Add a generic scalb implementation

This is a preparatory patch to enable building a _Float128
variant to ease reuse when building a _Float128 variant to
alias this long double only symbol.

Notably, stubs are added where missing to the native _Float128
sysdep dir to prevent building these newly templated variants
created inside the build directories.

Also noteworthy are the changes around LIBM_SVID_COMPAT.  These
changes are not intuitive.  The templated version is only
enabled when !LIBM_SVID_COMPAT, and the compat version is
predicated entirely on LIBM_SVID_COMPAT.  Thus, exactly one is
stubbed out entirely when building.  The nldbl scalb compat
files are updated to account for this.

Likewise, fixup the reuse of m68k's e_scalb{f,l}.c to include
it's override of e_scalb.c.  Otherwise, the search path finds
the templated copy in the build directory.  This could be
futher simplified by providing an overridden template, but I
lack the hardware to verify.

1 files changed, 57 insertions, 0 deletions

diff --git a/math/w_scalb_template.c b/math/w_scalb_template.c
new file mode 100644
index 0000000000..2745a29580
--- /dev/null
+++ b/math/w_scalb_template.c
@@ -0,0 +1,57 @@
+/* Wrapper to set errno for scalb.
+   Copyright (C) 2020 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/>.  */
+
+/* Only build wrappers from the templates for the types that define the macro
+   below.  This macro is set in math-type-macros-<type>.h in sysdeps/generic
+   for each floating-point type.  */
+#if __USE_WRAPPER_TEMPLATE
+
+#include <errno.h>
+#include <math.h>
+#include <math_private.h>
+
+/* Wrapper scalb */
+FLOAT M_DECL_FUNC (__scalb) (FLOAT x, FLOAT fn)
+{
+  FLOAT z = M_SUF (__ieee754_scalb) (x, fn);
+
+  if (__glibc_unlikely (!isfinite (z) || z == M_LIT (0.0)))
+    {
+      if (isnan (z))
+	{
+	  if (!isnan (x) && !isnan (fn))
+	    __set_errno (EDOM);
+	}
+      else if (isinf (z))
+	{
+	  if (!isinf (x) && !isinf (fn))
+	    __set_errno (ERANGE);
+	}
+      else
+	{
+	  /* z == 0.  */
+	  if (x != M_LIT (0.0) && !isinf (fn))
+	    __set_errno (ERANGE);
+	}
+    }
+  return z;
+}
+
+declare_mgen_alias (__scalb, scalb);
+
+#endif /* __USE_WRAPPER_TEMPLATE.  */