glsl: Eliminate ambiguity between function ins/outs and shader ins/outs

This patch replaces the three ir_variable_mode enums:

- ir_var_in
- ir_var_out
- ir_var_inout

with the following five:

- ir_var_shader_in
- ir_var_shader_out
- ir_var_function_in
- ir_var_function_out
- ir_var_function_inout

This eliminates a frustrating ambiguity: it used to be impossible to
tell whether an ir_var_{in,out} variable was a shader in/out or a
function in/out without seeing where the variable was declared in the
IR.  This complicated some optimization and lowering passes, and would
have become a problem for implementing varying structs.

In the lisp-style serialization of GLSL IR to strings performed by
ir_print_visitor.cpp and ir_reader.cpp, I've retained the names "in",
"out", and "inout" for function parameters, to avoid introducing code
churn to the src/glsl/builtins/ir/ directory.

Note: a couple of comments in the code seemed to indicate that we were
planning for a possible future in which geometry shaders could have
shader-scope inout variables.  Our GLSL grammar rejects shader-scope
inout variables, and I've been unable to find any evidence in the GLSL
standards documents (or extensions) that this will ever be allowed, so
I've eliminated these comments.

Reviewed-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp b/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp
index 7a12e084ff8..b9487532c59 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp
@@ -110,11 +110,13 @@ ir_vector_reference_visitor::get_variable_entry(ir_variable *var)
 
    switch (var->mode) {
    case ir_var_uniform:
-   case ir_var_in:
-   case ir_var_out:
-   case ir_var_inout:
+   case ir_var_shader_in:
+   case ir_var_shader_out:
+   case ir_var_function_in:
+   case ir_var_function_out:
+   case ir_var_function_inout:
       /* Can't split varyings or uniforms.  Function in/outs won't get split
-       * either, so don't care about the ambiguity.
+       * either.
        */
       return NULL;
    case ir_var_auto: