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exceptional entry
[Backport #21941]
In case of `--yjit-disable`, YJIT only starts to record environment
escapes after `RubyVM::YJIT.enable`. Previously we falsely assumed that
we always have a full history all the way back to VM boot. This had YJIT
install and run code that assume EP=BP when EP≠BP for some exceptional
entry into the middle of a running frame, if the environment escaped
before `YJIT.enable`.
The fix is to reject exceptional entry with an escaped environment.
Rename things and explain in more detail how the predicate for deciding
to assume EP=BP works. It's quite subtle since it reasons about all
parties in the system that push a control frame and then run JIT code.
Note that while can_assume_on_stack_env() checks the currently running
environment if it so happens to be the one YJIT is compiling against, it
can return true for any ISEQ. The check isn't necessary for fixing the
bug, and the load bearing part of this patch is the change to
exceptional entries.
This fix is flat on speed and space on ruby-bench headline benchmarks.
Many thanks for the community effort to create a small test case for
this bug.
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* ZJIT: Implement SingleRactorMode invalidation
* ZJIT: Add macro for compiling jumps
* ZJIT: Fix typo in comment
* YJIT: Fix typo in comment
* ZJIT: Avoid using unexported types in zjit.h
`enum ruby_vminsn_type` is declared in `insns.inc` and is not exported.
Using it in `zjit.h` would cause build errors when the file including it
doesn't include `insns.inc`.
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When YJIT is forced to discard all the code, that's bad for
performance, so there should be an easy way to know about it.
Notes:
Merged: https://github.com/ruby/ruby/pull/12882
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Notes:
Merged-By: k0kubun <takashikkbn@gmail.com>
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YJIT currently uses the YJIT root object to mark objects during GC and
update references during compaction. This object otherwise serves no
purpose.
This commit changes it YJIT to be step when marking the GC root. This
saves some memory from being allocated from the system and the GC.
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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* YJIT: Local variable register allocation
* locals are not stack temps
* Rename RegTemps to RegMappings
* Rename RegMapping to RegOpnd
* Rename local_size to num_locals
* s/stack value/operand/
* Rename spill_temps() to spill_regs()
* Clarify when num_locals becomes None
* Mention that InsnOut uses different registers
* Rename get_reg_mapping to get_reg_opnd
* Resurrect --yjit-temp-regs capability
* Use MAX_CTX_TEMPS and MAX_CTX_LOCALS
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Many functions take an outlined code block but do nothing more than
passing it along; only a couple of functions actually make use of it.
So, in most cases the `ocb` parameter is just boilerplate.
Most functions that take `ocb` already also take a `JITState` and this
commit moves `ocb` into `JITState` to remove the visual noise of the
`ocb` parameter.
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`mem::take` substitutes an empty instance which makes `jit.ep_is_bp()`
return false.
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We need the lock to patch code safely.
This might fix some Ractor related crashes seen on CI.
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Even though unused, it's supposed to take a pointer like the C side
expects.
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Previously, the update was done in the ISEQ callback. That effectively
never updated anything because the callback itself is given an intact
reference, so it could update its content, and `rb_gc_location(iseq)`
never returned a new address. Update the whole table once in the YJIT
root instead.
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* Revert "Revert "YJIT: Optimize local variables when EP == BP" (#10584)"
This reverts commit c8783441952217c18e523749c821f82cd7e5d222.
* YJIT: Take care of GC references in ISEQ invariants
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
---------
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
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This reverts commit 4cc58ea0b865f2fd20f1e881ddbd4c4fab0b072c.
Since the change landed call-threshold=1 CI runs have been timing out.
There has also been `verify-ctx` violations. Revert for now while we debug.
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* YJIT: Cancel on-stack jit_return on invalidation
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
* Use RUBY_VM_CONTROL_FRAME_STACK_OVERFLOW_P
---------
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
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We've long had a size restriction on the code memory region such that a
u32 could refer to everything. This commit capitalizes on this
restriction by shrinking the size of `CodePtr` to be 4 bytes from 8.
To derive a full raw pointer from a `CodePtr`, one needs a base pointer.
Both `CodeBlock` and `VirtualMemory` can be used for this purpose. The
base pointer is readily available everywhere, except for in the case of
the `jit_return` "branch". Generalize lea_label() to lea_jump_target()
in the IR to delay deriving the `jit_return` address until `compile()`,
when the base pointer is available.
