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 <[email protected]>
Reviewed-by: Jordan Justen <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 85fc5ce95da..de687d38545 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -265,9 +265,11 @@ protected:
 enum ir_variable_mode {
    ir_var_auto = 0,     /**< Function local variables and globals. */
    ir_var_uniform,      /**< Variable declared as a uniform. */
-   ir_var_in,
-   ir_var_out,
-   ir_var_inout,
+   ir_var_shader_in,
+   ir_var_shader_out,
+   ir_var_function_in,
+   ir_var_function_out,
+   ir_var_function_inout,
    ir_var_const_in,	/**< "in" param that must be a constant expression */
    ir_var_system_value, /**< Ex: front-face, instance-id, etc. */
    ir_var_temporary	/**< Temporary variable generated during compilation. */
@@ -401,7 +403,7 @@ public:
     *
     * \sa ir_variable_mode
     */
-   unsigned mode:3;
+   unsigned mode:4;
 
    /**
     * Interpolation mode for shader inputs / outputs