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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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WARNING: multiple messages have this Message-ID (diff)
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


  reply	other threads:[~2022-10-28 16:51 UTC|newest]

Thread overview: 28+ 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)
2022-10-28 16:47 ` Russell King (Oracle) [this message]
2022-10-28 16:47   ` [PATCH 1/5] ARM: findbit: document ARMv5 bit offset calculation Russell King (Oracle)
2022-10-28 17:05   ` Linus Torvalds
2022-10-28 17:05     ` Linus Torvalds
2022-10-28 17:45     ` Russell King (Oracle)
2022-10-28 17:45       ` Russell King (Oracle)
2022-10-28 18:37       ` Yury Norov
2022-10-28 18:37         ` Yury Norov
2022-10-28 19:42         ` Russell King (Oracle)
2022-10-28 19:42           ` Russell King (Oracle)
2022-10-28 19:01       ` Linus Torvalds
2022-10-28 19:01         ` Linus Torvalds
2022-10-28 19:10         ` Linus Torvalds
2022-10-28 19:10           ` Linus Torvalds
2022-10-28 19:46         ` Russell King (Oracle)
2022-10-28 19:46           ` Russell King (Oracle)
2022-10-28 20:26           ` Linus Torvalds
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 16:47   ` Russell King (Oracle)
2022-10-28 16:48 ` [PATCH 3/5] ARM: findbit: convert to macros Russell King (Oracle)
2022-10-28 16:48   ` Russell King (Oracle)
2022-10-28 16:48 ` [PATCH 4/5] ARM: findbit: operate by words Russell King (Oracle)
2022-10-28 16:48   ` Russell King (Oracle)
2022-10-28 16:48 ` [PATCH 5/5] ARM: findbit: add unwinder information Russell King (Oracle)
2022-10-28 16:48   ` Russell King (Oracle)

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