[Mesa-dev] [PATCH 1/3] i965/vec4/gs: restore the uniform values which was overwritten by failed vec4_gs_visitor execution

[Samuel Iglesias Gonsálvez]

We are going to add a packing feature to reduce the usage of the push
constant buffer. One of the consequences is that 'nr_params' would be
modified by vec4_visitor's run call, so we need to restore it if one of
them failed before executing the fallback ones. Same thing happens to the
uniforms values that would be reordered afterwards.

Fixes GL45-CTS.arrays_of_arrays_gl.InteractionFunctionCalls2 when
the dvec4 alignment and packing patch is applied.

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
Cc: "17.1" <mesa-stable at lists.freedesktop.org>
---
 src/intel/compiler/brw_vec4_gs_visitor.cpp | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/intel/compiler/brw_vec4_gs_visitor.cpp b/src/intel/compiler/brw_vec4_gs_visitor.cpp
index 4a8b5be30e..5fcd02831a 100644
--- a/src/intel/compiler/brw_vec4_gs_visitor.cpp
+++ b/src/intel/compiler/brw_vec4_gs_visitor.cpp
@@ -868,10 +868,36 @@ brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
 
          vec4_gs_visitor v(compiler, log_data, &c, prog_data, shader,
                            mem_ctx, true /* no_spills */, shader_time_index);
+
+         /* Backup 'nr_params' and 'param' as they can be modified by the
+          * the DUAL_OBJECT visitor. If it fails, we will run the fallback
+          * (DUAL_INSTANCED or SINGLE mode) and we need to restore original
+          * values.
+          */
+         const unsigned param_count = prog_data->base.base.nr_params;
+         gl_constant_value **param = ralloc_array(NULL, gl_constant_value*,
+                                                  param_count);
+         memcpy(param, prog_data->base.base.param,
+                sizeof(gl_constant_value*) * param_count);
+
          if (v.run()) {
+            /* Success! Backup is not needed */
+            ralloc_free(param);
             return brw_vec4_generate_assembly(compiler, log_data, mem_ctx,
                                               shader, &prog_data->base, v.cfg,
                                               final_assembly_size);
+         } else {
+            /* These variables could be modified by the execution of the GS
+             * visitor if it packed the uniforms in the push constant buffer.
+             * As it failed, we need restore them so we can start again with
+             * DUAL_INSTANCED or SINGLE mode.
+             *
+             * FIXME: Could more variables be modified by this execution?
+             */
+            memcpy(prog_data->base.base.param, param,
+                   sizeof(gl_constant_value*) * param_count);
+            prog_data->base.base.nr_params = param_count;
+            ralloc_free(param);
          }
       }
    }
-- 
2.11.0