Hi Arnd,
On Tue, Jan 07, 2020 at 11:09:13PM +0100, Arnd Bergmann wrote:
On Tue, Jan 7, 2020 at 11:00 PM Laurent Pinchart wrote:
On Tue, Jan 07, 2020 at 10:27:33PM +0100, Arnd Bergmann wrote:
With gcc -O3, the compiler can inline very aggressively, leading to rather large stack usage:
drivers/gpu/drm/panel/panel-tpo-td028ttec1.c: In function 'td028ttec1_prepare': drivers/gpu/drm/panel/panel-tpo-td028ttec1.c:233:1: error: the frame size of 2768 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] }
Marking jbt_reg_write_1() as noinline avoids the case where multiple instances of this function get inlined into the same stack frame and each one adds a copy of 'tx_buf'.
Fixes: mmtom ("init/Kconfig: enable -O3 for all arches") Signed-off-by: Arnd Bergmann arnd@arndb.de
Isn't this something that should be fixed at the compiler level ?
I suspect but have not verified that structleak gcc plugin is partly at fault here as well, it has caused similar problems elsewhere.
If you like I can try to dig deeper before that patch gets merged, and explain more in the changelog or open a gcc bug if necessary.
I think we'll need to merge this in the meantime, but if gcc is able to detect too large frame sizes, I think it should have the ability to take a frame size limit into account when optimizing. I haven't checked if this is already possible and just not honoured here (possibly due to a bug) or if the feature is entirely missing. In any case we'll likely have to live with this compiler issue for quite some time.