linux-kernel - [PATCH 0/3] s390: Fix and optimize _

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Message-ID: <20250910151216.646600-1-hca@linux.ibm.com>
Date: Wed, 10 Sep 2025 17:12:13 +0200
From: Heiko Carstens <hca@...ux.ibm.com>
To: Nathan Chancellor <nathan@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Juergen Christ <jchrist@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Sven Schnelle <svens@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>
Subject: [PATCH 0/3] s390: Fix and optimize __flogr() inline assembly

A recent optimization of the s390 specific ffs() and ffs64()
implementations leads to a new compiler warning. Instead of reverting the
optimization address this with the rather new assume attribute, which
generates even better code, if supported by compilers.

Since the assume attribute may be useful for others as well, add the
__assume macro to compiler attributes, so it is kernel wide available,
instead of adding an s390 specific optimization.

Heiko Carstens (3):
  Compiler Attributes: Add __assume macro
  s390/bitops: Limit return value range of __flogr()
  s390/bitops: Remove volatile qualifier from flogr() inline assembly

 arch/s390/include/asm/bitops.h      | 16 +++++++++-------
 include/linux/compiler_attributes.h | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 7 deletions(-)

-- 
2.48.1