#include <stdio.h>
typedef unsigned long u64;
void mul(u64 f[8], const u64 a[4], const u64 b[4]) {
// a0..a3 b0..b3 f0..f7 mu t0..t1 s0..s3s0..s3
u64 t0, t1, t2, mu;
asm volatile (
"movq %[a0], %[mu];"
"mulxq %[b0], %[f4], %[t0]; movq %[f4], %[f0];"
"mulxq %[b1], %[f5], %[t1]; addq %[t0], %[f5];"
"mulxq %[b2], %[f6], %[t2]; adcq %[t1], %[f6];"
"mulxq %[b3], %[f7], %[f4]; adcq %[t2], %[f7]; adcq $0, %[f4];"
"movq %[a1], %[mu];"
"mulxq %[b0], %[t2], %[t0]; addq %[t2], %[f5]; movq %[f5], %[f1];"
"mulxq %[b1], %[t2], %[t1]; adcq %[t2], %[f6];"
"mulxq %[b2], %[f5], %[t2]; adcq %[f5], %[f7];"
"mulxq %[b3], %[mu], %[f5]; adcq %[mu], %[f4]; adcq $0, %[f5];"
"addq %[t0], %[f6]; adcq %[t1], %[f7]; adcq %[t2], %[f4]; adcq $0, %[f5];"
"movq %[a2], %[mu];"
"mulxq %[b0], %[t2], %[t0]; addq %[t2], %[f6]; movq %[f6], %[f2];"
"mulxq %[b1], %[t2], %[t1]; adcq %[t2], %[f7];"
"mulxq %[b2], %[f6], %[t2]; adcq %[f6], %[f4];"
"mulxq %[b3], %[mu], %[f6]; adcq %[mu], %[f5]; adcq $0, %[f6];"
"addq %[t0], %[f7]; adcq %[t1], %[f4]; adcq %[t2], %[f5]; adcq $0, %[f6];"
"movq %[a3], %[mu];"
"mulxq %[b0], %[t2], %[t0]; addq %[t2], %[f7]; movq %[f7], %[f3];"
"mulxq %[b1], %[t2], %[t1]; adcq %[t2], %[f4];"
"mulxq %[b2], %[f7], %[t2]; adcq %[f7], %[f5];"
"mulxq %[b3], %[mu], %[f7]; adcq %[mu], %[f6]; adcq $0, %[f7];"
"addq %[t0], %[f4]; adcq %[t1], %[f5]; adcq %[t2], %[f6]; adcq $0, %[f7];"
:
[f0]"=&m"(f[0]), [f1]"=&m"(f[1]), [f2]"=&m"(f[2]), [f3]"=&m"(f[3]),
[f4]"=&r"(f[4]), [f5]"=&r"(f[5]), [f6]"=&r"(f[6]), [f7]"=&r"(f[7]),
[t0]"=&r"(t0),   [t1]"=&r"(t1),   [t2]"=&r"(t2),   [mu]"=&d"(mu):
[a0]"m"(a[0]),   [a1]"m"(a[1]),   [a2]"m"(a[2]),   [a3]"m"(a[3]),
[b0]"m"(b[0]),   [b1]"m"(b[1]),   [b2]"m"(b[2]),   [b3]"m"(b[3])
);
}


