[Mesa-dev] [PATCH 1/2] mesa: compute sampler index in ir_to_mesa rather than using UniformHash

[Timothy Arceri]

The aim of this is to work towards removing UniformHash from the program
struct so that we don't need to hold onto it in memory and pass it around
outside the linker.
---

 Note: This series applies on top of Dave's AoA series.

 src/mesa/program/ir_to_mesa.cpp | 81 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 3 deletions(-)

diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index 768d921..b4d88c9 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -1539,6 +1539,82 @@ get_assignment_lhs(ir_dereference *ir, ir_to_mesa_visitor *v)
    return dst_reg(v->result);
 }
 
+/* Calculate the sampler index and also calculate the base uniform location
+ * for struct members.
+ */
+static void
+calc_sampler_offsets(struct gl_shader_program *prog, ir_dereference *deref,
+                     unsigned *offset, unsigned *array_elements,
+                     unsigned *location)
+{
+   if (deref->ir_type == ir_type_dereference_variable)
+      return;
+
+   switch (deref->ir_type) {
+   case ir_type_dereference_array: {
+      ir_dereference_array *deref_arr = deref->as_dereference_array();
+      ir_constant *array_index =
+         deref_arr->array_index->constant_expression_value();
+
+      if (!array_index) {
+	 /* GLSL 1.10 and 1.20 allowed variable sampler array indices,
+	  * while GLSL 1.30 requires that the array indices be
+	  * constant integer expressions.  We don't expect any driver
+	  * to actually work with a really variable array index, so
+	  * all that would work would be an unrolled loop counter that ends
+	  * up being constant above.
+	  */
+	 ralloc_strcat(&prog->InfoLog,
+		       "warning: Variable sampler array index unsupported.\n"
+		       "This feature of the language was removed in GLSL 1.20 "
+		       "and is unlikely to be supported for 1.10 in Mesa.\n");
+      } else {
+         *offset += array_index->value.u[0] * *array_elements;
+      }
+
+      *array_elements *= deref_arr->array->type->length;
+
+      calc_sampler_offsets(prog, deref_arr->array->as_dereference(),
+                           offset, array_elements, location);
+      break;
+   }
+
+   case ir_type_dereference_record: {
+      ir_dereference_record *deref_record = deref->as_dereference_record();
+      unsigned field_index =
+         deref_record->record->type->field_index(deref_record->field);
+      *location +=
+         deref_record->record->type->record_location_offset(field_index);
+      calc_sampler_offsets(prog, deref_record->record->as_dereference(),
+                           offset, array_elements, location);
+      break;
+   }
+
+   default:
+      unreachable("Invalid deref type");
+      break;
+   }
+}
+
+static int
+get_sampler_uniform_value(class ir_dereference *sampler,
+                          struct gl_shader_program *shader_program,
+                          const struct gl_program *prog)
+{
+   GLuint shader = _mesa_program_enum_to_shader_stage(prog->Target);
+   ir_variable *var = sampler->variable_referenced();
+   unsigned location = var->data.location;
+   unsigned array_elements = 1;
+   unsigned offset = 0;
+
+   calc_sampler_offsets(shader_program, sampler, &offset, &array_elements,
+                        &location);
+
+   assert(shader_program->UniformStorage[location].opaque[shader].active);
+   return shader_program->UniformStorage[location].opaque[shader].index +
+          offset;
+}
+
 /**
  * Process the condition of a conditional assignment
  *
@@ -1988,9 +2064,8 @@ ir_to_mesa_visitor::visit(ir_texture *ir)
    if (ir->shadow_comparitor)
       inst->tex_shadow = GL_TRUE;
 
-   inst->sampler = _mesa_get_sampler_uniform_value(ir->sampler,
-						   this->shader_program,
-						   this->prog);
+   inst->sampler = get_sampler_uniform_value(ir->sampler, shader_program,
+                                             prog);
 
    switch (sampler_type->sampler_dimensionality) {
    case GLSL_SAMPLER_DIM_1D:
-- 
2.5.0