diff --git a/NEWS b/NEWS
index e295274..0b2ca04 100644
--- a/NEWS
+++ b/NEWS
@@ -51,7 +51,7 @@ Version 2.25
 
 * New <math.h> features are added from TS 18661-1:2014:
 
-  - Classification macros: issubnormal, iszero.
+  - Classification macros: iscanonical, issubnormal, iszero.
 
 * The <sys/quota.h> header now includes the <linux/quota.h> header.  Support
   for the Linux quota interface which predates kernel version 2.4.22 has
diff --git a/bits/iscanonical.h b/bits/iscanonical.h
new file mode 100644
index 0000000..97eb736
--- /dev/null
+++ b/bits/iscanonical.h
@@ -0,0 +1,28 @@
+/* Define iscanonical macro.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _MATH_H
+# error "Never use <bits/iscanonical.h> directly; include <math.h> instead."
+#endif
+
+/* Return nonzero value if X is canonical.  By default, we only have
+   IEEE interchange binary formats, in which all values are canonical,
+   but the argument must still be converted to its semantic type for
+   any exceptions arising from the conversion, before being
+   discarded.  */
+#define iscanonical(x) ((void) (__typeof (x)) (x), 1)
diff --git a/manual/arith.texi b/manual/arith.texi
index 58f3578..a13c46f 100644
--- a/manual/arith.texi
+++ b/manual/arith.texi
@@ -361,6 +361,23 @@ You should therefore use the specific macros whenever possible.
 
 @comment math.h
 @comment ISO
+@deftypefn {Macro} int iscanonical (@emph{float-type} @var{x})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+In some floating-point formats, some values have canonical (preferred)
+and noncanonical encodings (for IEEE interchange binary formats, all
+encodings are canonical).  This macro returns a nonzero value if
+@var{x} has a canonical encoding.  It is from TS 18661-1:2014.
+
+Note that some formats have multiple encodings of a value which are
+all equally canonical; @code{iscanonical} returns a nonzero value for
+all such encodings.  Also, formats may have encodings that do not
+correspond to any valid value of the type.  In ISO C terms these are
+@dfn{trap representations}; in @theglibc{}, @code{iscanonical} returns
+zero for such encodings.
+@end deftypefn
+
+@comment math.h
+@comment ISO
 @deftypefn {Macro} int isfinite (@emph{float-type} @var{x})
 @safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 This macro returns a nonzero value if @var{x} is finite: not plus or
diff --git a/manual/libm-err-tab.pl b/manual/libm-err-tab.pl
index 2386772..b36ef94 100755
--- a/manual/libm-err-tab.pl
+++ b/manual/libm-err-tab.pl
@@ -77,7 +77,7 @@ use vars qw (%results @all_floats %suffices @all_functions);
     "nextup", "pow", "remainder", "remquo", "rint", "round", "scalb",
     "scalbn", "sin", "sincos", "sinh", "sqrt", "tan", "tanh", "tgamma",
     "trunc", "y0", "y1", "yn" );
-# fpclassify, isnormal, isfinite, isinf, isnan, issignaling,
+# fpclassify, iscanonical, isnormal, isfinite, isinf, isnan, issignaling,
 # issubnormal, iszero, signbit, isgreater, isgreaterequal, isless,
 # islessequal, islessgreater, isunordered are not tabulated.
 
diff --git a/math/Makefile b/math/Makefile
index 7ccd59a..d2b4fd1 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -27,7 +27,7 @@ headers		:= math.h bits/mathcalls.h bits/mathinline.h bits/huge_val.h \
 		   fpu_control.h complex.h bits/cmathcalls.h fenv.h \
 		   bits/fenv.h bits/fenvinline.h bits/mathdef.h tgmath.h \
 		   bits/math-finite.h bits/math-vector.h \
-		   bits/libm-simd-decl-stubs.h
+		   bits/libm-simd-decl-stubs.h bits/iscanonical.h
 