On railsbench, this yields roughly a 1% reduction to `yjit_alloc_size`
(58,397,765 to 57,742,248).
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So that we get a reminder to check CodeBlock::has_dropped_bytes().
Internally, asm.compile() already checks it, and this patch just
propagates it out to the caller with a `#[must_use]`.
Code GC logic moved out one level in entry_stub_hit(), so the body
can freely use `?`
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Previously, the version-controlled `cruby_bindings.inc.rs` file
contained the build-time artifact `id.h`, which nobu mentioned hinders
the goal of having fewer magic numbers in the repository.
Lookup the IDs YJIT needs on boot. It costs cycles, but it's fine since
YJIT only uses a handful of IDs at the moment. No perceptible
degradation to boot time found in my testing.
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* YJIT: Introduce Target::SideExit
* YJIT: Obviate Insn::SideExitContext
* YJIT: Avoid cloning a Context for each insn
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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We crashed in some edge cases due to the recent change to not compile
encoded iseqs that are larger than `u16::MAX`.
- Match the C signature of rb_yjit_constant_ic_update() and clamp down
to `IseqIdx` size
- Return failure instead of panicking with `unwrap()` in codegen when
the iseq is too large
Co-authored-by: Maxime Chevalier-Boisvert <maxime.chevalierboisvert@shopify.com>
Co-authored-by: Noah Gibbs <noah.gibbs@shopify.com>
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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It was useful for evaluating 6068da8937d7e4358943f95e7450dae7179a7763
but I think we should remove it now to make the logic around
invalidation more straight forward.
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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`Rc` and `RefCell` both incur runtime space costs.
In addition, `RefCell` has given us some headaches with the
non obvious borrow panics it likes to throw out. The latest
one started with 7fd53eeb46db261bbc20025cdab70096245a5cbe
and is yet to be resolved.
Since we already rely on the GC to properly reclaim memory for `Block`
and `Branch`, we might as well stop paying the overhead of `Rc` and
`RefCell`. The `RefCell` panics go away with this change, too.
On 25 iterations of `railsbench` with a stats build I got
`yjit_alloc_size: 8,386,129 => 7,348,637`, with the new memory size 87.6%
of the status quo. This makes the metadata and machine code size roughly
line up one-to-one.
The general idea here is to use `&` shared references with
[interior mutability][1] with `Cell`, which doesn't take any extra
space. The `noalias` requirement that `&mut` imposes is way too hard to
meet and verify. Imagine replacing places where we would've gotten
`BorrowError` from `RefCell` with Rust/LLVM miscompiling us due to aliasing
violations. With shared references, we don't have to think about subtle
cases like the GC _sometimes_ calling the mark callback while codegen
has an aliasing reference in a stack frame below. We mostly only need to
worry about liveness, with which the GC already helps.
There is now a clean split between blocks and branches that are not yet
fully constructed and ones that are "in-service", so to speak. Working
with `PendingBranch` and `JITState` don't really involve `unsafe` stuff.
This change allows `Branch` and `Block` to not have as many optional
fields as many of them are only optional during compilation. Fields that
change post-compilation are wrapped in `Cell` to facilitate mutation
through shared references.
I do some `unsafe` dances here. I've included just a couple tests to run
with Miri (`cargo +nightly miri test miri`). We can add more Miri tests
if desired.
[1]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
Notes:
Merged: https://github.com/ruby/ruby/pull/7443
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Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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The code and comments in there have been disabled by comments for a long
time. The issues that the counter used to solve are now solved more
comprehensively by "runningness" [tracking][1] introduced by Code GC
and [delayed deallocation][2].
Having a single counter doesn't fit our current model where code pages
that could be touched or not are interleaved, anyway.
Just delete the code.
[1]: e7c71c6c9271b0c29f210769159090e17128e740
[2]: a0b0365e905e1ac51998ace7e6fc723406a2f157
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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YJIT: Use a boxed slice for outgoing branches
and cme dependencies
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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* Add job to check clippy lints in CI
* Address all remaining clippy lints
* Check lints on arm64 as well
* Apply latest clippy lints
* Do not exit 0 on clippy warnings
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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Previously we essentially never freed block even after invalidation.
Their reference count never reached zero for a couple of reasons:
1. `Branch::block` formed a cycle with the block holding the branch
2. Strong count on a branch that has ever contained a stub never
reached 0 because we increment the `.clone()` call for
`BranchRef::into_raw()` didn't have a matching decrement.
