avutil/tablegen: add tablegen libm compatibility shims

This is useful for build-time table generation (--enable-hardcoded-tables),
by providing compat shims for hosts that have broken libms.

This file is deliberately kept minimal; functions can always be added on
an as-needed basis.

Reviewed-by: Clément Bœsch <u@pkh.me>
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

libavutil/tablegen.h

@@ -0,0 +1,53 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Compatibility libm for table generation files
+ */
+
+#ifndef AVUTIL_TABLEGEN_H
+#define AVUTIL_TABLEGEN_H
+
+// we lack some functions on all host platforms, and we don't care about
+// performance and/or strict ISO C semantics as it's performed at build time
+static inline double ff_cbrt(double x)
+{
+    return x < 0 ? -pow(-x, 1.0 / 3.0) : pow(x, 1.0 / 3.0);
+}
+#define cbrt ff_cbrt
+
+static inline double ff_rint(double x)
+{
+    return x >= 0 ? floor(x + 0.5) : ceil(x - 0.5);
+}
+#define rint ff_rint
+
+static inline long long ff_llrint(double x)
+{
+    return rint(x);
+}
+#define llrint ff_llrint
+
+static inline long ff_lrint(double x)
+{
+    return rint(x);
+}
+#define lrint ff_lrint
+
+#endif /* AVUTIL_TABLEGEN_H */