cc86964ab3
- cdsl.ast defines classes representing abstract syntax trees. - cdsl.xform defines classes for instruction transformations. - base.legalize defines legalization patterns.
227 lines
7.1 KiB
Python
227 lines
7.1 KiB
Python
"""
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Instruction transformations.
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"""
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from __future__ import absolute_import
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from .ast import Def, Var, Apply
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try:
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from typing import Union, Iterator, Sequence, Iterable # noqa
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from .ast import Expr # noqa
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DefApply = Union[Def, Apply]
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except ImportError:
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pass
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def canonicalize_defapply(node):
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# type: (DefApply) -> Def
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"""
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Canonicalize a `Def` or `Apply` node into a `Def`.
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An `Apply` becomes a `Def` with an empty list of defs.
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"""
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if isinstance(node, Apply):
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return Def((), node)
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else:
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return node
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class Rtl(object):
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"""
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Register Transfer Language list.
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An RTL object contains a list of register assignments in the form of `Def`
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objects.
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An RTL list can represent both a source pattern to be matched, or a
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destination pattern to be inserted.
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"""
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def __init__(self, *args):
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# type: (*DefApply) -> None
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self.rtl = tuple(map(canonicalize_defapply, args))
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def __iter__(self):
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# type: () -> Iterator[Def]
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return iter(self.rtl)
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class XForm(object):
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"""
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An instruction transformation consists of a source and destination pattern.
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Patterns are expressed in *register transfer language* as tuples of
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`ast.Def` or `ast.Expr` nodes.
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A legalization pattern must have a source pattern containing only a single
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instruction.
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>>> from base.instructions import iconst, iadd, iadd_imm
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>>> a = Var('a')
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>>> c = Var('c')
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>>> v = Var('v')
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>>> x = Var('x')
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>>> XForm(
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... Rtl(c << iconst(v),
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... a << iadd(x, c)),
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... Rtl(a << iadd_imm(x, v)))
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XForm(inputs=[Var(v), Var(x)], defs=[Var(c, src), Var(a, src, dst)],
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c << iconst(v)
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a << iadd(x, c)
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=>
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a << iadd_imm(x, v)
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)
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"""
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def __init__(self, src, dst):
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# type: (Rtl, Rtl) -> None
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self.src = src
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self.dst = dst
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# Variables that are inputs to the source pattern.
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self.inputs = list() # type: List[Var]
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# Variables defined in either src or dst.
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self.defs = list() # type: List[Var]
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# Rewrite variables in src and dst RTL lists to our own copies.
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# Map name -> private Var.
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symtab = dict() # type: Dict[str, Var]
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self._rewrite_rtl(src, symtab, Var.SRCCTX)
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num_src_inputs = len(self.inputs)
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self._rewrite_rtl(dst, symtab, Var.DSTCTX)
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# Check for inconsistently used inputs.
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for i in self.inputs:
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if not i.is_input():
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raise AssertionError(
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"'{}' used as both input and def".format(i))
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# Check for spurious inputs in dst.
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if len(self.inputs) > num_src_inputs:
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raise AssertionError(
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"extra inputs in dst RTL: {}".format(
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self.inputs[num_src_inputs:]))
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def __repr__(self):
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s = "XForm(inputs={}, defs={},\n ".format(self.inputs, self.defs)
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s += '\n '.join(str(n) for n in self.src)
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s += '\n=>\n '
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s += '\n '.join(str(n) for n in self.dst)
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s += '\n)'
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return s
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def _rewrite_rtl(self, rtl, symtab, context):
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# type: (Rtl, Dict[str, Var], int) -> None
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for line in rtl.rtl:
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if isinstance(line, Def):
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line.defs = tuple(
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self._rewrite_defs(line, symtab, context))
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expr = line.expr
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else:
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expr = line
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self._rewrite_expr(expr, symtab, context)
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def _rewrite_expr(self, expr, symtab, context):
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# type: (Apply, Dict[str, Var], int) -> None
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"""
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Find all uses of variables in `expr` and replace them with our own
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local symbols.
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"""
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# Accept a whole expression tree.
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stack = [expr]
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while len(stack) > 0:
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expr = stack.pop()
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expr.args = tuple(
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self._rewrite_uses(expr, stack, symtab, context))
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def _rewrite_defs(self, line, symtab, context):
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# type: (Def, Dict[str, Var], int) -> Iterable[Var]
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"""
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Given a tuple of symbols defined in a Def, rewrite them to local
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symbols. Yield the new locals.
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"""
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for sym in line.defs:
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name = str(sym)
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if name in symtab:
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var = symtab[name]
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if var.get_def(context):
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raise AssertionError("'{}' multiply defined".format(name))
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else:
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var = Var(name)
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symtab[name] = var
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self.defs.append(var)
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var.set_def(context, line)
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yield var
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def _rewrite_uses(self, expr, stack, symtab, context):
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# type: (Apply, List[Apply], Dict[str, Var], int) -> Iterable[Expr]
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"""
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Given an `Apply` expr, rewrite all uses in its arguments to local
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variables. Yield a sequence of new arguments.
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Append any `Apply` arguments to `stack`.
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"""
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for arg, operand in zip(expr.args, expr.inst.ins):
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# Nested instructions are allowed. Visit recursively.
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if isinstance(arg, Apply):
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stack.append(arg)
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yield arg
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continue
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if not isinstance(arg, Var):
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assert not operand.is_value(), "Value arg must be `Var`"
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yield arg
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continue
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# This is supposed to be a symbolic value reference.
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name = str(arg)
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if name in symtab:
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var = symtab[name]
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# The variable must be used consistently as a def or input.
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if not var.is_input() and not var.get_def(context):
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raise AssertionError(
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"'{}' used as both input and def"
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.format(name))
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else:
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# First time use of variable.
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var = Var(name)
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symtab[name] = var
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self.inputs.append(var)
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yield var
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def verify_legalize(self):
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# type: () -> None
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"""
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Verify that this is a valid legalization XForm.
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- The source pattern must describe a single instruction.
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- All values defined in the output pattern must be defined in the
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destination pattern.
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"""
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assert len(self.src.rtl) == 1, "Legalize needs single instruction."
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for d in self.src.rtl[0].defs:
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if not d.is_output():
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raise AssertionError(
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'{} not defined in dest pattern'.format(d))
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class XFormGroup(object):
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"""
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A group of related transformations.
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"""
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def __init__(self, name, doc):
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# type: (str, str) -> None
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self.xforms = list() # type: List[XForm]
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self.name = name
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self.__doc__ = doc
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def legalize(self, src, dst):
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# type: (Union[Def, Apply], Rtl) -> None
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"""
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Add a legalization pattern to this group.
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:param src: Single `Def` or `Apply` to be legalized.
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:param dst: `Rtl` list of replacement instructions.
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"""
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xform = XForm(Rtl(src), dst)
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xform.verify_legalize()
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self.xforms.append(xform)
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