---
 src/glsl/linker.cpp |  659 ++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 550 insertions(+), 109 deletions(-)

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 5095751..66c1671 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1458,6 +1458,8 @@ private:
     * variable.  -1 if a location hasn't been assigned yet.
     */
    int location;
+   
+   unsigned horizontal_location;
 
    /**
     * If location != -1, the number of vector elements in this variable, or 1
@@ -1496,6 +1498,7 @@ tfeedback_decl::init(struct gl_context *ctx, struct 
gl_shader_program *prog,
     */
 
    this->location = -1;
+   this->horizontal_location = 0;
    this->orig_name = input;
    this->is_clip_distance_mesa = false;
 
@@ -1602,6 +1605,7 @@ tfeedback_decl::assign_location(struct gl_context *ctx,
       this->vector_elements = output_var->type->vector_elements;
       this->matrix_columns = output_var->type->matrix_columns;
       this->type = output_var->type->gl_type;
+      this->horizontal_location = output_var->horizontal_location;
    }
 
    /* From GL_EXT_transform_feedback:
@@ -1687,7 +1691,7 @@ tfeedback_decl::store(struct gl_context *ctx, struct 
gl_shader_program *prog,
       for (unsigned v = 0; v < this->matrix_columns; ++v) {
          unsigned num_components = this->vector_elements;
          assert(info->NumOutputs < max_outputs);
-         info->Outputs[info->NumOutputs].ComponentOffset = 0;
+         info->Outputs[info->NumOutputs].ComponentOffset = 
this->horizontal_location;
          if (this->is_clip_distance_mesa) {
             if (this->is_subscripted) {
                num_components = 1;
@@ -1809,6 +1813,456 @@ assign_varying_location(ir_variable *input_var, 
ir_variable *output_var,
    }
 }
 
+namespace pack {
+
+/**
+ * Varyings packing can be seen as an instance of the bin packing problem.
+ * It is a NP hard problem in general.
+ *
+ * ES 2.0 specs gives (GLSL_ES_Specification_1.0.17-3.pdf, p111) an algorithm
+ * that specifies a minimum requirement for when a set of varyings must be 
+ * supported.
+ * We almost follow the algorithm : the target architecture should be a
+ * 8x4 grid, we use a {number_of_available_reg}x4 grid.
+ */
+class buffer_representation
+{
+protected:
+   class delayed_location_assignment : public exec_node
+   {
+   public:
+       ir_variable *producer;
+       ir_variable *consumer;
+       unsigned location;
+       unsigned horizontal_location;
+       delayed_location_assignment(ir_variable *p, ir_variable *c)
+          : producer(p), consumer(c)
+       {
+       }
+       
+       bool is_before(const delayed_location_assignment *comparee) const
+       {
+          unsigned local_size = 
(producer->type->is_array())?producer->type->length:1;
+          unsigned comparee_size = 
(comparee->producer->type->is_array())?comparee->producer->type->length:1;
+          return local_size >= comparee_size;
+       }
+       
+       void set_location_to_vars(unsigned producer_offset, unsigned 
consumer_offset, unsigned location, unsigned horizontal_location)
+       {
+          producer->location = producer_offset + location;
+          producer->horizontal_location = horizontal_location;
+          if (consumer) {
+               consumer->location = consumer_offset + location;
+               consumer->horizontal_location = horizontal_location;
+          }
+       }
+       
+   };
+   
+   void *ctx;
+   unsigned number_of_regs;
+   bool * is_occupied;
+   unsigned occupied_space_in_column[4];
+   unsigned producer_offset, consumer_offset;
+   exec_list *stored_vars[8];
+   
+   
+   #define ARGMAX(i, j) (occupied_space_in_column[(i)] >= 
occupied_space_in_column[(j)])?(i):(j)
+   #define ARGMIN(i, j) (occupied_space_in_column[(i)] >= 
occupied_space_in_column[(j)])?(j):(i)
+   
+   /**
+    * Order index from most occupied column index to least occupied column 
index
+    */
+   void order(unsigned reordered[4]) const
+   {
+       unsigned mx1 = ARGMAX(0, 1), mx2 = ARGMAX(2, 3);
+       unsigned mn1 = ARGMIN(0, 1), mn2 = ARGMIN(2, 3);
