[Mesa-dev] [PATCH 1/7] blorp: Handle the RGB workaround more like other workarounds

[Jason Ekstrand]

The previous version was sort-of strapped on in that it just adjusted
the blit rectangle and trusted in the fact that we would use texelFetch
and round to the nearest integer to ensure that the component positions
matched.  This new version, while slightly more complicated, is more
accurate because all three components end up with exactly the same
dst_pos and so they will get interpolated and sampled at the same
texture coordinate.  This makes the workaround suitable for using with
scaled blits.
---
 src/intel/blorp/blorp_blit.c | 60 ++++++++++++++++++++++----------------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/src/intel/blorp/blorp_blit.c b/src/intel/blorp/blorp_blit.c
index 111f1c1..fc76fd4 100644
--- a/src/intel/blorp/blorp_blit.c
+++ b/src/intel/blorp/blorp_blit.c
@@ -1138,6 +1138,20 @@ brw_blorp_build_nir_shader(struct blorp_context *blorp, void *mem_ctx,
                                       key->dst_layout);
    }
 
+   nir_ssa_def *comp = NULL;
+   if (key->dst_rgb) {
+      /* The destination image is bound as a red texture three times as wide
+       * as the actual image.  Our shader is effectively running one color
+       * component at a time.  We need to save off the component and adjust
+       * the destination position.
+       */
+      assert(dst_pos->num_components == 2);
+      nir_ssa_def *dst_x = nir_channel(&b, dst_pos, 0);
+      comp = nir_umod(&b, dst_x, nir_imm_int(&b, 3));
+      dst_pos = nir_vec2(&b, nir_idiv(&b, dst_x, nir_imm_int(&b, 3)),
+                             nir_channel(&b, dst_pos, 1));
+   }
+
    /* Now (X, Y, S) = decode_msaa(dst_samples, detile(dst_tiling, offset)).
     *
     * That is: X, Y and S now contain the true coordinates and sample index of
@@ -1267,8 +1281,6 @@ brw_blorp_build_nir_shader(struct blorp_context *blorp, void *mem_ctx,
        * from the source color and write that to destination red.
        */
       assert(dst_pos->num_components == 2);
-      nir_ssa_def *comp =
-         nir_umod(&b, nir_channel(&b, dst_pos, 0), nir_imm_int(&b, 3));
 
       nir_ssa_def *color_component =
          nir_bcsel(&b, nir_ieq(&b, comp, nir_imm_int(&b, 0)),
@@ -1543,15 +1555,12 @@ struct blt_coords {
 
 static void
 surf_fake_rgb_with_red(const struct isl_device *isl_dev,
-                       struct brw_blorp_surface_info *info,
-                       uint32_t *x, uint32_t *width)
+                       struct brw_blorp_surface_info *info)
 {
    surf_convert_to_single_slice(isl_dev, info);
 
    info->surf.logical_level0_px.width *= 3;
    info->surf.phys_level0_sa.width *= 3;
-   *x *= 3;
-   *width *= 3;
 
    enum isl_format red_format;
    switch (info->view.format) {
@@ -1581,28 +1590,6 @@ surf_fake_rgb_with_red(const struct isl_device *isl_dev,
    info->surf.format = info->view.format = red_format;
 }
 
-static void
-fake_dest_rgb_with_red(const struct isl_device *dev,
-                       struct blorp_params *params,
-                       struct brw_blorp_blit_prog_key *wm_prog_key,
-                       struct blt_coords *coords)
-{
-   /* Handle RGB destinations for blorp_copy */
-   const struct isl_format_layout *dst_fmtl =
-      isl_format_get_layout(params->dst.surf.format);
-
-   if (dst_fmtl->bpb % 3 == 0) {
-      uint32_t dst_x = coords->x.dst0;
-      uint32_t dst_width = coords->x.dst1 - dst_x;
-      surf_fake_rgb_with_red(dev, &params->dst,
-                             &dst_x, &dst_width);
-      coords->x.dst0 = dst_x;
-      coords->x.dst1 = dst_x + dst_width;
-      wm_prog_key->dst_rgb = true;
-      wm_prog_key->need_dst_offset = true;
-   }
-}
-
 enum blit_shrink_status {
    BLIT_NO_SHRINK = 0,
    BLIT_WIDTH_SHRINK = 1,
@@ -1621,8 +1608,6 @@ try_blorp_blit(struct blorp_batch *batch,
 {
    const struct gen_device_info *devinfo = batch->blorp->isl_dev->info;
 
-   fake_dest_rgb_with_red(batch->blorp->isl_dev, params, wm_prog_key, coords);
-
    if (isl_format_has_sint_channel(params->src.view.format)) {
       wm_prog_key->texture_data_type = nir_type_int;
    } else if (isl_format_has_uint_channel(params->src.view.format)) {
@@ -1799,6 +1784,21 @@ try_blorp_blit(struct blorp_batch *batch,
 
    params->num_samples = params->dst.surf.samples;
 
+   if (isl_format_get_layout(params->dst.view.format)->bpb % 3 == 0) {
+      /* We can't render to  RGB formats natively because they aren't a
+       * power-of-two size.  Instead, we fake them by using a red format
+       * with the same channel type and size and emitting shader code to
+       * only write one channel at a time.
+       */
+      params->x0 *= 3;
+      params->x1 *= 3;
+
+      surf_fake_rgb_with_red(batch->blorp->isl_dev, &params->dst);
+
+      wm_prog_key->dst_rgb = true;
+      wm_prog_key->need_dst_offset = true;
+   }
+
    if (params->src.tile_x_sa || params->src.tile_y_sa) {
       assert(wm_prog_key->need_src_offset);
       surf_get_intratile_offset_px(&params->src,
-- 
2.5.0.400.gff86faf