From: Uros Bizjak <ubizjak@gmail.com>
To: x86@kernel.org, linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH] x86/bitops: Implement variable_ffz() as variable__ffs(~word)
Date: Thu, 27 Mar 2025 10:56:28 +0100 [thread overview]
Message-ID: <20250327095641.131483-1-ubizjak@gmail.com> (raw)
Find first zero (FFZ) can be implemented by negating the
input and using find first set (FFS).
No functional changes intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
arch/x86/include/asm/bitops.h | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index bbaf75ea6703..eebbc8889e70 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -267,10 +267,7 @@ static __always_inline unsigned long variable__ffs(unsigned long word)
static __always_inline unsigned long variable_ffz(unsigned long word)
{
- asm("tzcnt %1,%0"
- : "=r" (word)
- : "r" (~word));
- return word;
+ return variable__ffs(~word);
}
/**
--
2.49.0
next reply other threads:[~2025-03-27 9:56 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-27 9:56 Uros Bizjak [this message]
2025-03-28 22:36 ` [tip: x86/asm] x86/bitops: Simplify variable_ffz() as variable__ffs(~word) tip-bot2 for Uros Bizjak
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