svn merge ^/branches/released .

1 files changed, 1672 insertions, 1676 deletions

diff --git a/mesalib/src/glsl/linker.cpp b/mesalib/src/glsl/linker.cpp
index 9f4b4149c..bf7a56353 100644
--- a/mesalib/src/glsl/linker.cpp
+++ b/mesalib/src/glsl/linker.cpp
@@ -1,1676 +1,1672 @@
-/*

- * Copyright © 2010 Intel Corporation

- *

- * Permission is hereby granted, free of charge, to any person obtaining a

- * copy of this software and associated documentation files (the "Software"),

- * to deal in the Software without restriction, including without limitation

- * the rights to use, copy, modify, merge, publish, distribute, sublicense,

- * and/or sell copies of the Software, and to permit persons to whom the

- * Software is furnished to do so, subject to the following conditions:

- *

- * The above copyright notice and this permission notice (including the next

- * paragraph) shall be included in all copies or substantial portions of the

- * Software.

- *

- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

- * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

- * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER

- * DEALINGS IN THE SOFTWARE.

- */

-

-/**

- * \file linker.cpp

- * GLSL linker implementation

- *

- * Given a set of shaders that are to be linked to generate a final program,

- * there are three distinct stages.

- *

- * In the first stage shaders are partitioned into groups based on the shader

- * type.  All shaders of a particular type (e.g., vertex shaders) are linked

- * together.

- *

- *   - Undefined references in each shader are resolve to definitions in

- *     another shader.

- *   - Types and qualifiers of uniforms, outputs, and global variables defined

- *     in multiple shaders with the same name are verified to be the same.

- *   - Initializers for uniforms and global variables defined

- *     in multiple shaders with the same name are verified to be the same.

- *

- * The result, in the terminology of the GLSL spec, is a set of shader

- * executables for each processing unit.

- *

- * After the first stage is complete, a series of semantic checks are performed

- * on each of the shader executables.

- *

- *   - Each shader executable must define a \c main function.

- *   - Each vertex shader executable must write to \c gl_Position.

- *   - Each fragment shader executable must write to either \c gl_FragData or

- *     \c gl_FragColor.

- *

- * In the final stage individual shader executables are linked to create a

- * complete exectuable.

- *

- *   - Types of uniforms defined in multiple shader stages with the same name

- *     are verified to be the same.

- *   - Initializers for uniforms defined in multiple shader stages with the

- *     same name are verified to be the same.

- *   - Types and qualifiers of outputs defined in one stage are verified to

- *     be the same as the types and qualifiers of inputs defined with the same

- *     name in a later stage.

- *

- * \author Ian Romanick <ian.d.romanick@intel.com>

- */

-#include <cstdlib>

-#include <cstdio>

-#include <cstdarg>

-#include <climits>

-

-#include "main/core.h"

-#include "glsl_symbol_table.h"

-#include "ir.h"

-#include "program.h"

-#include "program/hash_table.h"

-#include "linker.h"

-#include "ir_optimization.h"

-

-extern "C" {

-#include "main/shaderobj.h"

-}

-

-/**

- * Visitor that determines whether or not a variable is ever written.

- */

-class find_assignment_visitor : public ir_hierarchical_visitor {

-public:

-   find_assignment_visitor(const char *name)

-      : name(name), found(false)

-   {

-      /* empty */

-   }

-

-   virtual ir_visitor_status visit_enter(ir_assignment *ir)

-   {

-      ir_variable *const var = ir->lhs->variable_referenced();

-

-      if (strcmp(name, var->name) == 0) {

-	 found = true;

-	 return visit_stop;

-      }

-

-      return visit_continue_with_parent;

-   }

-

-   virtual ir_visitor_status visit_enter(ir_call *ir)

-   {

-      exec_list_iterator sig_iter = ir->get_callee()->parameters.iterator();

-      foreach_iter(exec_list_iterator, iter, *ir) {

-	 ir_rvalue *param_rval = (ir_rvalue *)iter.get();

-	 ir_variable *sig_param = (ir_variable *)sig_iter.get();

-

-	 if (sig_param->mode == ir_var_out ||

-	     sig_param->mode == ir_var_inout) {

-	    ir_variable *var = param_rval->variable_referenced();

-	    if (var && strcmp(name, var->name) == 0) {

-	       found = true;

-	       return visit_stop;

-	    }

-	 }

-	 sig_iter.next();

-      }

-

-      return visit_continue_with_parent;

-   }

-

-   bool variable_found()

-   {

-      return found;

-   }

-

-private:

-   const char *name;       /**< Find writes to a variable with this name. */

-   bool found;             /**< Was a write to the variable found? */

-};

-

-

-/**

- * Visitor that determines whether or not a variable is ever read.

- */

-class find_deref_visitor : public ir_hierarchical_visitor {

-public:

-   find_deref_visitor(const char *name)

-      : name(name), found(false)

-   {

-      /* empty */

-   }

-

-   virtual ir_visitor_status visit(ir_dereference_variable *ir)

-   {

-      if (strcmp(this->name, ir->var->name) == 0) {

-	 this->found = true;

-	 return visit_stop;

-      }

-

-      return visit_continue;

-   }

-

-   bool variable_found() const

-   {

-      return this->found;

-   }

-

-private:

-   const char *name;       /**< Find writes to a variable with this name. */

-   bool found;             /**< Was a write to the variable found? */

-};

-

-

-void

-linker_error_printf(gl_shader_program *prog, const char *fmt, ...)

-{

-   va_list ap;

-

-   prog->InfoLog = talloc_strdup_append(prog->InfoLog, "error: ");

-   va_start(ap, fmt);

-   prog->InfoLog = talloc_vasprintf_append(prog->InfoLog, fmt, ap);

-   va_end(ap);

-}

-

-

-void

-invalidate_variable_locations(gl_shader *sh, enum ir_variable_mode mode,

-			      int generic_base)

-{

-   foreach_list(node, sh->ir) {

-      ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-      if ((var == NULL) || (var->mode != (unsigned) mode))

-	 continue;

-

-      /* Only assign locations for generic attributes / varyings / etc.

-       */

-      if ((var->location >= generic_base) && !var->explicit_location)

-	  var->location = -1;

-   }

-}

-

-

-/**

- * Determine the number of attribute slots required for a particular type

- *

- * This code is here because it implements the language rules of a specific

- * GLSL version.  Since it's a property of the language and not a property of

- * types in general, it doesn't really belong in glsl_type.

- */

-unsigned

-count_attribute_slots(const glsl_type *t)

-{

-   /* From page 31 (page 37 of the PDF) of the GLSL 1.50 spec:

-    *

-    *     "A scalar input counts the same amount against this limit as a vec4,

-    *     so applications may want to consider packing groups of four

-    *     unrelated float inputs together into a vector to better utilize the

-    *     capabilities of the underlying hardware. A matrix input will use up

-    *     multiple locations.  The number of locations used will equal the

-    *     number of columns in the matrix."

-    *

-    * The spec does not explicitly say how arrays are counted.  However, it

-    * should be safe to assume the total number of slots consumed by an array

-    * is the number of entries in the array multiplied by the number of slots

-    * consumed by a single element of the array.

-    */

-

-   if (t->is_array())

-      return t->array_size() * count_attribute_slots(t->element_type());

-

-   if (t->is_matrix())

-      return t->matrix_columns;

-

-   return 1;

-}

-

-

-/**

- * Verify that a vertex shader executable meets all semantic requirements

- *

- * \param shader  Vertex shader executable to be verified

- */

-bool

-validate_vertex_shader_executable(struct gl_shader_program *prog,

-				  struct gl_shader *shader)

-{

-   if (shader == NULL)

-      return true;

-

-   find_assignment_visitor find("gl_Position");

-   find.run(shader->ir);

-   if (!find.variable_found()) {

-      linker_error_printf(prog,

-			  "vertex shader does not write to `gl_Position'\n");

-      return false;

-   }

-

-   return true;

-}

-

-

-/**

- * Verify that a fragment shader executable meets all semantic requirements

- *

- * \param shader  Fragment shader executable to be verified

- */

-bool

-validate_fragment_shader_executable(struct gl_shader_program *prog,

-				    struct gl_shader *shader)

-{

-   if (shader == NULL)

-      return true;

-

-   find_assignment_visitor frag_color("gl_FragColor");

-   find_assignment_visitor frag_data("gl_FragData");

-

-   frag_color.run(shader->ir);

-   frag_data.run(shader->ir);

-

-   if (frag_color.variable_found() && frag_data.variable_found()) {

-      linker_error_printf(prog,  "fragment shader writes to both "

-			  "`gl_FragColor' and `gl_FragData'\n");

-      return false;

-   }

-

-   return true;

-}

-

-

-/**

- * Generate a string describing the mode of a variable

- */

-static const char *

-mode_string(const ir_variable *var)

-{

-   switch (var->mode) {

-   case ir_var_auto:

-      return (var->read_only) ? "global constant" : "global variable";

-

-   case ir_var_uniform: return "uniform";

-   case ir_var_in:      return "shader input";

-   case ir_var_out:     return "shader output";

-   case ir_var_inout:   return "shader inout";

-

-   case ir_var_temporary:

-   default:

-      assert(!"Should not get here.");

-      return "invalid variable";

-   }

-}

-

-

-/**

- * Perform validation of global variables used across multiple shaders

- */

-bool

-cross_validate_globals(struct gl_shader_program *prog,

-		       struct gl_shader **shader_list,

-		       unsigned num_shaders,

-		       bool uniforms_only)

-{

-   /* Examine all of the uniforms in all of the shaders and cross validate

-    * them.

