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authorPeter Zijlstra <peterz@infradead.org>2013-11-18 18:27:06 +0100
committerIngo Molnar <mingo@kernel.org>2013-12-11 15:52:34 +0100
commitbe5e610c0fd6ef772cafb9e0bd4128134804aef3 (patch)
tree4cc4da2eea52c51ce868944aba28edf171a2d871
parentba1f14fbe70965ae0fb1655a5275a62723f65b77 (diff)
downloadlinux-linaro-stable-be5e610c0fd6ef772cafb9e0bd4128134804aef3.tar.gz
math64: Add mul_u64_u32_shr()
Introduce mul_u64_u32_shr() as proposed by Andy a while back; it allows using 64x64->128 muls on 64bit archs and recent GCC which defines __SIZEOF_INT128__ and __int128. (This new method will be used by the scheduler.) Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: fweisbec@gmail.com Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/n/tip-hxjoeuzmrcaumR0uZwjpe2pv@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--include/linux/math64.h30
-rw-r--r--init/Kconfig6
3 files changed, 37 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e903c71f7e69..0952ecd60eca 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -26,6 +26,7 @@ config X86
select HAVE_AOUT if X86_32
select HAVE_UNSTABLE_SCHED_CLOCK
select ARCH_SUPPORTS_NUMA_BALANCING
+ select ARCH_SUPPORTS_INT128 if X86_64
select ARCH_WANTS_PROT_NUMA_PROT_NONE
select HAVE_IDE
select HAVE_OPROFILE
diff --git a/include/linux/math64.h b/include/linux/math64.h
index 69ed5f5e9f6e..c45c089bfdac 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -133,4 +133,34 @@ __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
return ret;
}
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
+
+#ifndef mul_u64_u32_shr
+static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
+{
+ return (u64)(((unsigned __int128)a * mul) >> shift);
+}
+#endif /* mul_u64_u32_shr */
+
+#else
+
+#ifndef mul_u64_u32_shr
+static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
+{
+ u32 ah, al;
+ u64 ret;
+
+ al = a;
+ ah = a >> 32;
+
+ ret = ((u64)al * mul) >> shift;
+ if (ah)
+ ret += ((u64)ah * mul) << (32 - shift);
+
+ return ret;
+}
+#endif /* mul_u64_u32_shr */
+
+#endif
+
#endif /* _LINUX_MATH64_H */
diff --git a/init/Kconfig b/init/Kconfig
index 79383d3aa5dc..4e5d96ab2034 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -809,6 +809,12 @@ config GENERIC_SCHED_CLOCK
config ARCH_SUPPORTS_NUMA_BALANCING
bool
+#
+# For architectures that know their GCC __int128 support is sound
+#
+config ARCH_SUPPORTS_INT128
+ bool
+
# For architectures that (ab)use NUMA to represent different memory regions
# all cpu-local but of different latencies, such as SuperH.
#