In addition to `NewCellVariable`, Dynamo has 3 ways of modeling cell objects:
1. For cells captured and created by the root frame, represent them as
their contents in `root_tx.symbolic_locals`, which `LOAD_DEREF` and
`STORE_DEREF` update directly, without going through `SideEffects`.
2. `ClosureVariable`: this is created when cells from (1) are captured
by a newly created function Dynamo is about to inline. It's a handle
with a name that redirects `LOAD_DEREF` and `STORE_DEREF` back (1),
to make `root_tx.symbolic_locals` up-to-date.
3. For cells that are captured by both the root frame and some
pre-existing function Dynamo is about to inline, represent those
cells as contents, and do not allow writes to them.
Note that (2) and (3) are mainly to conform with (1) -- to make sure
Dynamo has a consistent modeling of cells for the same cell objects.
In this patch, we represent all of these cells as `NewCellVariable`. The
main new code paths introduced are:
- using `NewCellVariable` to model cell objects created by the root
frame (the cells are passed in as input to `InstructionTranslator`),
this is what allows us to get rid of all 3 legacy paths above.
- adding a new `AutoDerefLocalSource` to deal with the python-code
level (guards) and bytecode level (codegen) auto-dereferencing
behavior, when accessing pre-existing python cells. This also
involves a tiny update to guard manager generation.
- plumbing some extra info into `LocalSource` and `CellVariable` so that
we can still emit `LOAD_DEREF`, `STORE_DEREF`, `LOAD_CLOSURE` (instead
of `make_cell`, `cell_contents` attribute access, and `LOAD_FAST`),
which is important for readability, performance, and some
assumptions `bytecode_transformation.py` makes.
As a result, this patch removes a lot of the now-dead code paths and
TODOs. Notably, it significantly simplified the `prune_dead_locals`
function, which was duplicating a lot of the logic from
`prune_dead_object_new`; this conveniently closes#137123.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/140153
Approved by: https://github.com/jansel
ghstack dependencies: #140330, #140152, #140436, #140435
This patch
1. Adds documentation to `PyCodegen.__call__`, `PyCodegen.tempvars` and
the `allow_cache` flag.
2. Merges a few existing code paths in `PyCodegen.__call__`.
3. removes the `elif var in cg.tempvars` code path in
`codegen_save_tempvars`, because it's no longer needed after #113725,
as we have up-to-date `VariableTracker.source` now.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/139670
Approved by: https://github.com/jansel
ghstack dependencies: #139538
This effectively undoes #115095, which is not longer be needed after #113725.
Why did we need #115095? I went back in history and found that [this line](https://github.com/pytorch/pytorch/pull/113725/files#diff-0bb1756725c4426408938314b0c9d3988ae5bf49994892d7038ad7746e209e9fR86)
actually fixed what #115095 fixed. Specifically, without the
`allow_cache` check for the "dup_top" optimization, we could incorrectly
codegen based on source, despite `codegen_update_mutated` requested to
codegen from value, for updates to pre-existing lists, etc. Since #113725 added
the `allow_cache` check, we no longer need the `mutable_side_effects_from_source`
code path from #115095.
However, #115442 introduced a `value_from_source` flag which didn't
account for the `mutable_side_effects_from_source` branch. So this patch
adds an extra check to keep existing behavior for export, and leaves a
TODO for investigating what exactly export wants from codegen, when it
comes to side effects and sources.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/139538
Approved by: https://github.com/jansel
This patch addresses the renaming part of #133027, specifically, it
renames the following and adds documentation for relevant classes.
1. `VariableTracker.mutable_local` to `mutation_type`
2. `MatableLocal `to `ValueMutationNew`
3. `MutableSideEffects `to `ValueMutationExisting`
4. `MutableLocalSource` to `SourceType`
5. `MutableLocalSource.Local` to `New`
Note that (2), (3) and (5) are mainly to bring consistency between them
and `AttributeMutationNew`, `AttributeMutationExisting`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/139339
Approved by: https://github.com/jansel, https://github.com/mlazos, https://github.com/anijain2305
As discussed with @ezyang, this set of diffs are extracting fixes to problems discovered to flipping `specialize_float=False` in https://github.com/pytorch/pytorch/pull/137782. Since these codepaths are exercised in existing tests, I'm going to bias towards shipping speed and put these up with the primary test plan as the global CI. These code paths are all tested via existing tests when `specialize_float=False` and it feels a bit wonky to add more gated tests that only test behavior when this flag is True, especially since these code paths are already covered. That being said, I'm happy to add individual tests if reviewers insist or have a different POV.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/138598
Approved by: https://github.com/ezyang
ghstack dependencies: #138595
This patch addresses parts of the side-effect refactor proposed in #133027;
specifically, it does 3 things:
1. Change `SideEffects.store_attr_mutations` and `PyCodegen.tempvars`
to index on `VariableTracker` rather than `MutableLocalBase`.