-    */

-   glsl_symbol_table variables;

-   for (unsigned i = 0; i < num_shaders; i++) {

-      if (shader_list[i] == NULL)

-	 continue;

-

-      foreach_list(node, shader_list[i]->ir) {

-	 ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-	 if (var == NULL)

-	    continue;

-

-	 if (uniforms_only && (var->mode != ir_var_uniform))

-	    continue;

-

-	 /* Don't cross validate temporaries that are at global scope.  These

-	  * will eventually get pulled into the shaders 'main'.

-	  */

-	 if (var->mode == ir_var_temporary)

-	    continue;

-

-	 /* If a global with this name has already been seen, verify that the

-	  * new instance has the same type.  In addition, if the globals have

-	  * initializers, the values of the initializers must be the same.

-	  */

-	 ir_variable *const existing = variables.get_variable(var->name);

-	 if (existing != NULL) {

-	    if (var->type != existing->type) {

-	       /* Consider the types to be "the same" if both types are arrays

-		* of the same type and one of the arrays is implicitly sized.

-		* In addition, set the type of the linked variable to the

-		* explicitly sized array.

-		*/

-	       if (var->type->is_array()

-		   && existing->type->is_array()

-		   && (var->type->fields.array == existing->type->fields.array)

-		   && ((var->type->length == 0)

-		       || (existing->type->length == 0))) {

-		  if (existing->type->length == 0) {

-		     existing->type = var->type;

-		     existing->max_array_access =

-			MAX2(existing->max_array_access,

-			     var->max_array_access);

-		  }

-	       } else {

-		  linker_error_printf(prog, "%s `%s' declared as type "

-				      "`%s' and type `%s'\n",

-				      mode_string(var),

-				      var->name, var->type->name,

-				      existing->type->name);

-		  return false;

-	       }

-	    }

-

-	    if (var->explicit_location) {

-	       if (existing->explicit_location

-		   && (var->location != existing->location)) {

-		     linker_error_printf(prog, "explicit locations for %s "

-					 "`%s' have differing values\n",

-					 mode_string(var), var->name);

-		     return false;

-	       }

-

-	       existing->location = var->location;

-	       existing->explicit_location = true;

-	    }

-

-	    /* FINISHME: Handle non-constant initializers.

-	     */

-	    if (var->constant_value != NULL) {

-	       if (existing->constant_value != NULL) {

-		  if (!var->constant_value->has_value(existing->constant_value)) {

-		     linker_error_printf(prog, "initializers for %s "

-					 "`%s' have differing values\n",

-					 mode_string(var), var->name);

-		     return false;

-		  }

-	       } else

-		  /* If the first-seen instance of a particular uniform did not

-		   * have an initializer but a later instance does, copy the

-		   * initializer to the version stored in the symbol table.

-		   */

-		  /* FINISHME: This is wrong.  The constant_value field should

-		   * FINISHME: not be modified!  Imagine a case where a shader

-		   * FINISHME: without an initializer is linked in two different

-		   * FINISHME: programs with shaders that have differing

-		   * FINISHME: initializers.  Linking with the first will

-		   * FINISHME: modify the shader, and linking with the second

-		   * FINISHME: will fail.

-		   */

-		  existing->constant_value =

-		     var->constant_value->clone(talloc_parent(existing), NULL);

-	    }

-

-	    if (existing->invariant != var->invariant) {

-	       linker_error_printf(prog, "declarations for %s `%s' have "

-	                           "mismatching invariant qualifiers\n",

-	                           mode_string(var), var->name);

-	       return false;

-	    }

-            if (existing->centroid != var->centroid) {

-               linker_error_printf(prog, "declarations for %s `%s' have "

-                                   "mismatching centroid qualifiers\n",

-                                   mode_string(var), var->name);

-               return false;

-            }

-	 } else

-	    variables.add_variable(var);

-      }

-   }

-

-   return true;

-}

-

-

-/**

- * Perform validation of uniforms used across multiple shader stages

- */

-bool

-cross_validate_uniforms(struct gl_shader_program *prog)

-{

-   return cross_validate_globals(prog, prog->_LinkedShaders,

-				 MESA_SHADER_TYPES, true);

-}

-

-

-/**

- * Validate that outputs from one stage match inputs of another

- */

-bool

-cross_validate_outputs_to_inputs(struct gl_shader_program *prog,

-				 gl_shader *producer, gl_shader *consumer)

-{

-   glsl_symbol_table parameters;

-   /* FINISHME: Figure these out dynamically. */

-   const char *const producer_stage = "vertex";

-   const char *const consumer_stage = "fragment";

-

-   /* Find all shader outputs in the "producer" stage.

-    */

-   foreach_list(node, producer->ir) {

-      ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-      /* FINISHME: For geometry shaders, this should also look for inout

-       * FINISHME: variables.

-       */

-      if ((var == NULL) || (var->mode != ir_var_out))

-	 continue;

-

-      parameters.add_variable(var);

-   }

-

-

-   /* Find all shader inputs in the "consumer" stage.  Any variables that have

-    * matching outputs already in the symbol table must have the same type and

-    * qualifiers.

-    */

-   foreach_list(node, consumer->ir) {

-      ir_variable *const input = ((ir_instruction *) node)->as_variable();

-

-      /* FINISHME: For geometry shaders, this should also look for inout

-       * FINISHME: variables.

-       */

-      if ((input == NULL) || (input->mode != ir_var_in))

-	 continue;

-

-      ir_variable *const output = parameters.get_variable(input->name);

-      if (output != NULL) {

-	 /* Check that the types match between stages.

-	  */

-	 if (input->type != output->type) {

-	    /* There is a bit of a special case for gl_TexCoord.  This

-	     * built-in is unsized by default.  Appliations that variable

-	     * access it must redeclare it with a size.  There is some

-	     * language in the GLSL spec that implies the fragment shader

-	     * and vertex shader do not have to agree on this size.  Other

-	     * driver behave this way, and one or two applications seem to

-	     * rely on it.

-	     *

-	     * Neither declaration needs to be modified here because the array

-	     * sizes are fixed later when update_array_sizes is called.

-	     *

-	     * From page 48 (page 54 of the PDF) of the GLSL 1.10 spec:

-	     *

-	     *     "Unlike user-defined varying variables, the built-in

-	     *     varying variables don't have a strict one-to-one

-	     *     correspondence between the vertex language and the

-	     *     fragment language."

-	     */

-	    if (!output->type->is_array()

-		|| (strncmp("gl_", output->name, 3) != 0)) {

-	       linker_error_printf(prog,

-				   "%s shader output `%s' declared as "

-				   "type `%s', but %s shader input declared "

-				   "as type `%s'\n",

-				   producer_stage, output->name,

-				   output->type->name,

-				   consumer_stage, input->type->name);

-	       return false;

-	    }

-	 }

-

-	 /* Check that all of the qualifiers match between stages.

-	  */

-	 if (input->centroid != output->centroid) {

-	    linker_error_printf(prog,

-				"%s shader output `%s' %s centroid qualifier, "

-				"but %s shader input %s centroid qualifier\n",

-				producer_stage,

-				output->name,

-				(output->centroid) ? "has" : "lacks",

-				consumer_stage,

-				(input->centroid) ? "has" : "lacks");

-	    return false;

-	 }

-

-	 if (input->invariant != output->invariant) {

-	    linker_error_printf(prog,

-				"%s shader output `%s' %s invariant qualifier, "

-				"but %s shader input %s invariant qualifier\n",

-				producer_stage,

-				output->name,

-				(output->invariant) ? "has" : "lacks",

-				consumer_stage,

-				(input->invariant) ? "has" : "lacks");

-	    return false;

-	 }

-

-	 if (input->interpolation != output->interpolation) {

-	    linker_error_printf(prog,

-				"%s shader output `%s' specifies %s "

-				"interpolation qualifier, "

-				"but %s shader input specifies %s "

-				"interpolation qualifier\n",

-				producer_stage,

-				output->name,

-				output->interpolation_string(),

-				consumer_stage,

-				input->interpolation_string());

-	    return false;

-	 }

-      }

-   }

-

-   return true;

-}

-

-

-/**

- * Populates a shaders symbol table with all global declarations

- */

-static void

-populate_symbol_table(gl_shader *sh)

-{

-   sh->symbols = new(sh) glsl_symbol_table;

-

-   foreach_list(node, sh->ir) {

-      ir_instruction *const inst = (ir_instruction *) node;

-      ir_variable *var;

-      ir_function *func;

-

-      if ((func = inst->as_function()) != NULL) {

-	 sh->symbols->add_function(func);

-      } else if ((var = inst->as_variable()) != NULL) {

-	 sh->symbols->add_variable(var);

-      }

-   }

-}

-

-

-/**

- * Remap variables referenced in an instruction tree

- *

- * This is used when instruction trees are cloned from one shader and placed in

- * another.  These trees will contain references to \c ir_variable nodes that

- * do not exist in the target shader.  This function finds these \c ir_variable

- * references and replaces the references with matching variables in the target

- * shader.

