BZ#13889: expl (709.75) wrongly overflows for ldbl-128ibm

The patch increase the high value to check if expl overflows. Current
high mark value is not really correct, the algorithm accepts high values.
It also adds a correct wrapper function to check for overflow and underflow.

2 files changed, 24 insertions, 6 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm/e_expl.c b/sysdeps/ieee754/ldbl-128ibm/e_expl.c
index 82363906b0..9fd61983e3 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_expl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_expl.c
@@ -70,11 +70,11 @@
 static const long double C[] = {
 /* Smallest integer x for which e^x overflows.  */
 #define himark C[0]
- 709.08956571282405153382846025171462914L,
+ 709.78271289338399678773454114191496482L,
 
 /* Largest integer x for which e^x underflows.  */
 #define lomark C[1]
--744.44007192138121808966388925909996033L,
+-744.44007192138126231410729844608163411L,
 
 /* 3x2^96 */
 #define THREEp96 C[2]
diff --git a/sysdeps/ieee754/ldbl-128ibm/w_expl.c b/sysdeps/ieee754/ldbl-128ibm/w_expl.c
index a5e72b2170..70fe5f693e 100644
--- a/sysdeps/ieee754/ldbl-128ibm/w_expl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/w_expl.c
@@ -1,6 +1,24 @@
-/* Looks like we can use ieee854 w_expl.c as is for IBM extended format. */
+#include <math.h>
+#include <math_private.h>
 #include <math_ldbl_opt.h>
-#undef weak_alias
-#define weak_alias(n,a)
-#include <sysdeps/ieee754/ldbl-128/w_expl.c>
+
+static const long double o_thres = 709.78271289338399678773454114191496482L;
+static const long double u_thres = -744.44007192138126231410729844608163411L;
+
+long double __expl(long double x)	/* wrapper exp  */
+{
+  long double z;
+  z = __ieee754_expl(x);
+  if (_LIB_VERSION == _IEEE_)
+    return z;
+  if (__finitel(x))
+    {
+      if (x >= o_thres)
+	return __kernel_standard_l(x,x,206); /* exp overflow  */
+      else if (x <= u_thres)
+	return __kernel_standard_l(x,x,207); /* exp underflow  */
+    }
+  return z;
+}
+hidden_def (__expl)
 long_double_symbol (libm, __expl, expl);