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If the last operation within a chunk is a function call, the call can
be executed in the same call frame without increasing the depth of the
call stack.
To enable this, a new OpTailCall instruction (similar to OpCall) is
introduced, but not yet emitted by the compiler.
Change-Id: I9ffbd7da6d2d6a8ec7a724646435dc6ee89712f2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6457
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This introduces a macro to do the forcing, but this solution isn't
very nice and also does not work in all cases yet.
Change-Id: Icd18862ec47edb82c0efc3af5835a6cb6126f629
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6456
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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These methods make it possible to trace the runtime execution of the
VM through an observer.
Change-Id: I90e26853ba2fe44748613e7f761ed5c1c5fc9ff7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6452
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This is a step towards hiding the internal fields of thunk, and making
the interface of the type more predictable.
Part of the preparation for implementing observers.
Change-Id: I1a88a96419c72eb9e2332b56a2dd94afa47e6f88
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6447
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Suggestion from sterni in cl/6282
Change-Id: I1adbdda9ff74f55a2f72892ffa524808b305f403
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6445
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This makes it easier to track exactly which lambda is which when
inspecting e.g. the concrete representation of a thunk.
At runtime all lambdas live in an Rc. To make this print the right
address, the construction of these Rcs had to be moved up right to the
point where the lambda is first emitted (and disassembled).
Change-Id: I6070e6c8ac55f0bd697966c4e7c5565c20d19106
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6435
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Change-Id: I65c6feb9f817b5b367d37204a1f57acfe4100d97
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6430
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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With this change the runtime trace contains much more exact
information about the context of the computation (entering/exiting
calls etc.)
This is in large part due to moving the tracer to be a field on the VM
itself, which enables consistent ordering of traces across the
execution, and tracing an execution with its *input* instead
of *output* stack.
Change-Id: Ibe525e6e7d869756501e52bef1a441619ce7332c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6419
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This makes it much easier to figure out what happened while debugging
this sort of thing.
Change-Id: I2e0e8096709adc647d63c04f213c547c415e5f44
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6418
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Previously, "calling" (setting up the VM run loop for executing a call
frame) and "running" (running this loop to completion) were separate
operations.
This was basically an attempt to avoid nesting `VM::run` invocations.
However, doing things this way introduced some tricky bugs for exiting
out of the call frames of thunks vs. builtins & closures.
For now, we unify the two operations and always return the value to
the caller directly. For now this makes calls a little less effective,
but it gives us a chance to nail down some other strange behaviours
and then re-optimise this afterwards.
To make sure we tackle this again further down I've added it to the
list of known possible optimisations.
Change-Id: I96828ab6a628136e0bac1bf03555faa4e6b74ece
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6415
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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The casting methods of `Value` are pretty verbose, and actually
incorrect before this commit as they did not account for inner thunk
values.
To address this, we first attempt to make them correct by introducing
a standard macro to generate them and traverse the inner thunk(s) if
necessary.
This is likely to be a performance hit as it will now involve more
cloning of values. We can do multiple things to alleviate this, but
should do some measurements first.
Change-Id: If315d6e2afe7b69db727df535bc6cbfb89a691aa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6412
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This makes it possible for builtins to force values on their own,
without the VM having to apply a strictness mask to the arguments
first.
Change-Id: Ib49a94e56ca2a8d515c39647381ab55a727766e3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6411
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Previously error spans were optional because the information about
code spans was not available at runtime. Now that this information has
been added, the error type will always carry a span.
This change is very invasive all throughout the codebase. This is due
to the fact that many functions that are called *by* the VM expected
to return `EvalResult`, but this no longer works as the span
information is not available to those functions - only to the VM
itself.
To work around this the majority of these functions have been changed
to return `Result<T, ErrorKind>` instead and an accompanying macro in
the VM constructs the "real" error.
Note that this implementatino currently has a bug where errors
occuring within thunks will yield the location at which the thunk was
forced, not the location at which the error occured within the code.
This will be fixed soon, but the commit is large enough as is.
