ir3_compiler/nir: fix imageSize() for buffer-backed images

[mesa.git] / src / gallium / drivers / freedreno / ir3 / ir3_shader.c

diff --git a/src/gallium/drivers/freedreno/ir3/ir3_shader.c b/src/gallium/drivers/freedreno/ir3/ir3_shader.c
index 9bf0a7f999c6d67d3da52e34e4a3b37d42bf3c27..b3127ff8c3844aea31441ff79b079d4ea002b1f6 100644 (file)
--- a/src/gallium/drivers/freedreno/ir3/ir3_shader.c
+++ b/src/gallium/drivers/freedreno/ir3/ir3_shader.c
@@ -699,6 +699,16 @@ emit_image_dims(struct fd_context *ctx, const struct ir3_shader_variant *v,
                                } else {
                                        dims[off + 2] = rsc->slices[lvl].size0;
                                }
+                       } else {
+                               /* For buffer-backed images, the log2 of the format's
+                                * bytes-per-pixel is placed on the 2nd slot. This is useful
+                                * when emitting image_size instructions, for which we need
+                                * to divide by bpp for image buffers. Since the bpp
+                                * can only be power-of-two, the division is implemented
+                                * as a SHR, and for that it is handy to have the log2 of
+                                * bpp as a constant. (log2 = first-set-bit - 1)
+                                */
+                               dims[off + 1] = ffs(dims[off + 0]) - 1;
                        }
                }