linux-kernel - Re: [PATCH] drm: omapdrm: reduce clang stack usage

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Message-Id: <d24e13cd-f327-4077-9119-ea6fcd11f9f9@app.fastmail.com>
Date: Thu, 12 Jun 2025 17:19:56 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Tomi Valkeinen" <tomi.valkeinen@...asonboard.com>,
 "Arnd Bergmann" <arnd@...nel.org>
Cc: "Nick Desaulniers" <nick.desaulniers+lkml@...il.com>,
 "Bill Wendling" <morbo@...gle.com>, "Justin Stitt" <justinstitt@...gle.com>,
 linux <linux@...blig.org>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
 "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
 "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "Dave Airlie" <airlied@...il.com>,
 "Simona Vetter" <simona@...ll.ch>, "Nathan Chancellor" <nathan@...nel.org>
Subject: Re: [PATCH] drm: omapdrm: reduce clang stack usage

On Thu, Jun 12, 2025, at 16:37, Tomi Valkeinen wrote:
> On 12/06/2025 15:40, Arnd Bergmann wrote:

> static u16 DISPC_OVL_BASE(enum omap_plane_id plane)
> {
>     static const u16 bases[] = {0x0080, 0x00BC, 0x014C, 0x0300, 0x0500};
>     return bases[plane];
> }
>
> In any case, I'll apply this with a small comment.

Thanks!

I've also opened an issue against llvm at
https://github.com/llvm/llvm-project/issues/143908

Hopefully we can pinpoint something in llvm that can be fixed
to improve similar issues in other code.

It does seem fairly obscure, as even changing the code
slightly seems to completely avoid the problem, e.g. if the
one of the loops grows too big to be unrolled.

    Arnd