+       
+       reordered[0] = ARGMAX(mx1, mx2);
+       unsigned semi_max = ARGMIN(mx1, mx2);
+       reordered[3] = ARGMIN(mn1, mn2);
+       unsigned semi_min = ARGMAX(mn1, mn2);
+       reordered[1] = ARGMAX(semi_max, semi_min);
+       reordered[2] = ARGMIN(semi_min, semi_max);
+   }
+   
+   #undef ARGMAX
+   #undef ARGMIN
+   
+   INLINE
+   bool& is_occupied_ref(unsigned index, unsigned components)
+   {
+       assert (components < 4 && index < number_of_regs);
+       return is_occupied[4 * index + components];
+   }
+   
+   bool is_range_free(unsigned reg, unsigned component_start, unsigned 
row_occupied, unsigned components_occupied)
+   {
+
+       if (component_start + components_occupied - 1 > 3)
+          return false;
+       if (reg + row_occupied - 1 > number_of_regs - 1)
+          return false;
+       for (unsigned j = 0; j < row_occupied; j++) {
+          for (unsigned i = 0; i < components_occupied; i++) {
+               if (is_occupied_ref(reg + j, component_start + i))
+                  return false;
+          }
+       }
+       return true;
+   }
+   
+   void mark_as_occupied(unsigned location, unsigned horizontal_location, 
unsigned size, unsigned components_occupied) 
+   {
+       for (unsigned j = 0; j < size; j++) {
+          for (unsigned i = 0; i < components_occupied; i++) {
+               is_occupied_ref(location + j, horizontal_location + i) = true;
+               occupied_space_in_column[horizontal_location + i] ++;
+          }
+       }
+   }
+   
+   void insert(delayed_location_assignment *dla, const glsl_type *const type)
+   {
+       if (type->is_array()) {
+          return insert(dla, type->fields.array);
+       }
+       
+       // MAT4
+       if (type->is_matrix() && type->vector_elements == 4) {
+          insert_largest_first(stored_vars[1], dla);
+          return;
+       }
+       
+       // MAT2
+       if (type->is_matrix() && type->vector_elements == 2) {
+          insert_largest_first(stored_vars[2], dla);
+          return;
+       }
+       
+       // {I,B,}VEC4
+       if (type->is_vector() && type->vector_elements == 4) {
+          insert_largest_first(stored_vars[3], dla);
+          return;
+       }
+       
+       // MAT3
+       if (type->is_matrix() && type->vector_elements == 3) {
+          insert_largest_first(stored_vars[4], dla);
+          return;
+       }
+       
+       // {I,B,}VEC3
+       if (type->is_vector() && type->vector_elements == 3) {
+          insert_largest_first(stored_vars[5], dla);
+          return;
+       }
+       
+       // {I,B,}VEC2
+       if (type->is_vector() && type->vector_elements == 2) {
+          insert_largest_first(stored_vars[6], dla);
+          return;
+       }
+
+       // float, int   
+       if (type->is_scalar()) {
+          insert_largest_first(stored_vars[7], dla);
+          return;
+       }
+       
+       assert(0 && "varying type not supported");
+       return;
+   }
+   
+   void
+   insert_largest_first(exec_list *lst, delayed_location_assignment *dla)
+   {
+       if (lst->is_empty()) {
+          lst->push_tail(dla);
+          return;
+       }
+       foreach_list(node, lst) {
+          delayed_location_assignment *dla_from_lst = (class 
delayed_location_assignment *) node;
+          if (dla->is_before(dla_from_lst)) {
+               dla_from_lst->insert_before(dla);
+               return;
+          }
+          
+       }
+   }
+   
+   void space_occupied (const glsl_type *const type, unsigned &components, 
unsigned &size)
+   {
+       if (type->is_array()) {
+          space_occupied(type->fields.array, components, size);
+          size *= type->length;
+          return;
+       }
+       
+       if (type == glsl_type::mat2_type) {
+          components = 4;
+          size = 2;
+          return;
+       }
+       
+       components = type->vector_elements;
+       size = type->matrix_columns;
+   }
+   
+   /**
+    * "For 2,3 and 4 component variables packing is started using the 1st 
column of the 1st row.
