[Bug rtl-optimization/89225] New: [9 Regression] LRA hang on ppc64le compiling glibc starting with r268404

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89225

            Bug ID: 89225
           Summary: [9 Regression] LRA hang on ppc64le compiling glibc
                    starting with r268404
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

The following testcase hangs in LRA with -O2 -fstack-protector-strong
-mlong-double-128 on powerpc64le-linux.

extern long double foo (long double);
extern double bar (double);
typedef long long int64_t;
typedef unsigned long long uint64_t;
typedef union { int64_t i[2]; long double x; double d[2]; } mynumber;
static const double t512 = 0x1p512, tm256 = 0x1p-256, two54 = 0x1p54, twom54 =
0x1p-54;

long double
foo (long double x)
{
  static const long double big = 134217728.0, big1 = 134217729.0;
  long double t, s, i;
  mynumber a, c;
  uint64_t k, l;
  int64_t m, n;
  double d;

  a.x = x;
  k = a.i[0] & 0x7fffffffffffffffL;

  if (k > 0x000fffff00000000L && k < 0x7ff0000000000000L)
    {
      if (x < 0)
        return (big1 - big1) / (big - big);
      l = (k & 0x001fffffffffffffL) | 0x3fe0000000000000L;
      if ((a.i[1] & 0x7fffffffffffffffL) != 0)
        {
          n = (int64_t) ((l - k) * 2) >> 53;
          m = (a.i[1] >> 52) & 0x7ff;
          if (m == 0)
            {
              a.d[1] *= two54;
              m = ((a.i[1] >> 52) & 0x7ff) - 54;
            }
          m += n;
          if (m > 0)
            a.i[1] = (a.i[1] & 0x800fffffffffffffL) | (m << 52);
          else if (m <= -54)
            {
              a.i[1] &= 0x8000000000000000L;
            }
          else
            {
              m += 54;
              a.i[1] = (a.i[1] & 0x800fffffffffffffL) | (m << 52);
              a.d[1] *= twom54;
            }
        }
      a.i[0] = l;
      s = a.x;
      d = bar (a.d[0]);
      c.i[0] = 0x2000000000000000L + ((k & 0x7fe0000000000000L) >> 1);
      c.i[1] = 0;
      i = d;
      t = 0.5L * (i + s / i);
      i = 0.5L * (t + s / t);
      return c.x * i;
    }
  else
    {
      if (k >= 0x7ff0000000000000L)

        return x * x + x;
      if (x == 0)
        return x;
      if (x < 0)
        return (big1 - big1) / (big - big);
      return tm256 * foo (x * t512);
    }
}