GCC target_clone support (functionality question)

[Jeff Law]

On 05/06/2017 12:44 AM, Richard Sandiford wrote:
> Michael Meissner <meissner@linux.vnet.ibm.com> writes:
>> This message is separated from the question about moving code, as it is a
>> questions about the functionality of target_clone support.
>>
>> Right now it looks like target_clone only generates the ifunc handler if there
>> is a call to the function in the object file.  It does not generate the ifunc
>> handler if there is no call.
>>
>> For the default function, it generates the normal name.  This means that any
>> function that calls the function from a different object module will only get
>> the standard function.  From a library and user perspective, I think this is
>> wrong.  Instead the default function should be generated with a different name,
>> and the ifunc function should list the standard name.  Then you don't have to
>> change all of the other calls in the object file, the normal ifunc handling
>> will handle it.  It also means you can more easily put this function in a
>> library and automatically call the appropriate version.
> 
> Yeah, that sounds much more useful.  One thing on my wish list is to
> support target_clone for Advanced SIMD vs. SVE on AArch64 (although
> it's unlikely that'll happen in the GCC 8 timeframe).  I'd naively
> assumed it would already work in the way you suggested.
Likewise.
jeff