Define a return instruction.

It is possible to return multiple values from a function, so ReturnData contains
a VariableArgs instance.

We don't want return instructions to appear as 'return (v1)', so tweak the
printing of VariableArgs so the parantheses are added externally.

meta/cretonne/base.py

@@ -95,6 +95,18 @@ trapnz = Instruction(
         """,
         ins=c)
 
+rvals = Operand('rvals', variable_args, doc='return values')
+
+x_return = Instruction(
+        'return', r"""
+        Return from the function.
+
+        Unconditionally transfer control to the calling function, passing the
+        provided return values. The list of return values must match the
+        function signature's return types.
+        """,
+        ins=rvals)
+
 #
 # Materializing constants.
 #

meta/cretonne/formats.py

@@ -43,6 +43,8 @@ BranchTable = InstructionFormat(value, jump_table)
 
 Call = InstructionFormat(
         function, variable_args, multiple_results=True, boxed_storage=True)
+Return = InstructionFormat(variable_args, boxed_storage=True)
+
 
 # Finally extract the names of global variables in this module.
 InstructionFormat.extract_names(globals())