Rename the VOID type to INVALID and clean up obsolete comments.

The VOID type isn't used for anything resembling what "void" means in C,
so rename it to INVALID to avoid confusion.

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

@@ -179,7 +179,7 @@ class SpecialType(ValueType):
     def __init__(self, name, membytes, doc):
         # type: (str, int, str) -> None
         super(SpecialType, self).__init__(name, membytes, doc)
-        # Assign numbers starting from 1. (0 is VOID)
+        # Assign numbers starting from 1. (0 is INVALID)
         ValueType.all_special_types.append(self)
         self.number = len(ValueType.all_special_types)
         assert self.number < LANE_BASE, 'Too many special types'

lib/codegen/meta-python/gen_encoding.py

@@ -22,8 +22,8 @@ This is the information available to us:
 ## Level 1 table lookup
 
 The CPU mode provides the first table. The key is the instruction's controlling
-type variable. If the instruction is not polymorphic, use `VOID` for the type
-variable. The table values are level 2 tables.
+type variable. If the instruction is not polymorphic, use `INVALID` for the
+type variable. The table values are level 2 tables.
 
 ## Level 2 table lookup
 
@@ -682,7 +682,7 @@ def emit_level1_hashtable(cpumode, level1, offt, fmt):
             # Empty hash table entry. Include the default legalization action.
             if not level2:
                 fmt.format(
-                        'Level1Entry {{ ty: ir::types::VOID, log2len: !0, '
+                        'Level1Entry {{ ty: ir::types::INVALID, log2len: !0, '
                         'offset: 0, legalize: {} }},',
                         level1.legalize_code)
                 continue
@@ -690,7 +690,7 @@ def emit_level1_hashtable(cpumode, level1, offt, fmt):
             if level2.ty is not None:
                 tyname = level2.ty.rust_name()
             else:
-                tyname = 'ir::types::VOID'
+                tyname = 'ir::types::INVALID'
 
             lcode = cpumode.isa.legalize_code(level2.legalize)
 

lib/codegen/meta-python/gen_instr.py

@@ -705,7 +705,7 @@ def gen_inst_builder(inst, fmt):
             args.append(inst.ctrl_typevar.name)
         elif not inst.is_polymorphic:
             # No controlling type variable needed.
-            args.append('types::VOID')
+            args.append('types::INVALID')
         else:
             assert inst.is_polymorphic and inst.use_typevar_operand
             # Infer the controlling type variable from the input operands.