On 09/22/2015 09:41 PM, Jeff Law wrote:
Essentially it allows us to more easily support
per-microarchitecture-optimized versions of functions. You list just
have to list the microarchitectures and the compiler handles the rest.
Very simple, very easy. I'd think it'd be particularly helpful for
vectorization.
You could emulate this with compiling the same source multiple times
with different flags/defines and wire up on ifunc by hand. But Evgeny's
approach is vastly simpler.
As far as I can tell the ifunc is generated automatically (and the
functionality is documented as such), so the new target_clone doesn't
buy much. But one thing I didn't was that the existing support is only
available in C++, while Evgeny's patch works for C. That is probably an
argument that could be made for its inclusion.
Or at least, it's supposed to work. As I said, I get verify_ssa failures
on the included testcases, and for a simpler one I just tried I get the
clones of the function, but not the resolver that ought to be generated.
Bernd
