llvm/compiler-rt/test/builtins/Unit/compiler_rt_logb_test.c

// RUN: %clang_builtins %s %librt -o %t && %run %t

#define DOUBLE_PRECISION
#include <math.h>
#include <stdio.h>
#include "fp_lib.h"

int test__compiler_rt_logb(fp_t x) {
#if defined(__ve__)
  if (fpclassify(x) == FP_SUBNORMAL)
    return 0;
#endif
  fp_t crt_value = __compiler_rt_logb(x);
  fp_t libm_value = logb(x);
  // Compare the values, considering all NaNs equivalent, as the spec doesn't
  // specify the NaN signedness/payload.
  if (crt_value != libm_value &&
      !(crt_isnan(crt_value) && crt_isnan(libm_value))) {
    printf("error: in __compiler_rt_logb(%a [%lX]) = %a [%lX] !=  %a [%lX]\n",
           x, toRep(x), crt_value, toRep(crt_value), libm_value,
           toRep(libm_value));
    return 1;
  }
  return 0;
}

double cases[] = {
    1.e-6, -1.e-6, NAN, -NAN, INFINITY, -INFINITY, -1,
    -0.0,  0.0,    1,   -2,   2,        -0.5,      0.5,
};

#ifndef __GLIBC_PREREQ
#define __GLIBC_PREREQ(x, y) 0
#endif

int main() {
  // Do not the run the compiler-rt logb test case if using GLIBC version
  // < 2.23. Older versions might not compute to the same value as the
  // compiler-rt value.
#if __GLIBC_PREREQ(2, 23)
  const unsigned N = sizeof(cases) / sizeof(cases[0]);
  unsigned i;
  for (i = 0; i < N; ++i) {
    if (test__compiler_rt_logb(cases[i])) return 1;
  }

  // Test a moving 1 bit, especially to handle denormal values.
  // Test the negation as well.
  rep_t x = signBit;
  while (x) {
    if (test__compiler_rt_logb(fromRep(x))) return 1;
    if (test__compiler_rt_logb(fromRep(signBit ^ x))) return 1;
    x >>= 1;
  }
  // Also try a couple moving ones
  x = signBit | (signBit >> 1) | (signBit >> 2);
  while (x) {
    if (test__compiler_rt_logb(fromRep(x))) return 1;
    if (test__compiler_rt_logb(fromRep(signBit ^ x))) return 1;
    x >>= 1;
  }
#else
  printf("skipped\n");
#endif

  return 0;
}