Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date: Thu, 30 Nov 2017 16:00:12 -0800
From: Andre McCurdy <armccurdy@...il.com>
To: musl@...ts.openwall.com
Cc: Andre McCurdy <armccurdy@...il.com>
Subject: [PATCH] arm: provide a_ctz_l and a_ctz_64 helper functions

Provide an ARM specific a_ctz_l helper function for architecture
versions for which it can be implemented efficiently via the "rbit"
instruction (ie all Thumb-2 capable versions of ARM v6 and above).

Signed-off-by: Andre McCurdy <armccurdy@...il.com>
---
 arch/arm/atomic_arch.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h
index 6e2e3b4..9242df8 100644
--- a/arch/arm/atomic_arch.h
+++ b/arch/arm/atomic_arch.h
@@ -91,4 +91,26 @@ static inline int a_clz_32(uint32_t x)
 	return x;
 }
 
+#if __ARM_ARCH_6T2__ || __ARM_ARCH_7A__ || __ARM_ARCH_7R__ || __ARM_ARCH >= 7
+
+#define a_ctz_l a_ctz_l
+static inline int a_ctz_l(unsigned long x)
+{
+	uint32_t xr;
+	__asm__ ("rbit %0, %1" : "=r"(xr) : "r"(x));
+	return a_clz_32(xr);
+}
+
+#define a_ctz_64 a_ctz_64
+static inline int a_ctz_64(uint64_t x)
+{
+	uint32_t y = x;
+	if (!y) {
+		y = x>>32;
+		return 32 + a_ctz_l(y);
+	}
+	return a_ctz_l(y);
+}
+
+#endif
 #endif
-- 
1.9.1

Powered by blists - more mailing lists

Your e-mail address:

Powered by Openwall GNU/*/Linux - Powered by OpenVZ