[gegl] gegl: add gegl-math.h inlinable overrides for some math functions

[Øyvind "pippin" Kolås <ok src gnome org>]

commit b84e7c6c3023b16b51545c9cd99b4b7e718c013d
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed May 27 20:10:29 2020 +0200

    gegl: add gegl-math.h inlinable overrides for some math functions
    
    We sometimes use fabs or fabsf and similar in innerloops, by providing
    our own small snippets for these the compiler is able to inline more
    agressively.

 gegl/gegl-math.h   | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gegl/gegl-plugin.h |  1 +
 gegl/meson.build   |  1 +
 3 files changed, 92 insertions(+)
---
diff --git a/gegl/gegl-math.h b/gegl/gegl-math.h
new file mode 100644
index 000000000..39926e61e
--- /dev/null
+++ b/gegl/gegl-math.h
@@ -0,0 +1,90 @@
+/* This file is part of GEGL
+ *
+ * GEGL 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 3 of the License, or (at your option) any later version.
+ *
+ * GEGL 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 GEGL; if not, see <https://www.gnu.org/licenses/>.
+ *
+ * Copyright 2020 Øyvind Kolås
+ */
+
+#ifndef __GEGL_MATH_H__
+#define __GEGL_MATH_H__
+#ifndef __cplusplus
+
+static inline float gegl_fabsf (float x)
+{
+  union {
+   float f;
+   guint32 i;
+  } u = {x};
+  u.i &= 0x7fffffff;
+  return u.f;
+}
+
+static inline double gegl_fabs (double x)
+{
+  union {
+   double d;
+   guint64 i;
+  } u = {x};
+  u.i &= 0x7fffffffffffffff;
+  return u.d;
+}
+
+static inline float gegl_floorf (float x)
+{
+  int i = (int)x;       /* truncate */
+  return i - ( i > x ); /* convert trunc to floor */
+}
+
+static inline float gegl_ceilf (float x)
+{
+  return - gegl_floorf (-x);
+}
+
+static inline double gegl_floor (double x)
+{
+  gint64 i = (gint64)x; /* truncate */
+  return i - ( i > x ); /* convert trunc to floor */
+}
+
+static inline double  gegl_ceil (double x)
+{
+  return - gegl_floor (-x);
+}
+
+static inline float gegl_fmodf (float x, float y)
+{
+  return x - y * gegl_floorf (x/y);
+}
+
+static inline double gegl_fmod (double x, double y)
+{
+  return x - y * gegl_floor (x/y);
+}
+
+/* in innerloops inlining these is much faster than the overhead of
+ * using implementations from elsewhere (that might be stricter than us
+ * on their behavior on nans and more) */
+
+#define fabs(x)    gegl_fabs(x)
+#define fabsf(x)   gegl_fabsf(x)
+#define floorf(x)  gegl_floorf(x)
+#define floor(x)   gegl_floor(x)
+#define ceilf(x)   gegl_ceilf(x)
+#define ceil(x)    gegl_ceil(x)
+#define fmodf(x,y) gegl_fmodf(x,y)
+#define fmod(x,y)  gegl_fmod(x,y)
+
+
+#endif
+#endif
diff --git a/gegl/gegl-plugin.h b/gegl/gegl-plugin.h
index ea82070b0..bffb310f0 100644
--- a/gegl/gegl-plugin.h
+++ b/gegl/gegl-plugin.h
@@ -28,6 +28,7 @@
 #include <glib-object.h>
 #include <gmodule.h>
 #include <gegl.h>
+#include <gegl-math.h>
 #include <gegl-types.h>
 #include <gegl-paramspecs.h>
 #include <gegl-audio-fragment.h>
diff --git a/gegl/meson.build b/gegl/meson.build
index 7e1bb0e5a..514f62107 100644
--- a/gegl/meson.build
+++ b/gegl/meson.build
@@ -45,6 +45,7 @@ gegl_headers = files(
   'gegl-cpuaccel.h',
   'gegl-debug.h',
   'gegl-op.h',
+  'gegl-math.h',
   'gegl-plugin.h',
 )