Switch SIMD type spelling to i32x4.

Add support for 'type variables' in type directives.

cranelift/docs/cton_lexer.py

@@ -15,10 +15,14 @@ class CretonneLexer(RegexLexer):
             (r';.*?$', Comment.Single),
             (r'\b(function|entry)\b', Keyword),
             (r'\b(align)\b', Name.Attribute),
-            (r'\b(v\d+)?(bool|i\d+|f32|f64)\b', Keyword.Type),
+            # Well known value types.
+            (r'\b(bool|i\d+|f32|f64)(x\d+)?\b', Keyword.Type),
             (r'\d+', Number.Integer),
             (r'0[xX][0-9a-fA-F]+', Number.Hex),
-            (r'(v|ss|ebb)\d+', Name.Variable),
+            # v<nn> = value
+            # ss<nn> = stack slot
+            (r'(v|ss)\d+', Name.Variable),
+            # ebb<nn> = extended basic block
             (r'(ebb)\d+', Name.Label),
             (r'(=)( *)([a-z]\w*)', bygroups(Operator, Whitespace, Name.Function)),
             (r'^( +)([a-z]\w*\b)(?! *[,=])', bygroups(Whitespace, Name.Function)),