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431 lines
19 KiB
431 lines
19 KiB
from typing import Dict, List, NoReturn, Sequence, Union
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from torchgen.api.types import (
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ArrayRefCType,
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BaseCType,
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Binding,
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boolT,
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ConstRefCType,
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deviceT,
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Expr,
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intArrayRefT,
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iOptTensorListRefT,
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layoutT,
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ListCType,
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longT,
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memoryFormatT,
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MutRefCType,
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NamedCType,
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opmath_t,
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OptionalCType,
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optionalIntArrayRefT,
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optionalScalarRefT,
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optionalSymIntArrayRefT,
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optionalTensorRefT,
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scalar_t,
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scalarT,
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scalarTypeT,
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SpecialArgName,
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symIntArrayRefT,
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SymIntT,
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tensorOptionsT,
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tensorT,
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VectorCType,
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)
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# This file implements a small program synthesis engine that implements
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# conversions between one API to another.
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#
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# The key data type in this file in NamedCType, short for Named C++ semantic type. A NamedCType
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# represents a C++ type, plus semantic information about what it represents.
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# For example, consider the argument "bool pin_memory"; its normal C++ type is
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# "bool", but its C++ semantic type also keeps track that this represents a
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# "pin_memory"; you can't just use a random other boolean in a context where you
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# need a "pin_memory"!
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#
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# The translator takes a list of needed NamedCTypes, and then figures out how
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# to construct expressions with these NamedCTypes from the given bindings. Many
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# of these expressions are trivial (I need a Tensor other; there's a Tensor
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# other scope); others are more nontrivial and may require packing/unpacking.
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# Some examples of non-trivial action:
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#
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# - Need the "dtype" binding? Well, maybe "dtype" isn't available
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# in the context, instead, "options" is, and you need to extract
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# it from there. (Gather)
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#
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# - Need the "context" binding? Well, maybe "context" isn't available
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# in the context, and you need to construct it from "dtype", "device",
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# etc. (Scatter)
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#
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# - Need the "memory_format" binding? Well, actually, it's available
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# from both "memory_format" and "options", so you had better make sure
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# they are consistent. (Join)
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options_ctype = NamedCType("options", ConstRefCType(BaseCType(tensorOptionsT)))
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out_tensor_ctype = NamedCType("out", ConstRefCType(BaseCType(tensorT)))
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longVec_ctype = VectorCType(BaseCType(longT))
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longSymVec_ctype = VectorCType(BaseCType(SymIntT))
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optionalLongVec_ctype = OptionalCType(VectorCType(BaseCType(longT)))
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optionalScalar_ctype = OptionalCType(BaseCType(scalarT))
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optionalTensor_ctype = OptionalCType(BaseCType(tensorT))
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class UnsatError(RuntimeError):
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pass
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# Given a set of in-scope bindings and a set of target bindings, synthesize
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# a list of expressions that uses only the in-scope bindings (bindings) that
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# have all of the types of goals. You may want to use this function if
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# you're generating code for a function like:
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#
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# void f({args}) {
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# g({exprs}); // g is a different API
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# }
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#
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# and you need to generate "exprs".
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#
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# Typically, a list of Bindings is convenient to get (you usually call something
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# like arguments() to get them); but technically you only need less information:
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# for 'bindings' an (un-ordered) list of Exprs is sufficient; similarly, for
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# 'goals', an (ordered) list of NamedCType goals is sufficient. If you are doing
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# something more complicated, e.g., tracking the set of bindings in a context,
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# you may find using these smaller types more convenient.
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def translate(
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bindings: Sequence[Union[Expr, Binding]],
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goals: Sequence[Union[NamedCType, Binding]],
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*,
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method: bool = False,
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allow_expensive_conversions: bool = False,
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) -> List[Expr]:
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binding_exprs: List[Expr] = []
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for b in bindings:
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if isinstance(b, Binding):
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binding_exprs.append(
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Expr(
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expr=b.name,
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type=b.nctype,
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)
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)
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else:
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binding_exprs.append(b)
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goal_ctypes: List[NamedCType] = []
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for g in goals:
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if isinstance(g, Binding):
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goal_ctypes.append(g.nctype)
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else:
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goal_ctypes.append(g)
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# Add all the bindings to the context
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ctx: Dict[NamedCType, str] = {}
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for b in binding_exprs:
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ctx[b.type] = b.expr
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# While we're at it, do some simple forward inference, looking through
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# constructors.
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#
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# NB: When should you do forward inference versus backward inference?