- *

- * If there is no matching variable in the target shader, a clone of the

- * \c ir_variable is made and added to the target shader.  The new variable is

- * added to \b both the instruction stream and the symbol table.

- *

- * \param inst         IR tree that is to be processed.

- * \param symbols      Symbol table containing global scope symbols in the

- *                     linked shader.

- * \param instructions Instruction stream where new variable declarations

- *                     should be added.

- */

-void

-remap_variables(ir_instruction *inst, struct gl_shader *target,

-		hash_table *temps)

-{

-   class remap_visitor : public ir_hierarchical_visitor {

-   public:

-	 remap_visitor(struct gl_shader *target,

-		    hash_table *temps)

-      {

-	 this->target = target;

-	 this->symbols = target->symbols;

-	 this->instructions = target->ir;

-	 this->temps = temps;

-      }

-

-      virtual ir_visitor_status visit(ir_dereference_variable *ir)

-      {

-	 if (ir->var->mode == ir_var_temporary) {

-	    ir_variable *var = (ir_variable *) hash_table_find(temps, ir->var);

-

-	    assert(var != NULL);

-	    ir->var = var;

-	    return visit_continue;

-	 }

-

-	 ir_variable *const existing =

-	    this->symbols->get_variable(ir->var->name);

-	 if (existing != NULL)

-	    ir->var = existing;

-	 else {

-	    ir_variable *copy = ir->var->clone(this->target, NULL);

-

-	    this->symbols->add_variable(copy);

-	    this->instructions->push_head(copy);

-	    ir->var = copy;

-	 }

-

-	 return visit_continue;

-      }

-

-   private:

-      struct gl_shader *target;

-      glsl_symbol_table *symbols;

-      exec_list *instructions;

-      hash_table *temps;

-   };

-

-   remap_visitor v(target, temps);

-

-   inst->accept(&v);

-}

-

-

-/**

- * Move non-declarations from one instruction stream to another

- *

- * The intended usage pattern of this function is to pass the pointer to the

- * head sentinel of a list (i.e., a pointer to the list cast to an \c exec_node

- * pointer) for \c last and \c false for \c make_copies on the first

- * call.  Successive calls pass the return value of the previous call for

- * \c last and \c true for \c make_copies.

- *

- * \param instructions Source instruction stream

- * \param last         Instruction after which new instructions should be

- *                     inserted in the target instruction stream

- * \param make_copies  Flag selecting whether instructions in \c instructions

- *                     should be copied (via \c ir_instruction::clone) into the

- *                     target list or moved.

- *

- * \return

- * The new "last" instruction in the target instruction stream.  This pointer

- * is suitable for use as the \c last parameter of a later call to this

- * function.

- */

-exec_node *

-move_non_declarations(exec_list *instructions, exec_node *last,

-		      bool make_copies, gl_shader *target)

-{

-   hash_table *temps = NULL;

-

-   if (make_copies)

-      temps = hash_table_ctor(0, hash_table_pointer_hash,

-			      hash_table_pointer_compare);

-

-   foreach_list_safe(node, instructions) {

-      ir_instruction *inst = (ir_instruction *) node;

-

-      if (inst->as_function())

-	 continue;

-

-      ir_variable *var = inst->as_variable();

-      if ((var != NULL) && (var->mode != ir_var_temporary))

-	 continue;

-

-      assert(inst->as_assignment()

-	     || ((var != NULL) && (var->mode == ir_var_temporary)));

-

-      if (make_copies) {

-	 inst = inst->clone(target, NULL);

-

-	 if (var != NULL)

-	    hash_table_insert(temps, inst, var);

-	 else

-	    remap_variables(inst, target, temps);

-      } else {

-	 inst->remove();

-      }

-

-      last->insert_after(inst);

-      last = inst;

-   }

-

-   if (make_copies)

-      hash_table_dtor(temps);

-

-   return last;

-}

-

-/**

- * Get the function signature for main from a shader

- */

-static ir_function_signature *

-get_main_function_signature(gl_shader *sh)

-{

-   ir_function *const f = sh->symbols->get_function("main");

-   if (f != NULL) {

-      exec_list void_parameters;

-

-      /* Look for the 'void main()' signature and ensure that it's defined.

-       * This keeps the linker from accidentally pick a shader that just

-       * contains a prototype for main.

-       *

-       * We don't have to check for multiple definitions of main (in multiple

-       * shaders) because that would have already been caught above.

-       */

-      ir_function_signature *sig = f->matching_signature(&void_parameters);

-      if ((sig != NULL) && sig->is_defined) {

-	 return sig;

-      }

-   }

-

-   return NULL;

-}

-

-

-/**

- * Combine a group of shaders for a single stage to generate a linked shader

- *

- * \note

- * If this function is supplied a single shader, it is cloned, and the new

- * shader is returned.

- */

-static struct gl_shader *

-link_intrastage_shaders(void *mem_ctx,

-			struct gl_context *ctx,

-			struct gl_shader_program *prog,

-			struct gl_shader **shader_list,

-			unsigned num_shaders)

-{

-   /* Check that global variables defined in multiple shaders are consistent.

-    */

-   if (!cross_validate_globals(prog, shader_list, num_shaders, false))

-      return NULL;

-

-   /* Check that there is only a single definition of each function signature

-    * across all shaders.

-    */

-   for (unsigned i = 0; i < (num_shaders - 1); i++) {

-      foreach_list(node, shader_list[i]->ir) {

-	 ir_function *const f = ((ir_instruction *) node)->as_function();

-

-	 if (f == NULL)

-	    continue;

-

-	 for (unsigned j = i + 1; j < num_shaders; j++) {

-	    ir_function *const other =

-	       shader_list[j]->symbols->get_function(f->name);

-

-	    /* If the other shader has no function (and therefore no function

-	     * signatures) with the same name, skip to the next shader.

-	     */

-	    if (other == NULL)

-	       continue;

-

-	    foreach_iter (exec_list_iterator, iter, *f) {

-	       ir_function_signature *sig =

-		  (ir_function_signature *) iter.get();

-

-	       if (!sig->is_defined || sig->is_builtin)

-		  continue;

-

-	       ir_function_signature *other_sig =

-		  other->exact_matching_signature(& sig->parameters);

-

-	       if ((other_sig != NULL) && other_sig->is_defined

-		   && !other_sig->is_builtin) {

-		  linker_error_printf(prog,

-				      "function `%s' is multiply defined",

-				      f->name);

-		  return NULL;

-	       }

-	    }

-	 }

-      }

-   }

-

-   /* Find the shader that defines main, and make a clone of it.

-    *

-    * Starting with the clone, search for undefined references.  If one is

-    * found, find the shader that defines it.  Clone the reference and add

-    * it to the shader.  Repeat until there are no undefined references or

-    * until a reference cannot be resolved.

-    */

-   gl_shader *main = NULL;

-   for (unsigned i = 0; i < num_shaders; i++) {

-      if (get_main_function_signature(shader_list[i]) != NULL) {

-	 main = shader_list[i];

-	 break;

-      }

-   }

-

-   if (main == NULL) {

-      linker_error_printf(prog, "%s shader lacks `main'\n",

-			  (shader_list[0]->Type == GL_VERTEX_SHADER)

-			  ? "vertex" : "fragment");

-      return NULL;

-   }

-

-   gl_shader *linked = ctx->Driver.NewShader(NULL, 0, main->Type);

-   linked->ir = new(linked) exec_list;

-   clone_ir_list(mem_ctx, linked->ir, main->ir);

-

-   populate_symbol_table(linked);

-

-   /* The a pointer to the main function in the final linked shader (i.e., the

-    * copy of the original shader that contained the main function).

-    */

-   ir_function_signature *const main_sig = get_main_function_signature(linked);

-

-   /* Move any instructions other than variable declarations or function

-    * declarations into main.

