[Parser][Printer] More parser/printer improvements (apache#12)

* Relax pretty printer initial prototype

* call into TVMScriptPrinter for PrimFuncs

* most round-trip tests pass

* address comments

* implement relax.output syntax for dataflow block outputs

* remove leftover comments

* fix Var constructor on ShapeExpr annotation

* add printing and parsing for simple PrimExpr and Call Attrs

python/tvm/relax/parser.py

@@ -94,14 +94,41 @@ def _tir_from_synr(
 
 # NOTE: call_dps is an actual registered operator
 class SpecialOp(Enum):
-    """Relax operator calls that have special semantics handled by the parser."""
+    """Relax operators that have special semantics handled by the parser."""
 
     MATCH_SHAPE = "relax.match_shape"
     CALL_PACKED = "relax.call_packed"
     DATAFLOW = "relax.dataflow"
     DATAFLOW_OUTPUT = "relax.output"
 
 
+class ArithmeticOp(Enum):
+    """Arithmetic operators that can desugar to either Relax or TIR PrimExpr operators."""
+
+    ADD = ast.BuiltinOp.Add
+    SUB = ast.BuiltinOp.Sub
+    MUL = ast.BuiltinOp.Mul
+    DIV = ast.BuiltinOp.Div
+    FLOOR_DIV = ast.BuiltinOp.FloorDiv
+
+
+RELAX_ARITHMETIC_OP_MAP = {
+    ArithmeticOp.ADD: relay.op.get("add"),
+    ArithmeticOp.SUB: relay.op.get("subtract"),
+    ArithmeticOp.MUL: relay.op.get("multiply"),
+    ArithmeticOp.DIV: relay.op.get("divide"),
+    ArithmeticOp.FLOOR_DIV: relay.op.get("floor_divide"),
+}
+
+PRIMEXPR_ARITHMETIC_OP_MAP = {
+    ArithmeticOp.ADD: tir.Add,
+    ArithmeticOp.SUB: tir.Sub,
+    ArithmeticOp.MUL: tir.Mul,
+    ArithmeticOp.DIV: tir.Div,
+    ArithmeticOp.FLOOR_DIV: tir.FloorDiv,
+}
+
+
 class RelaxTransformer(Transformer):
     def __init__(self, definition_scope):
         super().__init__()
@@ -367,16 +394,25 @@ def parse_primexpr(self, expr: ast.Expr, bind_free_vars: bool) -> tir.PrimExpr:
                     "cannot introduce new dimension variables in this expression",
                     expr.span,
                 )
+
         elif isinstance(expr, ast.Constant):
             if not isinstance(expr.value, int):
                 self.report_error("only integer constants are supported", expr.span)
             return tir.const(expr.value, "int32", self.to_tvm_span(expr.span))
+
+        elif isinstance(expr, ast.Call):
+            if not isinstance(expr.func_name, ast.Op):
+                self.report_error(
+                    "only built-in operators can be used in dimension expressions",
+                    expr.func_name.span,
+                )
+            op = PRIMEXPR_ARITHMETIC_OP_MAP[self.transform_expr(expr.func_name)]
+            # TODO(@altanh): it might not make sense to bind free variables
+            args = [self.parse_primexpr(arg, bind_free_vars) for arg in expr.params]
+            return op(*args, span=self.to_tvm_span(expr.span))
+
         else:
-            # TODO(@altanh): parse (simple) PrimExprs
-            self.report_error(
-                "only dimension variable expressions are currently supported",
-                expr.span,
-            )
+            self.report_error(f"unsupported dimension expression: {expr}", expr.span)
 
