linux-kernel - [PATCH v3 0/5] bitops: optimize code and add tests

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Date: Sun, 17 Dec 2023 16:12:45 +0900
From: Vincent Mailhol <mailhol.vincent@...adoo.fr>
To: Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Yury Norov <yury.norov@...il.com>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>,
	Douglas Anderson <dianders@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	Petr Mladek <pmladek@...e.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Zhaoyang Huang <zhaoyang.huang@...soc.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Marco Elver <elver@...gle.com>,
	Brian Cain <bcain@...cinc.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Matthew Wilcox <willy@...radead.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	linux-hexagon@...r.kernel.org,
	linux-m68k@...ts.linux-m68k.org,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH v3 0/5] bitops: optimize code and add tests

This series make sure that all the bitops operations (namely __ffs(),
ffs(), ffz(), __fls(), fls(), fls64()) correctly fold constant
expressions given that their argument is also a constant expression.

The first two patches optimize m68k architecture, the third and fourth
optimize the hexagon architecture bitops function, the fifth and final
patch adds test to assert that the constant folding occurs and that
the result is accurate.

This is tested on arm, arm64, hexagon, m68k, x86 and x86_64. For other
architectures, I am putting my trust into the kernel test robot to
send a report if ever one of the other architectures still lacks
bitops optimizations.
---

** Changelog **

v2 -> v3:

  - Add patches 1/5 and 2/5 to optimize m68k architecture bitops.
    Thanks to the kernel test robot for reporting!

  - Add patches 3/5 and 4/5 to optimize hexagon architecture bitops.
    Thanks to the kernel test robot for reporting!

  - Patch 5/5: mark test_bitops_const_eval() as __always_inline, this
    done, pass n (the test number) as a parameter. Previously, only
    BITS(10) was tested. Add tests for BITS(0) and BITS(31).

  Link: https://lore.kernel.org/all/20231130102717.1297492-1-mailhol.vincent@wanadoo.fr/

v1 -> v2:

  - Drop the RFC patch. v1 was not ready to be applied on x86 because
    of pending changes in arch/x86/include/asm/bitops.h. This was
    finally fixed by Nick in commit 3dae5c43badf ("x86/asm/bitops: Use
    __builtin_clz{l|ll} to evaluate constant expressions").
    Thanks Nick!

  - Update the commit description.

  - Introduce the test_const_eval() macro to factorize code.

  - No functional change.

  Link: https://lore.kernel.org/all/20221111081316.30373-1-mailhol.vincent@wanadoo.fr/

Vincent Mailhol (5):
  m68k/bitops: force inlining of all bitops functions
  m68k/bitops: use __builtin_{clz,ctzl,ffs} to evaluate constant
    expressions
  hexagon/bitops: force inlining of all bitops functions
  hexagon/bitops: use __builtin_{clz,ctzl,ffs} to evaluate constant
    expressions
  lib: test_bitops: add compile-time optimization/evaluations assertions

 arch/hexagon/include/asm/bitops.h | 37 ++++++++----
 arch/m68k/include/asm/bitops.h    | 99 +++++++++++++++++--------------
 lib/Kconfig.debug                 |  4 ++
 lib/test_bitops.c                 | 32 ++++++++++
 4 files changed, 118 insertions(+), 54 deletions(-)

-- 
2.25.1