See [this topic](https://forum.lazarus.freepascal.org/index.php/topic,64240.msg488276). With Intel syntax, I can do the following: ```pascal {$asmmode intel} procedure SetMiddleTo5(p: pointer; n: SizeUint); assembler; nostackframe; asm shr n, 1 // becomes “shr rdx, 1” (Win64) or “shr rsi, 1” (System V) mov byte ptr [p + n], 5 // becomes “mov byte ptr [rcx + rdx], 5” (Win64) or “mov byte ptr [rdi + rsi], 5” (System V) end; ``` Which often allows writing cross-ABI code without a single `{$ifdef}` or with less `{$ifdef}`s. In particular, it would allow to get rid of runtime adapters between ABIs (`{$ifndef win64} mov %rdx, %r8; ... {$endif}`) in [this file](https://gitlab.com/freepascal.org/fpc/source/-/blob/36a2835f8c95290fbd3002700726d4bfb2ac006c/rtl/x86_64/x86_64.inc) without any, or much, clutter. However, AT&T syntax does not seem to support parameter names in memory references: ```pascal {$asmmode att} procedure SetMiddleTo5(p: pointer; n: SizeUint); assembler; nostackframe; asm shrq $1, n // becomes “shrq $1, %rdx” (Win64) or “shrq $1, %rsi” (System V) movb $5, (p,n) // Invalid reference syntax. end; ```