     def transform_module(self, mod: ast.Module) -> IRModule:
         """Transforms the given synr Module to a Relax IRModule.
@@ -750,7 +786,10 @@ def transform_expr(self, expr: ast.Expr) -> rx.Expr:
         if isinstance(expr, ast.Attr):
             if expr.field.name == "shape":
                 obj = self.transform_expr(expr.object)
-                return relay.Call(relay.op.get("shape_of"), [obj], span=self.to_tvm_span(expr.span))
+                attrs = tvm.ir.attrs.make_node("relay.attrs.ShapeOfAttrs", dtype="int32")
+                return relay.Call(
+                    relay.op.get("shape_of"), [obj], attrs=attrs, span=self.to_tvm_span(expr.span)
+                )
             else:
                 # assume it's a hierarchical op identifier (e.g. nn.softmax, relax.call_dps)
                 op_name = self._parse_attrs_to_str(expr)
@@ -780,12 +819,30 @@ def transform_expr(self, expr: ast.Expr) -> rx.Expr:
                     )
                 op = rx.ExternFunc(extern_func.value, self.to_tvm_span(extern_func.span))
                 args = [self.transform_expr(expr.params[1])]
+            elif isinstance(op, ArithmeticOp):
+                args = [self.transform_expr(arg) for arg in expr.params]
+                if all([isinstance(arg, tir.PrimExpr) for arg in args]):
+                    return PRIMEXPR_ARITHMETIC_OP_MAP[op](*args, span=self.to_tvm_span(expr.span))
+                # otherwise it's just a normal Relax operator call
+                op = RELAX_ARITHMETIC_OP_MAP[op]
             elif isinstance(op, (tvm.ir.Op, relay.Expr)):
                 args = [self.transform_expr(arg) for arg in expr.params]
             else:
                 self.report_error(f"unsupported function in call: {op}", expr.func_name.span)
+
+            if isinstance(op, rx.ExternFunc) or (
+                isinstance(op, tvm.ir.Op) and op.attrs_type_key != ""
+            ):
+                attrs_type_key = "DictAttrs" if isinstance(op, rx.ExternFunc) else op.attrs_type_key
+                kwargs = {}
+                for key, val in expr.keyword_params.items():
+                    assert isinstance(key, ast.Constant) and isinstance(key.value, str)
+                    kwargs[key.value] = self.transform_expr(val)
+                attrs = tvm.ir.attrs.make_node(attrs_type_key, **kwargs)
+            else:
+                attrs = None
             # TODO(@altanh): should we check for correct arity here eagerly, or defer to a pass?
-            return relay.Call(op, args, span=self.to_tvm_span(expr.span))
+            return relay.Call(op, args, attrs=attrs, span=self.to_tvm_span(expr.span))
 
         elif isinstance(expr, ast.Tuple):
             fields = [self.transform_expr(field) for field in expr.values]
@@ -812,14 +869,27 @@ def transform_expr(self, expr: ast.Expr) -> rx.Expr:
                 return tir.IntImm("int32", expr.value, self.to_tvm_span(expr.span))
             elif isinstance(expr.value, float):
                 return tir.FloatImm("float32", expr.value, self.to_tvm_span(expr.span))
+            elif isinstance(expr.value, str):
+                # FIXME(@altanh): using StringImm seems to cause problems, but this loses span
+                return expr.value
+            elif expr.value is None:
+                return None
             else:
                 self.report_error(
-                    "unsupported constant expression (we currently only support int and float)",
+                    f"unsupported constant expression: {expr}",
                     expr.span,
                 )
 
+        elif isinstance(expr, ast.Op):
+            # TODO(@altanh): might need to generalize from ArithmeticOp if we decide to support
+            #                array slicing syntax
+            try:
+                return ArithmeticOp(expr.name)
+            except ValueError:
+                self.report_error(f"unsupported built-in operator: {expr.name}", expr.span)
+
         else:
-            self.report_error("unsupported expression", expr.span)
+            self.report_error(f"unsupported expression: {expr}", expr.span)
 
     def transform_block(self, block: ast.Block) -> rx.SeqExpr:
         """Transforms the given synr block to a Relax SeqExpr (sequence of Blocks with a final
@@ -842,7 +912,7 @@ def transform_block(self, block: ast.Block) -> rx.SeqExpr:
             parsed_stmt = self.transform_stmt(stmt)
             if isinstance(parsed_stmt, rx.DataflowBlock):
                 if current_block:
-                    # FIXME: span
+                    # FIXME(@altanh): need to manually construct span start & end
                     blocks.append(rx.BindingBlock(current_block, self.to_tvm_span(stmt.span)))
                     current_block = []
                 blocks.append(parsed_stmt)