Change-Id: Ib1ecb81a4d09d464a95ea7ea9e589f3bd08d5202
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6408
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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First pass at supporting `builtins` for tvix. The following tests appear to be
WAI:
```shell
$ cd tvix/eval
$ cargo build
$ cargo test
```
Change-Id: I27cce23d503b17a886d1109e285e8b4be4264977
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6405
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Note that I've allowed `needless_lifetimes` for the attribute set
iterator, as I find the type easier to understand with these
annotations present.
Change-Id: I33abb17837ee4813076cdb9a87f54bac4a37044e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6373
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This essentially makes the VM behave like `nix-instantiate --eval
--strict`, i.e. data structures are traversed strictly and thunks are
forced. Thunks embedded in closures are not forced.
This allows us to re-enable tests that were disabled because they
needed to output nested thunk contents, but is overall a behaviour
that must be configurable later on, as it is not cmopatible with e.g.
an evaluation of nixpkgs.
Change-Id: I5303a5c8e4322feab1384fdb7712fecb950afca5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6372
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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The VM previously took care of repeatedly forcing a thunk until it
reached an evaluated state. This logic is now encapsulated inside of
the `Thunk::force` implementation.
In addition, force no longer returns a reference to the value by
default, leaving it up to callers to decide whether they want to
borrow the value or not (a helper is provided for this).
Change-Id: I2aa7da922058ad1c57fbf8bfc7785aab7971c02b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6365
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This operation forces the evaluation of a thunk.
There is some potential here for making an implementation that avoids
some copies, but the thunk machinery is tricky to get right so the
first priority is to make sure it is correct by keeping the
implementation simple.
Change-Id: Ib381455b02f42ded717faff63f55afed4c8fb7e3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6352
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Implements an operation very similar to `OpClosure` which populates a
thunk's upvalues and leaves it on the stack.
Change-Id: I753b4dfeeaae6919316c7028ec361aaa13d87646
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6350
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This function is reusable between thunks & closures.
Change-Id: I44d5f9897b087a385c8e75027d2ff39c48a096f0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6349
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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CallFrame has to work for both thunks & closures (as a thunk is
basically a "weird 0-argument closure").
We opt to store the common, relevant fields directly in the frame to
avoid having to dereference through the nested structures
constantly (which would be especially annoying in the case of thunks).
Change-Id: I47781597b84ec5cd55502dba1713e92cf2592af3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6348
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This trait abstracts over the commonalities of upvalue handling
between closures and thunks.
It allows the VM to simplify the code used for setting up upvalues,
without duplicating between the two different types.
Note that this does not yet refactor the VM code to optimally make use
of this.
Change-Id: If8de5181f26ae1fa00d554f1ae6ea473ee4b6070
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6347
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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The logic in this method is *very* similar to `compile_lambda`. It is
intended to be called around any expression that should be
thunked (such as function applications, attribute set values, etc.).
Change-Id: Idfbb2daa9f4b735095378fb9c39a2fd07c8cff91
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6344
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This instruction finalises the initialisation of deferred upvalues in
closures (and soon, thunks).
The compiler does not yet emit this instruction, some more accounting
is needed for that.
Change-Id: Ic4181b26e19779e206f51e17388559400da5f93a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6337
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This will leave a sentinel value in the upvalue slot in which the
actual value is to be captured after resolution once a scope is fully
set up.
Change-Id: I12b37b0dc8d32603b03e675c3bd039468e70b354
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6336
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Uses the threaded through slot offset to determine whether
initialisation of a captured local upvalue must be defered to a later
point where all values of a scope are available.
This adds a new data representation to the opcode for this situation,
but the equivalent runtime handling is not yet implemented. This is in
part because there is more compiler machinery needed to find the
resolution point.
Change-Id: Ifd0c393f76abfe6e2d91483faf0f58947ab1dedc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6329
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Change-Id: I75c351619780fdc5186a54f3df9b244ada984069
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6324
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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The previous closure refactoring introduced a bug in which the same
closure object would get mutated constantly for each instance of a
closure, which is incorrect behaviour.
This commit instead introduces an explicit new Value variant for the
internal "blueprint" that the compiler generates (essentially just the
lambda) and uses this variant to construct the closure at runtime.