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# The general idea:
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#
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# - Backward inference WHEN the goal gets smaller
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# - Forward inference WHEN the hypothesis gets smaller
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#
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# This helps ensure termination: backward inference starts with a goal
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# and tries to make it simpler and simpler until it's trivial; if the
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# goal can grow in size, we blow up to a really huge goal size.
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# Similarly, with forward inference we take hypotheses and decompose
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# them into simpler hypotheses; if hypotheses could expand in size,
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# we also have potential nontermination. (In the code below, forward
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# inference is only ever carried out at a single step, but you could
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# imagine repeated application of forward inference being profitable.)
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#
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# A good starting point in the literature for exploring more about proof
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# search are these lecture notes
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# https://www.cs.cmu.edu/~fp/courses/oregon-m10/04-focusing.pdf
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#
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# TODO: My kingdom for a pattern matcher
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# https://www.python.org/dev/peps/pep-0634/
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#
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# TODO: This could get us in recomputation trouble if b.expr is nontrivial.
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# Fix this by implementing some sort of sharing so that if multiple
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# goals share the same expression, we only compute it once. This seems
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# to matter in practice as compiler is often unwilling to CSE nontrivial
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# expressions like scalar.to<scalar_t>()
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t = b.type
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if (
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isinstance(t, ConstRefCType)
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and isinstance(t.elem, OptionalCType)
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and isinstance(t.elem.elem, BaseCType)
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and str(t.elem.elem.type) == "at::Tensor"
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):
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ctx[
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NamedCType(t.elem.elem.name, ConstRefCType(BaseCType(tensorT)))
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] = f"({b.expr}.has_value() ? *{b.expr} : at::Tensor())"
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if t.type == ConstRefCType(OptionalCType(BaseCType(tensorT))):
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ctx[
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NamedCType(t.name, BaseCType(optionalTensorRefT))
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] = f"(({b.expr}.has_value() && (*{b.expr}).defined()) ? at::OptionalTensorRef(*{b.expr}) : at::OptionalTensorRef())"
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if t.type == ConstRefCType(BaseCType(scalarT)):
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ctx[NamedCType(t.name, BaseCType(opmath_t))] = f"({b.expr}).to<opmath_t>()"
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if t.type == ConstRefCType(OptionalCType(BaseCType(scalarT))):
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ctx[
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NamedCType(t.name, BaseCType(optionalScalarRefT))
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] = f"({b.expr}.has_value() ? at::OptionalScalarRef(&({b.expr}.value())) : at::OptionalScalarRef())"
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if t.type == BaseCType(scalar_t):
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ctx[
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NamedCType(t.name, BaseCType(opmath_t))
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] = f"static_cast<opmath_t>({b.expr})"
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# [Note: IOptTensorListRef]
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if t.type == ConstRefCType(ListCType(OptionalCType(BaseCType(tensorT)))):
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ctx[
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NamedCType(t.name, BaseCType(iOptTensorListRefT))
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] = f"at::IOptTensorListRef({b.expr})"
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# Add implicit bindings if the generated code is inside a Tensor method
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if method:
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ctx[
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NamedCType("self", MutRefCType(BaseCType(tensorT)))
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] = "const_cast<Tensor&>(*this)"
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ctx[
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NamedCType("self", ConstRefCType(BaseCType(tensorT)))
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] = "const_cast<Tensor&>(*this)"
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# This is better! Byte-for-byte compat
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# ctx[NamedCType("self", ConstRefCType(BaseCType(tensorT)))] = "*this"
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def unsat(goal: NamedCType) -> NoReturn:
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ctx_desc = "\n".join(
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f" {t.cpp_type()} {t.name}; // {e}" for t, e in ctx.items()
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)
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raise UnsatError(
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f"""
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Failed to synthesize the expression "{goal.cpp_type()} {goal.name}".
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When I failed, the following bindings were available in the context:
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{ctx_desc}
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This probably means there is a missing rule in the rules of torchgen.api.translate.
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Check this module for more information.
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"""
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)
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# A shitty backtracking search implementation. It's shitty because it
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# does backtracking via stack (bad idea!) and for the most part tries to
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# avoid backtracking. In particular, if
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# direct=True, we won't try to do any fancy synthesis, just trivial
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# conversions (e.g., "T a" is OK for "const T& a"). So all of the
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# existing rules in this function simply try to solve immediately,
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# and bail if things don't work out.