 # FPU support code.
 aux		:= setfpucw fpu_control
@@ -94,7 +94,7 @@ types = $(type-ldouble-$(long-double-fcts)) double float
 
 # long double support
 type-ldouble-suffix := l
-type-ldouble-routines := t_sincosl k_sincosl
+type-ldouble-routines := t_sincosl k_sincosl s_iscanonicall
 type-ldouble-yes := ldouble
 
 # double support
diff --git a/math/Versions b/math/Versions
index a429221..f702051 100644
--- a/math/Versions
+++ b/math/Versions
@@ -216,5 +216,6 @@ libm {
   }
   GLIBC_2.25 {
     fesetexcept; fetestexceptflag; fegetmode; fesetmode;
+    __iscanonicall;
   }
 }
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 872bafd..cbc7226 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -46,9 +46,9 @@
    cbrt, ceil, copysign, cos, cosh, drem, erf, erfc, exp, exp10, exp2, expm1,
    fabs, fdim, finite, floor, fma, fmax, fmin, fmod, fpclassify,
    frexp, gamma, hypot,
-   ilogb, isfinite, isinf, isnan, isnormal, issignaling, issubnormal, iszero,
-   isless, islessequal, isgreater, isgreaterequal, islessgreater, isunordered,
-   j0, j1, jn,
+   ilogb, iscanonical, isfinite, isinf, isnan, isnormal, issignaling,
+   issubnormal, iszero, isless, islessequal, isgreater,
+   isgreaterequal, islessgreater, isunordered, j0, j1, jn,
    ldexp, lgamma, log, log10, log1p, log2, logb,
    modf, nearbyint, nextafter, nexttoward,
    pow, pow10, remainder, remquo, rint, lrint, llrint,
@@ -8160,6 +8160,31 @@ ilogb_test (void)
   ALL_RM_TEST (ilogb, 1, ilogb_test_data, RUN_TEST_LOOP_f_i, END);
 }
 
+static const struct test_f_i_data iscanonical_test_data[] =
+  {
+    TEST_f_b (iscanonical, 0, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, minus_zero, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, 10, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, min_subnorm_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, -min_subnorm_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, min_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, -min_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, max_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, -max_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, plus_infty, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, minus_infty, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, qnan_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, -qnan_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, snan_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_b (iscanonical, -snan_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+  };
+
+static void
+iscanonical_test (void)
+{
+  ALL_RM_TEST (iscanonical, 1, iscanonical_test_data, RUN_TEST_LOOP_f_b_tg, END);
+}
+
 static const struct test_f_i_data isfinite_test_data[] =
   {
     TEST_f_b (isfinite, 0, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
@@ -12713,6 +12738,7 @@ main (int argc, char **argv)
   /* Classification macros:  */
   finite_test ();
   fpclassify_test ();
+  iscanonical_test ();
   isfinite_test ();
   isinf_test ();
   isnan_test ();
diff --git a/math/math.h b/math/math.h
index 1382baa..8cd6416 100644
--- a/math/math.h
+++ b/math/math.h
@@ -317,6 +317,8 @@ enum
 #endif /* Use ISO C99.  */
 
 #if __GLIBC_USE (IEC_60559_BFP_EXT)
+# include <bits/iscanonical.h>
+
 /* Return nonzero value if X is a signaling NaN.  */
 # ifdef __NO_LONG_DOUBLE_MATH
 #  define issignaling(x) \
diff --git a/math/s_iscanonicall.c b/math/s_iscanonicall.c
new file mode 100644
index 0000000..b5fd996
--- /dev/null
+++ b/math/s_iscanonicall.c
@@ -0,0 +1 @@
+/* Not needed by default.  */
diff --git a/sysdeps/ieee754/ldbl-128ibm/Makefile b/sysdeps/ieee754/ldbl-128ibm/Makefile
index 6242edd..56bebf8 100644
--- a/sysdeps/ieee754/ldbl-128ibm/Makefile
+++ b/sysdeps/ieee754/ldbl-128ibm/Makefile
@@ -11,5 +11,5 @@ endif
 
 ifeq ($(subdir),math)
 tests += test-fmodl-ldbl-128ibm test-remainderl-ldbl-128ibm \
-	 test-remquol-ldbl-128ibm
+	 test-remquol-ldbl-128ibm test-iscanonical-ldbl-128ibm
 endif
diff --git a/sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h b/sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h
new file mode 100644
index 0000000..cbc79ae
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h
@@ -0,0 +1,35 @@
+/* Define iscanonical macro.  ldbl-128ibm version.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _MATH_H
+# error "Never use <bits/iscanonical.h> directly; include <math.h> instead."