If the blueprint ever leaks out to a user somehow that is a critical
bug and tvix-eval will panic.
As a ~treat~ test for this, the fibonacci function is being used as it
is a self-recursive closure (i.e. different instantiations of the same
"blueprint") getting called with different values and it's good to
have it around.
Change-Id: I485de675e9bb0c599ed7d5dc0f001eb34ab4c15f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6323
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This puts together the puzzle pieces for threading dynamic
upvalues (that is, upvalues resolved from the `with`-stack) all the
way through.
Reading the test case enclosed in this commit and walking through it
is recommended to understand what problem is being tackled here.
In short, because the compiler can not statically know *which*
with-scope a dynamic argument is resolved from it needs to lay the
groundwork for resolving from *all* possible scopes.
There are multiple different approaches to doing this. The approach
chosen in this commit is that if a dynamic upvalue is detected, the
compiler will emit instructions to close over this dynamic value
in *all* enclosing lambda contexts.
It uses a new instruction for this that will leave around a sentinel
value in case an identifier could not be resolved, and wire the
location of this found value (or sentinel) up through the upvalues to
the next level of nesting.
In this tradeoff, tvix potentially closes over more upvalues than are
needed (but in practice, how often do people create *really* deep
`with`-stacks? and in *this* kind of code situation? maybe we should
even warn for this!) but avoids keeping the entire attribute sets
themselves around.
Looking at the test case, each surrounding closure will close
over *all* dynamic identifiers that are referenced later on visible to
it, but only the last one for each identifier will actually end up
being used.
This also covers our bases for an additional edge-case this creates,
in which an identifier potentially resolves to a dynamic upvalue *and*
to a dynamic value within the function's own scope (again, would
anyone really do this?) by introducing a resolution instruction for
that particular case.
There is likely some potential for cleaning up this code which is
quite ugly in some parts, but as this implementation is now carefully
calibrated to work I decided it is time to commit it and clean it up
in subsequent commits.
Change-Id: Ib701e3e6da39bd2c95938d1384036ff4f9fb3749
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6322
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Change-Id: I4b98eaea3ed5059c29938a117a9d59499a0bb95d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6318
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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With this change, it becomes possible for functions to call themselves
as they are being defined in local bindings.
Change-Id: Ib46a39ba17b1452b5673d96fa729d633d237241a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6314
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This is required to efficiently construct the upvalue array at
runtime, as there are situations where during Closure construction
multiple things already have a reference to the closure (e.g. a
self-reference).
Change-Id: I35263b845fdc695dc873de489f5168d39b370f6a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6312
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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These need to be handled specially by the runtime if the compiler
determines that a given local must be resolved via `with`.
Note that this implementation has a bug: It currently allows `with`
inside of nested lambdas to shadow statically known identifiers. This
will be cleaned up in the next commit.
Change-Id: If196b99cbd1a0f2dbb4a40a0e88cdb09a009c6b9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6299
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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The previous implementation of OpResolveWith manually controlled the
loop iteration, which skipped over the disassembler's tracing
instruction.
Instead, the resolution of dynamic variables has been delegated to a
new helper function. This has the additional benefit that the loop
labels are no longer required, making things a bit cleaner.
Change-Id: If22b74c3d49c74bf3a1ec4497cb761a9ee6cf2a4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6298
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Implements the final bit of logic remaining for wiring up closures,
which is the runtime construction of closure objects.
When encountering an OpClosure, the VM walks through the bytecode
collecting all the upvalue location operands (see commit introducing
the OpCode::Data* variants for details) and stores the runtime values
in the new closures upvalue vector.
After that, the handling of the closure itself becomes functionally
identical to that of lambdas.
With this initial implementation of closures there are several large
optimisation potentials available, the two most notable ones are:
- Distinguish the runtime representation of lambdas and closures
explicitly.
- Detect and handle multiple-arity functions directly in the compiler.
However, for both of these we should wait until we have appropriate
benchmarking infrastructure in place. This is because our test
implementations have shown that the complexity of either of these
changes is quite significant, and we do not yet know if they really
pay off.
