How can I write compile-time (pure) BigInt computations?

[renoX]

== Extrait de l'article de « Timon Gehr (timon.gehr at gmx.ch) »
> BigInt operates using hand-written assembly, if available for the
target architecture.
> inline asm cannot be used in CTFE.

A reasonable restriction, but I don't understand why this prevent
BigInt to be used in CTFE as BigInt also implement the functions
without the inline asm.
Why do the compiler set the D_InlineAsm_X86 target during the CTFE
pass?

Best regards,
renoX