[PATCH 2/2] math128, x86_64: Implement {mult,add}_u128 in 64bit asm

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: math128-x86_64.patch --]
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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>
---
 arch/x86/include/asm/Kbuild    |    1 -
 arch/x86/include/asm/math128.h |   39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/Kbuild
+++ b/arch/x86/include/asm/Kbuild
@@ -26,4 +26,3 @@ header-y += vsyscall.h
 genhdr-y += unistd_32.h
 genhdr-y += unistd_64.h
 genhdr-y += unistd_x32.h
-generic-y += math128.h
--- /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 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 mult_u64_u64 mult_u64_u64
+
+static inline 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 */