1 files changed, 63 insertions, 0 deletions
diff --git a/compiler-rt/test/builtins/Unit/compiler_rt_logb_test.c b/compiler-rt/test/builtins/Unit/compiler_rt_logb_test.c
new file mode 100644
index 00000000000..8bab4ab083a
--- /dev/null
+++ b/compiler-rt/test/builtins/Unit/compiler_rt_logb_test.c
@@ -0,0 +1,63 @@
+// RUN: %clang_builtins %s %librt -lm -o %t && %run %t
+//===-- compiler_rt_logb_test.c - Test __compiler_rt_logb -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file checks __compiler_rt_logb from the compiler_rt library for
+// conformance against libm.
+//
+//===----------------------------------------------------------------------===//
+
+#define DOUBLE_PRECISION
+#include <math.h>
+#include <stdio.h>
+#include "fp_lib.h"
+
+int test__compiler_rt_logb(fp_t x) {
+  fp_t crt_value = __compiler_rt_logb(x);
+  fp_t libm_value = logb(x);
+  // Compare actual rep, e.g. to avoid NaN != the same NaN
+  if (toRep(crt_value) != toRep(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,
+};
+
+int main() {
+  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;
+  }
+
+  return 0;
+}