target/linux/patches/4.14.8/mips64r6-multi3.patch

   1 MIPS: Implement __multi3 for GCC7 MIPS64r6 builds
   2
   3 Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
   4 Signed-off-by: James Hogan <jhogan@kernel.org>
   5
   6 diff -Nur linux-4.14.8.orig/arch/mips/lib/libgcc.h linux-4.14.8/arch/mips/lib/libgcc.h
   7 --- linux-4.14.8.orig/arch/mips/lib/libgcc.h    2017-12-20 10:10:38.000000000 +0100
   8 +++ linux-4.14.8/arch/mips/lib/libgcc.h 2017-12-25 16:58:38.258470502 +0100
   9 @@ -10,10 +10,18 @@
  10  struct DWstruct {
  11         int high, low;
  12  };
  13 +
  14 +struct TWstruct {
  15 +       long long high, low;
  16 +};
  17  #elif defined(__LITTLE_ENDIAN)
  18  struct DWstruct {
  19         int low, high;
  20  };
  21 +
  22 +struct TWstruct {
  23 +       long long low, high;
  24 +};
  25  #else
  26  #error I feel sick.
  27  #endif
  28 @@ -23,4 +31,13 @@
  29         long long ll;
  30  } DWunion;
  31
  32 +#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6)
  33 +typedef int ti_type __attribute__((mode(TI)));
  34 +
  35 +typedef union {
  36 +       struct TWstruct s;
  37 +       ti_type ti;
  38 +} TWunion;
  39 +#endif
  40 +
  41  #endif /* __ASM_LIBGCC_H */
  42 diff -Nur linux-4.14.8.orig/arch/mips/lib/Makefile linux-4.14.8/arch/mips/lib/Makefile
  43 --- linux-4.14.8.orig/arch/mips/lib/Makefile    2017-12-20 10:10:38.000000000 +0100
  44 +++ linux-4.14.8/arch/mips/lib/Makefile 2017-12-25 16:58:38.258470502 +0100
  45 @@ -16,4 +16,5 @@
  46  obj-$(CONFIG_CPU_TX39XX)       += r3k_dump_tlb.o
  47
  48  # libgcc-style stuff needed in the kernel
  49 -obj-y += ashldi3.o ashrdi3.o bswapsi.o bswapdi.o cmpdi2.o lshrdi3.o ucmpdi2.o
  50 +obj-y += ashldi3.o ashrdi3.o bswapsi.o bswapdi.o cmpdi2.o lshrdi3.o multi3.o \
  51 +        ucmpdi2.o
  52 diff -Nur linux-4.14.8.orig/arch/mips/lib/multi3.c linux-4.14.8/arch/mips/lib/multi3.c
  53 --- linux-4.14.8.orig/arch/mips/lib/multi3.c    1970-01-01 01:00:00.000000000 +0100
  54 +++ linux-4.14.8/arch/mips/lib/multi3.c 2017-12-25 16:58:38.258470502 +0100
  55 @@ -0,0 +1,52 @@
  56 +// SPDX-License-Identifier: GPL-2.0
  57 +#include <linux/export.h>
  58 +
  59 +#include "libgcc.h"
  60 +
  61 +/*
  62 + * GCC 7 suboptimally generates __multi3 calls for mips64r6, so for that
  63 + * specific case only we'll implement it here.
  64 + *
  65 + * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82981
  66 + */
  67 +#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ == 7)
  68 +
  69 +/* multiply 64-bit values, low 64-bits returned */
  70 +static inline long long notrace dmulu(long long a, long long b)
  71 +{
  72 +       long long res;
  73 +       asm ("dmulu %0,%1,%2" : "=r" (res) : "r" (a), "r" (b));
  74 +       return res;
  75 +}
  76 +
  77 +/* multiply 64-bit unsigned values, high 64-bits of 128-bit result returned */
  78 +static inline long long notrace dmuhu(long long a, long long b)
  79 +{
  80 +       long long res;
  81 +       asm ("dmuhu %0,%1,%2" : "=r" (res) : "r" (a), "r" (b));
  82 +       return res;
  83 +}
  84 +
  85 +/* multiply 128-bit values, low 128-bits returned */
  86 +ti_type notrace __multi3(ti_type a, ti_type b)
  87 +{
  88 +       TWunion res, aa, bb;
  89 +
  90 +       aa.ti = a;
  91 +       bb.ti = b;
  92 +
  93 +       /*
  94 +        * a * b =           (a.lo * b.lo)
  95 +        *         + 2^64  * (a.hi * b.lo + a.lo * b.hi)
  96 +        *        [+ 2^128 * (a.hi * b.hi)]
  97 +        */
  98 +       res.s.low = dmulu(aa.s.low, bb.s.low);
  99 +       res.s.high = dmuhu(aa.s.low, bb.s.low);
 100 +       res.s.high += dmulu(aa.s.high, bb.s.low);
 101 +       res.s.high += dmulu(aa.s.low, bb.s.high);
 102 +
 103 +       return res.ti;
 104 +}
 105 +EXPORT_SYMBOL(__multi3);
 106 +
 107 +#endif /* 64BIT && CPU_MIPSR6 && GCC7 */