127b22af5f
When an instruction doesn't have a valid encoding for the target ISA, it needs to be legalized. Different legalization strategies can be expressed as separate XFormGroup objects. Make the choice of XFormGroup configurable per CPU mode, rather than depending on a hard-coded default. Add a CPUMode.legalize_type() method which assigns an XFormGroup to controlling type variables and lets you set a default. Add a `legalize` field to Level1Entry so the first-level hash table lookup gives us the configured default legalization action for the instruction's controlling type variable.
259 lines
8.4 KiB
Python
259 lines
8.4 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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from .ti import ti_xform, TypeEnv, get_type_env
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try:
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from typing import Union, Iterator, Sequence, Iterable, List, Dict # 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 copy(self, m):
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# type: (Dict[Var, Var]) -> Rtl
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"""
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Return a copy of this rtl with all Vars substituted with copies or
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according to m. Update m as neccessary.
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"""
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return Rtl(*[d.copy(m) for d in 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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# Needed for testing type inference on XForms
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self.symtab = symtab
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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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# Perform type inference and cleanup
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raw_ti = get_type_env(ti_xform(self, TypeEnv()))
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raw_ti.normalize()
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self.ti = raw_ti.extract()
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# Sanity: The set of inferred free typevars should be a subset of the
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# TVs corresponding to Vars appearing in src
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free_typevars = set(self.ti.free_typevars())
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src_vars = set(self.inputs).union(
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[x for x in self.defs if not x.is_temp()])
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src_tvs = set([v.get_typevar() for v in src_vars])
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if (not free_typevars.issubset(src_tvs)):
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raise AssertionError(
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"Some free vars don't appear in src - {}"
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.format(free_typevars.difference(src_tvs)))
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# Update the type vars for each Var to their inferred values
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for v in self.inputs + self.defs:
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v.set_typevar(self.ti[v.get_typevar()])
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def __repr__(self):
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# type: () -> str
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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.rtl)
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s += '\n=>\n '
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s += '\n '.join(str(n) for n in self.dst.rtl)
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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 __str__(self):
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# type: () -> str
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return self.name
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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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