5g: fix build on Plan 9

5g/cgen.c:
. USED(n4) as it is only mentioned in unreachable code later;
. dropped unused assignments;
. commented out unreachable code;
5g/cgen64.c:
5g/ggen.c:
. dropped unused assignments of function return value;
5g/gg.h:
. added varargck pragmas;
5g/peep.c:
. USED(p1) used only in unreacheable code;
. commented out unreachable code;
5g/reg.c:
. dropped unused assignment;

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4953048

src/cmd/5g/cgen.c

@@ -852,6 +852,7 @@ bgen(Node *n, int true, Prog *to)
 	Node n1, n2, n3, n4, tmp;
 	Prog *p1, *p2;
 
+	USED(n4);			// in unreachable code below
 	if(debug['g']) {
 		dump("\nbgen", n);
 	}
@@ -862,9 +863,6 @@ bgen(Node *n, int true, Prog *to)
 	if(n->ninit != nil)
 		genlist(n->ninit);
 
-	nl = n->left;
-	nr = n->right;
-
 	if(n->type == T) {
 		convlit(&n, types[TBOOL]);
 		if(n->type == T)
@@ -877,7 +875,6 @@ bgen(Node *n, int true, Prog *to)
 		patch(gins(AEND, N, N), to);
 		goto ret;
 	}
-	nl = N;
 	nr = N;
 
 	switch(n->op) {
@@ -986,6 +983,7 @@ bgen(Node *n, int true, Prog *to)
 			regfree(&n1);
 			break;
 
+#ifdef	NOTDEF
 			a = optoas(a, types[tptr]);
 			regalloc(&n1, types[tptr], N);
 			regalloc(&n3, types[tptr], N);
@@ -1003,6 +1001,7 @@ bgen(Node *n, int true, Prog *to)
 			regfree(&n3);
 			regfree(&n1);
 			break;
+#endif
 		}
 
 		if(isinter(nl->type)) {
@@ -1021,6 +1020,7 @@ bgen(Node *n, int true, Prog *to)
 			regfree(&n1);
 			break;
 
+#ifdef	NOTDEF
 			a = optoas(a, types[tptr]);
 			regalloc(&n1, types[tptr], N);
 			regalloc(&n3, types[tptr], N);
@@ -1038,6 +1038,7 @@ bgen(Node *n, int true, Prog *to)
 			regfree(&n3);
 			regfree(&n4);
 			break;
+#endif
 		}
 
 		if(iscomplex[nl->type->etype]) {
@@ -1214,7 +1215,6 @@ sgen(Node *n, Node *res, int32 w)
 	// smaller operations for less aligned types.
 	// for example moving [4]byte must use 4 MOVB not 1 MOVW.
 	align = n->type->align;
-	op = 0;
 	switch(align) {
 	default:
 		fatal("sgen: invalid alignment %d for %T", align, n->type);
@@ -1315,7 +1315,6 @@ sgen(Node *n, Node *res, int32 w)
 			p->from.type = D_OREG;
 			p->from.offset = dir;
 			p->scond |= C_PBIT;
-			ploop = p;
 	
 			p = gins(op, &tmp, &dst);
 			p->to.type = D_OREG;

src/cmd/5g/cgen64.c

@@ -242,7 +242,7 @@ cgen64(Node *n, Node *res)
 			// shift is >= 1<<32
 			split64(r, &cl, &ch);
 			gmove(&ch, &s);
-			p1 = gins(ATST, &s, N);
+			gins(ATST, &s, N);
 			p6 = gbranch(ABNE, T);
 			gmove(&cl, &s);
 			splitclean();
@@ -250,7 +250,7 @@ cgen64(Node *n, Node *res)
 			gmove(r, &s);
 			p6 = P;
 		}
-		p1 = gins(ATST, &s, N);
+		gins(ATST, &s, N);
 
 		// shift == 0
 		p1 = gins(AMOVW, &bl, &al);
@@ -413,7 +413,7 @@ olsh_break:
 			gmove(r, &s);
 			p6 = P;
 		}
-		p1 = gins(ATST, &s, N);
+		gins(ATST, &s, N);
 
 		// shift == 0
 		p1 = gins(AMOVW, &bl, &al);
@@ -455,9 +455,9 @@ olsh_break:
 		p1 = gins(AMOVW, &bh, &al);
 		p1->scond = C_SCOND_EQ;
 		if(bh.type->etype == TINT32)
-			p1 = gshift(AMOVW, &bh, SHIFT_AR, 31, &ah);
+			gshift(AMOVW, &bh, SHIFT_AR, 31, &ah);
 		else
-			p1 = gins(AEOR, &ah, &ah);
+			gins(AEOR, &ah, &ah);
 		p4 = gbranch(ABEQ, T);
 
 		// check if shift is < 64

src/cmd/5g/gg.h

@@ -163,3 +163,6 @@ int	Yconv(Fmt*);
 void	listinit(void);
 
 void	zaddr(Biobuf*, Addr*, int);
+
+#pragma	varargck	type	"D"	Addr*
+#pragma	varargck	type	"M"	Addr*

src/cmd/5g/ggen.c

@@ -546,7 +546,7 @@ cgen_shift(int op, Node *nl, Node *nr, Node *res)
 	}
 
 	// test for shift being 0
-	p1 = gins(ATST, &n1, N);
+	gins(ATST, &n1, N);
 	p3 = gbranch(ABEQ, T);
 
 	// test and fix up large shifts

src/cmd/5g/peep.c

@@ -47,6 +47,9 @@ peep(void)
 	Reg *r, *r1, *r2;
 	Prog *p, *p1;
 	int t;
+
+	p1 = nil;
+	USED(p1);		// ... in unreachable code...
 /*
  * complete R structure
  */
@@ -117,12 +120,14 @@ loop1:
 			}
 			break;
 
+#ifdef	NOTDEF
 			if(p->scond == C_SCOND_NONE)
 			if(regtyp(&p->to))
 			if(isdconst(&p->from)) {
 				constprop(&p->from, &p->to, r->s1);
 			}
 			break;
+#endif
 		}
 	}
 	if(t)
@@ -130,6 +135,7 @@ loop1:
 
 return;
 
+#ifdef	NOTDEF
 	for(r=firstr; r!=R; r=r->link) {
 		p = r->prog;
 		switch(p->as) {
@@ -257,6 +263,7 @@ return;
 //	}
 
 	predicate();
+#endif
 }
 
 Reg*
@@ -1161,7 +1168,6 @@ copyu(Prog *p, Adr *v, Adr *s)
 				return 3;
 		return 0;
 	}
-	return 0;
 }
 
 /*

src/cmd/5g/reg.c

@@ -844,7 +844,6 @@ mkvar(Reg *r, Adr *a)
 
 	// mark registers used
 	t = a->type;
-	n = D_NONE;
 
 	flag = 0;
 	switch(t) {