r254112 - in /trunk/gcc: ChangeLog config/aarch...

[wilco at gcc dot gnu dot org]

Author: wilco
Date: Thu Oct 26 16:40:25 2017
New Revision: 254112

URL: https://gcc.gnu.org/viewcvs?rev=254112&root=gcc&view=rev
Log:
Simplify frame layout for stack probing

This patch makes some changes to the frame layout in order to simplify
stack probing.  We want to use the save of LR as a probe in any non-leaf
function.  With shrinkwrapping we may only save LR before a call, so it
is useful to define a fixed location in the callee-saves. So force LR at
the bottom of the callee-saves even with -fomit-frame-pointer.

Also remove a rarely used frame layout that saves the callee-saves first
with -fomit-frame-pointer.  Doing so allows the store of LR to be used as
a valid stack probe in all frames.

    gcc/
	* config/aarch64/aarch64.c (aarch64_layout_frame):
        Ensure LR is always stored at the bottom of the callee-saves.
        Remove rarely used frame layout which saves callee-saves at top of
        frame, so the store of LR can be used as a valid probe in all cases.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/aarch64/aarch64.c