+    *  Variables are then allocated to successive rows, aligning them to the 
1st column"
+    * (ES Spec)
+    */
+   void phase1() 
+   {
+       unsigned i, current_row = 0;
+       for (i = 1; i < 8; i++) {
+          foreach_list_safe (node, stored_vars[i]) {
+               delayed_location_assignment *dla = (class 
delayed_location_assignment *) node;
+               unsigned components, size;
+               space_occupied(dla->producer->type, components, size);
+               if (is_range_free(current_row, 0, size, components)) {
+                  dla->set_location_to_vars(producer_offset, consumer_offset, 
current_row, 0);
+                  mark_as_occupied(current_row, 0, size, components);
+                  dla->remove();
+                  current_row += size;
+               } else {
+                  return;
+               }
+          }
+       }
+   }
+   
+   /**
+    * "For 2 component variables, when there are no spare rows, the strategy 
is switched to using the
+    * highest numbered row and the lowest numbered column where the variable 
will fit. "
+    * (ES Spec)
+    */
+   void phase2()
+   {
+       int current_row = number_of_regs - 1;
+       foreach_list_safe (node, stored_vars[6]) {
+          delayed_location_assignment *dla = (class 
delayed_location_assignment *) node;
+          unsigned components, size;
+          space_occupied(dla->producer->type, components, size);
+          while (current_row >= 0) {
+               if (is_range_free(current_row, 0, size, 2)) {
+                  dla->set_location_to_vars(producer_offset, consumer_offset, 
current_row, 0);
+                  mark_as_occupied(current_row, 0, size, 2);
+                  dla->remove();
+                  current_row -= size;
+                  break;
+               } else if (is_range_free(current_row, 2, size, 2)) {
+                  dla->set_location_to_vars(producer_offset, consumer_offset, 
current_row, 2);
+                  mark_as_occupied(current_row, 2, size, 2);
+                  dla->remove();
+                  current_row -= size;
+                  break;   
+               } else {
+                  current_row --;
+               }
+          }
+          if (current_row < 0)
+               return;
+       }
+   }
+   
+   /**
+    * "[1 Component variables] are packed in order of size, largest first. 
+    * Each variable is placed in the column that leaves the least
+    * amount of space in the column and aligned to the lowest available rows 
within that column."
+    * (ES Spec)
+    */
+   void phase3()
+   {
+       foreach_list_safe (node, stored_vars[7]) {
+          delayed_location_assignment *dla = (class 
delayed_location_assignment *) node;
+          unsigned components, size;
+          space_occupied(dla->producer->type, components, size);
+          unsigned reordered_index[4];
+          // If we are here, no more space in first column
+          order(reordered_index);
+          for (unsigned i = 0; i < 4; i++) {
+               unsigned free_space = number_of_regs - 
occupied_space_in_column[reordered_index[i]];
+               if (size > free_space)
+                  continue;
+               else {
+                  // Find first free row ; empty space is ensured to be 
contiguous
+                  unsigned first_free_row = 0;
+                  while (!is_range_free(first_free_row,reordered_index[i],1,1))
+                       first_free_row ++ ;
+                  dla->set_location_to_vars(producer_offset, consumer_offset, 
first_free_row, reordered_index[i]);
+                  mark_as_occupied(first_free_row, reordered_index[i], size, 
1);
+                  dla->remove();
+                  break;
+               }
+          }
+       }
+   }
+   
+   static void report_error(gl_shader_program *prog, exec_list 
*failing_varyings)
+   {
+       foreach_list_const (node, failing_varyings) {
+          const delayed_location_assignment *dla = 
(delayed_location_assignment *) node;
+          linker_error(prog, "Fails to find sufficient resources for varying 
%s\n",
+                       dla->producer->name);   
+       }
+   }
+   
+public:
+   buffer_representation(unsigned p_offset, unsigned c_offset, unsigned n)
+      : ctx(ralloc_context(NULL)), number_of_regs(n), 
producer_offset(p_offset), consumer_offset(c_offset)
+   {
+       is_occupied = rzalloc_array(ctx, bool, 4 * number_of_regs);
+       for (unsigned i = 0; i < 8; i++) {
+          stored_vars[i] = new (ctx) exec_list();
+       }
+       memset(occupied_space_in_column, 0, sizeof(occupied_space_in_column));
+   }
+   
+   ~buffer_representation()
+   {
+       ralloc_free(ctx);
+   }
+   
+   void insert(ir_variable *producer, ir_variable *consumer)
+   {
+       assert(producer);
+       if (consumer)
+          assert(producer->type == consumer->type);
+       
+       delayed_location_assignment *dla = new (ctx) 
delayed_location_assignment(producer, consumer);
+       insert(dla, producer->type);
+   }
+   
+   // Note : We need prog to report errors
+   bool try_pack(gl_shader_program *prog)
+   {
+       phase1();
+       if (!stored_vars[1]->is_empty() || !stored_vars[2]->is_empty() || 
!stored_vars[3]->is_empty() || 
+           !stored_vars[4]->is_empty() || !stored_vars[5]->is_empty()) {
+           
+          /**
+           * "For 2 component variables, when there are no spare rows, ...
