisvert <maxime.chevalierboisvert@shopify.com>
Co-Authored-By: Kevin Newton <kddnewton@gmail.com>
Some platforms don't want memory to be marked as writeable and
executable at the same time. When we write to the code block, we
calculate the OS page that the buffer position maps to. Then we call
`mprotect` to allow writes on that particular page. As an optimization,
we cache the "last written" aligned page which allows us to amortize the
cost of the `mprotect` call. In other words, sequential writes to the
same page will only call `mprotect` on the page once.
When we're done writing, we call `mprotect` on the entire JIT buffer.
This means we don't need to keep track of which pages were marked as
writeable, we let the OS take care of that.
Co-authored-by: John Hawthorn <john@hawthorn.email>
Previously, YJIT crashes with rb_bug() when asked to compile new methods
while out of executable memory.
To handle this situation gracefully, this change keeps track of all the
blocks compiled each invocation in case YJIT runs out of memory in the
middle of a compliation sequence. The list is used to free all blocks in
case compilation fails.
yjit_gen_block() is renamed to gen_single_block() to make it distinct from
gen_block_version(). Call to limit_block_version() and block_t
allocation is moved into the function to help tidy error checking in the
outer loop.
limit_block_version() now returns by value. I feel that an out parameter
with conditional mutation is unnecessarily hard to read in code that
does not need to go for last drop performance. There is a good chance
that the optimizer is able to output identical code anyways.
Previously, YJIT assumed that it's always possible to generate a new
basic block when servicing a stub in branch_stub_hit(). When YJIT is out
of executable memory, for example, this assumption doesn't hold up.
Add handling to branch_stub_hit() for servicing stubs without consuming
more executable memory by adding a code path that exits to the
interpreter at the location the branch stub represents. The new code
path reconstructs interpreter state in branch_stub_hit() and then exits
with a new snippet called `code_for_exit_from_stub` that returns
`Qundef` from the YJIT native stack frame.
As this change adds another place where we regenerate code from
`branch_t`, extract the logic for it into a new function and call it
regenerate_branch(). While we are at it, make the branch shrinking code
path in branch_stub_hit() more explicit.
This new functionality is hard to test without full support for out of
memory conditions. To verify this change, I ran
`RUBY_YJIT_ENABLE=1 make check -j12` with the following patch to stress
test the new code path:
```diff
diff --git a/yjit_core.c b/yjit_core.c
index 4ab63d9806..5788b8c5ed 100644
--- a/yjit_core.c
+++ b/yjit_core.c
@@ -878,8 +878,12 @@ branch_stub_hit(branch_t *branch, const uint32_t target_idx, rb_execution_contex
cb_set_write_ptr(cb, branch->end_addr);
}
+if (rand() < RAND_MAX/2) {
// Compile the new block version
p_block = gen_block_version(target, target_ctx, ec);
+}else{
+ p_block = NULL;
+}
if (!p_block && branch_modified) {
// We couldn't generate a new block for the branch, but we modified the branch.
```
We can enable the new test along with other OOM tests once full support
lands.
Other small changes:
* yjit_utils.c (print_str): Update to work with new native frame shape.
Follow up for 8fa0ee4d40.
* yjit_iface.c (rb_yjit_init): Run yjit_init_core() after
yjit_init_codegen() so `cb` and `ocb` are available.
This commit adds an entry_exit field to block_t for use in
invalidate_block_version(). By patching the start of the block while
invalidating it, invalidate_block_version() can function correctly
while there is no executable memory left for new branch stubs.
This change additionally fixes correctness for situations where we
cannot patch incoming jumps to the invalidated block. In situations
such as Shopify/yjit#226, the address to the start of the block
is saved and used later, possibly after the block is invalidated.
The assume_* family of function now generate block->entry_exit before
remembering blocks for invalidation.
RubyVM::YJIT.simulate_oom! is introduced for testing out of memory
conditions. The test for it is disabled for now because OOM triggers
other failure conditions not addressed by this commit.