+#endif
+
+extern int __iscanonicall (long double __x)
+     __THROW __attribute__ ((__const__));
+
+/* Return nonzero value if X is canonical.  In IEEE interchange binary
+   formats, all values are canonical, but the argument must still be
+   converted to its semantic type for any exceptions arising from the
+   conversion, before being discarded; in IBM long double, there are
+   encodings that are not consistently handled as corresponding to any
+   particular value of the type, and we return 0 for those.  */
+#define iscanonical(x)				\
+  (sizeof (x) == sizeof (long double)		\
+   ? __iscanonicall (x)				\
+   : ((void) (__typeof (x)) (x), 1))
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_iscanonicall.c b/sysdeps/ieee754/ldbl-128ibm/s_iscanonicall.c
new file mode 100644
index 0000000..100b401
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/s_iscanonicall.c
@@ -0,0 +1,59 @@
+/* Test whether long double value is canonical.  ldbl-128ibm version.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <stdint.h>
+
+int
+__iscanonicall (long double x)
+{
+  double xhi, xlo;
+  uint64_t hx, lx;
+
+  ldbl_unpack (x, &xhi, &xlo);
+  EXTRACT_WORDS64 (hx, xhi);
+  EXTRACT_WORDS64 (lx, xlo);
+  int64_t ix = hx & 0x7fffffffffffffffULL;
+  int64_t iy = lx & 0x7fffffffffffffffULL;
+  int hexp = (ix & 0x7ff0000000000000LL) >> 52;
+  int lexp = (iy & 0x7ff0000000000000LL) >> 52;
+
+  if (iy == 0)
+    /* Low part 0 is always OK.  */
+    return 1;
+
+  if (hexp == 0x7ff)
+    /* If a NaN, the low part does not matter.  If an infinity, the
+       low part must be 0, in which case we have already returned.  */
+    return ix != 0x7ff0000000000000LL;
+
+  /* The high part is finite and the low part is nonzero.  There must
+     be sufficient difference between the exponents.  */
+  bool low_p2;
+  if (lexp == 0)
+    {
+      /* Adjust the exponent for subnormal low part.  */
+      lexp = 12 - __builtin_clzll (iy);
+      low_p2 = iy == (1LL << (51 + lexp));
+    }
+  else
+    low_p2 = (iy & 0xfffffffffffffLL) == 0;
+  int expdiff = hexp - lexp;
+  return expdiff > 53 || (expdiff == 53 && low_p2 && (ix & 1) == 0);
+}
diff --git a/sysdeps/ieee754/ldbl-128ibm/test-iscanonical-ldbl-128ibm.c b/sysdeps/ieee754/ldbl-128ibm/test-iscanonical-ldbl-128ibm.c
new file mode 100644
index 0000000..92b9c69
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/test-iscanonical-ldbl-128ibm.c
@@ -0,0 +1,203 @@
+/* Test iscanonical for ldbl-128ibm.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <float.h>
+#include <math.h>
+#include <math_private.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+struct test
+{
+  double hi, lo;
+  bool canonical;
+};
+
+static const struct test tests[] =
+  {
+    { __builtin_nan (""), 0.0, true },
+    { __builtin_nan (""), DBL_MAX, true },
+    { __builtin_nan (""), __builtin_inf (), true },
+    { __builtin_nan (""), __builtin_nan (""), true },
+    { __builtin_nan (""), __builtin_nans (""), true },
+    { __builtin_nans (""), 0.0, true },
+    { __builtin_nans (""), DBL_MAX, true },
+    { __builtin_nans (""), __builtin_inf (), true },
+    { __builtin_nans (""), __builtin_nan (""), true },
