glsl: Make read_from_write_only_variable_visitor ignore .length().

.length() on an unsized SSBO variable doesn't actually read any data
from the SSBO, and is allowed on variables marked 'writeonly'.

Fixes compute shader compilation in Shadow of Mordor.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index f3966d7e3f4cd4ae1a9f9112ed69bda740a975e4..13696a36b0cffe058be3503bfc17190e4c55b9fc 100644 (file)
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -106,6 +106,15 @@ public:
       return found;
    }
 
+   virtual ir_visitor_status visit_enter(ir_expression *ir)
+   {
+      /* .length() doesn't actually read anything */
+      if (ir->operation == ir_unop_ssbo_unsized_array_length)
+         return visit_continue_with_parent;
+
+      return visit_continue;
+   }
+
 private:
    ir_variable *found;
 };