Mesa (10.6): mesa/formats: Fix swizzle flipping for big-endian targets

[Emil Velikov]

Module: Mesa
Branch: 10.6
Commit: 096282a662a303c24f5de5d8a0eeb16239f0c537
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=096282a662a303c24f5de5d8a0eeb16239f0c537

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Sun Aug  9 23:45:44 2015 -0700

mesa/formats: Fix swizzle flipping for big-endian targets

The swizzle defines where in the format you should look for any given
channel.  When we flip the format around for BE targets, we need to change
the destinations of the swizzles, not the sources.  For example, say the
format is an RGBX format with a swizzle of xyz1 on LE.  Then it should be
wzy1 on BE;  however, the code as it was before, would have made it 1zyx on
BE which is clearly wrong.

Reviewed-by: Iago Toral <itoral at igalia.com>
Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>
Cc: "10.6 10.5" <mesa-stable at lists.freedesktop.org>
(cherry picked from commit 28d1a506c8d09fa66170978c85566c34cbf1cc0a)

---

 src/mesa/main/formats.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/mesa/main/formats.c b/src/mesa/main/formats.c
index 99a5ad3..a20a41d 100644
--- a/src/mesa/main/formats.c
+++ b/src/mesa/main/formats.c
@@ -354,14 +354,22 @@ _mesa_array_format_flip_channels(mesa_array_format format)
       return format;
 
    if (num_channels == 2) {
-      _mesa_array_format_set_swizzle(&format, swizzle[1], swizzle[0],
-                                     swizzle[2], swizzle[3]);
+      /* Assert that the swizzle makes sense for 2 channels */
+      for (unsigned i = 0; i < 4; i++)
+         assert(swizzle[i] != 2 && swizzle[i] != 3);
+
+      static const uint8_t flip_xy[6] = { 1, 0, 2, 3, 4, 5 };
+      _mesa_array_format_set_swizzle(&format,
+                                     flip_xy[swizzle[0]], flip_xy[swizzle[1]],
+                                     flip_xy[swizzle[2]], flip_xy[swizzle[3]]);
       return format;
    }
 
    if (num_channels == 4) {
-      _mesa_array_format_set_swizzle(&format, swizzle[3], swizzle[2],
-                                     swizzle[1], swizzle[0]);
+      static const uint8_t flip[6] = { 3, 2, 1, 0, 4, 5 };
+      _mesa_array_format_set_swizzle(&format,
+                                     flip[swizzle[0]], flip[swizzle[1]],
+                                     flip[swizzle[2]], flip[swizzle[3]]);
       return format;
    }