+           * Packing of any further 3 or 4 component variables will fail at 
this point."
+           * (ES Spec)
+           */
+          report_error(prog, stored_vars[1]);
+          report_error(prog, stored_vars[2]);
+          report_error(prog, stored_vars[3]);
+          report_error(prog, stored_vars[3]);
+          report_error(prog, stored_vars[4]);
+          report_error(prog, stored_vars[5]);
+          return false;
+          
+       }
+       
+       phase2();
+       if (!stored_vars[6]->is_empty()) {
+          report_error(prog, stored_vars[6]);
+          return false;
+       }
+       phase3();
+       if (!stored_vars[7]->is_empty()) {
+          report_error(prog, stored_vars[7]);
+          return false;
+       }
+       
+       return true;
+   }
+   
+   
+};
+
+}
+
+class varying_info : public exec_node
+{
+public:
+   ir_variable *produced;
+   ir_variable *consumed;
+   varying_info( ir_variable *p, ir_variable *c)
+      : produced(p), consumed(c)
+   {
+
+   }
+};
+
+/**
+ * This function packs varyings according to ES Spec recommandation.
+ * It will trigger "linker_error" if packing fails.
+ * This function is conservative, it does not try to pack varyings with 
different interpolation
+ */
+bool
+varying_pack(exec_list *lst, gl_shader_program *prog, unsigned max_varyings)
+{
+   // Heuristic : we allocate regs for each interpolation type wrt number of 
variables using them.
+   unsigned none_interp_count = 0, flat_interp_count = 0, smooth_interp_count 
= 0, noperspective_interp_count = 0;
+   
+   foreach_list_const(node, lst) {
+       const varying_info *vi = (class varying_info *) node;
+       switch (vi->produced->interpolation) {
+       case INTERP_QUALIFIER_NONE:
+          none_interp_count ++;
+          break;
+       case INTERP_QUALIFIER_SMOOTH:
+          smooth_interp_count ++;
+          break;
+       case INTERP_QUALIFIER_FLAT:
+          flat_interp_count ++;
+          break;
+       case INTERP_QUALIFIER_NOPERSPECTIVE:
+          noperspective_interp_count ++;
+          break;
+       }
+   }
+   
+   unsigned total = none_interp_count + smooth_interp_count + 
flat_interp_count + noperspective_interp_count;
+   if (!total)
+       return true;
+   
+   unsigned none_regs = (max_varyings * none_interp_count ) / total;
+   unsigned flat_regs = (max_varyings * flat_interp_count ) / total;
+   unsigned smooth_regs = (max_varyings * smooth_interp_count ) / total;
+   unsigned noperspective_regs = (max_varyings * noperspective_interp_count ) 
/ total;
+
+   pack::buffer_representation none_interp(VERT_RESULT_VAR0, FRAG_ATTRIB_VAR0, 
none_regs);
+   pack::buffer_representation flat_interp(VERT_RESULT_VAR0 + none_regs, 
FRAG_ATTRIB_VAR0 + none_regs, flat_regs);
+   pack::buffer_representation smooth_interp(VERT_RESULT_VAR0 + none_regs + 
flat_regs, FRAG_ATTRIB_VAR0 + none_regs + flat_regs, smooth_regs);
+   pack::buffer_representation noperspective_interp(VERT_RESULT_VAR0 + 
none_regs + flat_regs + smooth_regs,
+                                                    FRAG_ATTRIB_VAR0 + 
none_regs + flat_regs + smooth_regs,
+                                                    noperspective_regs);
+   
+   foreach_list(node, lst) {
+       varying_info *vi = (class varying_info *) node;
+       switch (vi->produced->interpolation) {
+       case INTERP_QUALIFIER_NONE:
+          none_interp.insert(vi->produced, vi->consumed);
+          break;
+       case INTERP_QUALIFIER_SMOOTH:
+          smooth_interp.insert(vi->produced, vi->consumed);
+          break;
+       case INTERP_QUALIFIER_FLAT:
+          flat_interp.insert(vi->produced, vi->consumed);
+          break;
+       case INTERP_QUALIFIER_NOPERSPECTIVE:
+          noperspective_interp.insert(vi->produced, vi->consumed);
+          break;
+       }
+   }
+   
+   if (!none_interp.try_pack(prog))
+       return false;
+   if (!flat_interp.try_pack(prog))
+       return false;
+   if (!smooth_interp.try_pack(prog))
+       return false;
+   if (!noperspective_interp.try_pack(prog))
+       return false;
+   
+   return true;
+}
 
 /**
  * Assign locations for all variables that are produced in one pipeline stage
