From 0e59b2698a7609183221e1266c1209611040609a Mon Sep 17 00:00:00 2001
From: Ian Romanick <ian.d.romanick@intel.com>
Date: Wed, 23 Jun 2010 11:23:01 -0700
Subject: linker: Initial implementation of varying slot allocation

---
 linker.cpp | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 76 insertions(+), 3 deletions(-)

diff --git a/linker.cpp b/linker.cpp
index 76c3e9d..500a329 100644
--- a/linker.cpp
+++ b/linker.cpp
@@ -661,6 +661,79 @@ assign_attribute_locations(glsl_shader *sh,
 }
 
 
+void
+assign_varying_locations(glsl_shader *producer, glsl_shader *consumer)
+{
+   /* FINISHME: Set dynamically when geometry shader support is added. */
+   unsigned output_index = VERT_RESULT_VAR0;
+   unsigned input_index = FRAG_ATTRIB_VAR0;
+
+   /* Operate in a total of three passes.
+    *
+    * 1. Assign locations for any matching inputs and outputs.
+    *
+    * 2. Mark output variables in the producer that do not have locations as
+    *    not being outputs.  This lets the optimizer eliminate them.
+    *
+    * 3. Mark input variables in the consumer that do not have locations as
+    *    not being inputs.  This lets the optimizer eliminate them.
+    */
+
+   invalidate_variable_locations(producer, ir_var_out, VERT_RESULT_VAR0);
+   invalidate_variable_locations(consumer, ir_var_in, FRAG_ATTRIB_VAR0);
+
+   foreach_list(node, &producer->ir) {
+      ir_variable *const output_var = ((ir_instruction *) node)->as_variable();
+
+      if ((output_var == NULL) || (output_var->mode != ir_var_out)
+	  || (output_var->location != -1))
+	 continue;
+
+      ir_variable *const input_var =
+	 consumer->symbols->get_variable(output_var->name);
+
+      if ((input_var == NULL) || (input_var->mode != ir_var_in))
+	 continue;
+
+      assert(input_var->location == -1);
+
+      /* FINISHME: Location assignment will need some changes when arrays,
+       * FINISHME: matrices, and structures are allowed as shader inputs /
+       * FINISHME: outputs.
+       */
+      output_var->location = output_index;
+      input_var->location = input_index;
+
+      output_index++;
+      input_index++;
+   }
+
+   foreach_list(node, &producer->ir) {
+      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+      if ((var == NULL) || (var->mode != ir_var_out))
+	 continue;
+
+      /* An 'out' variable is only really a shader output if its value is read
+       * by the following stage.
+       */
+      var->shader_out = (var->location != -1);
+   }
+
+   foreach_list(node, &consumer->ir) {
+      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+      if ((var == NULL) || (var->mode != ir_var_in))
+	 continue;
+
+      /* An 'in' variable is only really a shader input if its value is written
+       * by the previous stage.
+       */
+      var->shader_in = (var->location != -1);
+   }
+}
+
+
 void
 link_shaders(struct glsl_program *prog)
 {
@@ -750,9 +823,9 @@ link_shaders(struct glsl_program *prog)
 				      16))
 	 goto done;
 
-   /* FINISHME: Assign vertex shader output / fragment shader input
-    * FINISHME: locations.
-    */
+   for (unsigned i = 1; i < prog->_NumLinkedShaders; i++)
+      assign_varying_locations(prog->_LinkedShaders[i - 1],
+			       prog->_LinkedShaders[i]);
 
    /* FINISHME: Assign fragment shader output locations. */
 
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