From: "Toke Høiland-Jørgensen" <toke@toke.dk>
To: Rosen Penev <rosenp@gmail.com>, linux-wireless@vger.kernel.org
Cc: Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
open list <linux-kernel@vger.kernel.org>,
"open list:CLANG/LLVM BUILD SUPPORT:Keyword:b(?i:clang|llvm)b"
<llvm@lists.linux.dev>
Subject: Re: [PATCH ath-next] ath9k: eeprom: alias vpdTableI onto vpdTableL to shrink stack frame
Date: Thu, 18 Jun 2026 11:51:38 +0200 [thread overview]
Message-ID: <87pl1ofa6t.fsf@toke.dk> (raw)
In-Reply-To: <20260617234105.284358-1-rosenp@gmail.com>
Rosen Penev <rosenp@gmail.com> writes:
> vpdTableL, vpdTableR, and vpdTableI are never live simultaneously.
> vpdTableL and vpdTableR are consumed during the frequency-interpolation
> step that writes vpdTableI; after the if/else they are never read
> again. Reuse vpdTableL for the interpolated result (what was
> vpdTableI), reducing the stack frame by one 256-byte array.
>
> The read-via-write in the else branch is safe: ath9k_hw_interpolate()
> receives vpdTableL[i][j] by value as a function argument before the
> return value is written back to vpdTableL[i][j].
>
> Stack frame size change (x86_64, clang):
> before: 0x440 (1088 B)
> after: 0x330 (816 B)
Huh? These are static variables, how is this affecting stack usage?
I assume this is against your previous (broken) patch?
Anyway, adding this kind of aliasing to fix a problem that you
introduced by changing working code with no real benefit is not an
improvement. I'm OK with fixing actual bugs, but this is just mindless
churn...
-Toke
prev parent reply other threads:[~2026-06-18 9:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-17 23:41 [PATCH ath-next] ath9k: eeprom: alias vpdTableI onto vpdTableL to shrink stack frame Rosen Penev
2026-06-18 9:51 ` Toke Høiland-Jørgensen [this message]
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