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- MIPS: Implement __multi3 for GCC7 MIPS64r6 builds
- Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
- Signed-off-by: James Hogan <jhogan@kernel.org>
- diff -Nur linux-4.14.8.orig/arch/mips/lib/libgcc.h linux-4.14.8/arch/mips/lib/libgcc.h
- --- linux-4.14.8.orig/arch/mips/lib/libgcc.h 2017-12-20 10:10:38.000000000 +0100
- +++ linux-4.14.8/arch/mips/lib/libgcc.h 2017-12-25 16:58:38.258470502 +0100
- @@ -10,10 +10,18 @@
- struct DWstruct {
- int high, low;
- };
- +
- +struct TWstruct {
- + long long high, low;
- +};
- #elif defined(__LITTLE_ENDIAN)
- struct DWstruct {
- int low, high;
- };
- +
- +struct TWstruct {
- + long long low, high;
- +};
- #else
- #error I feel sick.
- #endif
- @@ -23,4 +31,13 @@
- long long ll;
- } DWunion;
-
- +#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6)
- +typedef int ti_type __attribute__((mode(TI)));
- +
- +typedef union {
- + struct TWstruct s;
- + ti_type ti;
- +} TWunion;
- +#endif
- +
- #endif /* __ASM_LIBGCC_H */
- diff -Nur linux-4.14.8.orig/arch/mips/lib/Makefile linux-4.14.8/arch/mips/lib/Makefile
- --- linux-4.14.8.orig/arch/mips/lib/Makefile 2017-12-20 10:10:38.000000000 +0100
- +++ linux-4.14.8/arch/mips/lib/Makefile 2017-12-25 16:58:38.258470502 +0100
- @@ -16,4 +16,5 @@
- obj-$(CONFIG_CPU_TX39XX) += r3k_dump_tlb.o
-
- # libgcc-style stuff needed in the kernel
- -obj-y += ashldi3.o ashrdi3.o bswapsi.o bswapdi.o cmpdi2.o lshrdi3.o ucmpdi2.o
- +obj-y += ashldi3.o ashrdi3.o bswapsi.o bswapdi.o cmpdi2.o lshrdi3.o multi3.o \
- + ucmpdi2.o
- diff -Nur linux-4.14.8.orig/arch/mips/lib/multi3.c linux-4.14.8/arch/mips/lib/multi3.c
- --- linux-4.14.8.orig/arch/mips/lib/multi3.c 1970-01-01 01:00:00.000000000 +0100
- +++ linux-4.14.8/arch/mips/lib/multi3.c 2017-12-25 16:58:38.258470502 +0100
- @@ -0,0 +1,52 @@
- +// SPDX-License-Identifier: GPL-2.0
- +#include <linux/export.h>
- +
- +#include "libgcc.h"
- +
- +/*
- + * GCC 7 suboptimally generates __multi3 calls for mips64r6, so for that
- + * specific case only we'll implement it here.
- + *
- + * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82981
- + */
- +#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ == 7)
- +
- +/* multiply 64-bit values, low 64-bits returned */
- +static inline long long notrace dmulu(long long a, long long b)
- +{
- + long long res;
- + asm ("dmulu %0,%1,%2" : "=r" (res) : "r" (a), "r" (b));
- + return res;
- +}
- +
- +/* multiply 64-bit unsigned values, high 64-bits of 128-bit result returned */
- +static inline long long notrace dmuhu(long long a, long long b)
- +{
- + long long res;
- + asm ("dmuhu %0,%1,%2" : "=r" (res) : "r" (a), "r" (b));
- + return res;
- +}
- +
- +/* multiply 128-bit values, low 128-bits returned */
- +ti_type notrace __multi3(ti_type a, ti_type b)
- +{
- + TWunion res, aa, bb;
- +
- + aa.ti = a;
- + bb.ti = b;
- +
- + /*
- + * a * b = (a.lo * b.lo)
- + * + 2^64 * (a.hi * b.lo + a.lo * b.hi)
- + * [+ 2^128 * (a.hi * b.hi)]
- + */
- + res.s.low = dmulu(aa.s.low, bb.s.low);
- + res.s.high = dmuhu(aa.s.low, bb.s.low);
- + res.s.high += dmulu(aa.s.high, bb.s.low);
- + res.s.high += dmulu(aa.s.low, bb.s.high);
- +
- + return res.ti;
- +}
- +EXPORT_SYMBOL(__multi3);
- +
- +#endif /* 64BIT && CPU_MIPSR6 && GCC7 */
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