[Patch ARM] Fix PR target/56846

[Thomas Preud'homme]

> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> owner@gcc.gnu.org] On Behalf Of Tony Wang
> 

> 
> Hi all,
> 
> The bug is reported at
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56846, and it’s about the
> problem that
> when exception handler is involved in the function, then
> _Unwind_Backtrace function will run into deadloop on
> arm target.

The patch (in r215101) can be backported without any change on 4.8 and
4.9 branches. I checked in QEMU with and without the patch on both
branches and it indeed solves the problem.

Testsuite run without regression when compiled with arm-none-eabi
cross compiler and executed on QEMU emulating Cortex-M3.

I also bootstrapped gcc on x86_64-linux-gnu and run the testsuite without
regressions.

Is it ok for backport?

Best regards,

Thomas