nir: add always_active_io to nir variable

Will be used in nir link pass to decided if we can remove a varying
or not.

Reviewed-by: Kenneth Graunke <[email protected]>
Reviewed-by: Eduardo Lima Mitev <[email protected]>

2 files changed, 11 insertions, 0 deletions

diff --git a/src/compiler/glsl/glsl_to_nir.cpp b/src/compiler/glsl/glsl_to_nir.cpp
index 99df6e0baf5..ce8da1ce438 100644
--- a/src/compiler/glsl/glsl_to_nir.cpp
+++ b/src/compiler/glsl/glsl_to_nir.cpp
@@ -315,6 +315,7 @@ nir_visitor::visit(ir_variable *ir)
    var->type = ir->type;
    var->name = ralloc_strdup(var, ir->name);
 
+   var->data.always_active_io = ir->data.always_active_io;
    var->data.read_only = ir->data.read_only;
    var->data.centroid = ir->data.centroid;
    var->data.sample = ir->data.sample;
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 8330e6d7ce7..fab2110f619 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -192,6 +192,16 @@ typedef struct nir_variable {
       unsigned invariant:1;
 
       /**
+       * When separate shader programs are enabled, only input/outputs between
+       * the stages of a multi-stage separate program can be safely removed
+       * from the shader interface. Other input/outputs must remains active.
+       *
+       * This is also used to make sure xfb varyings that are unused by the
+       * fragment shader are not removed.
+       */
+      unsigned always_active_io:1;
+
+      /**
        * Interpolation mode for shader inputs / outputs
        *
        * \sa glsl_interp_mode