compiler.embedding: add fast path for inference for lists of scalars in a host object.

artiq/compiler/embedding.py

@@ -323,6 +323,39 @@ class StitchingInferencer(Inferencer):
             else:
                 attributes = object_type.attributes
 
+            attr_value_type = None
+
+            if isinstance(attr_value, list):
+                # Fast path for lists of scalars.
+                IS_FLOAT = 1
+                IS_INT32 = 2
+                IS_INT64 = 4
+
+                state = 0
+                for elt in attr_value:
+                    if elt.__class__ == float:
+                        state |= IS_FLOAT
+                    elif elt.__class__ == int:
+                        if -2**31 < elt < 2**31-1:
+                            state |= IS_INT32
+                        elif -2**63 < elt < 2**63-1:
+                            state |= IS_INT64
+                        else:
+                            state = -1
+                            break
+                    else:
+                        state = -1
+
+                if state == IS_FLOAT:
+                    attr_value_type = builtins.TList(builtins.TFloat())
+                elif state == IS_INT32:
+                    attr_value_type = builtins.TList(builtins.TInt32())
+                elif state == IS_INT64:
+                    attr_value_type = builtins.TList(builtins.TInt64())
+
+            if attr_value_type is None:
+                # Slow path. We don't know what exactly is the attribute value,
+                # so we quote it only for the error message that may possibly result.
                 ast = self.quote(attr_value, object_loc.expanded_from)
 
                 def proxy_diagnostic(diag):
@@ -338,18 +371,19 @@ class StitchingInferencer(Inferencer):
                 proxy_engine.process = proxy_diagnostic
                 Inferencer(engine=proxy_engine).visit(ast)
                 IntMonomorphizer(engine=proxy_engine).visit(ast)
+                attr_value_type = ast.type
 
             if node.attr not in attributes:
                 # We just figured out what the type should be. Add it.
-                attributes[node.attr] = ast.type
+                attributes[node.attr] = attr_value_type
-            elif attributes[node.attr] != ast.type and not types.is_rpc_function(ast.type):
+            elif attributes[node.attr] != attr_value_type and not types.is_rpc_function(attr_value_type):
                 # Does this conflict with an earlier guess?
                 # RPC function types are exempt because RPCs are dynamically typed.
                 printer = types.TypePrinter()
                 diag = diagnostic.Diagnostic("error",
                     "host object has an attribute '{attr}' of type {typea}, which is"
                     " different from previously inferred type {typeb} for the same attribute",
-                    {"typea": printer.name(ast.type),
+                    {"typea": printer.name(attr_value_type),
                      "typeb": printer.name(attributes[node.attr]),
                      "attr": node.attr},
                     object_loc)