glsl: Add parser/compiler support for unsized array's length()

The unsized array length is computed with the following formula:

array.length() =
   max((buffer_object_size - offset_of_array) / stride_of_array, 0)

Of these, only the buffer size needs to be provided by the backends, the
frontend already knows the values of the two other variables.

This patch identifies the cases where we need to get the length of an
unsized array, injecting ir_unop_ssbo_unsized_array_length expressions
that will be lowered (in a later patch) to inject the formula mentioned
above.

It also adds the ir_unop_get_buffer_size expression that drivers will
implement to provide the buffer length.

v2:
- Do not define a triop that will force backends to implement the
  entire formula, they should only need to provide the buffer size
  since the other values are known by the frontend (Curro).

v3:
- Call state->has_shader_storage_buffer_objects() in ast_function.cpp instead
  of using state->ARB_shader_storage_buffer_object_enable (Tapani).

Signed-off-by: Samuel Iglesias Gonsalvez <[email protected]>
Reviewed-by: Kristian Høgsberg <[email protected]>

2 files changed, 10 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_channel_expressions.cpp b/src/mesa/drivers/dri/i965/brw_fs_channel_expressions.cpp
index a8883a35ef2..277b6cc3a60 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_channel_expressions.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_channel_expressions.cpp
@@ -379,6 +379,7 @@ ir_channel_expressions_visitor::visit_leave(ir_assignment *ir)
    }
 
    case ir_binop_ubo_load:
+   case ir_unop_get_buffer_size:
       unreachable("not yet supported");
 
    case ir_triop_fma:
@@ -430,6 +431,7 @@ ir_channel_expressions_visitor::visit_leave(ir_assignment *ir)
    case ir_triop_vector_insert:
    case ir_quadop_bitfield_insert:
    case ir_quadop_vector:
+   case ir_unop_ssbo_unsized_array_length:
       unreachable("should have been lowered");
 
    case ir_unop_unpack_half_2x16_split_x:
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index ac086a72eb1..3443e5cb759 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -1585,6 +1585,10 @@ vec4_visitor::visit(ir_expression *ir)
       emit(MOV(result_dst, op[0]));
       break;
 
+   case ir_unop_ssbo_unsized_array_length:
+      unreachable("not reached: should be handled by lower_ubo_reference");
+      break;
+
    case ir_binop_add:
       emit(ADD(result_dst, op[0], op[1]));
       break;
@@ -1791,6 +1795,10 @@ vec4_visitor::visit(ir_expression *ir)
       emit(RNDE(result_dst, op[0]));
       break;
 
+   case ir_unop_get_buffer_size:
+      unreachable("not reached: not implemented");
+      break;
+
    case ir_binop_min:
       emit_minmax(BRW_CONDITIONAL_L, result_dst, op[0], op[1]);
       break;