From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
To: Yury Norov <yury.norov@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/5] ARM: findbit: document ARMv5 bit offset calculation
Date: Fri, 28 Oct 2022 17:47:53 +0100 [thread overview]
Message-ID: <E1ooSWP-000FDy-5t@rmk-PC.armlinux.org.uk> (raw)
In-Reply-To: <Y1wHlSE0S5QZ+QCI@shell.armlinux.org.uk>
Document the ARMv5 bit offset calculation code.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
arch/arm/lib/findbit.S | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S
index 7fd3600db8ef..4c584bc4704b 100644
--- a/arch/arm/lib/findbit.S
+++ b/arch/arm/lib/findbit.S
@@ -172,10 +172,10 @@ ENDPROC(_find_next_bit_be)
.L_found:
#if __LINUX_ARM_ARCH__ >= 5
rsb r0, r3, #0
- and r3, r3, r0
- clz r3, r3
- rsb r3, r3, #31
- add r0, r2, r3
+ and r3, r3, r0 @ mask out lowest bit set
+ clz r3, r3 @ count high zero bits
+ rsb r3, r3, #31 @ offset of first set bit
+ add r0, r2, r3 @ add offset of first set bit
#else
tst r3, #0x0f
addeq r2, r2, #4
--
2.30.2
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next prev parent reply other threads:[~2022-10-28 16:51 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-28 16:47 [PATCH 0/5] ARM: findbit assembly updates Russell King (Oracle)
2022-10-28 16:47 ` Russell King (Oracle) [this message]
2022-10-28 17:05 ` [PATCH 1/5] ARM: findbit: document ARMv5 bit offset calculation Linus Torvalds
2022-10-28 17:45 ` Russell King (Oracle)
2022-10-28 18:37 ` Yury Norov
2022-10-28 19:42 ` Russell King (Oracle)
2022-10-28 19:01 ` Linus Torvalds
2022-10-28 19:10 ` Linus Torvalds
2022-10-28 19:46 ` Russell King (Oracle)
2022-10-28 20:26 ` Linus Torvalds
2022-10-28 16:47 ` [PATCH 2/5] ARM: findbit: provide more efficient ARMv7 implementation Russell King (Oracle)
2022-10-28 16:48 ` [PATCH 3/5] ARM: findbit: convert to macros Russell King (Oracle)
2022-10-28 16:48 ` [PATCH 4/5] ARM: findbit: operate by words Russell King (Oracle)
2022-10-28 16:48 ` [PATCH 5/5] ARM: findbit: add unwinder information Russell King (Oracle)
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