+    { __builtin_nans (""), __builtin_nans (""), true },
+    { __builtin_inf (), 0.0, true },
+    { __builtin_inf (), -0.0, true },
+    { -__builtin_inf (), 0.0, true },
+    { -__builtin_inf (), -0.0, true },
+    { __builtin_inf (), DBL_TRUE_MIN, false },
+    { __builtin_inf (), -DBL_TRUE_MIN, false },
+    { -__builtin_inf (), DBL_TRUE_MIN, false },
+    { -__builtin_inf (), -DBL_TRUE_MIN, false },
+    { __builtin_inf (), DBL_MIN, false },
+    { __builtin_inf (), -DBL_MIN, false },
+    { -__builtin_inf (), DBL_MIN, false },
+    { -__builtin_inf (), -DBL_MIN, false },
+    { __builtin_inf (), __builtin_inf (), false },
+    { __builtin_inf (), -__builtin_inf (), false },
+    { -__builtin_inf (), __builtin_inf (), false },
+    { -__builtin_inf (), -__builtin_inf (), false },
+    { __builtin_inf (), __builtin_nan (""), false },
+    { __builtin_inf (), -__builtin_nan (""), false },
+    { -__builtin_inf (), __builtin_nan (""), false },
+    { -__builtin_inf (), -__builtin_nan (""), false },
+    { 0.0, 0.0, true },
+    { 0.0, -0.0, true },
+    { -0.0, 0.0, true },
+    { -0.0, -0.0, true },
+    { 0.0, DBL_TRUE_MIN, false },
+    { 0.0, -DBL_TRUE_MIN, false },
+    { -0.0, DBL_TRUE_MIN, false },
+    { -0.0, -DBL_TRUE_MIN, false },
+    { 0.0, DBL_MAX, false },
+    { 0.0, -DBL_MAX, false },
+    { -0.0, DBL_MAX, false },
+    { -0.0, -DBL_MAX, false },
+    { 0.0, __builtin_inf (), false },
+    { 0.0, -__builtin_inf (), false },
+    { -0.0, __builtin_inf (), false },
+    { -0.0, -__builtin_inf (), false },
+    { 0.0, __builtin_nan (""), false },
+    { 0.0, -__builtin_nan (""), false },
+    { -0.0, __builtin_nan (""), false },
+    { -0.0, -__builtin_nan (""), false },
+    { 1.0, 0.0, true },
+    { 1.0, -0.0, true },
+    { -1.0, 0.0, true },
+    { -1.0, -0.0, true },
+    { 1.0, DBL_TRUE_MIN, true },
+    { 1.0, -DBL_TRUE_MIN, true },
+    { -1.0, DBL_TRUE_MIN, true },
+    { -1.0, -DBL_TRUE_MIN, true },
+    { 1.0, DBL_MAX, false },
+    { 1.0, -DBL_MAX, false },
+    { -1.0, DBL_MAX, false },
+    { -1.0, -DBL_MAX, false },
+    { 1.0, __builtin_inf (), false },
+    { 1.0, -__builtin_inf (), false },
+    { -1.0, __builtin_inf (), false },
+    { -1.0, -__builtin_inf (), false },
+    { 1.0, __builtin_nan (""), false },
+    { 1.0, -__builtin_nan (""), false },
+    { -1.0, __builtin_nan (""), false },
+    { -1.0, -__builtin_nan (""), false },
+    { 0x1p1023, 0x1.1p969, true },
+    { 0x1p1023, -0x1.1p969, true },
+    { -0x1p1023, 0x1.1p969, true },
+    { -0x1p1023, -0x1.1p969, true },
+    { 0x1p1023, 0x1.1p970, false },
+    { 0x1p1023, -0x1.1p970, false },
+    { -0x1p1023, 0x1.1p970, false },
+    { -0x1p1023, -0x1.1p970, false },
+    { 0x1p1023, 0x1p970, true },
+    { 0x1p1023, -0x1p970, true },
+    { -0x1p1023, 0x1p970, true },
+    { -0x1p1023, -0x1p970, true },
+    { 0x1.0000000000001p1023, 0x1p970, false },
+    { 0x1.0000000000001p1023, -0x1p970, false },
+    { -0x1.0000000000001p1023, 0x1p970, false },
+    { -0x1.0000000000001p1023, -0x1p970, false },
+    { 0x1p-969, 0x1.1p-1023, true },
+    { 0x1p-969, -0x1.1p-1023, true },
