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.

2 files changed, 61 insertions, 4 deletions

diff --git a/src/gallium/auxiliary/util/u_format.c b/src/gallium/auxiliary/util/u_format.c
index 43d09f19607..a4ee91b0cf9 100644
--- a/src/gallium/auxiliary/util/u_format.c
+++ b/src/gallium/auxiliary/util/u_format.c
@@ -121,6 +121,54 @@ 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)
 {
    unsigned chan;
@@ -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);
diff --git a/src/gallium/auxiliary/util/u_format.h b/src/gallium/auxiliary/util/u_format.h
index 59bd03b7740..03b73c0e98f 100644
--- a/src/gallium/auxiliary/util/u_format.h
+++ b/src/gallium/auxiliary/util/u_format.h
@@ -474,6 +474,15 @@ 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.
  *
  * That is, any format that matches the