diff --git a/libc/bionic/fpclassify.cpp b/libc/bionic/fpclassify.cpp
new file mode 100644
index 0000000..8231093
--- /dev/null
+++ b/libc/bionic/fpclassify.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+
+#include <math.h>
+#include <machine/ieee.h>
+
+// These aren't declared in our <math.h>.
+extern "C" int __isinf(double);
+extern "C" int __isnan(double);
+
+union float_u {
+  float f;
+  ieee_single bits;
+};
+
+union double_u {
+  double d;
+  ieee_double bits;
+};
+
+int __fpclassifyd(double d) {
+  double_u u;
+  u.d = d;
+  if (u.bits.dbl_exp == 0) {
+    return ((u.bits.dbl_fracl | u.bits.dbl_frach) == 0) ? FP_ZERO : FP_SUBNORMAL;
+  }
+  if (u.bits.dbl_exp == DBL_EXP_INFNAN) {
+    return ((u.bits.dbl_fracl | u.bits.dbl_frach) == 0) ? FP_INFINITE : FP_NAN;
+  }
+  return FP_NORMAL;
+}
+__strong_alias(__fpclassify, __fpclassifyd); // glibc uses __fpclassify, BSD __fpclassifyd.
+
+int __fpclassifyf(float f) {
+  float_u u;
+  u.f = f;
+  if (u.bits.sng_exp == 0) {
+    return (u.bits.sng_frac == 0) ? FP_ZERO : FP_SUBNORMAL;
+  }
+  if (u.bits.sng_exp == SNG_EXP_INFNAN) {
+    return (u.bits.sng_frac == 0) ? FP_INFINITE : FP_NAN;
+  }
+  return FP_NORMAL;
+}
+
+int __isinf(double d) {
+  return (__fpclassifyd(d) == FP_INFINITE);
+}
+__strong_alias(isinf, __isinf);
+
+int __isinff(float f) {
+  return (__fpclassifyf(f) == FP_INFINITE);
+}
+__strong_alias(isinff, __isinff);
+
+int __isnan(double d) {
+  return (__fpclassifyd(d) == FP_NAN);
+}
+__strong_alias(isnan, __isnan);
+
+int __isnanf(float f) {
+  return (__fpclassifyf(f) == FP_NAN);
+}
+__strong_alias(isnanf, __isnanf);
+
+#if __LP64__
+
+// LP64 uses 128-bit long doubles.
+
+union long_double_u {
+  long double ld;
+  struct {
+    unsigned long fracl:64;
+    unsigned long frach:48;
+    unsigned int exp:15;
+    unsigned int sign:1;
+  } bits;
+};
+
+int __fpclassifyl(long double ld) {
+  long_double_u u;
+  u.ld = ld;
+  if (u.bits.exp == 0) {
+    return ((u.bits.fracl | u.bits.frach) == 0) ? FP_ZERO : FP_SUBNORMAL;
+  }
+  if (u.bits.exp == EXT_EXP_INFNAN) {
+    return ((u.bits.fracl | u.bits.frach) == 0) ? FP_INFINITE : FP_NAN;
+  }
+  return FP_NORMAL;
+}
+
+int __isinfl(long double ld) {
+  return (__fpclassifyl(ld) == FP_INFINITE);
+}
+
+int __isnanl(long double ld) {
+  return (__fpclassifyl(ld) == FP_NAN);
+}
+
+#else
+
+// LP32 uses double as long double.
+
+__strong_alias(__fpclassifyl, __fpclassify);
+__strong_alias(__isinfl, __isinf);
+__strong_alias(__isnanl, __isnan);
+
+#endif
+
+__strong_alias(isinfl, __isinfl);
+__strong_alias(isnanl, __isnanl);