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, 3 insertions, 3 deletions

diff --git a/src/glsl/lower_packed_varyings.cpp b/src/glsl/lower_packed_varyings.cpp
index 9e7f274..8f05752 100644
--- a/src/glsl/lower_packed_varyings.cpp
+++ b/src/glsl/lower_packed_varyings.cpp
@@ -135,8 +135,8 @@ private:
    ir_variable **packed_varyings;
 
    /**
-    * Type of varying which is being lowered in this pass (either ir_var_in or
-    * ir_var_out).
+    * Type of varying which is being lowered in this pass (either
+    * ir_var_shader_in or ir_var_shader_out).
     */
    const ir_variable_mode mode;
 
@@ -336,7 +336,7 @@ lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
                                                           unpacked_var, name));
       ir_swizzle *swizzle = new(this->mem_ctx)
          ir_swizzle(packed_deref, swizzle_values, components);
-      if (this->mode == ir_var_out) {
+      if (this->mode == ir_var_shader_out) {
          ir_assignment *assignment
             = this->bitwise_assign_pack(swizzle, rvalue);
          this->main_instructions->push_tail(assignment);