glsl: fix incorrect optimisation in opt_constant_variable()

When handling function inputs the optimisation pass incorrectly
assumes the inputs are undefined. Here we simply change things to
assume inputs have always been assigned a value. Any further
optimisations will be taken care of once function inlining takes
place.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2984
Fixes: 65122e9e8038 ("ir_constant_variable: New pass to mark constant-assigned variables constant.")
Reviewed-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5413>

diff --git a/src/compiler/glsl/opt_constant_variable.cpp b/src/compiler/glsl/opt_constant_variable.cpp
index cc2760f560945ef0808633683c0d3dee31c88352..3f2b6a04b9ffaea9be0b02f59b274272c2ce7631 100644 (file)
--- a/src/compiler/glsl/opt_constant_variable.cpp
+++ b/src/compiler/glsl/opt_constant_variable.cpp
@@ -165,6 +165,15 @@ ir_constant_variable_visitor::visit_enter(ir_call *ir)
         entry = get_assignment_entry(var, this->ht);
         entry->assignment_count++;
       }
+
+      /* We don't know if the variable passed to this function has been
+       * assigned a value or if it is undefined, so for now we always assume
+       * it has been assigned a value. Once functions have been inlined any
+       * further potential optimisations will be taken care of.
+       */
+      struct assignment_entry *entry;
+      entry = get_assignment_entry(param, this->ht);
+      entry->assignment_count++;
    }
 
    /* Mark the return storage as having been assigned to */