-    */

-   exec_node *insertion_point =

-      move_non_declarations(linked->ir, (exec_node *) &main_sig->body, false,

-			    linked);

-

-   for (unsigned i = 0; i < num_shaders; i++) {

-      if (shader_list[i] == main)

-	 continue;

-

-      insertion_point = move_non_declarations(shader_list[i]->ir,

-					      insertion_point, true, linked);

-   }

-

-   /* Resolve initializers for global variables in the linked shader.

-    */

-   unsigned num_linking_shaders = num_shaders;

-   for (unsigned i = 0; i < num_shaders; i++)

-      num_linking_shaders += shader_list[i]->num_builtins_to_link;

-

-   gl_shader **linking_shaders =

-      (gl_shader **) calloc(num_linking_shaders, sizeof(gl_shader *));

-

-   memcpy(linking_shaders, shader_list,

-	  sizeof(linking_shaders[0]) * num_shaders);

-

-   unsigned idx = num_shaders;

-   for (unsigned i = 0; i < num_shaders; i++) {

-      memcpy(&linking_shaders[idx], shader_list[i]->builtins_to_link,

-	     sizeof(linking_shaders[0]) * shader_list[i]->num_builtins_to_link);

-      idx += shader_list[i]->num_builtins_to_link;

-   }

-

-   assert(idx == num_linking_shaders);

-

-   if (!link_function_calls(prog, linked, linking_shaders,

-			    num_linking_shaders)) {

-      ctx->Driver.DeleteShader(ctx, linked);

-      linked = NULL;

-   }

-

-   free(linking_shaders);

-

-   /* Make a pass over all global variables to ensure that arrays with

-    * unspecified sizes have a size specified.  The size is inferred from the

-    * max_array_access field.

-    */

-   if (linked != NULL) {

-      foreach_list(node, linked->ir) {

-	 ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-	 if (var == NULL)

-	    continue;

-

-	 if ((var->mode != ir_var_auto) && (var->mode != ir_var_temporary))

-	    continue;

-

-	 if (!var->type->is_array() || (var->type->length != 0))

-	    continue;

-

-	 const glsl_type *type =

-	    glsl_type::get_array_instance(var->type->fields.array,

-					  var->max_array_access);

-

-	 assert(type != NULL);

-	 var->type = type;

-      }

-   }

-

-   return linked;

-}

-

-

-struct uniform_node {

-   exec_node link;

-   struct gl_uniform *u;

-   unsigned slots;

-};

-

-/**

- * Update the sizes of linked shader uniform arrays to the maximum

- * array index used.

- *

- * From page 81 (page 95 of the PDF) of the OpenGL 2.1 spec:

- *

- *     If one or more elements of an array are active,

- *     GetActiveUniform will return the name of the array in name,

- *     subject to the restrictions listed above. The type of the array

- *     is returned in type. The size parameter contains the highest

- *     array element index used, plus one. The compiler or linker

- *     determines the highest index used.  There will be only one

- *     active uniform reported by the GL per uniform array.

-

- */

-static void

-update_array_sizes(struct gl_shader_program *prog)

-{

-   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {

-	 if (prog->_LinkedShaders[i] == NULL)

-	    continue;

-

-      foreach_list(node, prog->_LinkedShaders[i]->ir) {

-	 ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-	 if ((var == NULL) || (var->mode != ir_var_uniform &&

-			       var->mode != ir_var_in &&

-			       var->mode != ir_var_out) ||

-	     !var->type->is_array())

-	    continue;

-

-	 unsigned int size = var->max_array_access;

-	 for (unsigned j = 0; j < MESA_SHADER_TYPES; j++) {

-	       if (prog->_LinkedShaders[j] == NULL)

-		  continue;

-

-	    foreach_list(node2, prog->_LinkedShaders[j]->ir) {

-	       ir_variable *other_var = ((ir_instruction *) node2)->as_variable();

-	       if (!other_var)

-		  continue;

-

-	       if (strcmp(var->name, other_var->name) == 0 &&

-		   other_var->max_array_access > size) {

-		  size = other_var->max_array_access;

-	       }

-	    }

-	 }

-

-	 if (size + 1 != var->type->fields.array->length) {

-	    var->type = glsl_type::get_array_instance(var->type->fields.array,

-						      size + 1);

-	    /* FINISHME: We should update the types of array

-	     * dereferences of this variable now.

-	     */

-	 }

-      }

-   }

-}

-

-static void

-add_uniform(void *mem_ctx, exec_list *uniforms, struct hash_table *ht,

-	    const char *name, const glsl_type *type, GLenum shader_type,

-	    unsigned *next_shader_pos, unsigned *total_uniforms)

-{

-   if (type->is_record()) {

-      for (unsigned int i = 0; i < type->length; i++) {

-	 const glsl_type *field_type = type->fields.structure[i].type;

-	 char *field_name = talloc_asprintf(mem_ctx, "%s.%s", name,

-					    type->fields.structure[i].name);

-

-	 add_uniform(mem_ctx, uniforms, ht, field_name, field_type,

-		     shader_type, next_shader_pos, total_uniforms);

-      }

-   } else {

-      uniform_node *n = (uniform_node *) hash_table_find(ht, name);

-      unsigned int vec4_slots;

-      const glsl_type *array_elem_type = NULL;

-

-      if (type->is_array()) {

-	 array_elem_type = type->fields.array;

-	 /* Array of structures. */

-	 if (array_elem_type->is_record()) {

-	    for (unsigned int i = 0; i < type->length; i++) {

-	       char *elem_name = talloc_asprintf(mem_ctx, "%s[%d]", name, i);

-	       add_uniform(mem_ctx, uniforms, ht, elem_name, array_elem_type,

-			   shader_type, next_shader_pos, total_uniforms);

-	    }

-	    return;

-	 }

-      }

-

-      /* Fix the storage size of samplers at 1 vec4 each. Be sure to pad out

-       * vectors to vec4 slots.

-       */

-      if (type->is_array()) {

-	 if (array_elem_type->is_sampler())

-	    vec4_slots = type->length;

-	 else

-	    vec4_slots = type->length * array_elem_type->matrix_columns;

-      } else if (type->is_sampler()) {

-	 vec4_slots = 1;

-      } else {

-	 vec4_slots = type->matrix_columns;

-      }

-

-      if (n == NULL) {

-	 n = (uniform_node *) calloc(1, sizeof(struct uniform_node));

-	 n->u = (gl_uniform *) calloc(1, sizeof(struct gl_uniform));

-	 n->slots = vec4_slots;

-

-	 n->u->Name = strdup(name);

-	 n->u->Type = type;

-	 n->u->VertPos = -1;

-	 n->u->FragPos = -1;

-	 n->u->GeomPos = -1;

-	 (*total_uniforms)++;

-

-	 hash_table_insert(ht, n, name);

-	 uniforms->push_tail(& n->link);

-      }

-

-      switch (shader_type) {

-      case GL_VERTEX_SHADER:

-	 n->u->VertPos = *next_shader_pos;

-	 break;

-      case GL_FRAGMENT_SHADER:

-	 n->u->FragPos = *next_shader_pos;

-	 break;

-      case GL_GEOMETRY_SHADER:

-	 n->u->GeomPos = *next_shader_pos;

-	 break;

-      }

-

-      (*next_shader_pos) += vec4_slots;

-   }

-}

-

-void

-assign_uniform_locations(struct gl_shader_program *prog)

-{

-   /* */

-   exec_list uniforms;

-   unsigned total_uniforms = 0;

-   hash_table *ht = hash_table_ctor(32, hash_table_string_hash,

-				    hash_table_string_compare);

-   void *mem_ctx = talloc_new(NULL);

-

-   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {

-      if (prog->_LinkedShaders[i] == NULL)

-	 continue;

-

-      unsigned next_position = 0;

-

-      foreach_list(node, prog->_LinkedShaders[i]->ir) {

-	 ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-	 if ((var == NULL) || (var->mode != ir_var_uniform))

-	    continue;

-

-	 if (strncmp(var->name, "gl_", 3) == 0) {

-	    /* At the moment, we don't allocate uniform locations for

-	     * builtin uniforms.  It's permitted by spec, and we'll

-	     * likely switch to doing that at some point, but not yet.

-	     */

-	    continue;

-	 }

-

-	 var->location = next_position;

-	 add_uniform(mem_ctx, &uniforms, ht, var->name, var->type,

-		     prog->_LinkedShaders[i]->Type,

-		     &next_position, &total_uniforms);

-      }

-   }

-

-   talloc_free(mem_ctx);

-

-   gl_uniform_list *ul = (gl_uniform_list *)

-      calloc(1, sizeof(gl_uniform_list));

-

-   ul->Size = total_uniforms;

-   ul->NumUniforms = total_uniforms;

-   ul->Uniforms = (gl_uniform *) calloc(total_uniforms, sizeof(gl_uniform));

-

-   unsigned idx = 0;

-   uniform_node *next;

-   for (uniform_node *node = (uniform_node *) uniforms.head

-	   ; node->link.next != NULL

-	   ; node = next) {

-      next = (uniform_node *) node->link.next;

-

-      node->link.remove();

-      memcpy(&ul->Uniforms[idx], node->u, sizeof(gl_uniform));

-      idx++;

-

-      free(node->u);

-      free(node);

-   }

-

-   hash_table_dtor(ht);

-

-   prog->Uniforms = ul;

-}

-

-

-/**

- * Find a contiguous set of available bits in a bitmask

- *

- * \param used_mask     Bits representing used (1) and unused (0) locations

- * \param needed_count  Number of contiguous bits needed.

