glsl/linker: Make separate ir_variable field to mean "unmatched".

Previously, the linker used a value of -1 in ir_variable::location to
denote a generic input or output of the shader that had not yet been
matched up to a variable in another pipeline stage.

This patch introduces a new ir_variable field,
is_unmatched_generic_inout, for that purpose.

In future patches, this will allow us to separate the process of
matching varyings between shader stages from the processes of
assigning locations to those varying.  That will in turn pave the way
for packing varyings.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

2 files changed, 23 insertions, 4 deletions

diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 89c516c877d..e2ecb3d9dfd 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -437,6 +437,15 @@ public:
    unsigned has_initializer:1;
 
    /**
+    * Is this variable a generic output or input that has not yet been matched
+    * up to a variable in another stage of the pipeline?
+    *
+    * This is used by the linker as scratch storage while assigning locations
+    * to generic inputs and outputs.
+    */
+   unsigned is_unmatched_generic_inout:1;
+
+   /**
     * \brief Layout qualifier for gl_FragDepth.
     *
     * This is not equal to \c ir_depth_layout_none if and only if this
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 2523dc99d6f..ee6dc2596d0 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -225,6 +225,11 @@ link_invalidate_variable_locations(gl_shader *sh, int input_base,
        */
       if ((var->location >= base) && !var->explicit_location)
          var->location = -1;
+
+      if ((var->location == -1) && !var->explicit_location)
+         var->is_unmatched_generic_inout = 1;
+      else
+         var->is_unmatched_generic_inout = 0;
    }
 }
 
@@ -1362,6 +1367,7 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 	 if (prog->AttributeBindings->get(binding, var->name)) {
 	    assert(binding >= VERT_ATTRIB_GENERIC0);
 	    var->location = binding;
+            var->is_unmatched_generic_inout = 0;
 	 }
       } else if (target_index == MESA_SHADER_FRAGMENT) {
 	 unsigned binding;
@@ -1370,6 +1376,7 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 	 if (prog->FragDataBindings->get(binding, var->name)) {
 	    assert(binding >= FRAG_RESULT_DATA0);
 	    var->location = binding;
+            var->is_unmatched_generic_inout = 0;
 
 	    if (prog->FragDataIndexBindings->get(index, var->name)) {
 	       var->index = index;
@@ -1485,6 +1492,7 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
       }
 
       to_assign[i].var->location = generic_base + location;
+      to_assign[i].var->is_unmatched_generic_inout = 0;
       used_locations |= (use_mask << location);
    }
 
@@ -1508,7 +1516,7 @@ demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)
        * its value is used by other shader stages.  This will cause the variable
        * to have a location assigned.
        */
-      if (var->location == -1) {
+      if (var->is_unmatched_generic_inout) {
 	 var->mode = ir_var_auto;
       }
    }
@@ -1985,7 +1993,7 @@ void
 assign_varying_location(ir_variable *input_var, ir_variable *output_var,
                         unsigned *input_index, unsigned *output_index)
 {
-   if (output_var->location != -1) {
+   if (!output_var->is_unmatched_generic_inout) {
       /* Location already assigned. */
       return;
    }
@@ -1993,9 +2001,11 @@ assign_varying_location(ir_variable *input_var, ir_variable *output_var,
    if (input_var) {
       assert(input_var->location == -1);
       input_var->location = *input_index;
+      input_var->is_unmatched_generic_inout = 0;
    }
 
    output_var->location = *output_index;
+   output_var->is_unmatched_generic_inout = 0;
 
    /* FINISHME: Support for "varying" records in GLSL 1.50. */
    assert(!output_var->type->is_record());
@@ -2105,7 +2115,7 @@ assign_varying_locations(struct gl_context *ctx,
 
          if (!tfeedback_decls[i].is_assigned() &&
              tfeedback_decls[i].matches_var(output_var)) {
-            if (output_var->location == -1) {
+            if (output_var->is_unmatched_generic_inout) {
                assign_varying_location(input_var, output_var, &input_index,
                                        &output_index);
             }
@@ -2124,7 +2134,7 @@ assign_varying_locations(struct gl_context *ctx,
          if ((var == NULL) || (var->mode != ir_var_in))
             continue;
 
-         if (var->location == -1) {
+         if (var->is_unmatched_generic_inout) {
             if (prog->Version <= 120) {
                /* On page 25 (page 31 of the PDF) of the GLSL 1.20 spec:
                 *