-mgeneral-regs-only changes preprocessor macros

J.W. Jagersma jwjagersma@gmail.com
Tue Jun 25 18:42:00 GMT 2019


On 2019-06-25 19:59, Xi Ruoyao wrote:
> On 2019-06-25 15:36 +0200, J.W. Jagersma wrote:
>> Say I have a header which defines a type conditionally based on the
>> __SSE__ macro:
>>
>> #ifdef __SSE__
>>       struct X { ... };
>> #else
>>       struct X { ... };
>> #endif
>>
>> This header is included in multiple compilation units, some of which are
>> compiled with -mgeneral-regs-only. I don't want any fpu/simd code there.
>> Now this flag also undefines __SSE__, which I suppose makes sense, but
>> it breaks the ABI between translation units.
>> Is there some way to avoid generating fpu code without affecting
>> preprocessor macros?
> 
> How about just "pretend" to have __SSE__?
> 
> cat > test.c << EOF
> #ifndef __SSE__
> #error
> #endif
> int main(){}
> EOF
> 
> gcc test.c -mgeneral-regs-only -D__SSE__
> 

Ideally I'd have the macros defined by -march so I don't need to 
complicate the build process for different architectures. I suppose I 
could work this out in the makefile, but a different solution would be 
preferable.



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