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diff --git a/winsup/mingw/mingwex/math/expm1l.c b/winsup/mingw/mingwex/math/expm1l.c
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+/*
+ * Written 2005 by Gregory W. Chicares <chicares@cox.net> with
+ * help from Danny Smith. dannysmith@users.sourceforge.net>.
+ * Public domain.
+ *
+ * F2XM1's input is constrained to (-1, +1), so the domain of
+ * 'x * LOG2EL' is (-LOGE2L, +LOGE2L). Outside that domain,
+ * delegating to expl() handles C99 7.12.6.3/2 range errors.
+ *
+ * Constants from moshier.net, file cephes/ldouble/constl.c,
+ * are used instead of M_LN2 and M_LOG2E, which would not be
+ * visible with 'gcc std=c99'.  The use of these extended precision
+ * constants also allows gcc to replace them with x87 opcodes.
+ */
+
+#include <math.h> /* expl() */
+#include "cephes_mconf.h"
+
+long double expm1l (long double x)
+{
+  if (fabsl(x) < LOGE2L)
+    {
+      x *= LOG2EL;
+      __asm__("f2xm1" : "=t" (x) : "0" (x));
+      return x;
+    }
+  else
+    return expl(x) - 1.0L;
+}