2. Remove the `source` field from `MutableSideEffects` and
`AttributeMutation`, and use `VariableTracker.source` instead.
3. Plumb a `overridden_sources: Dict[Source, Source]` from
`handle_aliases_for_stolen_lists` to `PyCodegen` so that we don't
update `VariableTracker.source` in place, while still preserving what
`handle_aliases_for_stolen_lists` needed (i.e., modifying codegen for
certain `VariableTracker`).
(1) and (2) are merged in 1 patch because of some dependency between
a. `OutputGraph.handle_aliases_for_stolen_lists` which iterates over
`sideSideEffects.store_attr_mutations.keys()`, and potentially update
its source field to be completely different.
b. `SideEffects.codegen_update_mutated`, which happens after the above
and uses `cg(var.mutable_local.source)`.
where if we apply (1) only, (b) breaks, and if we apply (2) only, (a)
breaks.
(3) is needed for correctness, see comments in the PR for details.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/137905
Approved by: https://github.com/jansel, https://github.com/anijain2305, https://github.com/mlazos
Significant bytecode generation API change!
The new suggested convention to generating bytecode to call a function is now to wrap instructions that push a callable to the stack with `add_push_null`, then that callable is called with `create_call_function` with `push_null=False` (see diff for examples).
In Python 3.13, NULL is now expected to be pushed after the callable. In <=3.12, the NULL was pushed before the callable. This change abstracts away the exact placement of the NULL, but the developer must be aware that a NULL may be needed when codegen'ing a callable.
This abstraction also reduces the need for the `push_null=True` option in `create_call_function`, which removes the need to rotate a NULL to the right place on the stack with a sequence of `SWAP` instructions.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/129172
Approved by: https://github.com/jansel
The big idea is that floats are treated as Tensors on input/output to the FX graph, but on the inside, we immediately call item() on the synthetic Tensor and record regular float operations on it. Canonicalization to Tensor operations will happen in a standalone FX pass. This behavior is controlled by `specialize_float` config variable when set to False.
The generated graph looks like this for the test `test_unspec_float_output`:
```
def forward(self, L_x_: "f32[3]", L_y_: "f32[]"):
l_x_ = L_x_
l_y_ = L_y_
# File: /data/users/ezyang/a/pytorch/test/dynamo/test_unspec.py:511 in f, code: return x + 1, y * 2
add: "f32[3]" = l_x_ + 1; l_x_ = None
item: "Sym(zf0)" = l_y_.item(); l_y_ = None
mul: "Sym(2*zf0)" = item * 2; item = None
scalar_tensor: "f32[]" = torch.scalar_tensor(mul); mul = None
return (add, scalar_tensor)
```
The ingredients:
* **torch/_dynamo/variables/builder.py** When `specialize_float` is False, we wrap float literals with `wrap_symfloat`. This is an unholy mashup of `wrap_symint` and `wrap_unspecialized_primitive`. The overall strategy is that we first generate a tensor argument (because that's what we want to show up into the FX graph), but then immediately call item() on the tensor argument to get a SymNodeVariable, which we will do the rest of the tracing with. Importantly, this SymNodeVariable is backed with the source of the original float: this means we can guard on the resulting value (something we could NOT do with UnspecializedPythonVariable). This has to be done manually, because if you literally call item() on the tensor, you will end up with an unbacked float. There is a bit of copy paste from wrap_symint and wrap_unspecialized_primitive which we can try to factor out, but this really is its own thing and you should review every line of code in the function.
* **torch/fx/experimental/symbolic_shapes.py** We now can generate guards on float inputs, and these guards are handled inside of ShapeEnv. So we need to be able to allocate (backed!) float symbols, and produce guards for them. Fairly straightforward generalization.
* **torch/_dynamo/codegen.py** I also need to maintain the invariant that there are no float outputs to the FX graph. I chose to do this at codegen time. When we detect a SymNodeVariable on the return stack for a float, we on the fly convert it (via `as_tensor`) to a TensorVariable, which is the true output. We then special case the output bytecode to call item() on it again. The tensor conversion is memoized on SymNodeVariable since we typically run the code generation process twice.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/125325
Approved by: https://github.com/lezcano, https://github.com/jansel
We split install_global_once into two APIs:
- `install_global_by_id(prefix, value) -> name`: installs a global if it hasn't
been installed yet
- `install_global(prefix, value) -> name`: always installs the global (and
generates a unique name for it)
Then, we refactor most callsites of `install_global_unsafe` to one of
the previous. Some callsites cannot be refactored because we create the
global name first, do a lot of stuff with it, and then install it.
This fixes more test flakiness.
