Implement jump tables (#453)

* Add 'jump_table_entry' and 'indirect_jump' instructions.

* Update CodeSink to keep track of code size. Pretty up clif-util's disassembly output.

* Only disassemble the machine portion of output. Pretty print the read-only data after it.

* Update switch frontend code to use new br_table instruction w/ default.

lib/codegen/meta-python/cdsl/instructions.py

@@ -89,6 +89,7 @@ class Instruction(object):
     :param constraints: Tuple of instruction-specific TypeConstraints.
     :param is_terminator: This is a terminator instruction.
     :param is_branch: This is a branch instruction.
+    :param is_indirect_branch: This is an indirect branch instruction.
     :param is_call: This is a call instruction.
     :param is_return: This is a return instruction.
     :param can_trap: This instruction can trap.
@@ -103,6 +104,8 @@ class Instruction(object):
     ATTRIBS = {
             'is_terminator': 'True for instructions that terminate the EBB.',
             'is_branch': 'True for all branch or jump instructions.',
+            'is_indirect_branch':
+            'True for all indirect branch or jump instructions.',
             'is_call': 'Is this a call instruction?',
             'is_return': 'Is this a return instruction?',
             'can_load': 'Can this instruction read from memory?',

lib/codegen/meta-python/cdsl/isa.py

@@ -469,7 +469,7 @@ class Encoding(object):
                 "Format {} must match recipe: {}".format(
                     self.inst.format, recipe.format))
 
-        if self.inst.is_branch:
+        if self.inst.is_branch and not self.inst.is_indirect_branch:
             assert recipe.branch_range, (
                     'Recipe {} for {} must have a branch_range'
                     .format(recipe, self.inst.name))