FixesShopify/yjit#226
* Add --yjit-no-type-prop so we can test YJIT without type propagation
* Fix typo in command line option
* Leave just two test workflows enable for YJIT
* New code page allocation logic
* Fix leaked globals
* Fix leaked symbols, yjit asm tests
* Make COUNTED_EXIT take a jit argument, so we can eliminate global ocb
* Remove extra whitespace
* Change block start_pos/end_pos to be pointers instead of uint32_t
* Change branch end_pos and start_pos to end_addr, start_addr
This change fixes `-v --yjit-stats`. Previously in this situation,
YJIT._print_stats wasn't defined as yjit.rb is not evaluated when there
is only "-v" and no Ruby code to run.
For upstreaming, we want functions we export either prefixed with "rb_"
or made static. Historically we haven't been following this rule, so we
were "leaking" a lot of symbols as `make leak-globals` would tell us.
This change unifies everything YJIT into a single compilation unit,
yjit.o, and makes everything unprefixed static to pass `make leak-globals`.
This manual "unified build" setup is similar to that of vm.o.
Having everything in one compilation unit allows static functions to
be visible across YJIT files and removes the need for declarations in
headers in some cases. Unnecessary declarations were removed.
Other changes of note:
- switched to MJIT_SYMBOL_EXPORT_BEGIN which indicates stuff as being
off limits for native extensions
- the first include of each YJIT file is change to be "internal.h"
- undefined MAP_STACK before explicitly redefining it since it
collide's with a definition in system headers. Consider renaming?
YJIT expects the VM to invalidate opt_getinlinecache when updating the
constant cache, and the invalidation used to happen even when YJIT can't
use the cached value.
Once the first invalidation happens, the block for opt_getinlinecache
becomes a stub. When the stub is hit, YJIT fails to compile the
instruction as the cache is not usable. The stub becomes a block that
exits for opt_getinlinecache which can be invalidated again. Some
workloads that bust the interpreter's constant cache can create an
invalidation loop with this behavior.
Check if the cache is usable become doing invalidation to fix this
problem.
In the test harness, evaluate the test script in a lambda instead of a
proc so `return` doesn't return out of the harness.
For use cases where you want to collect the metrics
for a specific piece of code (typically a web request)
you can have the stats turned off by default and then
turn them on at runtime before executing the code you care
about.
This change fixes some cases where YJIT fails to fire tracing events.
Most of the situations YJIT did not handle correctly involves enabling
tracing while running inside generated code.
A new operation to invalidate all generated code is added, which uses
patching to make generated code exit at the next VM instruction
boundary. A new routine called `jit_prepare_routine_call()` is
introduced to facilitate this and should be used when generating code
that could allocate, or could otherwise use `RB_VM_LOCK_ENTER()`.
The `c_return` event is fired in the middle of an instruction as opposed
to at an instruction boundary, so it requires special handling. C method
call return points are patched to go to a fucntion which does everything
the interpreter does, including firing the `c_return` event. The
generated code for C method calls normally does not fire the event.
Invalided code should not change after patching so the exits are not
clobbered. A new variable is introduced to track the region of code that
should not change.
RUBY_DEBUG have a very significant performance overhead. Enough that
YJIT with RUBY_DEBUG is noticeably slower than the interpreter without
RUBY_DEBUG.
This makes it hard to collect yjit-stats in production environments.
By allowing to collect JIT statistics without the RUBy_DEBUG overhead,
I hope to make such use cases smoother.
If `--disable-jit-support` is passed to configure, then `jit_func` is
removed from the iseq body and we can't compile YJIT. This commit
detects when the JIT function pointer is gone and disables YJIT in that
case.
Always using `ret` to return to the interpreter means that we never have
to check the VM_FRAME_FLAG_FINISH flag.
In the case that we return `Qundef`, the interpreter will execute the
cfp. We can take advantage of this by setting the PC to the instruction
we can't handle, and let the interpreter pick up the ball from there.
If we return a value other than Qundef, the interpreter will take that
value as the "return value" from the JIT and push that to the SP of the
caller
The leave instruction puts the return value on the top of the calling
frame's stack. YJIT does the same thing for leave instructions.
However, when we're returning back to the interpreter, the leave
instruction _should not_ put the return value on the top of the stack,
but put it in RAX and use RET. This commit pops the last value from the
stack pointer and puts it in RAX so that the interpreter is happy with
SP.
Alan Wu
Nobuyoshi Nakada
John Hawthorn
Takashi Kokubun
Aaron Patterson
Maxime Chevalier-Boisvert
180909
Noah Gibbs
Jean Boussier