This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: Reload patch for PA call rewrite.
- From: "John David Anglin" <dave at hiauly1 dot hia dot nrc dot ca>
- To: law at redhat dot com
- Cc: rth at redhat dot com, gcc-patches at gcc dot gnu dot org
- Date: Thu, 24 Oct 2002 14:48:08 -0400 (EDT)
- Subject: Re: Reload patch for PA call rewrite.
> Eliminating a generic tail call may be a lose, particularly on processors
> which use a branch target stack as the call/return sites no longer match
> perfectly -- thus causing a branch mis-predict penalty when the callee
> returns. This was something I've always wanted to measure for modern
> PAs and ia32 implementations, but never got around to doing so.
As far as I can tell, we currently don't implement the branch target
stack feature. I can see that with my proposed PA2.0 additions to
various call sequences that this wouldn't be too hard to add.
Jeff, do you know which PA processors implement the branch target feature?
My concern about sibcalls was more basic. We can't share frames
between the sibcall callee and caller. So, the overhead for a sibcall
and regular call are essentially the same.
Dave
--
J. David Anglin dave.anglin@nrc.ca
National Research Council of Canada (613) 990-0752 (FAX: 952-6605)