On Sun, Mar 6, 2016 at 1:39 PM, Uros Bizjak <ubiz...@gmail.com> wrote:
> Hello!
>
> Attached patch prevents red-zone with -fPIC for leaf functions on
> i686. The idea is to mark when set_got is expanded as a call to a pc
> thunk, and use this flag to prevent red-zone in the current function.
>
> Please note that using red-zone with i686 violates all known ABIs, but
> some future ABI can trip on this limitation. The failure mode is quite
> tricky, so IMO it warrants a couple of lines as a safety net.
>
> The testcase is not suitable for the testsuite (it uses -mred-zone for
> i686 target), but I have checked that the testcase works OK when
> compiled with the patched compiler even when -mred-zone is used
> together with -fPIC.
>
> Jakub, HJ - what do you think?
>
> 2016-03-01 Uros Bizjak <ubiz...@gmail.com>
>
> PR target/70064
> * config/i386/i386.h (machine_function): Add
> pc_thunk_call_expanded flag.
> (ix86_pc_thunk_call_expanded): New define.
> * config/i386/i386.md (set_got, set_got_labelled): New expanders.
> (*set_got): Rename insn pattern from set_got.
> (*set_got_labelled): Rename inst pattern from set_got_labelled.
> * config/i386/i386.c (ix86_compute_frame_layout): Use
> ix86_pc_thunk_call_expanded to prevent red-zone.
>
> The patch is bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
>
I think red zone should only be allowed for x86-64 psABI.
--
H.J.