+    { -0x1p-969, 0x1.1p-1023, true },
+    { -0x1p-969, -0x1.1p-1023, true },
+    { 0x1p-969, 0x1.1p-1022, false },
+    { 0x1p-969, -0x1.1p-1022, false },
+    { -0x1p-969, 0x1.1p-1022, false },
+    { -0x1p-969, -0x1.1p-1022, false },
+    { 0x1p-969, 0x1p-1022, true },
+    { 0x1p-969, -0x1p-1022, true },
+    { -0x1p-969, 0x1p-1022, true },
+    { -0x1p-969, -0x1p-1022, true },
+    { 0x1.0000000000001p-969, 0x1p-1022, false },
+    { 0x1.0000000000001p-969, -0x1p-1022, false },
+    { -0x1.0000000000001p-969, 0x1p-1022, false },
+    { -0x1.0000000000001p-969, -0x1p-1022, false },
+    { 0x1p-970, 0x1.1p-1024, true },
+    { 0x1p-970, -0x1.1p-1024, true },
+    { -0x1p-970, 0x1.1p-1024, true },
+    { -0x1p-970, -0x1.1p-1024, true },
+    { 0x1p-970, 0x1.1p-1023, false },
+    { 0x1p-970, -0x1.1p-1023, false },
+    { -0x1p-970, 0x1.1p-1023, false },
+    { -0x1p-970, -0x1.1p-1023, false },
+    { 0x1p-970, 0x1p-1023, true },
+    { 0x1p-970, -0x1p-1023, true },
+    { -0x1p-970, 0x1p-1023, true },
+    { -0x1p-970, -0x1p-1023, true },
+    { 0x1.0000000000001p-970, 0x1p-1023, false },
+    { 0x1.0000000000001p-970, -0x1p-1023, false },
+    { -0x1.0000000000001p-970, 0x1p-1023, false },
+    { -0x1.0000000000001p-970, -0x1p-1023, false },
+    { 0x1p-1000, 0x1.1p-1054, true },
+    { 0x1p-1000, -0x1.1p-1054, true },
+    { -0x1p-1000, 0x1.1p-1054, true },
+    { -0x1p-1000, -0x1.1p-1054, true },
+    { 0x1p-1000, 0x1.1p-1053, false },
+    { 0x1p-1000, -0x1.1p-1053, false },
+    { -0x1p-1000, 0x1.1p-1053, false },
+    { -0x1p-1000, -0x1.1p-1053, false },
+    { 0x1p-1000, 0x1p-1053, true },
+    { 0x1p-1000, -0x1p-1053, true },
+    { -0x1p-1000, 0x1p-1053, true },
+    { -0x1p-1000, -0x1p-1053, true },
+    { 0x1.0000000000001p-1000, 0x1p-1053, false },
+    { 0x1.0000000000001p-1000, -0x1p-1053, false },
+    { -0x1.0000000000001p-1000, 0x1p-1053, false },
+    { -0x1.0000000000001p-1000, -0x1p-1053, false },
+    { 0x1p-1021, 0x1p-1074, true },
+    { 0x1p-1021, -0x1p-1074, true },
+    { -0x1p-1021, 0x1p-1074, true },
+    { -0x1p-1021, -0x1p-1074, true },
+    { 0x1.0000000000001p-1021, 0x1p-1074, false },
+    { 0x1.0000000000001p-1021, -0x1p-1074, false },
+    { -0x1.0000000000001p-1021, 0x1p-1074, false },
+    { -0x1.0000000000001p-1021, -0x1p-1074, false },
+    { 0x1p-1022, 0x1p-1074, false },
+    { 0x1p-1022, -0x1p-1074, false },
+    { -0x1p-1022, 0x1p-1074, false },
+    { -0x1p-1022, -0x1p-1074, false },
+  };
+
+static int
+do_test (void)
+{
+  int result = 0;
+
+  for (size_t i = 0; i < sizeof (tests) / sizeof (tests[0]); i++)
+    {
+      long double ld = ldbl_pack (tests[i].hi, tests[i].lo);
+      bool canonical = iscanonical (ld);
+      if (canonical == tests[i].canonical)
+	printf ("PASS: test %zu\n", i);
+      else
+	{
+	  printf ("FAIL: test %zu\n", i);
+	  result = 1;
+	}
+    }
+
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/sysdeps/ieee754/ldbl-96/Makefile b/sysdeps/ieee754/ldbl-96/Makefile
new file mode 100644
index 0000000..bf9676e
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-96/Makefile
@@ -0,0 +1,21 @@
+# Makefile for sysdeps/ieee754/ldbl-96.
