6g: fix build on Plan 9

src/cmd/6g/cgen.c
src/cmd/6g/gobj.c
src/cmd/6g/reg.c
. dropped unused assignments;
src/cmd/6g/gg.h
. added varargck pragmas;
src/cmd/6g/list.c
. adjusted print format for ulong casts;
src/cmd/6g/peep.c
. dropped redundant increment;

R=golang-dev
CC=golang-dev, rsc
https://golang.org/cl/4953049

src/cmd/6g/cgen.c

@@ -729,9 +729,6 @@ 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)
@@ -744,7 +741,6 @@ bgen(Node *n, int true, Prog *to)
 		patch(gins(AEND, N, N), to);
 		goto ret;
 	}
-	nl = N;
 	nr = N;
 
 	switch(n->op) {

src/cmd/6g/gg.h

@@ -153,3 +153,5 @@ void	listinit(void);
 
 void	zaddr(Biobuf*, Addr*, int, int);
 
+#pragma	varargck	type	"D"	Addr*
+#pragma	varargck	type	"lD"	Addr*

src/cmd/6g/gobj.c

@@ -623,7 +623,6 @@ out:
 		// but 6l has a bug, and it can't handle
 		// JMP instructions too close to the top of
 		// a new function.
-		p = pc;
 		gins(ANOP, N, N);
 	}
 

src/cmd/6g/list.c

@@ -133,7 +133,7 @@ Dconv(Fmt *fp)
 		if(fp->flags & FmtLong) {
 			d1 = a->offset & 0xffffffffLL;
 			d2 = (a->offset>>32) & 0xffffffffLL;
-			snprint(str, sizeof(str), "$%ud-%ud", (ulong)d1, (ulong)d2);
+			snprint(str, sizeof(str), "$%lud-%lud", (ulong)d1, (ulong)d2);
 			break;
 		}
 		snprint(str, sizeof(str), "$%lld", a->offset);

src/cmd/6g/peep.c

@@ -993,7 +993,6 @@ loop:
 		if(p->from.dval == p0->from.dval)
 		if(p->from.index == p0->from.index) {
 			excise(r);
-			t++;
 			goto loop;
 		}
 		break;

src/cmd/6g/reg.c

@@ -179,7 +179,6 @@ regopt(Prog *firstp)
 	r1 = R;
 	firstr = R;
 	lastr = R;
-	nvar = 0;
 
 	/*
 	 * control flow is more complicated in generated go code