nv50: cannot kill branch if immediate is used

The immediate's bits eat the condition bits.

src/gallium/drivers/nv50/nv50_program.c

@@ -453,6 +453,7 @@ static INLINE void
 set_pred(struct nv50_pc *pc, unsigned pred, unsigned idx,
 	 struct nv50_program_exec *e)
 {
+	assert(!is_immd(e));
 	set_long(pc, e);
 	e->inst[1] &= ~((0x1f << 7) | (0x3 << 12));
 	e->inst[1] |= (pred << 7) | (idx << 12);
@@ -2118,6 +2119,8 @@ nv50_kill_branch(struct nv50_pc *pc)
 
 	if (pc->if_insn[lvl]->next != pc->p->exec_tail)
 		return FALSE;
+	if (is_immd(pc->p->exec_tail))
+		return FALSE;
 
 	/* if ccode == 'true', the BRA is from an ELSE and the predicate
 	 * reg may no longer be valid, since we currently always use $p0