+# Copyright (C) 2016 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+ifeq ($(subdir),math)
+tests += test-iscanonical-ldbl-96
+endif
diff --git a/sysdeps/ieee754/ldbl-96/bits/iscanonical.h b/sysdeps/ieee754/ldbl-96/bits/iscanonical.h
new file mode 100644
index 0000000..af0c72c
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-96/bits/iscanonical.h
@@ -0,0 +1,35 @@
+/* Define iscanonical macro.  ldbl-96 version.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _MATH_H
+# error "Never use <bits/iscanonical.h> directly; include <math.h> instead."
+#endif
+
+extern int __iscanonicall (long double __x)
+     __THROW __attribute__ ((__const__));
+
+/* Return nonzero value if X is canonical.  In IEEE interchange binary
+   formats, all values are canonical, but the argument must still be
+   converted to its semantic type for any exceptions arising from the
+   conversion, before being discarded; in extended precision, there
+   are encodings that are not consistently handled as corresponding to
+   any particular value of the type, and we return 0 for those.  */
+#define iscanonical(x)				\
+  (sizeof (x) == sizeof (long double)		\
+   ? __iscanonicall (x)				\
+   : ((void) (__typeof (x)) (x), 1))
diff --git a/sysdeps/ieee754/ldbl-96/s_iscanonicall.c b/sysdeps/ieee754/ldbl-96/s_iscanonicall.c
new file mode 100644
index 0000000..f820030
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-96/s_iscanonicall.c
@@ -0,0 +1,43 @@
+/* Test whether long double value is canonical.  ldbl-96 version.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <float.h>
+#include <math.h>
+#include <math_private.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+int
+__iscanonicall (long double x)
+{
+  uint32_t se, i0, i1 __attribute__ ((unused));
+
+  GET_LDOUBLE_WORDS (se, i0, i1, x);
+  int32_t ix = se & 0x7fff;
+  bool mant_high = (i0 & 0x80000000) != 0;
+
+  if (LDBL_MIN_EXP == -16381)
+    /* Intel variant: the high mantissa bit should have a value
+       determined by the exponent.  */
+    return ix > 0 ? mant_high : !mant_high;
+  else
+    /* M68K variant: both values of the high bit are valid for the
+       greatest and smallest exponents, while other exponents require
+       the high bit to be set.  */
+    return ix == 0 || ix == 0x7fff || mant_high;
+}
diff --git a/sysdeps/ieee754/ldbl-96/test-iscanonical-ldbl-96.c b/sysdeps/ieee754/ldbl-96/test-iscanonical-ldbl-96.c
new file mode 100644
index 0000000..6827aa8
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-96/test-iscanonical-ldbl-96.c
@@ -0,0 +1,114 @@
+/* Test iscanonical for ldbl-96.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <float.h>
+#include <math.h>
+#include <math_private.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+struct test
+{
+  bool sign;
+  uint16_t exponent;
+  bool high;
+  uint64_t mantissa;
+  bool canonical;
+};
+
+#define M68K_VARIANT (LDBL_MIN_EXP == -16382)
+
+static const struct test tests[] =
+  {
+    { false, 0, true, 0, M68K_VARIANT },
+    { true, 0, true, 0, M68K_VARIANT },
+    { false, 0, true, 1, M68K_VARIANT },
+    { true, 0, true, 1, M68K_VARIANT },
+    { false, 0, true, 0x100000000ULL, M68K_VARIANT },
+    { true, 0, true, 0x100000000ULL, M68K_VARIANT },
+    { false, 0, false, 0, true },
+    { true, 0, false, 0, true },
+    { false, 0, false, 1, true },
+    { true, 0, false, 1, true },
+    { false, 0, false, 0x100000000ULL, true },
+    { true, 0, false, 0x100000000ULL, true },
+    { false, 1, true, 0, true },
+    { true, 1, true, 0, true },
+    { false, 1, true, 1, true },
+    { true, 1, true, 1, true },
+    { false, 1, true, 0x100000000ULL, true },
+    { true, 1, true, 0x100000000ULL, true },
+    { false, 1, false, 0, false },
+    { true, 1, false, 0, false },
+    { false, 1, false, 1, false },
+    { true, 1, false, 1, false },
+    { false, 1, false, 0x100000000ULL, false },
+    { true, 1, false, 0x100000000ULL, false },
+    { false, 0x7ffe, true, 0, true },
+    { true, 0x7ffe, true, 0, true },