void mulX(u64 f[8], const u64 a[4], const u64 b[4]) {
// a0..a3 b0..b3 f0..f7 mu t0..t1 s0..s3s0..s3
u64 t0, t1, mu, s0, s1, s2, s3;
asm volatile (
"movq %[a0], %[mu];"
"mulxq %[b0], %[t0], %[s1]; movq %[t0], %[f0];"
"mulxq %[b1], %[t0], %[s2]; addq %[t0], %[s1];"
"mulxq %[b2], %[t0], %[s3]; adcq %[t0], %[s2];"
"mulxq %[b3], %[t0], %[s0]; adcq %[t0], %[s3];  adcq $0, %[s0]; xorl %k[t1], %k[t1];"
"movq %[a1], %[mu];"
"mulxq %[b0], %[t0], %[t1]; adoxq %[t0], %[s1]; adcxq %[t1], %[s2]; movq %[s1], %[f1];"
"mulxq %[b1], %[t0], %[t1]; adoxq %[t0], %[s2]; adcxq %[t1], %[s3];"
"mulxq %[b2], %[t0], %[t1]; adoxq %[t0], %[s3]; adcxq %[t1], %[s0];"
"mulxq %[b3], %[t0], %[t1]; adoxq %[t0], %[s0]; movl $0, %k[s1];"
                                               "adoxq %[s1], %[s1]; adcxq %[t1], %[s1];"
"movq %[a2], %[mu];"
"mulxq %[b0], %[t0], %[t1]; adoxq %[t0], %[s2]; adcxq %[t1], %[s3]; movq %[s2], %[f2];"
"mulxq %[b1], %[t0], %[t1]; adoxq %[t0], %[s3]; adcxq %[t1], %[s0];"
"mulxq %[b2], %[t0], %[t1]; adoxq %[t0], %[s0]; adcxq %[t1], %[s1];"
"mulxq %[b3], %[t0], %[t1]; adoxq %[t0], %[s1]; movl $0, %k[s2];"
                                               "adoxq %[s2], %[s2]; adcxq %[t1], %[s2];"
"movq %[a3], %[mu];"
"mulxq %[b0], %[t0], %[t1]; adoxq %[t0], %[s3]; adcxq %[t1], %[s0]; movq %[s3], %[f3];"
"mulxq %[b1], %[t0], %[t1]; adoxq %[t0], %[s0]; adcxq %[t1], %[s1]; movq %[s0], %[f4];"
"mulxq %[b2], %[t0], %[t1]; adoxq %[t0], %[s1]; adcxq %[t1], %[s2]; movq %[s1], %[f5];"
"mulxq %[b3], %[t0], %[t1]; adoxq %[t0], %[s2]; movl $0, %k[s3];    movq %[s2], %[f6];"
                                               "adoxq %[s3], %[s3]; adcxq %[t1], %[s3];"
                                                                   "movq %[s3], %[f7];":
[f0]"=&m"(f[0]), [f1]"=&m"(f[1]), [f2]"=&m"(f[2]), [f3]"=&m"(f[3]),
[f4]"=&m"(f[4]), [f5]"=&m"(f[5]), [f6]"=&m"(f[6]), [f7]"=&m"(f[7]),
[t0]"=&r"(t0),   [t1]"=&r"(t1),   [mu]"=&d"(mu),
[s0]"=&r"(s0),   [s1]"=&r"(s1),   [s2]"=&r"(s2),   [s3]"=&r"(s3):
[a0]"m"(a[0]),   [a1]"m"(a[1]),   [a2]"m"(a[2]),   [a3]"m"(a[3]),
[b0]"m"(b[0]),   [b1]"m"(b[1]),   [b2]"m"(b[2]),   [b3]"m"(b[3])
);
}

int main() {
    u64 a[4] = {1,2,3,4};
    u64 b[4] = {5,4,3,2};
    u64 c[8];
    for (unsigned i=0; ++i; )mulCall(c, a, b);
}

/*
$ gcc -DmulCall=mul -O2 66.c && sudo perf stat ./a.out # X

 Performance counter stats for './a.out':

         27,690.80 msec task-clock                #    0.998 CPUs utilized
             3,247      context-switches          #  117.259 /sec
               586      cpu-migrations            #   21.162 /sec
                45      page-faults               #    1.625 /sec
   106,431,860,062      cycles                    #    3.844 GHz                      (83.31%)
       428,297,182      stalled-cycles-frontend   #    0.40% frontend cycles idle     (83.34%)
    74,221,128,251      stalled-cycles-backend    #   69.74% backend cycles idle      (83.33%)
   301,156,490,496      instructions              #    2.83  insn per cycle
                                                  #    0.25  stalled cycles per insn  (83.34%)
    12,946,750,221      branches                  #  467.547 M/sec                    (83.33%)
         2,007,761      branch-misses             #    0.02% of all branches          (83.34%)

      27.738868676 seconds time elapsed

      27.680633000 seconds user
       0.011993000 seconds sys


$ gcc -DmulCall=mulX -O2 66.c && sudo perf stat ./a.out # X

 Performance counter stats for './a.out':

         28,449.67 msec task-clock                #    0.998 CPUs utilized
             3,481      context-switches          #  122.356 /sec
               533      cpu-migrations            #   18.735 /sec
                47      page-faults               #    1.652 /sec
   110,006,534,480      cycles                    #    3.867 GHz                      (83.34%)
       565,459,105      stalled-cycles-frontend   #    0.51% frontend cycles idle     (83.31%)
    73,662,756,220      stalled-cycles-backend    #   66.96% backend cycles idle      (83.33%)
   309,508,804,581      instructions              #    2.81  insn per cycle
                                                  #    0.24  stalled cycles per insn  (83.34%)
    12,955,065,685      branches                  #  455.368 M/sec                    (83.33%)
         2,288,864      branch-misses             #    0.02% of all branches          (83.35%)

      28.498440635 seconds time elapsed

      28.398338000 seconds user
       0.051945000 seconds sys

*/