Test Plan:
- Existing tests; I can't reliably repro the flakiness
Pull Request resolved: https://github.com/pytorch/pytorch/pull/118100
Approved by: https://github.com/ezyang, https://github.com/mlazos
Fixes https://github.com/pytorch/pytorch/issues/117851
In tests, we ran into an issue where:
- In frame A, Dynamo would install a global
- We call reset()
- reset() did not delete the installed global due to a refcycle
- In frame B, Dynamo would re-use the same global
- Python gc ran, deleting the installed global, leading to the compiled
version of frame B raising NameNotFound
This PR changes the following:
- module globals are now installed at a per-frame basis.
- renames install_global to install_global_unsafe: if the names are not
unique and end up being re-used across frames, then we've got trouble.
Test Plan:
- I tested that this got rid of the test flakiness locally. I'm not sure
how to easily write a test for this, because I don't actually know
what the refcycle in the above is.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/117998
Approved by: https://github.com/ezyang, https://github.com/anijain2305
This prepares the PR where we implement sets in terms of dicts.
To do so, rather than storing internally a dictionary that maps literals
to VariableTrackers, it stores (pretty much) a dictionary from VTs to VTs.
To do so, keys are wrapped in an opaque internal class _Hashable.
The Hashable class is opaque on purpose so that it fails hard if
if it inadvertently leaks back into user code.
We also found and fixed a number of latent bugs and inconsistencies
in the way dynamo checked what can be a dict key. More generally, we
make much clearer what are the things that need to be modified to add
a new supported key type to Dicts.
Fixes [#107595](https://www.internalfb.com/tasks?t=107595)
Fixes [#111603](https://www.internalfb.com/tasks?t=111603)
Re-PR of https://github.com/pytorch/pytorch/pull/111196 sadly due to reverts, we could not reuse @lezcano's original PR.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/116785
Approved by: https://github.com/mlazos
1. Removes calls to `replace_all` and `clone` and makes VTs mutable.
2. Properly handles Tuple Iterator mutation. Previously TupleIterator variables would only be properly reconstructed if they were advanced at least once in a frame. On calls to `next`, the source information would be lost (due to constructing a new iterator without using builder), which would ensure that during codegen the variable would be reconstructed from scratch. Now that VTs are mutated, the source is never lost, so we need to properly track mutation and handle it by replaying calls to `next` at the end of the modified bytecode.
3. Added test for checking iadd side effects, this was missing in our unit test coverage.
4. Fixed two incorrect sources, DelayGraphBreakVariable, and UserMethodVariable both relied on setting the source to AttrSource(parent, name) at the callsite of `var_getattr`.
5. Fixed a bug in inplace adding for lists, it would set the resulting VariableTracker's source to `None` which would utilize a different reconstruct path in codegen. Now this is handled explicitly by reconstructing vars when allow_cache=`False`, so that during side effect replay, the mutated var is correctly updated.
In subsequent PRs:
* Refactoring side effect tracking to be significantly simpler (I think we only need an `is_modified` flag)
* Refactor `next_variables` iterator to match the signature of `next`
* Remove all references to `options` in the code
* Refactor VTs representing mutable collections to implement their own mutation update handling
* Remove clone and/or make it specific to lists for creating slices
* Add mutation tracking/replay for sets
* Add mutation tracking/replay for iter.py
* Removing setting source in builder (it's set at the top level after a var is returned)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/113725
Approved by: https://github.com/jansel
This prepares the PR where we implement sets in terms of dicts.
To do so, rather than storing internally a dictionary that maps literals
to VariableTrackers, it stores (pretty much) a dictionary from VTs to VTs.
To do so, keys are wrapped in an opaque internal class `_Hashable`.
The Hashable class is opaque on purpose so that it fails hard if
if it inadvertently leaks back into user code.
We also found and fixed a number of latent bugs and inconsistencies
in the way dynamo checked what can be a dict key. More generally, we
make much clearer what are the things that need to be modified to add
a new supported key type to Dicts.
Fixes https://github.com/pytorch/pytorch/issues/107595
Fixes https://github.com/pytorch/pytorch/issues/111603
Pull Request resolved: https://github.com/pytorch/pytorch/pull/111196
Approved by: https://github.com/jansel
As part of this diff, I have upgraded the `python_version` config setting to 3.11. `bytecode_transformation.py` (and a few other files) have functions using APIs only available in Python 3.11+. Those APIs are gated by a sys.version_info check in their typeshed .pyi files. So setting the min version to 3.11 allows those functions to typecheck properly.
An alternative is to make the relevant types Any:
```
if sys.version_info >= (3, 11):
_Positions = dis.Positions
else:
_Positions = Any
```
However, with python_version = 3.8, that means we're not getting any useful typechecking signal when encountering values of type _Position.
Changing the python_version to 3.11 does mean that we will stop typechecking codepaths that run only on lower versions, but that seems a small price to pay. It does also mean that we won't catch code that uses newer APIs without the appropriate version check, but again, not sure this has much of an impact.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/112561
Approved by: https://github.com/ezyang
