[PATCH][AArch64 - v4] Simplify eh_return implementation

[James Greenhalgh]

On Mon, Jan 16, 2017 at 03:00:48PM +0000, Wilco Dijkstra wrote:
> Here is the updated version:
> 
> This patch simplifies the handling of the EH return value.  We force the use of the
> frame pointer so the return location is always at FP + 8.  This means we can emit
> a simple volatile access in EH_RETURN_HANDLER_RTX without needing md
> patterns, splitters and frame offset calculations.  The new implementation also
> fixes various bugs in aarch64_final_eh_return_addr, which does not work with
> -fomit-frame-pointer, alloca or outgoing arguments.
> 
> Bootstrap OK, GCC Regression OK, OK for trunk? Would it be useful to backport
> this to GCC6.x?

This is OK for trunk. I think it would be useful on GCC 6, but give it a few
days on trunk to wait for fallout before backporting.

Thanks,
James

> 
> ChangeLog:
> 
> 2017-01-16  Wilco Dijkstra  <wdijkstr@arm.com>
> 
>         PR77455
> gcc/
>         * config/aarch64/aarch64.md (eh_return): Remove pattern and splitter.
>         * config/aarch64/aarch64.h (AARCH64_EH_STACKADJ_REGNUM): Remove.
>         (EH_RETURN_HANDLER_RTX): New define.
>         * config/aarch64/aarch64.c (aarch64_frame_pointer_required):
>         Force frame pointer in EH return functions.
>         (aarch64_expand_epilogue): Add barrier for eh_return.
>         (aarch64_final_eh_return_addr): Remove.
>         (aarch64_eh_return_handler_rtx): New function.
>         * config/aarch64/aarch64-protos.h (aarch64_final_eh_return_addr):
>         Remove.
>         (aarch64_eh_return_handler_rtx): New prototype.
> 
> testsuite/
>         * gcc.target/aarch64/eh_return.c: New test.