util: Helper function to determined whether two formats can be memcpy'ed.

These are the non-trivial conversions that this function recognizes,
which was produced by u_format_compatible_test.c:

  b8g8r8a8_unorm -> b8g8r8x8_unorm
  a8r8g8b8_unorm -> x8r8g8b8_unorm
  b5g5r5a1_unorm -> b5g5r5x1_unorm
  b4g4r4a4_unorm -> b4g4r4x4_unorm
  l8_unorm -> r8_unorm
  i8_unorm -> l8_unorm
  i8_unorm -> a8_unorm
  i8_unorm -> r8_unorm
  l16_unorm -> r16_unorm
  z24_unorm_s8_uscaled -> z24x8_unorm
  s8_uscaled_z24_unorm -> x8z24_unorm
  r8g8b8a8_unorm -> r8g8b8x8_unorm
  a8b8g8r8_srgb -> x8b8g8r8_srgb
  b8g8r8a8_srgb -> b8g8r8x8_srgb
  a8r8g8b8_srgb -> x8r8g8b8_srgb
  a8b8g8r8_unorm -> x8b8g8r8_unorm
  r10g10b10a2_uscaled -> r10g10b10x2_uscaled
  r10sg10sb10sa2u_norm -> r10g10b10x2_snorm

State trackers and pipe drivers should be updated to take advantage of
this knowledge, e.g., in surface_copy.

src/gallium/auxiliary/util/u_format.c

@@ -120,6 +120,54 @@ util_format_write_4ub(enum pipe_format format, const uint8_t *src, unsigned src_
 }
 
 
+boolean
+util_is_format_compatible(const struct util_format_description *src_desc,
+                          const struct util_format_description *dst_desc)
+{
+   unsigned chan;
+
+   if (src_desc->format == dst_desc->format) {
+      return TRUE;
+   }
+
+   if (src_desc->layout != UTIL_FORMAT_LAYOUT_PLAIN ||
+       dst_desc->layout != UTIL_FORMAT_LAYOUT_PLAIN) {
+      return FALSE;
+   }
+
+   if (src_desc->block.bits != dst_desc->block.bits ||
+       src_desc->nr_channels != dst_desc->nr_channels ||
+       src_desc->colorspace != dst_desc->colorspace) {
+      return FALSE;
+   }
+
+   for (chan = 0; chan < 4; ++chan) {
+      if (src_desc->channel[chan].size !=
+          dst_desc->channel[chan].size) {
+         return FALSE;
+      }
+   }
+
+   for (chan = 0; chan < 4; ++chan) {
+      enum util_format_swizzle swizzle = dst_desc->swizzle[chan];
+
+      if (swizzle < 4) {
+         if (src_desc->swizzle[chan] != swizzle) {
+            return FALSE;
+         }
+         if ((src_desc->channel[swizzle].type !=
+              dst_desc->channel[swizzle].type) ||
+             (src_desc->channel[swizzle].normalized !=
+              dst_desc->channel[swizzle].normalized)) {
+            return FALSE;
+         }
+      }
+   }
+
+   return TRUE;
+}
+
+
 boolean
 util_format_fits_8unorm(const struct util_format_description *format_desc)
 {
@@ -193,7 +241,10 @@ util_format_translate(enum pipe_format dst_format,
    unsigned dst_step;
    unsigned src_step;
 
-   if (dst_format == src_format) {
+   dst_format_desc = util_format_description(dst_format);
+   src_format_desc = util_format_description(src_format);
+
+   if (util_is_format_compatible(src_format_desc, dst_format_desc)) {
       /*
        * Trivial case.
        */
@@ -204,9 +255,6 @@ util_format_translate(enum pipe_format dst_format,
       return;
    }
 
-   dst_format_desc = util_format_description(dst_format);
-   src_format_desc = util_format_description(src_format);
-
    assert(dst_x % dst_format_desc->block.width == 0);
    assert(dst_y % dst_format_desc->block.height == 0);
    assert(src_x % src_format_desc->block.width == 0);

src/gallium/auxiliary/util/u_format.h

@@ -473,6 +473,15 @@ util_format_colormask(const struct util_format_description *desc)
 }
 
 
+/**
+ * Whether the src format can be blitted to destation format with a simple
+ * memcpy.
+ */
+boolean
+util_is_format_compatible(const struct util_format_description *src_desc,
+                          const struct util_format_description *dst_desc);
+
+
 /**
  * Whether this format is a rgab8 variant.
  *

src/gallium/tests/unit/Makefile

@@ -23,6 +23,7 @@ SOURCES = \
 	u_cache_test.c \
 	u_half_test.c \
 	u_format_test.c \
+	u_format_compatible_test.c \
 	translate_test.c
 
 

src/gallium/tests/unit/SConscript

@@ -14,6 +14,7 @@ progs = [
     'pipe_barrier_test',
     'u_cache_test',
     'u_format_test',
+    'u_format_compatible_test',
     'u_half_test',
     'translate_test'
 ]

src/gallium/tests/unit/u_format_compatible_test.c

@@ -0,0 +1,76 @@
+/**************************************************************************
+ *
+ * Copyright 2009-2010 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * 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.
+ *
+ **************************************************************************/
+
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "util/u_format.h"
+
+
+static boolean
+test_all(void)
+{
+   enum pipe_format src_format;
+   enum pipe_format dst_format;
+
+   for (src_format = 1; src_format < PIPE_FORMAT_COUNT; ++src_format) {
+      const struct util_format_description *src_format_desc;
+      src_format_desc = util_format_description(src_format);
+      if (!src_format_desc) {
+         continue;
+      }
+
+      for (dst_format = 1; dst_format < PIPE_FORMAT_COUNT; ++dst_format) {
+	 const struct util_format_description *dst_format_desc;
+	 dst_format_desc = util_format_description(dst_format);
+	 if (!dst_format_desc) {
+	    continue;
+	 }
+
+         if (dst_format == src_format) {
+            continue;
+         }
+
+	 if (util_is_format_compatible(src_format_desc, dst_format_desc)) {
+	    debug_printf("%s -> %s\n", src_format_desc->short_name, dst_format_desc->short_name);
+	 }
+      }
+   }
+
+   return TRUE;
+}
+
+
+int main(int argc, char **argv)
+{
+   boolean success;
+
+   success = test_all();
+
+   return success ? 0 : 1;
+}