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, 2 insertions, 2 deletions

diff --git a/src/glsl/lower_output_reads.cpp b/src/glsl/lower_output_reads.cpp
index a6192a51707..b93e254ec9b 100644
--- a/src/glsl/lower_output_reads.cpp
+++ b/src/glsl/lower_output_reads.cpp
@@ -41,7 +41,7 @@ class output_read_remover : public ir_hierarchical_visitor {
 protected:
    /**
     * A hash table mapping from the original ir_variable shader outputs
-    * (ir_var_out mode) to the new temporaries to be used instead.
+    * (ir_var_shader_out mode) to the new temporaries to be used instead.
     */
    hash_table *replacements;
 
@@ -86,7 +86,7 @@ output_read_remover::~output_read_remover()
 ir_visitor_status
 output_read_remover::visit(ir_dereference_variable *ir)
 {
-   if (ir->var->mode != ir_var_out)
+   if (ir->var->mode != ir_var_shader_out)
       return visit_continue;
 
    ir_variable *temp = (ir_variable *) hash_table_find(replacements, ir->var);