[Mesa-dev] [PATCH] glsl: remove interpolateAt* instructions for demoted inputs

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

This fixes 8 fs-interpolateat* piglit crashes on radeonsi, because it can't
handle non-input operands in interpolateAt*.
---
 src/compiler/glsl/link_varyings.cpp |  5 +++++
 src/compiler/glsl/opt_algebraic.cpp | 10 ++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index 1fad310..85ca044 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -586,20 +586,25 @@ remove_unused_shader_inputs_and_outputs(bool is_separate_shader_object,
 
       if (var == NULL || var->data.mode != int(mode))
          continue;
 
       /* A shader 'in' or 'out' variable is only really an input or output if
        * its value is used by other shader stages. This will cause the
        * variable to have a location assigned.
        */
       if (var->data.is_unmatched_generic_inout && !var->data.is_xfb_only) {
          assert(var->data.mode != ir_var_temporary);
+
+         /* Assign zeros to demoted inputs to allow more optimizations. */
+         if (var->data.mode == ir_var_shader_in && !var->constant_value)
+            var->constant_value = ir_constant::zero(var, var->type);
+
          var->data.mode = ir_var_auto;
       }
    }
 
    /* Eliminate code that is now dead due to unused inputs/outputs being
     * demoted.
     */
    while (do_dead_code(sh->ir, false))
       ;
 
diff --git a/src/compiler/glsl/opt_algebraic.cpp b/src/compiler/glsl/opt_algebraic.cpp
index f5858c8..2829a78 100644
--- a/src/compiler/glsl/opt_algebraic.cpp
+++ b/src/compiler/glsl/opt_algebraic.cpp
@@ -954,20 +954,30 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
       }
       break;
 
    case ir_triop_csel:
       if (is_vec_one(op_const[0]))
 	 return ir->operands[1];
       if (is_vec_zero(op_const[0]))
 	 return ir->operands[2];
       break;
 
+   /* Remove interpolateAt* instructions for demoted inputs. They are
+    * assigned a constant expression to facilitate this.
+    */
+   case ir_unop_interpolate_at_centroid:
+   case ir_binop_interpolate_at_offset:
+   case ir_binop_interpolate_at_sample:
+      if (op_const[0])
+         return ir->operands[0];
+      break;
+
    default:
       break;
    }
 
    return ir;
 }
 
 void
 ir_algebraic_visitor::handle_rvalue(ir_rvalue **rvalue)
 {
-- 
2.7.4