[Bug target/85434] Address of stack protector guard spilled to stack on ARM

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85434

--- Comment #11 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
I've started to work on a new patch according to review feedbacks. I've reached
the stage where I can compile without -fPIC with the stack protect test being
an UNSPEC split after register allocation as suggested.

Next steps are:

1) do the same for the stack protect set (ie setting the canari)
2) add support for PIC access to the guard
3) include the conditional branch in the combined stack protect test to ensure
the register holding the result of the comparison is not spilled before it's
used for the conditional branch
4) clear all registers involved before branching
5) cleanup the patch