Cleanup, typechecking and documentation nits

lib/cretonne/meta/cdsl/xform.py

@@ -5,7 +5,6 @@ from __future__ import absolute_import
 from .ast import Def, Var, Apply
 from .ti import ti_xform, TypeEnv, get_type_env
 from functools import reduce
-from .typevar import TypeVar
 
 try:
     from typing import Union, Iterator, Sequence, Iterable, List, Dict  # noqa
@@ -13,6 +12,7 @@ try:
     from .ast import Expr, VarMap  # noqa
     from .isa import TargetISA  # noqa
     from .ti import TypeConstraint  # noqa
+    from .typevar import TypeVar  # noqa
     DefApply = Union[Def, Apply]
 except ImportError:
     pass
@@ -70,12 +70,17 @@ class Rtl(object):
 
     def free_vars(self):
         # type: () -> Set[Var]
-        """ Return the set of free Vars used in self"""
+        """Return the set of free Vars corresp. to SSA vals used in self"""
         def flow_f(s, d):
             # type: (Set[Var], Def) -> Set[Var]
             """Compute the change in the set of free vars across a Def"""
             s = s.difference(set(d.defs))
-            return s.union(set(a for a in d.expr.args if isinstance(a, Var)))
+            uses = set(d.expr.args[i] for i in d.expr.inst.value_opnums)
+            for v in uses:
+                assert isinstance(v, Var)
+                s.add(v)
+
+            return s
 
         return reduce(flow_f, reversed(self.rtl), set([]))
 
@@ -107,8 +112,9 @@ class Rtl(object):
         # type: (Rtl) -> None
         """
         Given that there is only 1 possible concrete typing T for self, assign
-        a singleton TV with the single type t=T[v] for each Var v \in self.
-        Its an error to call this on an Rtl with more than 1 possible typing.
+        a singleton TV with type t=T[v] for each Var v \in self.  Its an error
+        to call this on an Rtl with more than 1 possible typing.  This modifies
+        the Rtl in-place.
         """
         from .ti import ti_rtl, TypeEnv
         # 1) Infer the types of all vars in res
@@ -123,10 +129,8 @@ class Rtl(object):
 
         # 3) Assign the only possible type to each variable.
         for v in typenv.vars:
-            if v.get_typevar().singleton_type() is not None:
-                continue
-
-            v.set_typevar(TypeVar.singleton(typing[v].singleton_type()))
+            assert typing[v].singleton_type() is not None
+            v.set_typevar(typing[v])
 
 
 class XForm(object):

lib/cretonne/meta/semantics/elaborate.py

@@ -44,15 +44,20 @@ def find_matching_xform(d):
 def cleanup_semantics(r, outputs):
     # type: (Rtl, Set[Var]) -> Rtl
     """
-    The elaboration process creates a lot of redundant instruction pairs of the
-    shape:
+    The elaboration process creates a lot of redundant prim_to_bv conversions.
+    Cleanup the following cases:
 
+    1) prim_to_bv/prim_from_bv pair:
         a.0 << prim_from_bv(bva.0)
         ...
-        bva.1 << prim_to_bv(a.0)
+        bva.1 << prim_to_bv(a.0)  <-- redundant, replace by bva.0
         ...
 
-    Contract these to ease manual inspection.
+    2) prim_to_bv/prim_to-bv pair:
+        bva.0 << prim_to_bv(a)
+        ...
+        bva.1 << prim_to_bv(a) <-- redundant, replace by bva.0
+        ...
     """
     new_defs = []  # type: List[Def]
     subst_m = {v: v for v in r.vars()}  # type: VarMap

lib/cretonne/meta/semantics/smtlib.py

@@ -10,8 +10,9 @@ from .elaborate import elaborate
 
 try:
     from typing import TYPE_CHECKING, Tuple # noqa
-    from cdsl.xform import Rtl # noqa
+    from cdsl.xform import Rtl, XForm # noqa
     from cdsl.ast import VarMap # noqa
+    from cdsl.ti import VarTyping # noqa
 except ImportError:
     TYPE_CHECKING = False
 
