mesa: Add _mesa_format_fallback_rgbx_to_rgba() [v2]

The new function takes a mesa_format and, if the format is an alpha
format with a non-alpha variant, returns the non-alpha format.
Otherwise, it returns the original format.

Example:
  input -> output

  // Fallback exists
  MESA_FORMAT_R8G8B8X8_UNORM -> MESA_FORMAT_R8G8B8A8_UNORM
  MESA_FORMAT_RGBX_UNORM16 -> MESA_FORMAT_RGBA_UNORM16

  // No fallback
  MESA_FORMAT_R8G8B8A8_UNORM -> MESA_FORMAT_R8G8B8A8_UNORM
  MESA_FORMAT_Z_FLOAT32 -> MESA_FORMAT_Z_FLOAT32

i965 will use this for EGLImages and DRIimages.

v2 (Jason Ekstrand):
 - Use mako
 - Rework to be easier to read
 - Write directly to the output file

Reviewed-by: Kenneth Graunke <[email protected]>

3 files changed, 108 insertions, 0 deletions

diff --git a/src/mesa/main/.gitignore b/src/mesa/main/.gitignore
index 836d8f104a8..8cc33cfee68 100644
--- a/src/mesa/main/.gitignore
+++ b/src/mesa/main/.gitignore
@@ -4,6 +4,7 @@ enums.c
 remap_helper.h
 get_hash.h
 get_hash.h.tmp
+format_fallback.c
 format_info.h
 format_info.c
 format_pack.c
diff --git a/src/mesa/main/format_fallback.py b/src/mesa/main/format_fallback.py
new file mode 100644
index 00000000000..e3b9916f6ee
--- /dev/null
+++ b/src/mesa/main/format_fallback.py
@@ -0,0 +1,104 @@
+COPYRIGHT = """\
+/*
+ * Copyright 2017 Google
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+"""
+
+# stdlib
+import argparse
+from sys import stdout
+from mako.template import Template
+
+# local
+import format_parser
+
+def parse_args():
+    p = argparse.ArgumentParser()
+    p.add_argument("csv")
+    p.add_argument("out")
+    return p.parse_args()
+
+def get_rgbx_to_rgba_map(formats):
+    names = {fmt.name for fmt in formats}
+
+    for fmt in formats:
+        if not fmt.has_channel('r') or not fmt.has_channel('x'):
+            continue
+
+        # The condition above will still let MESA_FORMAT_R9G9B9E5_FLOAT
+        # through.  We need to ensure it actually has an X in the name.
+        if not 'X' in fmt.name:
+            continue
+
+        rgbx_name = fmt.name
+        rgba_name = rgbx_name.replace("X", "A")
+        if rgba_name not in names:
+            continue;
+
+        yield rgbx_name, rgba_name
+
+TEMPLATE = Template(COPYRIGHT + """
+#include "formats.h"
+
+/**
+ * If the format has an alpha channel, and there exists a non-alpha
+ * variant of the format with an identical bit layout, then return
+ * the non-alpha format. Otherwise return the original format.
+ *
+ * Examples:
+ *    Fallback exists:
+ *       MESA_FORMAT_R8G8B8X8_UNORM -> MESA_FORMAT_R8G8B8A8_UNORM
+ *       MESA_FORMAT_RGBX_UNORM16 -> MESA_FORMAT_RGBA_UNORM16
+ *
+ *    No fallback:
+ *       MESA_FORMAT_R8G8B8A8_UNORM -> MESA_FORMAT_R8G8B8A8_UNORM
+ *       MESA_FORMAT_Z_FLOAT32 -> MESA_FORMAT_Z_FLOAT32
+ */
+mesa_format
+_mesa_format_fallback_rgbx_to_rgba(mesa_format format)
+{
+   switch (format) {
+%for rgbx, rgba in rgbx_to_rgba_map:
+   case ${rgbx}:
+      return ${rgba};
+%endfor
+   default:
+      return format;
+   }
+}
+""");
+
+def main():
+    pargs = parse_args()
+
+    formats = list(format_parser.parse(pargs.csv))
+
+    template_env = {
+        'rgbx_to_rgba_map': list(get_rgbx_to_rgba_map(formats)),
+    }
+
+    with open(pargs.out, 'w') as f:
+        f.write(TEMPLATE.render(**template_env))
+
+if __name__ == "__main__":
+    main()
diff --git a/src/mesa/main/formats.h b/src/mesa/main/formats.h
index b88466f0368..62b5e0c1a7e 100644
--- a/src/mesa/main/formats.h
+++ b/src/mesa/main/formats.h
@@ -762,6 +762,9 @@ _mesa_format_matches_format_and_type(mesa_format mesa_format,
 				     GLenum format, GLenum type,
 				     GLboolean swapBytes, GLenum *error);
 
+mesa_format
+_mesa_format_fallback_rgbx_to_rgba(mesa_format format);
+
 #ifdef __cplusplus
 }
 #endif