Fix VM memory allocation optimizations by reducing what we allocate on the heap

internal/vm/frame.go

@@ -11,23 +11,39 @@ type Frame struct {
 	basePointer int
 }
 
-func NewFrame(cl *object.Closure, basePointer int) *Frame {
-	return &Frame{
+func NewFrame(cl *object.Closure, basePointer int) Frame {
+	return Frame{
 		cl:          cl,
 		basePointer: basePointer,
 	}
 }
 
+func (f *Frame) Closure() *object.Closure {
+	return f.cl
+}
+
+func (f *Frame) GetFree(idx uint8) object.Object {
+	return f.cl.Free[idx]
+}
+
+func (f *Frame) SetFree(idx uint8, obj object.Object) {
+	f.cl.Free[idx] = obj
+}
+
+func (f *Frame) SetIP(ip int) {
+	f.ip = ip
+}
+
+func (f Frame) PeekNextOp() code.Opcode {
+	return code.Opcode(f.cl.Fn.Instructions[f.ip])
+}
+
 func (f *Frame) ReadNextOp() code.Opcode {
 	op := code.Opcode(f.cl.Fn.Instructions[f.ip])
 	f.ip++
 	return op
 }
 
-func (f *Frame) PeekNextOp() code.Opcode {
-	return code.Opcode(f.cl.Fn.Instructions[f.ip])
-}
-
 func (f *Frame) ReadUint8() uint8 {
 	n := code.ReadUint8(f.cl.Fn.Instructions[f.ip:])
 	f.ip++
@@ -40,6 +56,6 @@ func (f *Frame) ReadUint16() uint16 {
 	return n
 }
 
-func (f *Frame) Instructions() code.Instructions {
+func (f Frame) Instructions() code.Instructions {
 	return f.cl.Fn.Instructions
 }