[PATCH] D15340: Separate CSRs into a subset handled via explicit copies and a subset handled by prologue/epilogue

[Manman Ren via llvm-commits]

manmanren added a comment.

In http://reviews.llvm.org/D15340#307215, @qcolombet wrote:

> Hi Manman,
>
> Thanks for doing this!
>
> A quick comment, would it be possible to have a command line option to force the use of this special handling as a follow-up patch?


It depends on what the command line option will do :]

The implementation currently only works for CXX_FAST_TLS and we can probably generalize it to other calling conventions.
Also as pointed out by Hal in AArch64 patch (http://reviews.llvm.org/D15341), we may need to update that patch to handle unwinding by inserting cfi directives.

> It’s been a while I’d like to make some measurements to check how interesting this approach would be compared to our current handling of CSRs in reg alloc.


Is there any special handling of CSRs in reg alloc? I remember from a while back that we only add a penalty for first usage of a CSR.

Thank you for reviewing!
Manman

> Thanks again!

>  Q.



http://reviews.llvm.org/D15340