glsl: Teach ir_variable_refcount about ir_loop::counter variables.

If an ir_loop has a non-null "counter" field, the variable referred to
by this field is implicitly read and written by the loop.  We need to
account for this in ir_variable_refcount, otherwise there is a danger
we will try to dead-code-eliminate the loop counter variable.

Note: at the moment the dead code elimination bug doesn't occur due to
a bug in ir_hierarchical_visitor: it doesn't visit the "counter"
field, so dead code elimination doesn't treat it as a candidate for
elimination.  But the patch to follow will fix that bug, so we need to
fix ir_variable_refcount first in order to avoid breaking dead code
elimination.

Reviewed-by: Eric Anholt <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/glsl/ir_variable_refcount.h b/src/glsl/ir_variable_refcount.h
index c15e8110d04..03fa7b5b467 100644
--- a/src/glsl/ir_variable_refcount.h
+++ b/src/glsl/ir_variable_refcount.h
@@ -60,6 +60,7 @@ public:
 
    virtual ir_visitor_status visit_enter(ir_function_signature *);
    virtual ir_visitor_status visit_leave(ir_assignment *);
+   virtual ir_visitor_status visit_leave(ir_loop *);
 
    ir_variable_refcount_entry *get_variable_entry(ir_variable *var);