target attributes, pragmas and preprocessor macros

Kyrill Tkachov kyrylo.tkachov@arm.com
Mon May 18 08:25:00 GMT 2015


Hi Christian,

On 18/05/15 07:26, Christian Bruel wrote:
> Hi Kyrill,
>
> On 05/13/2015 05:43 PM, Kyrill Tkachov wrote:
>> Hi all,
>>
>> Are target attributes supposed to redefine the preprocessor macros available?
>> For example, on aarch64 if the file is compiled with floating point support
>> the __ARM_FEATURE_FMA predefine is available. If the user adds to a function
>> a target attribute disabling floating point, then is __ARM_FEATURE_FMA supposed
>> to be undefined in the body of that function?
>>
>> Looking at some backends, it seems that only #pragmas are supposed to have that effect,
>> but I just wanted to confirm.
>>
> yes they do, But careful, even the "inherited" macros should be redefined...

Thanks.
Implementation question then.
Is TARGET_PRAGMA_PARSE actually called during preprocessing time?
I built an x86_64 toolchain, compiled a file with target pragmas in it,
put a breakpoint on the hook entry and it only triggered later on during parsing.
Same for an aarch64 implementation of target pragmas that I'm working on.
Am I just doing something wrong? Or is there some other place where I should
be looking?

Thanks,
Kyrill

>
> for instance for arm/thumb we can have something like:
>
> #pragma GCC target ("thumb")
>
> #ifndef __thumb__
> #error "__thumb__ is not defined"
> #endif
>
> #ifdef __thumb2__
> #ifndef __ARM_32BIT_STATE
> #error  "__ARM_32BIT_STATE is not defined"
> #endif
> #else /* thumb1 */
> #ifdef __ARM_32BIT_STATE
> #error  "__ARM_32BIT_STATE is defined"
> #endif
> #endif /* thumb1 */
>
> ...
>
>> Thanks,
>> Kyrill
>>
> Cheers
>
> Christian
>



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