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[cc2-qbe] Improve load()

This function was a bit low level function, and it was generating
a lot of code in every call. This new version has an interface
that is a bit ugly, but the result code is far better.

--- a/cc2/arch/qbe/cgen.c

+++ b/cc2/arch/qbe/cgen.c

@@ -5,6 +5,12 @@

 #include "arch.h"

 #include "../../cc2.h"

+enum lflags {

+	FORCE = 1 << 0,

+	LOADL = 1 << 1,

+	LOADR = 1 << 2

+};

+

 enum sflags {

 	ISTMP  = 1,

 	ISCONS = 2

@@ -104,48 +110,58 @@

 	return np;

 }

+/*

+ * load() load the address passed in a child of np in a temporary

+ * if it is not already in a temporay. It can be forced to load

+ * using the FORCE flag

+ */

 static Node *

-load(Node *np)

+load(Node *np, int flags)

 {

-	Node *new;

 	int op;

-	Type *tp = &np->type;

+	Type *tp;

+	Node *child;

-	new = tmpnode(newnode());

-	new->left = np;

-	new->type = *tp;

+	child = (flags & LOADL) ? np->left : np->right;

+	tp = &child->type;

-	switch (tp->size) {

-	case 1:

-		op = ASLDB;

-		break;

-	case 2:

-		op = ASLDH;

-		break;

-	case 4:

-		op = (tp->flags & INTF) ? ASLDW : ASLDS;

-		break;

-	case 8:

-		op = (tp->flags & INTF) ? ASLDL : ASLDD;

-		break;

-	default:

-		abort();

+	if ((flags & FORCE) || !(child->flags & (ISTMP|ISCONS))) {

+		Node *new = tmpnode(newnode());

+		new->type = *tp;

+		new->left = child;

+

+		switch (tp->size) {

+		case 1:

+			op = ASLDB;

+			break;

+		case 2:

+			op = ASLDH;

+			break;

+		case 4:

+			op = (tp->flags & INTF) ? ASLDW : ASLDS;

+			break;

+		case 8:

+			op = (tp->flags & INTF) ? ASLDL : ASLDD;

+			break;

+		default:

+			abort();

+		}

+		code(op, new, child, NULL);

+		child = new;

 	}

-	code(op, new, np, NULL);

-	return new;

+	return (flags & LOADL) ? (np->left = child) : (np->right = child);

 }

 static Node *

-cast(Node *nd, Node *ns)

+cast(Node *nd)

 {

 	Type *ts, *td;

-	Node *tmp;

+	Node *tmp, *ns;

 	int op, disint, sisint;

 	extern Type uint32type, int32type;

-	if ((ns->flags & (ISTMP|ISCONS)) == 0)

-		ns = nd->left = load(ns);

+	ns = load(nd, LOADL);

 	td = &nd->type;

 	ts = &ns->type;

 	disint = (td->flags & INTF) != 0;

@@ -194,7 +210,7 @@

 			tmp = tmpnode(newnode());

 			tmp->type = (ts->flags&SIGNF) ? int32type : uint32type;

 			tmp->left = ns;

-			nd->left = ns = cast(tmp, ns);

+			nd->left = ns = cast(tmp);

 		case 4:

 			op = (td->size == 8) ? ASSWTOD : ASSWTOS;

 			break;

@@ -274,11 +290,7 @@

 			abort();

 		}

 		op = tbl[np->op] + off;

-		if ((l->flags & (ISTMP|ISCONS)) == 0)

-			l = np->left = load(l);

-		if ((r->flags & (ISTMP|ISCONS)) == 0)

-			r = np->right = load(r);

-		code(op, tmpnode(np), l, r);

+		code(op, tmpnode(np), load(np, LOADL), load(np, LOADR));

 		return np;

 	case ONOP:

 	case OBLOOP:

@@ -285,7 +297,7 @@

 	case OELOOP:

 		return NULL;

 	case OCAST:

-		return cast(np, l);

+		return cast(np);

 	case OADDR:

 		np->flags |= ISTMP;

 		np->op = OTMP;

@@ -292,7 +304,9 @@

 		np->u.sym = l->u.sym;

 		return np;

 	case OPTR:

-		np->left = load(load(l));

+		load(np, LOADL);

+		/* FIXME: The type of the loaded value is not np->type */

+		load(np, LOADL|FORCE);

 		return tmpnode(np);

 	case OCPL:

 	case OPAR:

@@ -328,9 +342,8 @@

 	case OOR:

 		abort();

 	case OBRANCH:

-		if (l && (l->flags & (ISTMP|ISCONS)) == 0)

-			l = np->left = load(l);

 		next = np->next;

+		l = load(np, LOADL);

 		if (next->label) {

 			sym = getsym(TMPSYM);

 			sym->kind = SLABEL;

@@ -351,9 +364,7 @@

 		deltree(ifno);

 		return NULL;

 	case ORET:

-		if (l && (l->flags & (ISTMP|ISCONS)) == 0)

-			l = np->left = load(l);

-		code(ASRET, l, NULL, NULL);

+		code(ASRET, load(np, LOADL), NULL, NULL);

 		return NULL;

 	case OCASE:

 	case ODEFAULT: