https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117265
--- Comment #4 from H. Peter Anvin <hpa at zytor dot com> --- On October 22, 2024 1:19:05 PM PDT, "pinskia at gcc dot gnu.org" <gcc-bugzi...@gcc.gnu.org> wrote: >https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117265 > >Andrew Pinski <pinskia at gcc dot gnu.org> changed: > > What |Removed |Added >---------------------------------------------------------------------------- > Severity|normal |enhancement > Keywords| |inline-asm > I will dig up some examples, but it mostly involves cases where the assembler needs to apply conditionals (.if, or loops) *based on the operands given.* Here is an artificial example, mostly to come up with something short: .macro emulate_instruction reg .ifnc \reg, %rax xchg %rax, \reg .endif rax_only_instruction .ifnc \reg, %rax xchg %rax, \reg .endif .endm Using cpp + string concatenation is what we do in most cases, but it is unnecessary painful since it generally means writing two versions, one for C using quoted strings and one for assembly using ##. It has also completely prevented some highly useful things like a macro to "find a register not used by any of these operands, but don't disturb the compiler register allocation." That macro is some 200 lines long, and replicating it everywhere would be a nightmare.
