i915: Blit RGBX<->RGBA drawpixels

The blitter already has code to accommodate filling in the alpha channel
for BGRX destination formats, so expand this to also allow filling the
alpha channgel in RGBX formats.

More importantly for the next patch is moving the test into its own
function for the purpose of exporting the check to the callers.

v2: Fix alpha expansion as spotted by Alexander with the fix suggested by
Kenneth

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Alexander Monakov <amonakov@gmail.com>
Cc: Kristian Høgsberg <krh@bitplanet.net>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by Kenneth Graunke <kenneth@whitecape.org>
Cc: mesa-stable@lists.freedesktop.org

(cherry picked from commit c2d0606827412b710dcaed80268fc665de8c9c5d)

1 files changed, 29 insertions, 7 deletions

diff --git a/src/mesa/drivers/dri/i965/intel_blit.c b/src/mesa/drivers/dri/i965/intel_blit.c
index 247816d20f..efdbfe7ca5 100644
--- a/src/mesa/drivers/dri/i965/intel_blit.c
+++ b/src/mesa/drivers/dri/i965/intel_blit.c
@@ -139,6 +139,31 @@ blt_pitch(struct intel_mipmap_tree *mt)
    return pitch;
 }
 
+static bool
+blt_compatible_formats(mesa_format src, mesa_format dst)
+{
+   /* The BLT doesn't handle sRGB conversion */
+   assert(src == _mesa_get_srgb_format_linear(src));
+   assert(dst == _mesa_get_srgb_format_linear(dst));
+
+   /* No swizzle or format conversions possible, except... */
+   if (src == dst)
+      return true;
+
+   /* ...we can either discard the alpha channel when going from A->X,
+    * or we can fill the alpha channel with 0xff when going from X->A
+    */
+   if (src == MESA_FORMAT_B8G8R8A8_UNORM || src == MESA_FORMAT_B8G8R8X8_UNORM)
+      return (dst == MESA_FORMAT_B8G8R8A8_UNORM ||
+              dst == MESA_FORMAT_B8G8R8X8_UNORM);
+
+   if (src == MESA_FORMAT_R8G8B8A8_UNORM || src == MESA_FORMAT_R8G8B8X8_UNORM)
+      return (dst == MESA_FORMAT_R8G8B8A8_UNORM ||
+              dst == MESA_FORMAT_R8G8B8X8_UNORM);
+
+   return false;
+}
+
 /**
  * Implements a rectangular block transfer (blit) of pixels between two
  * miptrees.
@@ -181,11 +206,7 @@ intel_miptree_blit(struct brw_context *brw,
     * the X channel don't matter), and XRGB8888 to ARGB8888 by setting the A
     * channel to 1.0 at the end.
     */
-   if (src_format != dst_format &&
-      ((src_format != MESA_FORMAT_B8G8R8A8_UNORM &&
-        src_format != MESA_FORMAT_B8G8R8X8_UNORM) ||
-       (dst_format != MESA_FORMAT_B8G8R8A8_UNORM &&
-        dst_format != MESA_FORMAT_B8G8R8X8_UNORM))) {
+   if (!blt_compatible_formats(src_format, dst_format)) {
       perf_debug("%s: Can't use hardware blitter from %s to %s, "
                  "falling back.\n", __FUNCTION__,
                  _mesa_get_format_name(src_format),
@@ -270,8 +291,9 @@ intel_miptree_blit(struct brw_context *brw,
       return false;
    }
 
-   if (src_mt->format == MESA_FORMAT_B8G8R8X8_UNORM &&
-       dst_mt->format == MESA_FORMAT_B8G8R8A8_UNORM) {
+   /* XXX This could be done in a single pass using XY_FULL_MONO_PATTERN_BLT */
+   if (_mesa_get_format_bits(src_format, GL_ALPHA_BITS) == 0 &&
+       _mesa_get_format_bits(dst_format, GL_ALPHA_BITS) > 0) {
       intel_miptree_set_alpha_to_one(brw, dst_mt,
                                      dst_x, dst_y,
                                      width, height);