- *

- * \return

- * Base location of the available bits on success or -1 on failure.

- */

-int

-find_available_slots(unsigned used_mask, unsigned needed_count)

-{

-   unsigned needed_mask = (1 << needed_count) - 1;

-   const int max_bit_to_test = (8 * sizeof(used_mask)) - needed_count;

-

-   /* The comparison to 32 is redundant, but without it GCC emits "warning:

-    * cannot optimize possibly infinite loops" for the loop below.

-    */

-   if ((needed_count == 0) || (max_bit_to_test < 0) || (max_bit_to_test > 32))

-      return -1;

-

-   for (int i = 0; i <= max_bit_to_test; i++) {

-      if ((needed_mask & ~used_mask) == needed_mask)

-	 return i;

-

-      needed_mask <<= 1;

-   }

-

-   return -1;

-}

-

-

-bool

-assign_attribute_locations(gl_shader_program *prog, unsigned max_attribute_index)

-{

-   /* Mark invalid attribute locations as being used.

-    */

-   unsigned used_locations = (max_attribute_index >= 32)

-      ? ~0 : ~((1 << max_attribute_index) - 1);

-

-   gl_shader *const sh = prog->_LinkedShaders[0];

-   assert(sh->Type == GL_VERTEX_SHADER);

-

-   /* Operate in a total of four passes.

-    *

-    * 1. Invalidate the location assignments for all vertex shader inputs.

-    *

-    * 2. Assign locations for inputs that have user-defined (via

-    *    glBindVertexAttribLocation) locatoins.

-    *

-    * 3. Sort the attributes without assigned locations by number of slots

-    *    required in decreasing order.  Fragmentation caused by attribute

-    *    locations assigned by the application may prevent large attributes

-    *    from having enough contiguous space.

-    *

-    * 4. Assign locations to any inputs without assigned locations.

-    */

-

-   invalidate_variable_locations(sh, ir_var_in, VERT_ATTRIB_GENERIC0);

-

-   if (prog->Attributes != NULL) {

-      for (unsigned i = 0; i < prog->Attributes->NumParameters; i++) {

-	 ir_variable *const var =

-	    sh->symbols->get_variable(prog->Attributes->Parameters[i].Name);

-

-	 /* Note: attributes that occupy multiple slots, such as arrays or

-	  * matrices, may appear in the attrib array multiple times.

-	  */

-	 if ((var == NULL) || (var->location != -1))

-	    continue;

-

-	 /* From page 61 of the OpenGL 4.0 spec:

-	  *

-	  *     "LinkProgram will fail if the attribute bindings assigned by

-	  *     BindAttribLocation do not leave not enough space to assign a

-	  *     location for an active matrix attribute or an active attribute

-	  *     array, both of which require multiple contiguous generic

-	  *     attributes."

-	  *

-	  * Previous versions of the spec contain similar language but omit the

-	  * bit about attribute arrays.

-	  *

-	  * Page 61 of the OpenGL 4.0 spec also says:

-	  *

-	  *     "It is possible for an application to bind more than one

-	  *     attribute name to the same location. This is referred to as

-	  *     aliasing. This will only work if only one of the aliased

-	  *     attributes is active in the executable program, or if no path

-	  *     through the shader consumes more than one attribute of a set

-	  *     of attributes aliased to the same location. A link error can

-	  *     occur if the linker determines that every path through the

-	  *     shader consumes multiple aliased attributes, but

-	  *     implementations are not required to generate an error in this

-	  *     case."

-	  *

-	  * These two paragraphs are either somewhat contradictory, or I don't

-	  * fully understand one or both of them.

-	  */

-	 /* FINISHME: The code as currently written does not support attribute

-	  * FINISHME: location aliasing (see comment above).

-	  */

-	 const int attr = prog->Attributes->Parameters[i].StateIndexes[0];

-	 const unsigned slots = count_attribute_slots(var->type);

-

-	 /* Mask representing the contiguous slots that will be used by this

-	  * attribute.

-	  */

-	 const unsigned use_mask = (1 << slots) - 1;

-

-	 /* Generate a link error if the set of bits requested for this

-	  * attribute overlaps any previously allocated bits.

-	  */

-	 if ((~(use_mask << attr) & used_locations) != used_locations) {

-	    linker_error_printf(prog,

-				"insufficient contiguous attribute locations "

-				"available for vertex shader input `%s'",

-				var->name);

-	    return false;

-	 }

-

-	 var->location = VERT_ATTRIB_GENERIC0 + attr;

-	 used_locations |= (use_mask << attr);

-      }

-   }

-

-   /* Temporary storage for the set of attributes that need locations assigned.

-    */

-   struct temp_attr {

-      unsigned slots;

-      ir_variable *var;

-

-      /* Used below in the call to qsort. */

-      static int compare(const void *a, const void *b)

-      {

-	 const temp_attr *const l = (const temp_attr *) a;

-	 const temp_attr *const r = (const temp_attr *) b;

-

-	 /* Reversed because we want a descending order sort below. */

-	 return r->slots - l->slots;

-      }

-   } to_assign[16];

-

-   unsigned num_attr = 0;

-

-   foreach_list(node, sh->ir) {

-      ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-      if ((var == NULL) || (var->mode != ir_var_in))

-	 continue;

-

-      if (var->explicit_location) {

-	 const unsigned slots = count_attribute_slots(var->type);

-	 const unsigned use_mask = (1 << slots) - 1;

-	 const int attr = var->location - VERT_ATTRIB_GENERIC0;

-

-	 if ((var->location >= (int)(max_attribute_index + VERT_ATTRIB_GENERIC0))

-	     || (var->location < 0)) {

-	    linker_error_printf(prog,

-				"invalid explicit location %d specified for "

-				"`%s'\n",

-				(var->location < 0) ? var->location : attr,

-				var->name);

-	    return false;

-	 } else if (var->location >= VERT_ATTRIB_GENERIC0) {

-	    used_locations |= (use_mask << attr);

-	 }

-      }

-

-      /* The location was explicitly assigned, nothing to do here.

-       */

-      if (var->location != -1)

-	 continue;

-

-      to_assign[num_attr].slots = count_attribute_slots(var->type);

-      to_assign[num_attr].var = var;

-      num_attr++;

-   }

-

-   /* If all of the attributes were assigned locations by the application (or

-    * are built-in attributes with fixed locations), return early.  This should

-    * be the common case.

-    */

-   if (num_attr == 0)

-      return true;

-

-   qsort(to_assign, num_attr, sizeof(to_assign[0]), temp_attr::compare);

-

-   /* VERT_ATTRIB_GENERIC0 is a psdueo-alias for VERT_ATTRIB_POS.  It can only

-    * be explicitly assigned by via glBindAttribLocation.  Mark it as reserved

-    * to prevent it from being automatically allocated below.

-    */

-   find_deref_visitor find("gl_Vertex");

-   find.run(sh->ir);

-   if (find.variable_found())

-      used_locations |= (1 << 0);

-

-   for (unsigned i = 0; i < num_attr; i++) {

-      /* Mask representing the contiguous slots that will be used by this

-       * attribute.

-       */

-      const unsigned use_mask = (1 << to_assign[i].slots) - 1;

-

-      int location = find_available_slots(used_locations, to_assign[i].slots);

-

-      if (location < 0) {

-	 linker_error_printf(prog,

-			     "insufficient contiguous attribute locations "

-			     "available for vertex shader input `%s'",

-			     to_assign[i].var->name);

-	 return false;

-      }

-

-      to_assign[i].var->location = VERT_ATTRIB_GENERIC0 + location;

-      used_locations |= (use_mask << location);

-   }

-

-   return true;

-}

-

-

-/**

- * Demote shader inputs and outputs that are not used in other stages

- */

-void

-demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)

-{

-   foreach_list(node, sh->ir) {

-      ir_variable *const var = ((ir_instruction *) node)->as_variable();

-

-      if ((var == NULL) || (var->mode != int(mode)))

-	 continue;

-

-      /* A shader 'in' or 'out' variable is only really an input or output if

-       * its value is used by other shader stages.  This will cause the variable

-       * to have a location assigned.