@@ -1832,15 +2286,14 @@ assign_varying_location(ir_variable *input_var, 
ir_variable *output_var,
  */
 bool
 assign_varying_locations(struct gl_context *ctx,
-                        struct gl_shader_program *prog,
-                        gl_shader *producer, gl_shader *consumer,
+                         struct gl_shader_program *prog,
+                         gl_shader *producer, gl_shader *consumer,
                          unsigned num_tfeedback_decls,
                          tfeedback_decl *tfeedback_decls)
 {
-   /* FINISHME: Set dynamically when geometry shader support is added. */
-   unsigned output_index = VERT_RESULT_VAR0;
-   unsigned input_index = FRAG_ATTRIB_VAR0;
-
+   void *rctx = ralloc_context(NULL);
+   exec_list *delayed_assignment = new (rctx) exec_list();
+   
    /* Operate in a total of three passes.
     *
     * 1. Assign locations for any matching inputs and outputs.
@@ -1851,115 +2304,103 @@ assign_varying_locations(struct gl_context *ctx,
     * 3. Mark input variables in the consumer that do not have locations as
     *    not being inputs.  This lets the optimizer eliminate them.
     */
-
+   
    link_invalidate_variable_locations(producer, ir_var_out, VERT_RESULT_VAR0);
    if (consumer)
-      link_invalidate_variable_locations(consumer, ir_var_in, 
FRAG_ATTRIB_VAR0);
-
+       link_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))
-        continue;
-
-      ir_variable *input_var =
-        consumer ? consumer->symbols->get_variable(output_var->name) : NULL;
-
-      if (input_var && input_var->mode != ir_var_in)
-         input_var = NULL;
-
-      if (input_var) {
-         assign_varying_location(input_var, output_var, &input_index,
-                                 &output_index);
-      }
-
-      for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
-         if (!tfeedback_decls[i].is_assigned() &&
-             tfeedback_decls[i].matches_var(output_var)) {
-            if (output_var->location == -1) {
-               assign_varying_location(input_var, output_var, &input_index,
-                                       &output_index);
-            }
-            if (!tfeedback_decls[i].assign_location(ctx, prog, output_var))
-               return false;
-         }
-      }
+       ir_variable *const output_var = ((ir_instruction *) 
node)->as_variable();
+       
+       if ((output_var == NULL) || (output_var->mode != ir_var_out))
+          continue;
+       
+       ir_variable *input_var =
+             consumer ? consumer->symbols->get_variable(output_var->name) : 
NULL;
+       
+       if (input_var && input_var->mode != ir_var_in)
+          input_var = NULL;
+       
+       varying_info *vi = NULL;
+       
+       if (input_var) {
+          vi = new (rctx) varying_info (output_var, input_var);
+          delayed_assignment->push_tail(vi);
+       }
+       
+       for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
+          if (!tfeedback_decls[i].is_assigned() &&
+              tfeedback_decls[i].matches_var(output_var)) {
+               if (output_var->location != -1) {
+                  if (!tfeedback_decls[i].assign_location(ctx, prog, 
output_var)) {
+                       ralloc_free(rctx);
+                       return false;
+                  }
+               } else if (!vi) {
+                  vi = new (rctx) varying_info (output_var, NULL);
+                  delayed_assignment->push_tail(vi);
+               }
+          }
+       }
    }
 
-   unsigned varying_vectors = 0;
-
-   if (consumer) {
-      foreach_list(node, consumer->ir) {
-         ir_variable *const var = ((ir_instruction *) node)->as_variable();
-
-         if ((var == NULL) || (var->mode != ir_var_in))
-            continue;
-
-         if (var->location == -1) {
-            if (prog->Version <= 120) {
-               /* On page 25 (page 31 of the PDF) of the GLSL 1.20 spec:
-                *
-                *     Only those varying variables used (i.e. read) in
-                *     the fragment shader executable must be written to
-                *     by the vertex shader executable; declaring
-                *     superfluous varying variables in a vertex shader is
-                *     permissible.
