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[cc2-qbe] Add OBRANCH generation

OBRANCH is similar to OJMP, but it has a condition expression
and two labels instead of only one. A new function label()
is created to convert labels into nodes, which are needed
for jumps. Before this commit the code was making tricks
to link labels and nodes. This is not the best solution,
but it is the simpler.

--- a/cc2/arch/qbe/arch.h

+++ b/cc2/arch/qbe/arch.h

@@ -131,5 +131,6 @@

 	ASTRUNCD,

 	ASJMP,

+	ASBRANCH,

 	ASRET,

 };

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

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

@@ -216,7 +216,7 @@

 Node *

 cgen(Node *np)

 {

-	Node *l, *r;

+	Node *l, *r, *ifyes, *ifno, *next;

 	Symbol *sym;

 	Type *tp;

 	int op, off;

@@ -335,9 +335,27 @@

 	case OOR:

 		abort();

 	case OBRANCH:

-		abort();

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

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

+		next = np->next;

+		if (next->label) {

+			sym = getsym(TMPSYM);

+			sym->kind = SLABEL;

+			next->label = sym;

+		}

+		ifyes = label(np->u.sym);

+		ifno = label(next->label);

+		op = ASBRANCH;

+		np = np->left;

+		goto emit_jump;

 	case OJMP:

-		code(ASJMP, np, NULL, NULL);

+		ifyes = label(np->u.sym);

+		op = ASJMP;

+		np = ifno = NULL;

+	emit_jump:

+		code(op, np, ifyes, ifno);

+		deltree(ifyes);

+		deltree(ifno);

 		return NULL;

 	case ORET:

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

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

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

@@ -9,7 +9,8 @@

 #define ADDR_LEN (IDENTSIZ+64)

-static void binary(void), unary(void), store(void), jmp(void), ret(void);

+static void binary(void), unary(void), store(void), jmp(void), ret(void),

+            branch(void);

 static struct opdata {

 	void (*fun)(void);

@@ -122,6 +123,7 @@

 	[ASEXTS] = {.fun = unary, .txt = "exts", .letter = 'd'},

 	[ASSLTOS]= {.fun = unary, .txt = "truncd", .letter = 's'},

+	[ASBRANCH] = {.fun = branch},

 	[ASJMP]  = {.fun = jmp},

 	[ASRET]  = {.fun = ret},

 };

@@ -403,7 +405,18 @@

 static void

 jmp(void)

 {

-	printf("\t\tjmp\t%s\n", addr2txt(&pc->to));

+	printf("\t\tjmp\t%s\n", addr2txt(&pc->from1));

+}

+

+static void

+branch(void)

+{

+	char to[ADDR_LEN], from1[ADDR_LEN], from2[ADDR_LEN];

+

+	strcpy(to, addr2txt(&pc->to));

+	strcpy(from1, addr2txt(&pc->from1));

+	strcpy(from2, addr2txt(&pc->from2));

+	printf("\t\tjnz\t%s,%s,%s\n", to, from1, from2);

 }

 void

--- a/cc2/cc2.h

+++ b/cc2/cc2.h

@@ -202,6 +202,7 @@

 extern void code(int op, Node *to, Node *from1, Node *from2);

 extern void defvar(Symbol *), defpar(Symbol *), defglobal(Symbol *);

 extern void setlabel(Symbol *sym);

+extern Node *label(Symbol *sym);

 /* node.c */

 #define SETCUR  1

--- a/cc2/code.c

+++ b/cc2/code.c

@@ -38,7 +38,6 @@

 		addr->kind = OCONST;

 		addr->u.i = np->u.i;

 		break;

-	case OJMP:

 	case OLABEL:

 		addr->kind = SLABEL;

 		goto symbol;

@@ -50,9 +49,19 @@

 	symbol:

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

 		break;

-	default:

-		abort();

 	}

+}

+

+Node *

+label(Symbol *sym)

+{

+	Node *np;

+

+	np = newnode();

+	np->op = OLABEL;

+	np->u.sym = sym;

+

+	return np;

 }

 void