shader: on GLES drop write flag for images we read from

On GL WR translates to writable, but on GLES we translate this
to writeonly because for most formats one has to specify one or
the other, so if we have an image with the TGSI WR specification,
and read from it, we drop the Writable flag. For the images that
allow RW this is of no consequence, and for the others a write
access will fail instead of the read access, but this doesn't
constitue a regression because we couldn't do both - read and
write - anyway.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>

src/vrend_shader.c

@@ -2715,6 +2715,15 @@ translate_load(struct dump_ctx *ctx,
          break;
       }
 
+      /* On GL WR translates to writable, but on GLES we translate this to writeonly
+       * because for most formats one has to specify one or the other, so if we have an
+       * image with the TGSI WR specification, and read from it, we drop the Writable flag.
+       * For the images that allow RW this is of no consequence, and for the others a write
+       * access will fail instead of the read access, but this doesn't constitue a regression
+       * because we couldn't do both, read and write, anyway. */
+      if (ctx->cfg->use_gles && ctx->images[sinfo->sreg_index].decl.Writable)
+         ctx->images[sinfo->sreg_index].decl.Writable = 0;
+
       emit_buff(ctx, "%s = %s(imageLoad(%s, %s(%s(%s))%s)%s);\n", dsts[0], get_string(dtypeprefix), srcs[0],
                get_string(coord_prefix), conversion, srcs[1], ms_str, wm);
    } else if (src->Register.File == TGSI_FILE_BUFFER ||