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/ir.cpp b/src/glsl/ir.cpp
index 703f5ec58ef..75a9f24cf29 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -1553,8 +1553,8 @@ modes_match(unsigned a, unsigned b)
       return true;
 
    /* Accept "in" vs. "const in" */
-   if ((a == ir_var_const_in && b == ir_var_in) ||
-       (b == ir_var_const_in && a == ir_var_in))
+   if ((a == ir_var_const_in && b == ir_var_function_in) ||
+       (b == ir_var_const_in && a == ir_var_function_in))
       return true;
 
    return false;