Mesa (master): iris: Convert RGBX to RGBA always.

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Module: Mesa
Branch: master
Commit: 1281368d02a22d08a892fbfda4cecc1219cde895
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1281368d02a22d08a892fbfda4cecc1219cde895

Author: Rafael Antognolli <rafael.antognolli at intel.com>
Date:   Thu Mar  7 15:32:38 2019 -0800

iris: Convert RGBX to RGBA always.

In i965, we disable the use of RGBX formats, so the higher layers of
Mesa choose the equivalent RGBA format, and swizzle the alpha channel to
1.0.

However, Gallium won't do that. We need to explicitly convert it to
RGBA.

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

 src/gallium/drivers/iris/iris_formats.c | 41 ++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/src/gallium/drivers/iris/iris_formats.c b/src/gallium/drivers/iris/iris_formats.c
index 91c86efca4d..ec7fd77f3a9 100644
--- a/src/gallium/drivers/iris/iris_formats.c
+++ b/src/gallium/drivers/iris/iris_formats.c
@@ -344,20 +344,33 @@ iris_format_for_usage(const struct gen_device_info *devinfo,
       swizzle = ISL_SWIZZLE(RED, GREEN, BLUE, ONE);
    }
 
-   if (usage & ISL_SURF_USAGE_RENDER_TARGET_BIT) {
-      if (isl_format_is_rgbx(format) &&
-          !isl_format_supports_rendering(devinfo, format)) {
-         format = isl_format_rgbx_to_rgba(format);
-      } else if (pformat == PIPE_FORMAT_A8_UNORM) {
-         /* Most of the hardware A/LA formats are not renderable, except
-          * for A8_UNORM.  SURFACE_STATE's shader channel select fields
-          * cannot be used to swap RGB and A channels when rendering (as
-          * it could impact alpha blending), so we have to use the actual
-          * A8_UNORM format when rendering.
-          */
-         format = ISL_FORMAT_A8_UNORM;
-         swizzle = ISL_SWIZZLE_IDENTITY;
-      }
+   if ((usage & ISL_SURF_USAGE_RENDER_TARGET_BIT) &&
+       pformat == PIPE_FORMAT_A8_UNORM) {
+      /* Most of the hardware A/LA formats are not renderable, except
+       * for A8_UNORM.  SURFACE_STATE's shader channel select fields
+       * cannot be used to swap RGB and A channels when rendering (as
+       * it could impact alpha blending), so we have to use the actual
+       * A8_UNORM format when rendering.
+       */
+      format = ISL_FORMAT_A8_UNORM;
+      swizzle = ISL_SWIZZLE_IDENTITY;
+   }
+
+   /* We choose RGBA over RGBX for rendering the hardware doesn't support
+    * rendering to RGBX. However, when this internal override is used on Gen9+,
+    * fast clears don't work correctly.
+    *
+    * i965 fixes this by pretending to not support RGBX formats, and the higher
+    * layers of Mesa pick the RGBA format instead. Gallium doesn't work that
+    * way, and might choose a different format, like BGRX instead of RGBX,
+    * which will also cause problems when sampling from a surface fast cleared
+    * as RGBX. So we always choose RGBA instead of RGBX explicitly
+    * here.
+    */
+   if (isl_format_is_rgbx(format) &&
+       !isl_format_supports_rendering(devinfo, format)) {
+      format = isl_format_rgbx_to_rgba(format);
+      swizzle = ISL_SWIZZLE(RED, GREEN, BLUE, ONE);
    }
 
    return (struct iris_format_info) { .fmt = format, .swizzle = swizzle };