@@ -34,10 +35,12 @@ def to_smt(r):
     assert r.is_concrete()
     # Should contain only primitives
     primitives = set(PRIMITIVES.instructions)
-    assert all(d.expr.inst in primitives for d in r.rtl)
+    assert set(d.expr.inst for d in r.rtl).issubset(primitives)
 
     q = ""
     m = {}  # type: VarMap
+
+    # Build declarations for any bitvector Vars
     for v in r.vars():
         typ = v.get_typevar().singleton_type()
         if not isinstance(typ, BVType):
@@ -45,9 +48,11 @@ def to_smt(r):
 
         q += "(declare-fun {} () {})\n".format(v.name, bvtype_to_sort(typ))
 
+    # Encode each instruction as a equality assertion
     for d in r.rtl:
         inst = d.expr.inst
 
+        # For prim_to_bv/prim_from_bv just update var_m. No assertion needed
         if inst == prim_to_bv:
             assert isinstance(d.expr.args[0], Var)
             m[d.expr.args[0]] = d.defs[0]
@@ -82,13 +87,13 @@ def to_smt(r):
                   .format(df, toW-fromW, arg)
         elif inst == bvsplit:
             arg = d.expr.args[0]
+            assert isinstance(arg, Var)
             arg_typ = arg.get_typevar().singleton_type()
             width = arg_typ.width()
             assert (width % 2 == 0)
 
             lo = d.defs[0]
             hi = d.defs[1]
-            assert isinstance(arg, Var)
 
             exp = "(and "
             exp += "(= {} ((_ extract {} {}) {})) "\
@@ -97,9 +102,10 @@ def to_smt(r):
                    .format(hi, width-1, width//2, arg)
             exp += ")"
         elif inst == bvconcat:
+            assert isinstance(d.expr.args[0], Var) and \
+                isinstance(d.expr.args[1], Var)
             lo = d.expr.args[0]
             hi = d.expr.args[1]
-            assert isinstance(lo, Var) and isinstance(hi, Var)
             df = d.defs[0]
 
             # Z3 Concat expects hi bits first, then lo bits
@@ -127,6 +133,14 @@ def equivalent(r1, r2, inp_m, out_m):
     Otherwise, the satisfying example for the query gives us values
     for which the two Rtls disagree.
     """
+    # Sanity - inp_m is a bijection from the set of inputs of r1 to the set of
+    # inputs of r2
+    assert set(r1.free_vars()) == set(inp_m.keys())
+    assert set(r2.free_vars()) == set(inp_m.values())
+
+    # Note that the same rule is not expected to hold for out_m due to
+    # temporaries/intermediates.
+
     # Rename the vars in r1 and r2 with unique suffixes to avoid conflicts
     src_m = {v: Var(v.name + ".a", v.get_typevar()) for v in r1.vars()}
     dst_m = {v: Var(v.name + ".b", v.get_typevar()) for v in r2.vars()}
@@ -145,7 +159,6 @@ def equivalent(r1, r2, inp_m, out_m):
     args_eq_exp = "(and \n"
 
     for v in r1.free_vars():
-        assert v in inp_m
         args_eq_exp += "(= {} {})\n".format(m1[v], m2[inp_m[v]])
     args_eq_exp += ")"
 
@@ -171,12 +184,12 @@ def equivalent(r1, r2, inp_m, out_m):
 def xform_correct(x, typing):
     # type: (XForm, VarTyping) -> str
     """
-    Given an XForm x and a concrete variable typing for x typing, build the
-    smtlib query asserting that x is correct for the given typing.
+    Given an XForm x and a concrete variable typing for x build the smtlib
+    query asserting that x is correct for the given typing.
     """
     assert x.ti.permits(typing)
 
-    # Create copies of the x.src and x.dst with the concrete types in typing.
+    # Create copies of the x.src and x.dst with their concrete types
     src_m = {v: Var(v.name, typing[v]) for v in x.src.vars()}
     src = x.src.copy(src_m)
     dst = x.apply(src)
@@ -191,8 +204,6 @@ def xform_correct(x, typing):
             inp_m[src_m[v]] = dst_m[v]
         elif v.is_output():
             out_m[src_m[v]] = dst_m[v]
-        else:
-            assert False, "Haven't decided what to do with intermediates yet"
 
     # Get the primitive semantic Rtls for src and dst
     prim_src = elaborate(src)