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[cc1] Emit constant auto initalizers

In the case of automatic variables of type struct or array
is better to instace a hidden element and memcpy it instead
of copying field by field. In the case of unions the best
option depends of the field initialized.

--- a/cc1/init.c

+++ b/cc1/init.c

@@ -289,6 +289,42 @@

 	return mkcompound(&in);

 }

+static void

+autoinit(Symbol *sym, Node *np)

+{

+	Symbol *hidden;

+	Type *tp = sym->type;

+	size_t n; /* FIXME: It should be SIZET */

+

+	if (!(np->flags & NCONST))

+		abort(); /* TODO: Implement not constant initializers */

+

+repeat:

+	switch (tp->op) {

+	case UNION:

+		n = tp->n.elem-1;

+		tp = tp->p.fields[n]->type;

+		np = np->sym->u.init[n];

+		goto repeat;

+	case ARY:

+	case STRUCT:

+		hidden = newsym(NS_IDEN, NULL);

+		hidden->type = sym->type;

+		hidden->flags |= SLOCAL | SHASINIT;

+		emit(ODECL, hidden);

+		emit(OINIT, np);

+		emit(ODECL, sym);

+		emit(OEXPR,

+		     node(OASSIGN, tp, varnode(sym), varnode(hidden)));

+		break;

+	default:

+		emit(ODECL, sym);

+		np = node(OASSIGN, tp, varnode(sym), np);

+		emit(OEXPR, np);

+		break;

+	}

+}

+

 void

 initializer(Symbol *sym, Type *tp)

 {

@@ -318,8 +354,6 @@

 		errorp("'%s' has both '%s' and initializer",

 		       sym->name, (flags&SEXTERN) ? "extern" : "typedef");

 	} else {

-		emit(ODECL, sym);

-		np = node(OASSIGN, tp, varnode(sym), np);

-		emit(OEXPR, np);

+		autoinit(sym, np);

 	}

 }