-       */

-      if (var->location == -1) {

-	 var->mode = ir_var_auto;

-      }

-   }

-}

-

-

-void

-assign_varying_locations(struct gl_shader_program *prog,

-			 gl_shader *producer, gl_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);

-

-      output_var->location = output_index;

-      input_var->location = input_index;

-

-      /* FINISHME: Support for "varying" records in GLSL 1.50. */

-      assert(!output_var->type->is_record());

-

-      if (output_var->type->is_array()) {

-	 const unsigned slots = output_var->type->length

-	    * output_var->type->fields.array->matrix_columns;

-

-	 output_index += slots;

-	 input_index += slots;

-      } else {

-	 const unsigned slots = output_var->type->matrix_columns;

-

-	 output_index += slots;

-	 input_index += slots;

-      }

-   }

-

-   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_printf(prog, "fragment shader varying %s not written "

-				"by vertex shader\n.", var->name);

-	    prog->LinkStatus = false;

-	 }

-

-	 /* An 'in' variable is only really a shader input if its

-	  * value is written by the previous stage.

-	  */

-	 var->mode = ir_var_auto;

-      }

-   }

-}

-

-

-void

-link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)

-{

-   void *mem_ctx = talloc_init("temporary linker context");

-

-   prog->LinkStatus = false;

-   prog->Validated = false;

-   prog->_Used = false;

-

-   if (prog->InfoLog != NULL)

-      talloc_free(prog->InfoLog);

-

-   prog->InfoLog = talloc_strdup(NULL, "");

-

-   /* Separate the shaders into groups based on their type.

-    */

-   struct gl_shader **vert_shader_list;

-   unsigned num_vert_shaders = 0;

-   struct gl_shader **frag_shader_list;

-   unsigned num_frag_shaders = 0;

-

-   vert_shader_list = (struct gl_shader **)

-      calloc(2 * prog->NumShaders, sizeof(struct gl_shader *));

-   frag_shader_list =  &vert_shader_list[prog->NumShaders];

-

-   unsigned min_version = UINT_MAX;

-   unsigned max_version = 0;

-   for (unsigned i = 0; i < prog->NumShaders; i++) {

-      min_version = MIN2(min_version, prog->Shaders[i]->Version);

-      max_version = MAX2(max_version, prog->Shaders[i]->Version);

-

-      switch (prog->Shaders[i]->Type) {

-      case GL_VERTEX_SHADER:

-	 vert_shader_list[num_vert_shaders] = prog->Shaders[i];

-	 num_vert_shaders++;

-	 break;

-      case GL_FRAGMENT_SHADER:

-	 frag_shader_list[num_frag_shaders] = prog->Shaders[i];

-	 num_frag_shaders++;

-	 break;

-      case GL_GEOMETRY_SHADER:

-	 /* FINISHME: Support geometry shaders. */

-	 assert(prog->Shaders[i]->Type != GL_GEOMETRY_SHADER);

-	 break;

-      }

-   }

-

-   /* Previous to GLSL version 1.30, different compilation units could mix and

-    * match shading language versions.  With GLSL 1.30 and later, the versions

-    * of all shaders must match.

-    */

-   assert(min_version >= 100);

-   assert(max_version <= 130);

-   if ((max_version >= 130 || min_version == 100)

-       && min_version != max_version) {

-      linker_error_printf(prog, "all shaders must use same shading "

-			  "language version\n");

-      goto done;

-   }

-

-   prog->Version = max_version;

-

-   for (unsigned int i = 0; i < MESA_SHADER_TYPES; i++) {

-      if (prog->_LinkedShaders[i] != NULL)

-	 ctx->Driver.DeleteShader(ctx, prog->_LinkedShaders[i]);

-

-      prog->_LinkedShaders[i] = NULL;

-   }

-

-   /* Link all shaders for a particular stage and validate the result.

-    */

-   if (num_vert_shaders > 0) {

-      gl_shader *const sh =

-	 link_intrastage_shaders(mem_ctx, ctx, prog, vert_shader_list,

-				 num_vert_shaders);

-

-      if (sh == NULL)

-	 goto done;

-

-      if (!validate_vertex_shader_executable(prog, sh))

-	 goto done;

-

-      _mesa_reference_shader(ctx, &prog->_LinkedShaders[MESA_SHADER_VERTEX],

-			     sh);

-   }

-

-   if (num_frag_shaders > 0) {

-      gl_shader *const sh =

-	 link_intrastage_shaders(mem_ctx, ctx, prog, frag_shader_list,

-				 num_frag_shaders);

-

-      if (sh == NULL)

-	 goto done;

-

-      if (!validate_fragment_shader_executable(prog, sh))

-	 goto done;

-

-      _mesa_reference_shader(ctx, &prog->_LinkedShaders[MESA_SHADER_FRAGMENT],

-			     sh);

-   }

-

-   /* Here begins the inter-stage linking phase.  Some initial validation is

-    * performed, then locations are assigned for uniforms, attributes, and

-    * varyings.

-    */

-   if (cross_validate_uniforms(prog)) {

-      unsigned prev;

-

-      for (prev = 0; prev < MESA_SHADER_TYPES; prev++) {

-	 if (prog->_LinkedShaders[prev] != NULL)

-	    break;

-      }

-

-      /* Validate the inputs of each stage with the output of the preceeding

-       * stage.

-       */

-      for (unsigned i = prev + 1; i < MESA_SHADER_TYPES; i++) {

-	 if (prog->_LinkedShaders[i] == NULL)

-	    continue;

-

-	 if (!cross_validate_outputs_to_inputs(prog,

-					       prog->_LinkedShaders[prev],

-					       prog->_LinkedShaders[i]))

-	    goto done;

-

-	 prev = i;

-      }

-

-      prog->LinkStatus = true;

-   }

-

-   /* Do common optimization before assigning storage for attributes,

-    * uniforms, and varyings.  Later optimization could possibly make

-    * some of that unused.

-    */

-   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {

-      if (prog->_LinkedShaders[i] == NULL)

-	 continue;

-

-      while (do_common_optimization(prog->_LinkedShaders[i]->ir, true, 32))

-	 ;

-   }

-

-   update_array_sizes(prog);

-

-   assign_uniform_locations(prog);

-

-   if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) {

-      /* FINISHME: The value of the max_attribute_index parameter is

-       * FINISHME: implementation dependent based on the value of

-       * FINISHME: GL_MAX_VERTEX_ATTRIBS.  GL_MAX_VERTEX_ATTRIBS must be

-       * FINISHME: at least 16, so hardcode 16 for now.

-       */

-      if (!assign_attribute_locations(prog, 16)) {

-	 prog->LinkStatus = false;

-	 goto done;

-      }

-   }

-

-   unsigned prev;

-   for (prev = 0; prev < MESA_SHADER_TYPES; prev++) {

-      if (prog->_LinkedShaders[prev] != NULL)

-	 break;

-   }

-

-   for (unsigned i = prev + 1; i < MESA_SHADER_TYPES; i++) {

-      if (prog->_LinkedShaders[i] == NULL)

-	 continue;

-

-      assign_varying_locations(prog,

-			       prog->_LinkedShaders[prev],

-			       prog->_LinkedShaders[i]);

-      prev = i;

-   }

-

-   if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) {

-      demote_shader_inputs_and_outputs(prog->_LinkedShaders[MESA_SHADER_VERTEX],

-				       ir_var_out);

-   }

-

-   if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) {

-      gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_GEOMETRY];

-

-      demote_shader_inputs_and_outputs(sh, ir_var_in);

-      demote_shader_inputs_and_outputs(sh, ir_var_inout);

-      demote_shader_inputs_and_outputs(sh, ir_var_out);

-   }

-

-   if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] != NULL) {

-      gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_FRAGMENT];

-

-      demote_shader_inputs_and_outputs(sh, ir_var_in);

-   }

-

-   /* FINISHME: Assign fragment shader output locations. */

-

-done:

-   free(vert_shader_list);

-

-   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {

-      if (prog->_LinkedShaders[i] == NULL)

-	 continue;

-

-      /* Retain any live IR, but trash the rest. */

-      reparent_ir(prog->_LinkedShaders[i]->ir, prog->_LinkedShaders[i]->ir);

-   }

-

-   talloc_free(mem_ctx);

