[LLVMdev] AVX support

[Eli Friedman]

On Wed, Nov 7, 2012 at 12:19 PM, Manny Ko <Manny.Ko at imgtec.com> wrote:
> We have been using LLVM 3.1 to support JITing of AVX.  From dumping the MC
> generating by the MCJIT I noticed it always emits ‘VZEROUPPER’ to clear the
> high 128 bit before calling another function.  In some cases I know the
> function called either only use AVX or does not use SSE. I will like to
> inform the backend it is safe not to emit that instruction.
>
>
>
> Have not been able to figure out how to do that.
>
>
>
> Any suggestion will be greatly appreciated.

I don't think there's any way at the moment.  The relevant function is
VZeroUpperInserter::processBasicBlock; we could possibly special case
certain calls (maybe based on the calling convention?).

-Eli