-                *
-                * We interpret this text as meaning that the VS must
-                * write the variable for the FS to read it.  See
-                * "glsl1-varying read but not written" in piglit.
-                */
-
-               linker_error(prog, "fragment shader varying %s not written "
-                            "by vertex shader\n.", var->name);
-            }
-
-            /* An 'in' variable is only really a shader input if its
-             * value is written by the previous stage.
-             */
-            var->mode = ir_var_auto;
-         } else {
-            /* The packing rules are used for vertex shader inputs are also
-             * used for fragment shader inputs.
-             */
-            varying_vectors += count_attribute_slots(var->type);
-         }
-      }
+   // Should be driver dependant function
+   if (!varying_pack(delayed_assignment, prog, ctx->Const.MaxVarying)) {
+       ralloc_free(rctx);
+       return false;
    }
-
-   if (ctx->API == API_OPENGLES2 || prog->Version == 100) {
-      if (varying_vectors > ctx->Const.MaxVarying) {
-         if (ctx->Const.GLSLSkipStrictMaxVaryingLimitCheck) {
-            linker_warning(prog, "shader uses too many varying vectors "
-                           "(%u > %u), but the driver will try to optimize "
-                           "them out; this is non-portable out-of-spec "
-                           "behavior\n",
-                           varying_vectors, ctx->Const.MaxVarying);
-         } else {
-            linker_error(prog, "shader uses too many varying vectors "
-                         "(%u > %u)\n",
-                         varying_vectors, ctx->Const.MaxVarying);
-            return false;
-         }
-      }
-   } else {
-      const unsigned float_components = varying_vectors * 4;
-      if (float_components > ctx->Const.MaxVarying * 4) {
-         if (ctx->Const.GLSLSkipStrictMaxVaryingLimitCheck) {
-            linker_warning(prog, "shader uses too many varying components "
-                           "(%u > %u), but the driver will try to optimize "
-                           "them out; this is non-portable out-of-spec "
-                           "behavior\n",
-                           float_components, ctx->Const.MaxVarying * 4);
-         } else {
-            linker_error(prog, "shader uses too many varying components "
-                         "(%u > %u)\n",
-                         float_components, ctx->Const.MaxVarying * 4);
-            return false;
-         }
-      }
+   
+   // Do TFB assignments
+   foreach_list(node, delayed_assignment) {
+       varying_info *vi = (varying_info *) node;
+       for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
+          printf("name is %s, at %d,%d\n", vi->produced->name, 
vi->produced->location, vi->produced->horizontal_location);
+          printf("assigned is 
%d\n",tfeedback_decls[i].matches_var(vi->produced));
+          if (!tfeedback_decls[i].is_assigned() &&
+              tfeedback_decls[i].matches_var(vi->produced)) {
+               if (!tfeedback_decls[i].assign_location(ctx, prog, 
vi->produced)) {
+                  ralloc_free(rctx);
+                  return false;
+               }
+          }
+       }
+   }             
+   //linker_error(prog, "protect");
+   
+   if (consumer) {
+       foreach_list(node, consumer->ir) {
+          ir_variable *const var = ((ir_instruction *) node)->as_variable();
+          
+          if ((var == NULL) || (var->mode != ir_var_in))
+               continue;
+          
+          if (var->location == -1) {
+               if (prog->Version <= 120) {
+                  /* On page 25 (page 31 of the PDF) of the GLSL 1.20 spec:
+                   *
+                   *     Only those varying variables used (i.e. read) in
+                   *     the fragment shader executable must be written to
+                   *     by the vertex shader executable; declaring
+                   *     superfluous varying variables in a vertex shader is
+                   *     permissible.
+                   *
+                   * We interpret this text as meaning that the VS must
+                   * write the variable for the FS to read it.  See
+                   * "glsl1-varying read but not written" in piglit.
+                   */
+                  
+                  linker_error(prog, "fragment shader varying %s not written "
+                               "by vertex shader\n.", var->name);
+               }
+               
+               /* An 'in' variable is only really a shader input if its
+                * value is written by the previous stage.
+                */
+               var->mode = ir_var_auto;
+          } 
+       }
    }
-
+   ralloc_free(rctx);
    return true;
 }
 
-- 
1.7.7

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