glsl: Allow int -> uint implicit conversions on function parameters

V2: Fix crashes during linking, where the parse state is NULL. In this
case, all required checks have already been done, so we assume the
extension is enabled.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/glsl_types.cpp

@@ -688,10 +688,23 @@ glsl_type::can_implicitly_convert_to(const glsl_type *desired,
    if (this->matrix_columns > 1 || desired->matrix_columns > 1)
       return false;
 
+   /* Vector size must match. */
+   if (this->vector_elements != desired->vector_elements)
+      return false;
+
    /* int and uint can be converted to float. */
-   return desired->is_float()
-          && this->is_integer()
-          && this->vector_elements == desired->vector_elements;
+   if (desired->is_float() && this->is_integer())
+      return true;
+
+   /* With GLSL 4.0 / ARB_gpu_shader5, int can be converted to uint.
+    * Note that state may be NULL here, when resolving function calls in the
+    * linker. By this time, all the state-dependent checks have already
+    * happened though, so allow anything that's allowed in any shader version. */
+   if ((!state || state->is_version(400, 0) || state->ARB_gpu_shader5_enable) &&
+         desired->base_type == GLSL_TYPE_UINT && this->base_type == GLSL_TYPE_INT)
+      return true;
+
+   return false;
 }
 
 unsigned