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def solve(goal: NamedCType, *, direct: bool) -> str:
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def direct_solve(goal: NamedCType) -> str:
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return solve(goal, direct=True)
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if goal in ctx:
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# Trivial
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return ctx[goal]
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# const & is satisfied with mutable &
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if isinstance(goal.type, ConstRefCType):
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try:
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# WARNING: not strictly decreasing; be careful not
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# to add a direct conversion that goes satisfies
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# mutable& with const&
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return solve(
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NamedCType(goal.name, MutRefCType(goal.type.elem)), direct=direct
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)
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except UnsatError:
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pass
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# mutable & is satisfied with value
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if isinstance(goal.type, MutRefCType):
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try:
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return solve(NamedCType(goal.name, goal.type.elem), direct=direct)
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except UnsatError:
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pass
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# TODO: These are referentially equal, shouldn't have to do this;
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# ensuring we don't use type synonym IntArrayRef in codegen would
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# help
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if goal.type == ArrayRefCType(BaseCType(longT)):
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return solve(NamedCType(goal.name, BaseCType(intArrayRefT)), direct=direct)
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if direct:
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unsat(goal)
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# For now, all of these rules are mutually exclusive.
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if goal == NamedCType("memory_format", OptionalCType(BaseCType(memoryFormatT))):
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memory_format = direct_solve(
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NamedCType(
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SpecialArgName.possibly_redundant_memory_format,
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OptionalCType(BaseCType(memoryFormatT)),
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)
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)
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# No need to join "memory_format" and "options" if the target API takes "options" directly.
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# Otherwise it will cause the redundant memory_format error.
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if options_ctype in goal_ctypes:
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return memory_format
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try:
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options = direct_solve(options_ctype)
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return f"c10::impl::check_tensor_options_and_extract_memory_format({options}, {memory_format})"
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except UnsatError:
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return memory_format
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elif goal == NamedCType("options", BaseCType(tensorOptionsT)):
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dtype = direct_solve(
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NamedCType("dtype", OptionalCType(BaseCType(scalarTypeT)))
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)
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pin_memory = direct_solve(
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NamedCType("pin_memory", OptionalCType(BaseCType(boolT)))
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)
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device = direct_solve(
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NamedCType("device", OptionalCType(BaseCType(deviceT)))
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)
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layout = direct_solve(
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NamedCType("layout", OptionalCType(BaseCType(layoutT)))
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)
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return f"TensorOptions().dtype({dtype}).layout({layout}).device({device}).pinned_memory({pin_memory})"
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elif goal == NamedCType("dtype", OptionalCType(BaseCType(scalarTypeT))):
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try:
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options = direct_solve(options_ctype)
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return f"c10::optTypeMetaToScalarType({options}.dtype_opt())"
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except UnsatError:
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out_tensor = direct_solve(out_tensor_ctype)
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return f"{out_tensor}.scalar_type()"
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elif goal == NamedCType("layout", OptionalCType(BaseCType(layoutT))):
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try:
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options = direct_solve(options_ctype)
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return f"{options}.layout_opt()"
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except UnsatError:
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out_tensor = direct_solve(out_tensor_ctype)
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return f"{out_tensor}.layout()"
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elif goal == NamedCType("device", OptionalCType(BaseCType(deviceT))):
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try:
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options = direct_solve(options_ctype)
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return f"{options}.device_opt()"
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except UnsatError:
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out_tensor = direct_solve(out_tensor_ctype)
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return f"{out_tensor}.device()"
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elif goal == NamedCType("pin_memory", OptionalCType(BaseCType(boolT))):
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try:
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options = direct_solve(options_ctype)
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return f"{options}.pinned_memory_opt()"
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except UnsatError:
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# If we're calling a factory op from its out= variant,
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# We don't actually care about the value of pin_memory.
