Itanium® Architecture for Programmers: Understanding 64-Bit Processors and EPIC Principles

E.6. Recursive Macros

Macros may redefine themselves. In recursive instances, the macro must contain a conditional directive that will terminate the recursion. When a macro is redefined (or when it redefines itself), the previous definition is supplanted by the current one.

Macros may invoke themselves recursively. Consider the factorial function, implemented as a recursive macro:

.macro   factorial INT
 .if \INT
   factorial (\INT-1)
   F = F * \INT
 .else
   F = 1
 .endc
.endm

We encourage you to trace the effect of invoking this macro with a small value of INT, such as 4. The final value of the symbol F could be shown by using it in a mov instruction:

.auto
factorial 4
mov     r14 = F
.default

In this case, the mov instruction will assemble with an immediate ...