glsl: don't drop instructions from unreachable terminators continue branch

These instructions will be executed on every iteration of the loop
we cannot drop them.

V2:
- move removal of unreachable terminators from the terminator list
  to the same place they are removed from the IR as suggested by
  Nicolai.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>

src/compiler/glsl/loop_analysis.h

@@ -34,6 +34,13 @@
 extern class loop_state *
 analyze_loop_variables(exec_list *instructions);
 
+static inline bool
+is_break(ir_instruction *ir)
+{
+   return ir != NULL && ir->ir_type == ir_type_loop_jump &&
+      ((ir_loop_jump *) ir)->is_break();
+}
+
 
 extern bool
 unroll_loops(exec_list *instructions, loop_state *ls,