+    { false, 0x7ffe, true, 1, true },
+    { true, 0x7ffe, true, 1, true },
+    { false, 0x7ffe, true, 0x100000000ULL, true },
+    { true, 0x7ffe, true, 0x100000000ULL, true },
+    { false, 0x7ffe, false, 0, false },
+    { true, 0x7ffe, false, 0, false },
+    { false, 0x7ffe, false, 1, false },
+    { true, 0x7ffe, false, 1, false },
+    { false, 0x7ffe, false, 0x100000000ULL, false },
+    { true, 0x7ffe, false, 0x100000000ULL, false },
+    { false, 0x7fff, true, 0, true },
+    { true, 0x7fff, true, 0, true },
+    { false, 0x7fff, true, 1, true },
+    { true, 0x7fff, true, 1, true },
+    { false, 0x7fff, true, 0x100000000ULL, true },
+    { true, 0x7fff, true, 0x100000000ULL, true },
+    { false, 0x7fff, false, 0, M68K_VARIANT },
+    { true, 0x7fff, false, 0, M68K_VARIANT },
+    { false, 0x7fff, false, 1, M68K_VARIANT },
+    { true, 0x7fff, false, 1, M68K_VARIANT },
+    { false, 0x7fff, false, 0x100000000ULL, M68K_VARIANT },
+    { true, 0x7fff, false, 0x100000000ULL, M68K_VARIANT },
+  };
+
+static int
+do_test (void)
+{
+  int result = 0;
+
+  for (size_t i = 0; i < sizeof (tests) / sizeof (tests[0]); i++)
+    {
+      long double ld;
+      SET_LDOUBLE_WORDS (ld, tests[i].exponent | (tests[i].sign << 15),
+			 (tests[i].mantissa >> 32) | (tests[i].high << 31),
+			 tests[i].mantissa & 0xffffffffULL);
+      bool canonical = iscanonical (ld);
+      if (canonical == tests[i].canonical)
+	printf ("PASS: test %zu\n", i);
+      else
+	{
+	  printf ("FAIL: test %zu\n", i);
+	  result = 1;
+	}
+    }
+
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/sysdeps/unix/sysv/linux/i386/libm.abilist b/sysdeps/unix/sysv/linux/i386/libm.abilist
index 63b8da9..19e9792 100644
--- a/sysdeps/unix/sysv/linux/i386/libm.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libm.abilist
@@ -423,6 +423,7 @@ GLIBC_2.24 nextup F
 GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/ia64/libm.abilist b/sysdeps/unix/sysv/linux/ia64/libm.abilist
index 611a84f..1a32e2c 100644
--- a/sysdeps/unix/sysv/linux/ia64/libm.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libm.abilist
@@ -352,6 +352,7 @@ GLIBC_2.24 nextup F
 GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist
index 77f9c7b..2a8cba4 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist
@@ -421,6 +421,7 @@ GLIBC_2.24 nextup F
 GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist
index 456f47e..155daf5 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist
@@ -423,6 +423,7 @@ GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
 GLIBC_2.25 __fe_dfl_mode D 0x8
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist
index b2e4a73..7b38632 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist
@@ -422,6 +422,7 @@ GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
 GLIBC_2.25 __fe_dfl_mode D 0x8
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist
index 907d8b7..26c8d41 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist
@@ -417,6 +417,7 @@ GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
 GLIBC_2.25 __fe_dfl_mode D 0x8
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist
index 307423d..0e76e88 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist
@@ -98,6 +98,7 @@ GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
 GLIBC_2.25 __fe_dfl_mode D 0x8
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libm.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libm.abilist
index 65e5bae..1965316 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libm.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libm.abilist
@@ -412,6 +412,7 @@ GLIBC_2.24 nextup F
 GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist
index ff520cb..82207c9 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist
@@ -411,6 +411,7 @@ GLIBC_2.24 nextup F
 GLIBC_2.24 nextupf F
 GLIBC_2.24 nextupl F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __iscanonicall F
 GLIBC_2.25 fegetmode F
 GLIBC_2.25 fesetexcept F
 GLIBC_2.25 fesetmode F
