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[cc2] Addapt cc2 to new switch IR

In the new switch IR all the jump table is written interlaced
with the body statements, and this code moves all the switch
related statements in order to get them at the beginning and
in consecutive positions.

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

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

@@ -387,8 +387,8 @@

 		return NULL;

 	case OCASE:

 	case ODEFAULT:

-	case OTABLE:

-	case OSWITCH:

+	case OESWITCH:

+	case OBSWITCH:

 	default:

 		abort();

 	}

--- a/cc2/cc2.h

+++ b/cc2/cc2.h

@@ -99,8 +99,8 @@

 	OELOOP   = 'e',

 	OCASE    = 'v',

 	ODEFAULT = 'f',

-	OTABLE   = 't',

-	OSWITCH  = 's',

+	OBSWITCH = 's',

+	OESWITCH = 't',

 };

 enum nerrors {

@@ -116,6 +116,9 @@

 	ELNBLNE,       /* line without new line */

 	EFERROR,       /* error reading from file:%s*/

 	EBADID,        /* incorrect symbol id */

+	EWTACKO,       /* switch stack overflow */

+	EWTACKU,       /* switch stack underflow */

+	ENOSWTC,       /* Out of switch statement */

 	ENUMERR

 };

--- a/cc2/parser.c

+++ b/cc2/parser.c

@@ -30,10 +30,18 @@

 	unsigned op;

 };

+struct swtch {

+	int nr;

+	Node *last;

+};

+

+static struct swtch swtbl[NR_BLOCK], *swp = swtbl;

+

 typedef void parsefun(char *, union tokenop);

 static parsefun type, symbol, getname, unary, binary, ternary, call,

                 constant, composed, binit, einit,

-                jump, oreturn, loop, assign, casetbl;

+                jump, oreturn, loop, assign,

+                ocase, bswitch, eswitch;

 typedef void evalfun(void);

 static evalfun vardecl, beginfun, endfun, endpars, stmt,

@@ -123,22 +131,21 @@

 	['b']   = {     NULL,    loop, .u.op =        OBLOOP},

 	['e']   = {     NULL,    loop, .u.op =        OELOOP},

-	['v']   = {     NULL,    jump, .u.op =         OCASE},

-	['s']   = {     NULL,    jump, .u.op =       OSWITCH},

-

-	['f']   = {     NULL, casetbl, .u.op =      ODEFAULT},

-	['t']   = {     NULL, casetbl, .u.op =        OTABLE}

+	['v']   = {     NULL,   ocase, .u.op =         OCASE},

+	['f']   = {     NULL,   ocase, .u.op =      ODEFAULT},

+	['t']   = {     NULL, eswitch, .u.op =      OESWITCH},

+	['s']   = {     NULL, bswitch, .u.op =      OBSWITCH},

 };

 static int sclass, inpars, ininit, endf, lineno;

 static void *stack[STACKSIZ], **sp = stack;

-static void

+static Node *

 push(void *elem)

 {

 	if (sp == stack[STACKSIZ])

 		error(ESTACKO);

-	*sp++ = elem;

+	return *sp++ = elem;

 }

 static void *

@@ -327,6 +334,48 @@

 }

 static void

+waft(Node *np)

+{

+	Node *p;

+

+	if (swp == swtbl)

+		error(EWTACKU);

+	p = swp[-1].last;

+

+	np->next = p->next;

+	np->prev = p;

+	p->next = np;

+	swp[-1].last = np;

+}

+

+static void

+bswitch(char *token, union tokenop u)

+{

+	if (swp++ == &swtbl[NR_BLOCK+1])

+		error(EWTACKO);

+	jump(token, u);

+	swp->nr = 0;

+	swp->last = push(pop());

+}

+

+static void

+eswitch(char *token, union tokenop u)

+{

+	if (swp == swtbl)

+		error(EWTACKU);

+	jump(token, u);

+	waft(pop());

+	--swp;

+}

+

+static void

+ocase(char *token, union tokenop u)

+{

+	jump(token, u);

+	waft(pop());

+}

+

+static void

 jump(char *token, union tokenop u)

 {

 	Node *aux, *np = newnode(u.op);

@@ -333,7 +382,7 @@

 	eval(strtok(NULL, "\t\n"));

-	if (u.op != OJMP)

+	if (u.op == OBRANCH || u.op == OCASE)

 		np->left = pop();

 	aux = pop();

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

@@ -342,16 +391,6 @@

 }

 static void

-casetbl(char *token, union tokenop u)

-{

-	Node *np = newnode(u.op);

-

-	eval(strtok(NULL, "\t\n"));

-	np->left = pop();

-	push(np);

-}

-

-static void

 loop(char *token, union tokenop u)

 {

 	push(newnode(u.op));

@@ -564,6 +603,8 @@

 {

 	Node *np;

+	if (empty())

+		return;

 	np = pop();

 	if (ininit) {

 		data(np);