[PATCH 02/16] math128, x86_64: Implement {mul,add}_u128 in 64bit asm

[Juri Lelli <juri.lelli@gmail.com>]

From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Enable __int128 usage when available, if not, provide asm versions of
mul_u64_u64 and add_u128.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-67zk6v8agsi8m7k1bdcd0srw@git.kernel.org
---
 arch/x86/include/asm/math128.h |   39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 arch/x86/include/asm/math128.h

diff --git a/arch/x86/include/asm/math128.h b/arch/x86/include/asm/math128.h
new file mode 100644
index 0000000..c0e2a6c
--- /dev/null
+++ b/arch/x86/include/asm/math128.h
@@ -0,0 +1,39 @@
+#ifndef _ASM_MATH128_H
+#define _ASM_MATH128_H
+
+#ifdef CONFIG_X86_64
+
+#ifdef __SIZEOF_INT128__
+#define ARCH_HAS_INT128
+#endif
+
+#ifndef ARCH_HAS_INT128
+
+static inline u128 mul_u64_u64(u64 a, u64 b)
+{
+       u128 res;
+
+       asm("mulq %2"
+               : "=a" (res.lo), "=d" (res.hi)
+               :  "rm" (b), "0" (a));
+
+       return res;
+}
+#define mul_u64_u64 mul_u64_u64
+
+static inline u128 add_u128(u128 a, u128 b)
+{
+       u128 res;
+
+       asm("addq %2,%0;\n"
+           "adcq %3,%1;\n"
+               : "=rm" (res.lo), "=rm" (res.hi)
+               : "r" (b.lo), "r" (b.hi), "0" (a.lo), "1" (a.hi));
+
+       return res;
+}
+#define add_u128 add_u128
+
+#endif /* ARCH_HAS_INT128 */
+#endif /* CONFIG_X86_64 */
+#endif /* _ASM_MATH128_H */
-- 
1.7.9.5