[qfcc] Implement field access for multi-vector expressions

Of course as an r-value (I think), but it makes getting only the desired
part of a geometric algebra expression much nicer.

tools/qfcc/include/expr.h

@@ -579,6 +579,8 @@ expr_t *new_zero_expr (struct type_s *type);
 */
 expr_t *new_name_expr (const char *name);
 
+struct symbol_s *get_name (expr_t *e) __attribute__((pure));
+
 /** Create a new string constant expression node.
 
 	\param string_val	The string constant being represented.

tools/qfcc/source/algebra.c

@@ -490,7 +490,10 @@ algebra_mvec_type (algebra_t *algebra, pr_uint_t group_mask)
 		algebra->mvec_types[group_mask] = new_type ();
 		*algebra->mvec_types[group_mask] = (type_t) {
 			.type = algebra->type->type,
-			.name = "basis group",
+			.name = save_string (va (0, "algebra(%s(%d,%d,%d):%04x)",
+									 algebra->type->name,
+									 algebra->plus, algebra->minus,
+									 algebra->zero, group_mask)),
 			.alignment = algebra_alignment (algebra->type, components),
 			.width = components,
 			.meta = ty_algebra,

tools/qfcc/source/expr.c

@@ -1463,23 +1463,30 @@ prepend_expr (expr_t *block, expr_t *e)
 	return block;
 }
 
+symbol_t *
+get_name (expr_t *e)
+{
+	if (e->type == ex_symbol) {
+		return e->e.symbol;
+	}
+	return 0;
+}
+
 symbol_t *
 get_struct_field (const type_t *t1, expr_t *e1, expr_t *e2)
 {
-	symtab_t   *strct = 0;
-	if (is_algebra (t1)) {
-		error (e1, "dereferencing pointer to incomplete type");
-		return 0;
-	} else {
-		strct = t1->t.symtab;
-	}
-	symbol_t   *sym = e2->e.symbol;//FIXME need to check
+	symtab_t   *strct = t1->t.symtab;
+	symbol_t   *sym = get_name (e2);
 	symbol_t   *field;
 
 	if (!strct) {
 		error (e1, "dereferencing pointer to incomplete type");
 		return 0;
 	}
+	if (!sym) {
+		error (e2, "field reference is not a name");
+		return 0;
+	}
 	field = symtab_lookup (strct, sym->name);
 	if (!field && !is_entity(t1)) {
 		const char *name = t1->name;
@@ -2295,7 +2302,7 @@ function_expr (expr_t *fexpr, expr_t *params)
 expr_t *
 branch_expr (int op, expr_t *test, expr_t *label)
 {
-	// need to translated op due to precedence rules dictating the layout
+	// need to translate op due to precedence rules dictating the layout
 	// of the token ids
 	static pr_branch_e branch_type [] = {
 		pr_branch_eq,

tools/qfcc/source/expr_algebra.c

@@ -59,6 +59,21 @@ get_group (type_t *type, algebra_t *algebra)
 	return BITOP_LOG2 (group_mask);
 }
 
+static pr_uint_t
+get_group_mask (type_t *type, algebra_t *algebra)
+{
+	auto layout = &algebra->layout;
+	if (!is_algebra (type)) {
+		int group = layout->group_map[layout->mask_map[0]][0];
+		return 1u << group;
+	} else {
+		if (type->type == ev_invalid) {
+			return (1 << algebra->layout.count) - 1;
+		}
+		return type->t.multivec->group_mask;
+	}
+}
+
 static bool __attribute__((const))
 is_neg (const expr_t *e)
 {
@@ -2268,9 +2283,41 @@ algebra_field_expr (expr_t *mvec, expr_t *field_name)
 		return new_offset_alias_expr (field->type, mvec, field->s.offset);
 	}
 	if (mvec->type == ex_multivec) {
-		internal_error (mvec, "not implemented");
+		auto field_sym = get_name (field_name);
+		if (!field_sym) {
+			return error (field_name, "multi-vector reference is not a name");
+		}
+		auto multivec = mvec_type->t.multivec;
+		auto mvec_struct = multivec->mvec_sym->type->t.symtab;
+		auto field = symtab_lookup (mvec_struct, field_sym->name);
+		if (!field) {
+			mvec_struct = algebra->mvec_sym->type->t.symtab;
+			field = symtab_lookup (mvec_struct, field_sym->name);
+			if (field) {
+				debug (field_name, "'%s' not in sub-type '%s' of '%s', "
+					   "returning zero of type '%s'", field_sym->name,
+					   mvec_type->name, algebra->mvec_sym->type->name,
+					   mvec_type->name);
+				return new_zero_expr (field->type);
+			}
+			return error (field_name, "'%s' has no member named '%s'",
+						  mvec_type->name, field_sym->name);
+		}
+		auto layout = &algebra->layout;
+		expr_t *a[layout->count] = {};
+		mvec_scatter (a, mvec_expr (mvec, algebra), algebra);
+		pr_uint_t group_mask = get_group_mask (field->type, algebra);
+		for (int i = 0; i < layout->count; i++) {
+			if (!(group_mask & (1u << i))) {
+				a[i] = 0;
+			}
+		}
+		return mvec_gather (a, algebra);
 	} else {
 		auto multivec = mvec_type->t.multivec;
+		if (!multivec->mvec_sym) {
+			return error (mvec, "'%s' not a multi-vector", mvec_type->name);
+		}
 		auto mvec_struct = multivec->mvec_sym->type;
 		auto field = get_struct_field (mvec_struct, mvec, field_name);
 		if (!field) {