Shows broken core on my AMD Ryzen 2700X (use taskset to pin to core 3 and run a few times)

broken_amd_core_test.c

#include <math.h>
#include <stdio.h>

struct transform {
    double x1;
    double y1;
    double x2;
    double y2;
};

double
do_transform (struct transform trf, double progress)
{
  if (progress <= 0)
    return 0;
  if (progress >= 1)
    return 1;

      {
        static const double epsilon = 0.00001;
        double tmin, t, tmax;

        //tmin = 0.0;
        //tmax = 1.0;
        tmin = 0.93507255859375005;
        tmax = 0.93507255859375016;
        t = progress;

        double tmin_last = 1.0;
        double tmax_last = 0.0;

        while (tmin < tmax)
          {
                 if (tmin_last == tmin && tmax_last == tmax) {
                     exit(1);
                 }

                 double sample;
                 sample = (((1.0 + 3 * trf.x1 - 3 * trf.x2) * t
                           +      -6 * trf.x1 + 3 * trf.x2) * t
                           +       3 * trf.x1                       ) * t;

                 double const delta = fabs(sample - progress);
                 printf("sample: %f, delta: %f\n", sample, delta);
                 if (delta < epsilon)
                   break;

                 tmin_last = tmin;
                 tmax_last = tmax;
                 if (progress > sample)
                   tmin = t;
                 else
                   tmax = t;
                 t = (tmax + tmin) * .5;
              }

            return (((1.0 + 3 * trf.y1 - 3 * trf.y2) * t
                    +      -6 * trf.y1 + 3 * trf.y2) * t
                    +       3 * trf.y1                       ) * t;
      }
}

int main () {
    struct transform volatile t = {0, 0, 0.57999999999999996, 1};

    double const initial = 0.91668500000000031;

    printf("result: %f\n", do_transform(t, initial));

    return 0;
}