+/*
+ * Currently, only integers (REG_S64) can be pushed into the stack.
+ */
+#define estack_push(stack, top, ax, bx, ax_t, bx_t) \
+ do { \
+ assert((top) < FILTER_STACK_LEN - 1); \
+ (stack)->e[(top) - 1].u.v = (bx); \
+ (stack)->e[(top) - 1].type = (bx_t); \
+ (bx) = (ax); \
+ (bx_t) = (ax_t); \
+ ++(top); \
+ } while (0)
+
+#define estack_pop(stack, top, ax, bx, ax_t, bx_t) \
+ do { \
+ assert((top) > FILTER_STACK_EMPTY); \
+ (ax) = (bx); \
+ (ax_t) = (bx_t); \
+ (bx) = (stack)->e[(top) - 2].u.v; \
+ (bx_t) = (stack)->e[(top) - 2].type; \
+ (top)--; \
+ } while (0)