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-rw-r--r--math/s_clog10l.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/math/s_clog10l.c b/math/s_clog10l.c
index 2a380f6f3b..d50f616578 100644
--- a/math/s_clog10l.c
+++ b/math/s_clog10l.c
@@ -22,6 +22,13 @@
#include <math_private.h>
#include <float.h>
+/* To avoid spurious underflows, use this definition to treat IBM long
+ double as approximating an IEEE-style format. */
+#if LDBL_MANT_DIG == 106
+# undef LDBL_EPSILON
+# define LDBL_EPSILON 0x1p-106L
+#endif
+
/* log_10 (2). */
#define M_LOG10_2l 0.3010299956639811952137388947244930267682L
@@ -75,6 +82,13 @@ __clog10l (__complex__ long double x)
else
__real__ result = __log1pl (absy2) * (M_LOG10El / 2.0L);
}
+ else if (absx > 1.0L && absx < 2.0L && absy < 1.0L && scale == 0)
+ {
+ long double d2m1 = (absx - 1.0L) * (absx + 1.0L);
+ if (absy >= LDBL_EPSILON)
+ d2m1 += absy * absy;
+ __real__ result = __log1pl (d2m1) * (M_LOG10El / 2.0L);
+ }
else
{
long double d = __ieee754_hypotl (absx, absy);