It's not safe to immediately deallocate blocks during
invalidation since `branch_stub_hit()` can end up
running with a branch pointer from an invalidated branch.
To plug the leaks, we wait until code GC or global invalidation and
deallocate the blocks for iseqs that are definitely not running.
Notes:
Merged: https://github.com/ruby/ruby/pull/6833
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When we run global invalidation for TracePoints or code GC, we clear out
all blocks in our assumptions table but we don't deallocate the backing
buffers. Let's reclaim some memory during these rare events.
Notes:
Merged: https://github.com/ruby/ruby/pull/6833
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YJIT: Skip padding jumps to side exits
Co-authored-by: Maxime Chevalier-Boisvert <maxime.chevalierboisvert@shopify.com>
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
Co-authored-by: Maxime Chevalier-Boisvert <maxime.chevalierboisvert@shopify.com>
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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* YJIT: Stop wrapping CmePtr with CmeDependency
* YJIT: Fix an outdated comment [ci skip]
Notes:
Merged-By: k0kubun <takashikkbn@gmail.com>
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Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
Co-authored-by: Alan Wu <alansi.xingwu@shopify.com>
Notes:
Merged-By: k0kubun <takashikkbn@gmail.com>
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We switch to a new page when we detect dropped_bytes flipping from false
to true. Previously, when we patch code for invalidation during code gc,
we start with the flag being set to true, so we failed to apply patches
that straddle pages. We would write out jumps half way and then stop,
which left the code corrupted.
Reset the flag before patching so we patch across pages properly.
Notes:
Merged: https://github.com/ruby/ruby/pull/6686
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Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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Notes:
Merged-By: k0kubun <takashikkbn@gmail.com>
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* YJIT: Count freed ISEQs
* YJIT: Avoid creating payloads for non-JITed ISEQs
Notes:
Merged-By: k0kubun <takashikkbn@gmail.com>
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Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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* Add rb_callable_method_entry_or_negative
* YJIT: Implement specialized respond_to?
This implements a specialized respond_to? in YJIT.
* Update yjit/src/codegen.rs
Co-authored-by: Maxime Chevalier-Boisvert <maximechevalierb@gmail.com>
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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Previously YARV bytecode implemented constant caching by having a pair
of instructions, opt_getinlinecache and opt_setinlinecache, wrapping a
series of getconstant calls (with putobject providing supporting
arguments).
This commit replaces that pattern with a new instruction,
opt_getconstant_path, handling both getting/setting the inline cache and
fetching the constant on a cache miss.
This is implemented by storing the full constant path as a
null-terminated array of IDs inside of the IC structure. idNULL is used
to signal an absolute constant reference.
$ ./miniruby --dump=insns -e '::Foo::Bar::Baz'
== disasm: #<ISeq:<main>@-e:1 (1,0)-(1,13)> (catch: FALSE)
0000 opt_getconstant_path <ic:0 ::Foo::Bar::Baz> ( 1)[Li]
0002 leave
The motivation for this is that we had increasingly found the need to
disassemble the instructions between the opt_getinlinecache and
opt_setinlinecache in order to determine the constant we are fetching,
or otherwise store metadata.
This disassembly was done:
* In opt_setinlinecache, to register the IC against the constant names
it is using for granular invalidation.
* In rb_iseq_free, to unregister the IC from the invalidation table.
* In YJIT to find the position of a opt_getinlinecache instruction to
invalidate it when the cache is populated
* In YJIT to register the constant names being used for invalidation.
With this change we no longe need disassemly for these (in fact
rb_iseq_each is now unused), as the list of constant names being
referenced is held in the IC. This should also make it possible to make
more optimizations in the future.
This may also reduce the size of iseqs, as previously each segment
required 32 bytes (on 64-bit platforms) for each constant segment. This
implementation only stores one ID per-segment.
There should be no significant performance change between this and the
previous implementation. Previously opt_getinlinecache was a "leaf"
instruction, but it included a jump (almost always to a separate cache
line). Now opt_getconstant_path is a non-leaf (it may
raise/autoload/call const_missing) but it does not jump. These seem to
even out.
Notes:
Merged: https://github.com/ruby/ruby/pull/6187
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Previously, we patched in an x64 JMP even on A64, which resulted in
invalid machine code. Use the new assembler to generate a jump instead.
