Tagging.v3

// Copyright 2022 Ben L. Titzer. All rights reserved.
// See LICENSE for details of Apache 2.0 license.

// Configures the representation of values on a (native) value stack.
class Tagging(tagged: bool, simd: bool) {
	def raw: int = if(simd, 16, 8);				// XXX: make unsigned
	def tag_size: int = if(tagged, raw, 0);			// XXX: make unsigned
	def slot_size: int = if(tagged, u31.!(raw * 2), raw);	// XXX: make unsigned
	def slot_size_log: u6 = if(tagged, if(simd, 5, 4), if(simd, 4, 3));
	def value_size: int = slot_size - tag_size;

	def maybeRefTag(tag: byte) -> bool {
		match (i7.view(tag)) {
			BpTypeCode.I32.val,
			BpTypeCode.I64.val,
			BpTypeCode.F32.val,
			BpTypeCode.F64.val,
			BpTypeCode.V128.val,
			BpTypeCode.I8.val,
			BpTypeCode.I16.val => return false;

			BpTypeCode.NOCONT.val,
			BpTypeCode.CONTREF.val,
			BpTypeCode.FUNCREF.val,
			BpTypeCode.EXTERNREF.val,
			BpTypeCode.ANYREF.val,
			BpTypeCode.EQREF.val,
			BpTypeCode.REF_NULL.val,
			BpTypeCode.REF.val,
			BpTypeCode.I31REF.val,
			BpTypeCode.STRUCTREF.val,
			BpTypeCode.ARRAYREF.val,
			BpTypeCode.NULLREF.val,
			BpTypeCode.NULLEXTERNREF.val,
			BpTypeCode.NULLFUNCREF.val => return true;
		}
		return false;
	}
}