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, 5 insertions, 3 deletions

diff --git a/src/glsl/opt_tree_grafting.cpp b/src/glsl/opt_tree_grafting.cpp
index 25b18ea940c..113abb7b043 100644
--- a/src/glsl/opt_tree_grafting.cpp
+++ b/src/glsl/opt_tree_grafting.cpp
@@ -211,7 +211,8 @@ ir_tree_grafting_visitor::visit_enter(ir_call *ir)
       ir_rvalue *ir = (ir_rvalue *)iter.get();
       ir_rvalue *new_ir = ir;
 
-      if (sig_param->mode != ir_var_in && sig_param->mode != ir_var_const_in) {
+      if (sig_param->mode != ir_var_function_in
+          && sig_param->mode != ir_var_const_in) {
 	 if (check_graft(ir, sig_param) == visit_stop)
 	    return visit_stop;
 	 continue;
@@ -350,8 +351,9 @@ tree_grafting_basic_block(ir_instruction *bb_first,
       if (!lhs_var)
 	 continue;
 
-      if (lhs_var->mode == ir_var_out ||
-	  lhs_var->mode == ir_var_inout)
+      if (lhs_var->mode == ir_var_function_out ||
+	  lhs_var->mode == ir_var_function_inout ||
+          lhs_var->mode == ir_var_shader_out)
 	 continue;
 
       ir_variable_refcount_entry *entry = info->refs->get_variable_entry(lhs_var);