Introduce mul_u64_u32_shr() as proposed by Andy a while back; it
allows using 64x64->128 muls on 64bit archs and recent GCC.
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: fweis...@gmail.com
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Ingo Molnar <mi...@redhat.com>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---
arch/x86/Kconfig | 1 +
include/linux/math64.h | 30 ++++++++++++++++++++++++++++++
init/Kconfig | 6 ++++++
3 files changed, 37 insertions(+)
--- 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
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -133,4 +133,34 @@ __iter_div_u64_rem(u64 dividend, u32 div
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 */
--- 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.
#
--
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