-}

+/*
+ * Copyright © 2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * \file linker.cpp
+ * GLSL linker implementation
+ *
+ * Given a set of shaders that are to be linked to generate a final program,
+ * there are three distinct stages.
+ *
+ * In the first stage shaders are partitioned into groups based on the shader
+ * type.  All shaders of a particular type (e.g., vertex shaders) are linked
+ * together.
+ *
+ *   - Undefined references in each shader are resolve to definitions in
+ *     another shader.
+ *   - Types and qualifiers of uniforms, outputs, and global variables defined
+ *     in multiple shaders with the same name are verified to be the same.
+ *   - Initializers for uniforms and global variables defined
+ *     in multiple shaders with the same name are verified to be the same.
+ *
+ * The result, in the terminology of the GLSL spec, is a set of shader
+ * executables for each processing unit.
+ *
+ * After the first stage is complete, a series of semantic checks are performed
+ * on each of the shader executables.
+ *
+ *   - Each shader executable must define a \c main function.
+ *   - Each vertex shader executable must write to \c gl_Position.
+ *   - Each fragment shader executable must write to either \c gl_FragData or
+ *     \c gl_FragColor.
+ *
+ * In the final stage individual shader executables are linked to create a
+ * complete exectuable.
+ *
+ *   - Types of uniforms defined in multiple shader stages with the same name
+ *     are verified to be the same.
+ *   - Initializers for uniforms defined in multiple shader stages with the
+ *     same name are verified to be the same.
+ *   - Types and qualifiers of outputs defined in one stage are verified to
+ *     be the same as the types and qualifiers of inputs defined with the same
+ *     name in a later stage.
+ *
+ * \author Ian Romanick <ian.d.romanick@intel.com>
+ */
+#include <cstdlib>
+#include <cstdio>
+#include <cstdarg>
+#include <climits>
+
+#include "main/core.h"
+#include "glsl_symbol_table.h"
+#include "ir.h"
+#include "program.h"
+#include "program/hash_table.h"
+#include "linker.h"
+#include "ir_optimization.h"
+
+extern "C" {
+#include "main/shaderobj.h"
+}
+
+/**
+ * Visitor that determines whether or not a variable is ever written.
+ */
+class find_assignment_visitor : public ir_hierarchical_visitor {
+public:
+   find_assignment_visitor(const char *name)
+      : name(name), found(false)
+   {
+      /* empty */
+   }
+
+   virtual ir_visitor_status visit_enter(ir_assignment *ir)
+   {
+      ir_variable *const var = ir->lhs->variable_referenced();
+
+      if (strcmp(name, var->name) == 0) {
+	 found = true;
+	 return visit_stop;
+      }
+
+      return visit_continue_with_parent;
+   }
+
+   virtual ir_visitor_status visit_enter(ir_call *ir)
+   {
+      exec_list_iterator sig_iter = ir->get_callee()->parameters.iterator();
+      foreach_iter(exec_list_iterator, iter, *ir) {
+	 ir_rvalue *param_rval = (ir_rvalue *)iter.get();
+	 ir_variable *sig_param = (ir_variable *)sig_iter.get();
+
+	 if (sig_param->mode == ir_var_out ||
+	     sig_param->mode == ir_var_inout) {
+	    ir_variable *var = param_rval->variable_referenced();
+	    if (var && strcmp(name, var->name) == 0) {
+	       found = true;
+	       return visit_stop;
+	    }
+	 }
+	 sig_iter.next();
+      }
+
+      return visit_continue_with_parent;
+   }
+
+   bool variable_found()
+   {
+      return found;
+   }
+
+private:
+   const char *name;       /**< Find writes to a variable with this name. */
+   bool found;             /**< Was a write to the variable found? */
+};
+
+
+/**
+ * Visitor that determines whether or not a variable is ever read.
+ */
+class find_deref_visitor : public ir_hierarchical_visitor {
+public:
+   find_deref_visitor(const char *name)
+      : name(name), found(false)
+   {
+      /* empty */
+   }
+
+   virtual ir_visitor_status visit(ir_dereference_variable *ir)
+   {
+      if (strcmp(this->name, ir->var->name) == 0) {
+	 this->found = true;
+	 return visit_stop;
+      }
+
+      return visit_continue;
+   }
+
+   bool variable_found() const
+   {
+      return this->found;
+   }
+
+private:
+   const char *name;       /**< Find writes to a variable with this name. */
+   bool found;             /**< Was a write to the variable found? */
+};
+
+
+void
+linker_error_printf(gl_shader_program *prog, const char *fmt, ...)
+{
+   va_list ap;
+
+   prog->InfoLog = talloc_strdup_append(prog->InfoLog, "error: ");
+   va_start(ap, fmt);
+   prog->InfoLog = talloc_vasprintf_append(prog->InfoLog, fmt, ap);
+   va_end(ap);
+}
+
+
+void
+invalidate_variable_locations(gl_shader *sh, enum ir_variable_mode mode,
+			      int generic_base)
+{
+   foreach_list(node, sh->ir) {
+      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+      if ((var == NULL) || (var->mode != (unsigned) mode))
+	 continue;
+
+      /* Only assign locations for generic attributes / varyings / etc.
+       */
+      if ((var->location >= generic_base) && !var->explicit_location)
+	  var->location = -1;
+   }
+}
+
+
+/**
+ * Determine the number of attribute slots required for a particular type
+ *
+ * This code is here because it implements the language rules of a specific
+ * GLSL version.  Since it's a property of the language and not a property of
+ * types in general, it doesn't really belong in glsl_type.
+ */
+unsigned
+count_attribute_slots(const glsl_type *t)
+{
+   /* From page 31 (page 37 of the PDF) of the GLSL 1.50 spec:
+    *
+    *     "A scalar input counts the same amount against this limit as a vec4,
+    *     so applications may want to consider packing groups of four
+    *     unrelated float inputs together into a vector to better utilize the
+    *     capabilities of the underlying hardware. A matrix input will use up
+    *     multiple locations.  The number of locations used will equal the
+    *     number of columns in the matrix."
+    *
+    * The spec does not explicitly say how arrays are counted.  However, it
+    * should be safe to assume the total number of slots consumed by an array
+    * is the number of entries in the array multiplied by the number of slots
+    * consumed by a single element of the array.
+    */
+
+   if (t->is_array())
+      return t->array_size() * count_attribute_slots(t->element_type());
+
+   if (t->is_matrix())
+      return t->matrix_columns;
+
+   return 1;
+}
+
+
+/**
+ * Verify that a vertex shader executable meets all semantic requirements
+ *
+ * \param shader  Vertex shader executable to be verified
+ */
+bool
+validate_vertex_shader_executable(struct gl_shader_program *prog,
+				  struct gl_shader *shader)
+{
+   if (shader == NULL)
+      return true;
+
+   find_assignment_visitor find("gl_Position");
+   find.run(shader->ir);
+   if (!find.variable_found()) {
+      linker_error_printf(prog,
+			  "vertex shader does not write to `gl_Position'\n");
+      return false;
+   }
+
+   return true;
+}
+
+
+/**
+ * Verify that a fragment shader executable meets all semantic requirements
+ *
+ * \param shader  Fragment shader executable to be verified
+ */
+bool
+validate_fragment_shader_executable(struct gl_shader_program *prog,
+				    struct gl_shader *shader)
+{
+   if (shader == NULL)
+      return true;
+
+   find_assignment_visitor frag_color("gl_FragColor");
+   find_assignment_visitor frag_data("gl_FragData");
+
+   frag_color.run(shader->ir);
+   frag_data.run(shader->ir);
+
+   if (frag_color.variable_found() && frag_data.variable_found()) {
+      linker_error_printf(prog,  "fragment shader writes to both "
+			  "`gl_FragColor' and `gl_FragData'\n");
+      return false;
+   }
+
+   return true;
+}
+
+
+/**
+ * Generate a string describing the mode of a variable
+ */
+static const char *
+mode_string(const ir_variable *var)
+{
+   switch (var->mode) {
+   case ir_var_auto:
+      return (var->read_only) ? "global constant" : "global variable";
+
+   case ir_var_uniform: return "uniform";
+   case ir_var_in:      return "shader input";
+   case ir_var_out:     return "shader output";
+   case ir_var_inout:   return "shader inout";
+
+   case ir_var_temporary:
+   default:
+      assert(!"Should not get here.");
+      return "invalid variable";
+   }
+}
+
+
+/**
+ * Perform validation of global variables used across multiple shaders
+ */
+bool
+cross_validate_globals(struct gl_shader_program *prog,
+		       struct gl_shader **shader_list,
+		       unsigned num_shaders,
+		       bool uniforms_only)
+{
+   /* Examine all of the uniforms in all of the shaders and cross validate
+    * them.
+    */
+   glsl_symbol_table variables;
+   for (unsigned i = 0; i < num_shaders; i++) {
+      if (shader_list[i] == NULL)
+	 continue;
+
+      foreach_list(node, shader_list[i]->ir) {
+	 ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+	 if (var == NULL)
+	    continue;
+
+	 if (uniforms_only && (var->mode != ir_var_uniform))
+	    continue;
+
+	 /* Don't cross validate temporaries that are at global scope.  These
+	  * will eventually get pulled into the shaders 'main'.
+	  */
+	 if (var->mode == ir_var_temporary)
+	    continue;
+
+	 /* If a global with this name has already been seen, verify that the
+	  * new instance has the same type.  In addition, if the globals have
+	  * initializers, the values of the initializers must be the same.
