compilers were inconsistent about

whether no register argument was
REGARG == 0 or REGARG < 0.
use REGARG < 0 because arm needs 0 for R0.

R=ken
OCL=31562
CL=31566

src/cmd/6c/cgen.c

@@ -923,6 +923,8 @@ cgen(Node *n, Node *nn)
 
 			return;
 		}
+		o = 0;
+		if(REGARG >= 0)
 			o = reg[REGARG];
 		gargs(r, &nod, &nod1);
 		if(l->addable < INDEXED) {
@@ -932,7 +934,7 @@ cgen(Node *n, Node *nn)
 			regfree(&nod);
 		} else
 			gopcode(OFUNC, n->type, Z, l);
-		if(REGARG)
+		if(REGARG >= 0)
 			if(o != reg[REGARG])
 				reg[REGARG]--;
 		if(nn != Z) {

src/cmd/6c/peep.c

@@ -799,7 +799,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 	case ACALL:	/* funny */
 		if(REGEXT && v->type <= REGEXT && v->type > exregoffset)
 			return 2;
-		if(REGARG && v->type == REGARG)
+		if(REGARG >= 0 && v->type == REGARG)
 			return 2;
 
 		if(s != A) {
@@ -812,7 +812,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 		return 3;
 
 	case ATEXT:	/* funny */
-		if(REGARG && v->type == REGARG)
+		if(REGARG >= 0 && v->type == REGARG)
 			return 3;
 		return 0;
 	}

src/cmd/6c/txt.c

@@ -247,7 +247,7 @@ garg1(Node *n, Node *tn1, Node *tn2, int f, Node **fnxp)
 			sugen(n, tn2, n->type->width);
 		return;
 	}
-	if(REGARG && curarg == 0 && typechlpv[n->type->etype]) {
+	if(REGARG >= 0 && curarg == 0 && typechlpv[n->type->etype]) {
 		regaalloc1(tn1, n);
 		if(n->complex >= FNX) {
 			cgen(*fnxp, tn1);
@@ -437,8 +437,8 @@ regsalloc(Node *n, Node *nn)
 void
 regaalloc1(Node *n, Node *nn)
 {
-	if(REGARG == 0)
-		diag(n, "regaalloc1 and REGARG==0");
+	if(REGARG < 0)
+		diag(n, "regaalloc1 and REGARG<0");
 	nodreg(n, nn, REGARG);
 	reg[REGARG]++;
 	curarg = align(curarg, nn->type, Aarg1);

src/cmd/6l/6.out.h

@@ -832,7 +832,7 @@ enum
 	T_SCONST	= 1<<5,
 	T_64		= 1<<6,
 
-	REGARG		= 0,
+	REGARG		= -1,
 	REGRET		= D_AX,
 	FREGRET		= D_X0,
 	REGSP		= D_SP,

src/cmd/8c/cgen.c

@@ -925,7 +925,7 @@ cgen(Node *n, Node *nn)
 			regfree(&nod);
 		} else
 			gopcode(OFUNC, n->type, Z, l);
-		if(REGARG && reg[REGARG])
+		if(REGARG >= 0 && reg[REGARG])
 			reg[REGARG]--;
 		if(nn != Z) {
 			regret(&nod, n);

src/cmd/8c/peep.c

@@ -713,7 +713,7 @@ copyu(Prog *p, Adr *v, Adr *s)
 		return 3;
 
 	case ACALL:	/* funny */
-		if(REGARG && v->type == REGARG)
+		if(REGARG >= 0 && v->type == REGARG)
 			return 2;
 
 		if(s != A) {

src/cmd/8c/txt.c

@@ -233,7 +233,7 @@ garg1(Node *n, Node *tn1, Node *tn2, int f, Node **fnxp)
 			sugen(n, tn2, n->type->width);
 		return;
 	}
-	if(REGARG && curarg == 0 && typeilp[n->type->etype]) {
+	if(REGARG >= 0 && curarg == 0 && typeilp[n->type->etype]) {
 		regaalloc1(tn1, n);
 		if(n->complex >= FNX) {
 			cgen(*fnxp, tn1);

src/cmd/8l/8.out.h

@@ -460,7 +460,7 @@ enum
 	T_SCONST	= 1<<5,
 	T_OFFSET2	= 1<<6,
 
-	REGARG		= 0,
+	REGARG		= -1,
 	REGRET		= D_AX,
 	FREGRET		= D_F0,
 	REGSP		= D_SP,

src/cmd/cc/pgen.c

@@ -83,7 +83,7 @@ codgen(Node *n, Node *nn)
 	/*
 	 * isolate first argument
 	 */
-	if(REGARG) {
+	if(REGARG >= 0) {
 		if(typesuv[thisfn->link->etype]) {
 			nod1 = *nodret->left;
 			nodreg(&nod, &nod1, REGARG);