14 files changed, 92 insertions, 0 deletions
diff --git a/math/e_exp2_template.c b/math/e_exp2_template.c
index 94a21054c2..30ed4af49b 100644
--- a/math/e_exp2_template.c
+++ b/math/e_exp2_template.c
@@ -18,6 +18,7 @@
 
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 #define declare_mgen_finite_alias_x(from, to) \
diff --git a/math/k_casinh_template.c b/math/k_casinh_template.c
index f7b679e55f..451f05c279 100644
--- a/math/k_casinh_template.c
+++ b/math/k_casinh_template.c
@@ -21,6 +21,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 /* Return the complex inverse hyperbolic sine of finite nonzero Z,
diff --git a/math/math-underflow.h b/math/math-underflow.h
new file mode 100644
index 0000000000..c5e5c79768
--- /dev/null
+++ b/math/math-underflow.h
@@ -0,0 +1,79 @@
+/* Check for underflow and force underflow exceptions.
+   Copyright (C) 2015-2018 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_UNDERFLOW_H
+#define _MATH_UNDERFLOW_H	1
+
+#include <float.h>
+#include <math.h>
+
+#include <math-barriers.h>
+
+#define fabs_tg(x) __MATH_TG ((x), (__typeof (x)) __builtin_fabs, (x))
+
+/* These must be function-like macros because some __MATH_TG
+   implementations macro-expand the function-name argument before
+   concatenating a suffix to it.  */
+#define min_of_type_f() FLT_MIN
+#define min_of_type_() DBL_MIN
+#define min_of_type_l() LDBL_MIN
+#define min_of_type_f128() FLT128_MIN
+
+#define min_of_type(x) __MATH_TG ((x), (__typeof (x)) min_of_type_, ())
+
+/* If X (which is not a NaN) is subnormal, force an underflow
+   exception.  */
+#define math_check_force_underflow(x)				\
+  do								\
+    {								\
+      __typeof (x) force_underflow_tmp = (x);			\
+      if (fabs_tg (force_underflow_tmp)				\
+	  < min_of_type (force_underflow_tmp))			\
+	{							\
+	  __typeof (force_underflow_tmp) force_underflow_tmp2	\
+	    = force_underflow_tmp * force_underflow_tmp;	\
+	  math_force_eval (force_underflow_tmp2);		\
+	}							\
+    }								\
+  while (0)
+/* Likewise, but X is also known to be nonnegative.  */
+#define math_check_force_underflow_nonneg(x)			\
+  do								\
+    {								\
+      __typeof (x) force_underflow_tmp = (x);			\
+      if (force_underflow_tmp					\
+	  < min_of_type (force_underflow_tmp))			\
+	{							\
+	  __typeof (force_underflow_tmp) force_underflow_tmp2	\
+	    = force_underflow_tmp * force_underflow_tmp;	\
+	  math_force_eval (force_underflow_tmp2);		\
+	}							\
+    }								\
+  while (0)
+/* Likewise, for both real and imaginary parts of a complex
+   result.  */
+#define math_check_force_underflow_complex(x)				\
+  do									\
+    {									\
+      __typeof (x) force_underflow_complex_tmp = (x);			\
+      math_check_force_underflow (__real__ force_underflow_complex_tmp); \
+      math_check_force_underflow (__imag__ force_underflow_complex_tmp); \
+    }									\
+  while (0)
+
+#endif /* math-underflow.h */
diff --git a/math/s_catan_template.c b/math/s_catan_template.c
index c3894c5a0a..19f4e11cb4 100644
--- a/math/s_catan_template.c
+++ b/math/s_catan_template.c
@@ -20,6 +20,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_catanh_template.c b/math/s_catanh_template.c
index fdeeb589e1..245a1a6412 100644
--- a/math/s_catanh_template.c
+++ b/math/s_catanh_template.c
@@ -20,6 +20,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_ccosh_template.c b/math/s_ccosh_template.c
index 6840c4819e..1664f0690a 100644
--- a/math/s_ccosh_template.c
+++ b/math/s_ccosh_template.c
@@ -21,6 +21,7 @@
 #include <fenv.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_cexp_template.c b/math/s_cexp_template.c
index e099e42a4c..5fdab1e5ac 100644
--- a/math/s_cexp_template.c
+++ b/math/s_cexp_template.c
@@ -21,6 +21,7 @@
 #include <fenv.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_clog10_template.c b/math/s_clog10_template.c
index 82a52faebf..a947502e94 100644
--- a/math/s_clog10_template.c
+++ b/math/s_clog10_template.c
@@ -20,6 +20,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 /* log_10 (2).  */
diff --git a/math/s_clog_template.c b/math/s_clog_template.c
index 8aa1f74c8b..1248cac593 100644
--- a/math/s_clog_template.c
+++ b/math/s_clog_template.c
@@ -20,6 +20,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_csin_template.c b/math/s_csin_template.c
index d6af614177..5f95e92ee0 100644
--- a/math/s_csin_template.c
+++ b/math/s_csin_template.c
@@ -21,6 +21,7 @@
 #include <fenv.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_csinh_template.c b/math/s_csinh_template.c
index 6466ae80c9..95f28c2b66 100644
--- a/math/s_csinh_template.c
+++ b/math/s_csinh_template.c
@@ -21,6 +21,7 @@
 #include <fenv.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_csqrt_template.c b/math/s_csqrt_template.c
index dcf14c7537..b1153906b9 100644
--- a/math/s_csqrt_template.c
+++ b/math/s_csqrt_template.c
@@ -21,6 +21,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_ctan_template.c b/math/s_ctan_template.c
index af898d8f81..ab11c25299 100644
--- a/math/s_ctan_template.c
+++ b/math/s_ctan_template.c
@@ -21,6 +21,7 @@
 #include <fenv.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT
diff --git a/math/s_ctanh_template.c b/math/s_ctanh_template.c
index 9527ab4ccc..bd1292239f 100644
--- a/math/s_ctanh_template.c
+++ b/math/s_ctanh_template.c
@@ -21,6 +21,7 @@
 #include <fenv.h>
 #include <math.h>
 #include <math_private.h>
+#include <math-underflow.h>
 #include <float.h>
 
 CFLOAT