hopefully fix an off-by-1 vararg copy issue

ir.c

@@ -3151,14 +3151,14 @@ static bool gen_function_varargs_copy(ir_function *self)
     stmt.o3.s1 = 0;
     maxparams = numparams + self->max_varargs;
     for (i = numparams; i < maxparams; ++i) {
-        if (i <= 8) {
+        if (i < 8) {
             stmt.o1.u1 = OFS_PARM0 + 3*i;
             stmt.o2.u1 = ir_value_code_addr(self->locals[i]);
             code_push_statement(&stmt, self->context.line);
             continue;
         }
-        ext = i - 9;
-        if (ext >= vec_size(ir->extparams))
+        ext = i - 8;
+        while (ext >= vec_size(ir->extparams))
             ir_gen_extparam(ir);
 
         ep = ir->extparams[ext];

tests/varargs2.qc

@@ -0,0 +1,12 @@
+void past8(float a, float b, float c, float d, ...count)
+{
+    float i;
+    print("out:");
+    for (i = 0; i < count; ++i)
+        print(" ", ftos(...(i, float)), "");
+    print("\n");
+}
+
+void main() {
+    past8(1, 2, 3, 4, 10, 20, 30, 40, 50, 60, 70, 80);
+}

tests/varargs2.tmpl

@@ -0,0 +1,5 @@
+I: varargs2.qc
+D: non-builtin vararg support test 2
+T: -execute
+C: -std=fteqcc -fvariadic-args
+M: out: 10 20 30 40 50 60 70 80