intel/compiler: Fix illegal mutation in get_nir_image_intrinsic_image

get_nir_image_intrinsic_image() was incorrectly mutating the value held
by the register which holds the intrinsic's first source (image index).

If this happened to be the register for an SSA def which is also used
elsewhere in the program, this meant that we would clobber that value
in subsequent uses.

Note that this only affects i965, because neither anv nor iris use the
binding table start sections, so nothing is ever added here.

Fixes KHR-GL46.compute_shader.resources-max on i965 with Eric Anholt's
MR !3240 applied.  That MR reorders SSBOs and ABOs, so that test uses
image 0 and SSBO 0, causing this code to brilliantly add binding table
index 45 to both the image (correct) and the SSBO (bzzt, wrong!).

Fixes: 09f1de97a76 ("anv,i965: Lower away image derefs in the driver")
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3404>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3404>

diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index fca69bd184d64dd9c57a810f4a6884e15ec758f0..886751d066211ef61d356c7db43ce27c48ed5d0a 100644 (file)
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -3976,17 +3976,20 @@ fs_visitor::get_nir_image_intrinsic_image(const brw::fs_builder &bld,
                                           nir_intrinsic_instr *instr)
 {
    fs_reg image = retype(get_nir_src_imm(instr->src[0]), BRW_REGISTER_TYPE_UD);
+   fs_reg surf_index = image;
 
    if (stage_prog_data->binding_table.image_start > 0) {
       if (image.file == BRW_IMMEDIATE_VALUE) {
-         image.d += stage_prog_data->binding_table.image_start;
+         surf_index =
+            brw_imm_ud(image.d + stage_prog_data->binding_table.image_start);
       } else {
-         bld.ADD(image, image,
+         surf_index = vgrf(glsl_type::uint_type);
+         bld.ADD(surf_index, image,
                  brw_imm_d(stage_prog_data->binding_table.image_start));
       }
    }
 
-   return bld.emit_uniformize(image);
+   return bld.emit_uniformize(surf_index);
 }
 
 fs_reg