Change-Id: I077e977810fd5cb2b1ecd7f1a119e728025dd786
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6295
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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This resolves an upvalue at runtime by pushing it on the stack from
the closure's upvalue vector.
Change-Id: Ic3e7a7ecd9f7032f679114a1995e5bbf83062fcf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6294
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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In preparation for implementing calling of closures, store a closure
directly in the VMs call frame.
Change-Id: Iad24cd8c49fee4ebd4d0c84ffaa4c2505ee3dfd6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6293
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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Fully implements the instructions for compiling closure
objects (without runtime handling yet).
Closure (and thunk) objects are created at runtime by capturing all
known upvalues. To represent this, the instructions for creating them
need to have a variable number of arguments. Due to that, this commit
introduces new variants in OpCode that are not actually operations,
but data.
If the VM is implemented correctly, the instruction pointer should
never point at these. Due to this, the VM will panic if it sees a data
operand during an execution run.
Change-Id: Ic56b49b3a42736dc437751e76df0e89c8d0619c6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6291
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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This adds a new upvalue tracking structure in the compiler to resolve
upvalues and track their positions within a function when compiling a
closure.
The compiler will emit runtime upvalue access instructions after this
commit, but the creation of the runtime closure object etc. is not yet
wired up.
Change-Id: Ib0c2c25f686bfd45f797c528753068858e3a770d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6289
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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Change-Id: Ibde0b2baa1128a74c1364ee9a6330b62db3da699
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6288
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Change-Id: I9b9de1f681972c205d4d20bc5731d2ce79858edb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6287
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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This adds a transparent wrapper around `usize` used for jump offsets
in the opcodes. This is a step towards getting rid of ambiguous plain
`usize` usage in the opcode.
Change-Id: I21e35e67d94b32d68251908b96c7f62b6f56a8bb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6282
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Refactors the update function to take the attribute sets by value
instead.
To facilitate this, we use an equivalent of the currently unstable
`Rc::clone_or_unwrap` in the VM when encountering attribute sets, so
that in cases where the only references to the attrs being updated are
the ones on the stack those clones are avoided completely.
This does make update() a little bit more tricky internally, as some
optimised branches can directly return the moved value, and others
need to destructure with ownership. For this reason there are now two
different match statements handling the different ownership cases.
Change-Id: Ia77d3ba5c86afb75b9f1f51758bda61729ba5aab
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6279
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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grfn suggested clearer naming for these in cl/6166.
Change-Id: I83164bf1d1902ebd42272e9d5d63819a0f6a72c5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6277
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
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This struct will carry the upvalue machinery in addition to the lambda
itself. For now, all lambdas are wrapped in closures (though
technically analysis of the environment can later remove innermost
Closure wrapper, but this optimisation may not be worth it).
Change-Id: If2b68549ec1ea4ab838fdc47a2181c694ac937f2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6269
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
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This avoids copying around the value more than needed.
Change-Id: I35949d16dad7fb8f76e0f641eaccf48322144777
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6263
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
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Builtins are represented as a Rust function pointer that accepts a
vector of arguments, which represents variable arity builtins.
Change-Id: Ibab7e662a646caf1172695d876d2f55e187c03dd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6251
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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Nix functions always have a single argument and we do not yet make
efforts to optimise this in Tvix for known multi-argument functions
being directly applied.
For this reason, the call instruction is fairly simple and just calls
out to construct a new call frame.
Note that the logic for terminating the run loop has moved to the top
of the dispatch; this is because the loop run needs to be skipped if
the call frame for the current lambda has just been dropped.
Change-Id: I259bc07e19c1e55cd0a65207fa8105b23052b967
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6249
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
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Change-Id: Ia7ff572af90ae379b23bbd0f5215cd13a4dc0ab5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6248
Reviewed-by: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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This wires up most of the machinery for executing different call
frames inside of the VM and stuffs the top-level lambda which the
compiler outputs in there, as well.
Change-Id: Ib6201b3e3be1af96a4d195f6eb147f452860ffc3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6242
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
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