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out_tensor = direct_solve(out_tensor_ctype)
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return "c10::nullopt"
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# We can always do translations from value types to reference types, like vector<int> -> IntArrayRef
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elif goal.type == BaseCType(intArrayRefT):
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try:
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return direct_solve(NamedCType(goal.name, longVec_ctype))
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except UnsatError:
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# We can also go SymIntArrayRef -> IntArrayRef
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symIntArrayRef_type = direct_solve(
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NamedCType(goal.name, BaseCType(symIntArrayRefT))
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)
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return f"C10_AS_INTARRAYREF_SLOW({symIntArrayRef_type})"
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elif goal.type == BaseCType(symIntArrayRefT):
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try:
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r = direct_solve(NamedCType(goal.name, BaseCType(intArrayRefT)))
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return f"c10::fromIntArrayRefSlow({r})"
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except UnsatError:
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return direct_solve(NamedCType(goal.name, longSymVec_ctype))
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elif goal.type == BaseCType(SymIntT):
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return direct_solve(NamedCType(goal.name, BaseCType(longT)))
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elif goal.type == OptionalCType(BaseCType(SymIntT)):
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argname = direct_solve(
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NamedCType(goal.name, OptionalCType(BaseCType(longT)))
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)
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return f"{argname}.has_value() ? c10::make_optional(c10::SymInt(*{argname})) : c10::nullopt"
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elif goal.type == BaseCType(longT):
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symInt_type = direct_solve(NamedCType(goal.name, BaseCType(SymIntT)))
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return f"{symInt_type}.guard_int(__FILE__, __LINE__)"
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elif goal.type == OptionalCType(BaseCType(longT)):
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argname = direct_solve(
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NamedCType(goal.name, OptionalCType(BaseCType(SymIntT)))
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)
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return f"{argname}.has_value() ? c10::make_optional({argname}->guard_int(__FILE__, __LINE__)) : c10::nullopt"
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elif goal.type == BaseCType(optionalIntArrayRefT):
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try:
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return direct_solve(NamedCType(goal.name, optionalLongVec_ctype))
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except UnsatError:
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argname = direct_solve(
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NamedCType(goal.name, BaseCType(optionalSymIntArrayRefT))
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)
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return f"{argname}.has_value() ? c10::make_optional(C10_AS_INTARRAYREF_SLOW(*{argname})) : c10::nullopt"
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elif goal.type == BaseCType(optionalSymIntArrayRefT):
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# TODO: You might also want to solve this from longSymVec_ctype or
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# an optional version of it
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argname = direct_solve(
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NamedCType(goal.name, BaseCType(optionalIntArrayRefT))
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)
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return f"{argname}.has_value() ? c10::make_optional(c10::fromIntArrayRefSlow(*{argname})) : c10::nullopt"
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elif goal.type == BaseCType(optionalScalarRefT):
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return direct_solve(NamedCType(goal.name, optionalScalar_ctype))
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elif goal.type == BaseCType(optionalTensorRefT):
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return direct_solve(NamedCType(goal.name, optionalTensor_ctype))
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# Note [translation from C++ reference to value types]
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# The below cases are all for when we have an argument with a reference type,
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# and a corresponding goal with a value type.
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# These are needed when we populate the inputs to a lambda capture and we need
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# to guarantee the lifetime of each captured argument.
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# We guard it with an explicit kwarg because converting to a value type is expensive
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# (O(n)) to convert from IntArrayRef to vector<int>),
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# so the caller of translate() should be explicit that they need it.
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if allow_expensive_conversions:
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if goal.type == VectorCType(BaseCType(longT)):
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intArrayRef_ctype = NamedCType(goal.name, BaseCType(intArrayRefT))
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argname = direct_solve(intArrayRef_ctype)
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return f"{argname}.vec()"
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if goal.type == VectorCType(BaseCType(SymIntT)):
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symIntArrayRef_ctype = NamedCType(goal.name, BaseCType(symIntArrayRefT))
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argname = direct_solve(symIntArrayRef_ctype)
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return f"{argname}.vec()"
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elif goal.type == OptionalCType(VectorCType(BaseCType(longT))):
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optionalIntArrayRef_ctype = NamedCType(
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goal.name, BaseCType(optionalIntArrayRefT)
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)
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argname = direct_solve(optionalIntArrayRef_ctype)
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return f"{argname}.has_value() ? c10::make_optional({argname}->vec()) : c10::nullopt"
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elif goal.type == OptionalCType(BaseCType(scalarT)):
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optionalScalarRef_ctype = NamedCType(
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goal.name, BaseCType(optionalScalarRefT)
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)
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argname = direct_solve(optionalScalarRef_ctype)
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return f"{argname}.has_value() ? c10::make_optional({argname}) : c10::nullopt"
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elif goal.type == OptionalCType(BaseCType(scalarT)):
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optionalTensorRef_ctype = NamedCType(
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goal.name, BaseCType(optionalTensorRefT)
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)
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argname = direct_solve(optionalTensorRef_ctype)
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return f"{argname}.has_value() ? c10::make_optional({argname}) : c10::nullopt"
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# Technically, we also need to handle cases of C++ containers holding reference types.
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# But there currently aren't any ops that require lambda capture codegen
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# With arguments like std::vector<IntArrayRef>.
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# If that changes, we'll have to add the translation here.
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# We allow const casting on tensors, since const-correctness is a bit broken for at::Tensor.
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# We could probably generalize this to non-tensor types too.
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if goal.type == MutRefCType(BaseCType(tensorT)):
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const_ref_tensor_ctype = NamedCType(
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goal.name, ConstRefCType(BaseCType(tensorT))
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)
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argname = direct_solve(const_ref_tensor_ctype)
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return f"const_cast<Tensor&>({argname})"
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unsat(goal)
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return [Expr(solve(g, direct=False), g) for g in goal_ctypes]
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