[llvm-dev] clang/llvm support for %= in inline assembly

Sean Silva via llvm-dev llvm-dev at lists.llvm.org
Sun Feb 5 01:50:23 PST 2017

I think we may already support it. At least that's the implication from the
post-commit thread of r288093, in particular this reply from Reid

Do you have a test case?

-- Sean Silva

On Sat, Feb 4, 2017 at 10:30 PM, Andrew Kelley via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> from https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
> Under certain circumstances, GCC may duplicate (or remove duplicates of)
>> your assembly code when optimizing. This can lead to unexpected duplicate
>> symbol errors during compilation if your asm code defines symbols or
>> labels. Using ‘%=’ (see AssemblerTemplate) may help resolve this problem.
> ‘%=’
>> Outputs a number that is unique to each instance of the asm statement in
>> the entire compilation. This option is useful when creating local labels
>> and referring to them multiple times in a single template that generates
>> multiple assembler instructions.
> I tried to implement %= in my front-end but I ran into this problem with
> the optimizer. So in order to have this feature, LLVM would need to support
> it in the IR language.
> As far as I can tell, Clang does not support this feature. Is it a
> reasonable feature request?
> Regards,
> Andrew
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