[LLVMdev] "target-features" and "target-cpu" attributes

[Bill Wendling]

On Oct 10, 2013, at 4:22 AM, Dmitry Babokin <babokin at gmail.com> wrote:

> Bill,
> 
> Thanks for answering. To make sure that we are on the same page, let's agree on definitions :) Here, by fat binaries I mean the binary, where some functions are compiled for one flavor of x86, while others are compiled for another flavor of x86. I care about the usage model, which is important for LTO - a dispatch function (compiled for the least common denominator) + plus set of specialized functions for sse4, avx ,avx2 and etc., which are called by dispatch function depending on runtime cpu id check.
> 
Okay. The terminology was a bit overloaded. :-)

> lipo may help achieving this on Darwin, but it's not exactly what I need. I need a solution suitable for LTO. Actually lipo may work for me as a workaround, but I need cross platform solution.
> 
> The current solution doesn't really address this (on x86 at least), as sub-target is not recreated if feature string doesn't match the sub-target. Instead it tries to satisfy feature string requirements using existing sub-target and this leads to the fails, that were noticed by Ben. Please correct me if my understanding is wrong.
> 
> So do I understand you correctly, that your new solution supposed to solve this problem?
> 
That's correct. It still needs to be implemented (of course), but that's the eventual goal.

-bw