https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #21 from H. Peter Anvin ---
I think this could be a really useful performance improvement in general. The
Linux exception and syscall paths have a fair number of tail calls on the
primary path, and this would make it possible to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #20 from H.J. Lu ---
In Linux kernel 6.7.0 on x86-64, do_exit is changed from
do_exit:
endbr64
call
push %r15
push %r14
push %r13
push %r12
mov%rdi,%r12
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #19 from H. Peter Anvin ---
I'm away for the long weekend, but I'll try it out on Tuesday.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #18 from H.J. Lu ---
(In reply to H.J. Lu from comment #17)
> Please try users/hjl/pr113312/gcc-13 branch:
>
> https://gitlab.com/x86-gcc/gcc/-/tree/users/hjl/pr113312/gcc-
> 13?ref_type=heads
>
> It supports
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #17 from H.J. Lu ---
Please try users/hjl/pr113312/gcc-13 branch:
https://gitlab.com/x86-gcc/gcc/-/tree/users/hjl/pr113312/gcc-13?ref_type=heads
It supports no_callee_saved_registers attribute. It should also avoid saving
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #16 from H.J. Lu ---
I updated users/hjl/pr113312/master branch to handle function pointers.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #15 from H. Peter Anvin ---
That should be fine for this use case, obviously.
I should add the following: the reason the assembly stub isn't a problem for
FRED whereas it is a bit of a nuisance for IDT-style delivery is that with
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #14 from H.J. Lu ---
Here is a branch for __attribute__((no_callee_saved_registers)):
https://gitlab.com/x86-gcc/gcc/-/commits/users/hjl/pr113312/master
Calling a function with __attribute__((no_callee_saved_registers))
doesn't
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #13 from H. Peter Anvin ---
No, it will not. Most OSes flows will want to merge the kernel and user flows
at some point for some handlers, so it isn't clear that that makes sense.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
Florian Weimer changed:
What|Removed |Added
CC||fw at gcc dot gnu.org
--- Comment #12
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
Hongtao Liu changed:
What|Removed |Added
CC||liuhongt at gcc dot gnu.org
--- Comment
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #10 from H. Peter Anvin ---
Right, is there such an attribute (that's what I'm asking for in bug 103503)?
All I see in the gcc documentation is no_calle*R*_saved_registers, which,
again, is the exact opposite.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #9 from H.J. Lu ---
(In reply to H.J. Lu from comment #8)
> (In reply to H.J. Lu from comment #7)
> > (In reply to H. Peter Anvin from comment #6)
> > > Of course. That's not what we want in the Linux kernel specifically,
> > >
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #8 from H.J. Lu ---
(In reply to H.J. Lu from comment #7)
> (In reply to H. Peter Anvin from comment #6)
> > Of course. That's not what we want in the Linux kernel specifically, though.
> > It's really up to the OS.
>
>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #7 from H.J. Lu ---
(In reply to H. Peter Anvin from comment #6)
> Of course. That's not what we want in the Linux kernel specifically, though.
> It's really up to the OS.
no_callee_saved_registers attribute is sufficient. One can
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #6 from H. Peter Anvin ---
Of course. That's not what we want in the Linux kernel specifically, though.
It's really up to the OS.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #5 from H.J. Lu ---
(In reply to H. Peter Anvin from comment #3)
> Created attachment 57032 [details]
> FRED assembly entry stub (example, slightly modified from the Linux kernel)
Can you do
asm_fred_entry_\type:
endbr64
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #4 from H. Peter Anvin ---
(In reply to H.J. Lu from comment #2)
> (In reply to H. Peter Anvin from comment #1)
> > This is actually a specific use case of the feature requested in bug 103503.
>
> This covers #1. Should FRED
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #3 from H. Peter Anvin ---
Created attachment 57032
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57032=edit
FRED assembly entry stub (example, slightly modified from the Linux kernel)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
H.J. Lu changed:
What|Removed |Added
Last reconfirmed||2024-01-11
Ever confirmed|0
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113312
--- Comment #1 from H. Peter Anvin ---
This is actually a specific use case of the feature requested in bug 103503.
21 matches
Mail list logo