Add an assert to make sure patches don't step on each other since it's
less clear cut on A64, where the size of the jump varies depending on
its placement relative to the target.
Fixes a lot of tests that use `set_trace_func` in `test_insns.rb`.
PR: https://github.com/Shopify/ruby/pull/379
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When running with `--yjit-stats` turned on, yjit can inform the user
what the most common exits are. While this is useful information it
doesn't tell you the source location of the code that exited or what the
code that exited looks like. This change intends to fix that.
To use the feature, run yjit with the `--yjit-trace-exits` option,
which will record the backtrace for every exit that occurs. This functionality
requires the stats feature to be turned on. Calling `--yjit-trace-exits`
will automatically set the `--yjit-stats` option.
Users must call `RubyVM::YJIT.dump_exit_locations(filename)` which will
Marshal dump the contents of `RubyVM::YJIT.exit_locations` into a file
based on the passed filename.
*Example usage:*
Given the following script, we write to a file called
`concat_array.dump` the results of `RubyVM::YJIT.exit_locations`.
```ruby
def concat_array
["t", "r", *x = "u", "e"].join
end
1000.times do
concat_array
end
RubyVM::YJIT.dump_exit_locations("concat_array.dump")
```
When we run the file with this branch and the appropriate flags the
stacktrace will be recorded. Note Stackprof needs to be installed or you
need to point to the library directly.
```
./ruby --yjit --yjit-call-threshold=1 --yjit-trace-exits -I/Users/eileencodes/open_source/stackprof/lib test.rb
```
We can then read the dump file with Stackprof:
```
./ruby -I/Users/eileencodes/open_source/stackprof/lib/ /Users/eileencodes/open_source/stackprof/bin/stackprof --text concat_array.dump
```
Results will look similar to the following:
```
==================================
Mode: ()
Samples: 1817 (0.00% miss rate)
GC: 0 (0.00%)
==================================
TOTAL (pct) SAMPLES (pct) FRAME
1001 (55.1%) 1001 (55.1%) concatarray
335 (18.4%) 335 (18.4%) invokeblock
178 (9.8%) 178 (9.8%) send
140 (7.7%) 140 (7.7%) opt_getinlinecache
...etc...
```
Simply inspecting the `concatarray` method will give `SOURCE
UNAVAILABLE` because the source is insns.def.
```
./ruby -I/Users/eileencodes/open_source/stackprof/lib/ /Users/eileencodes/open_source/stackprof/bin/stackprof --text concat_array.dump --method concatarray
```
Result:
```
concatarray (nonexistent.def:1)
samples: 1001 self (55.1%) / 1001 total (55.1%)
callers:
1000 ( 99.9%) Object#concat_array
1 ( 0.1%) Gem.suffixes
callees (0 total):
code:
SOURCE UNAVAILABLE
```
However if we go deeper to the callee we can see the exact
source of the `concatarray` exit.
```
./ruby -I/Users/eileencodes/open_source/stackprof/lib/ /Users/eileencodes/open_source/stackprof/bin/stackprof --text concat_array.dump --method Object#concat_array
```
```
Object#concat_array (/Users/eileencodes/open_source/rust_ruby/test.rb:1)
samples: 0 self (0.0%) / 1000 total (55.0%)
callers:
1000 ( 100.0%) block in <main>
callees (1000 total):
1000 ( 100.0%) concatarray
code:
| 1 | def concat_array
1000 (55.0%) | 2 | ["t", "r", *x = "u", "e"].join
| 3 | end
```
The `--walk` option is recommended for this feature as it make it
easier to traverse the tree of exits.
*Goals of this feature:*
This feature is meant to give more information when working on YJIT.
The idea is that if we know what code is exiting we can decide what
areas to prioritize when fixing exits. In some cases this means adding
prioritizing avoiding certain exits in yjit. In more complex cases it
might mean changing the Ruby code to be more performant when run with
yjit. Ultimately the more information we have about what code is exiting
AND why, the better we can make yjit.
*Known limitations:*
* Due to tracing exits, running this on large codebases like Rails
can be quite slow.
* On complex methods it can still be difficult to pinpoint the exact cause of
an exit.
* Stackprof is a requirement to to view the backtrace information from
the dump file.
Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>
Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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Constants that can't be imported via bindgen should have
a comment saying why not.
Notes:
Merged-By: maximecb <maximecb@ruby-lang.org>
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Notes:
Merged: https://github.com/ruby/ruby/pull/5948
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