+	  */
+	 ir_variable *const existing = variables.get_variable(var->name);
+	 if (existing != NULL) {
+	    if (var->type != existing->type) {
+	       /* Consider the types to be "the same" if both types are arrays
+		* of the same type and one of the arrays is implicitly sized.
+		* In addition, set the type of the linked variable to the
+		* explicitly sized array.
+		*/
+	       if (var->type->is_array()
+		   && existing->type->is_array()
+		   && (var->type->fields.array == existing->type->fields.array)
+		   && ((var->type->length == 0)
+		       || (existing->type->length == 0))) {
+		  if (var->type->length != 0) {
+		     existing->type = var->type;
+		  }
+	       } else {
+		  linker_error_printf(prog, "%s `%s' declared as type "
+				      "`%s' and type `%s'\n",
+				      mode_string(var),
+				      var->name, var->type->name,
+				      existing->type->name);
+		  return false;
+	       }
+	    }
+
+	    if (var->explicit_location) {
+	       if (existing->explicit_location
+		   && (var->location != existing->location)) {
+		     linker_error_printf(prog, "explicit locations for %s "
+					 "`%s' have differing values\n",
+					 mode_string(var), var->name);
+		     return false;
+	       }
+
+	       existing->location = var->location;
+	       existing->explicit_location = true;
+	    }
+
+	    /* FINISHME: Handle non-constant initializers.
+	     */
+	    if (var->constant_value != NULL) {
+	       if (existing->constant_value != NULL) {
+		  if (!var->constant_value->has_value(existing->constant_value)) {
+		     linker_error_printf(prog, "initializers for %s "
+					 "`%s' have differing values\n",
+					 mode_string(var), var->name);
+		     return false;
+		  }
+	       } else
+		  /* If the first-seen instance of a particular uniform did not
+		   * have an initializer but a later instance does, copy the
+		   * initializer to the version stored in the symbol table.
+		   */
+		  /* FINISHME: This is wrong.  The constant_value field should
+		   * FINISHME: not be modified!  Imagine a case where a shader
+		   * FINISHME: without an initializer is linked in two different
+		   * FINISHME: programs with shaders that have differing
+		   * FINISHME: initializers.  Linking with the first will
+		   * FINISHME: modify the shader, and linking with the second
+		   * FINISHME: will fail.
+		   */
+		  existing->constant_value =
+		     var->constant_value->clone(talloc_parent(existing), NULL);
+	    }
+
+	    if (existing->invariant != var->invariant) {
+	       linker_error_printf(prog, "declarations for %s `%s' have "
+	                           "mismatching invariant qualifiers\n",
+	                           mode_string(var), var->name);
+	       return false;
+	    }
+            if (existing->centroid != var->centroid) {
+               linker_error_printf(prog, "declarations for %s `%s' have "
+                                   "mismatching centroid qualifiers\n",
+                                   mode_string(var), var->name);
+               return false;
+            }
+	 } else
+	    variables.add_variable(var);
+      }
+   }
+
+   return true;
+}
+
+
+/**
+ * Perform validation of uniforms used across multiple shader stages
+ */
+bool
+cross_validate_uniforms(struct gl_shader_program *prog)
+{
+   return cross_validate_globals(prog, prog->_LinkedShaders,
+				 MESA_SHADER_TYPES, true);
+}
+
+
+/**
+ * Validate that outputs from one stage match inputs of another
+ */
+bool
+cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
+				 gl_shader *producer, gl_shader *consumer)
+{
+   glsl_symbol_table parameters;
+   /* FINISHME: Figure these out dynamically. */
+   const char *const producer_stage = "vertex";
+   const char *const consumer_stage = "fragment";
+
+   /* Find all shader outputs in the "producer" stage.
+    */
+   foreach_list(node, producer->ir) {
+      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+      /* FINISHME: For geometry shaders, this should also look for inout
+       * FINISHME: variables.
+       */
+      if ((var == NULL) || (var->mode != ir_var_out))
+	 continue;
+
+      parameters.add_variable(var);
+   }
+
+
+   /* Find all shader inputs in the "consumer" stage.  Any variables that have
+    * matching outputs already in the symbol table must have the same type and
+    * qualifiers.
+    */
+   foreach_list(node, consumer->ir) {
+      ir_variable *const input = ((ir_instruction *) node)->as_variable();
+
+      /* FINISHME: For geometry shaders, this should also look for inout
+       * FINISHME: variables.
+       */
+      if ((input == NULL) || (input->mode != ir_var_in))
+	 continue;
+
+      ir_variable *const output = parameters.get_variable(input->name);
+      if (output != NULL) {
+	 /* Check that the types match between stages.
+	  */
+	 if (input->type != output->type) {
+	    /* There is a bit of a special case for gl_TexCoord.  This
+	     * built-in is unsized by default.  Appliations that variable
+	     * access it must redeclare it with a size.  There is some
+	     * language in the GLSL spec that implies the fragment shader
+	     * and vertex shader do not have to agree on this size.  Other
+	     * driver behave this way, and one or two applications seem to
+	     * rely on it.
+	     *
+	     * Neither declaration needs to be modified here because the array
+	     * sizes are fixed later when update_array_sizes is called.
+	     *
+	     * From page 48 (page 54 of the PDF) of the GLSL 1.10 spec:
+	     *
+	     *     "Unlike user-defined varying variables, the built-in
+	     *     varying variables don't have a strict one-to-one
+	     *     correspondence between the vertex language and the
+	     *     fragment language."
+	     */
+	    if (!output->type->is_array()
+		|| (strncmp("gl_", output->name, 3) != 0)) {
+	       linker_error_printf(prog,
+				   "%s shader output `%s' declared as "
+				   "type `%s', but %s shader input declared "
+				   "as type `%s'\n",
+				   producer_stage, output->name,
+				   output->type->name,
+				   consumer_stage, input->type->name);
+	       return false;
+	    }
+	 }
+
+	 /* Check that all of the qualifiers match between stages.
+	  */
+	 if (input->centroid != output->centroid) {
+	    linker_error_printf(prog,
+				"%s shader output `%s' %s centroid qualifier, "
+				"but %s shader input %s centroid qualifier\n",
+				producer_stage,
+				output->name,
+				(output->centroid) ? "has" : "lacks",
+				consumer_stage,
+				(input->centroid) ? "has" : "lacks");
+	    return false;
+	 }
+
+	 if (input->invariant != output->invariant) {
+	    linker_error_printf(prog,
+				"%s shader output `%s' %s invariant qualifier, "
+				"but %s shader input %s invariant qualifier\n",
+				producer_stage,
+				output->name,
+				(output->invariant) ? "has" : "lacks",
+				consumer_stage,
+				(input->invariant) ? "has" : "lacks");
+	    return false;
+	 }
+
+	 if (input->interpolation != output->interpolation) {
+	    linker_error_printf(prog,
+				"%s shader output `%s' specifies %s "
+				"interpolation qualifier, "
+				"but %s shader input specifies %s "
+				"interpolation qualifier\n",
+				producer_stage,
+				output->name,
+				output->interpolation_string(),
+				consumer_stage,
+				input->interpolation_string());
+	    return false;
+	 }
+      }
+   }
+
+   return true;
+}
+
+
+/**
+ * Populates a shaders symbol table with all global declarations
+ */
+static void
+populate_symbol_table(gl_shader *sh)
+{
+   sh->symbols = new(sh) glsl_symbol_table;
+
+   foreach_list(node, sh->ir) {
+      ir_instruction *const inst = (ir_instruction *) node;
+      ir_variable *var;
+      ir_function *func;
+
+      if ((func = inst->as_function()) != NULL) {
+	 sh->symbols->add_function(func);
+      } else if ((var = inst->as_variable()) != NULL) {
+	 sh->symbols->add_variable(var);
+      }
+   }
+}
+
+
+/**
+ * Remap variables referenced in an instruction tree
+ *
+ * This is used when instruction trees are cloned from one shader and placed in
+ * another.  These trees will contain references to \c ir_variable nodes that
+ * do not exist in the target shader.  This function finds these \c ir_variable
+ * references and replaces the references with matching variables in the target
+ * shader.
+ *
+ * If there is no matching variable in the target shader, a clone of the
+ * \c ir_variable is made and added to the target shader.  The new variable is
+ * added to \b both the instruction stream and the symbol table.
+ *
+ * \param inst         IR tree that is to be processed.
+ * \param symbols      Symbol table containing global scope symbols in the
+ *                     linked shader.
+ * \param instructions Instruction stream where new variable declarations
+ *                     should be added.
+ */
+void
+remap_variables(ir_instruction *inst, struct gl_shader *target,
+		hash_table *temps)
+{
+   class remap_visitor : public ir_hierarchical_visitor {
+   public:
+	 remap_visitor(struct gl_shader *target,
+		    hash_table *temps)
+      {
+	 this->target = target;
+	 this->symbols = target->symbols;
+	 this->instructions = target->ir;
+	 this->temps = temps;
+      }
+
+      virtual ir_visitor_status visit(ir_dereference_variable *ir)
+      {
+	 if (ir->var->mode == ir_var_temporary) {
+	    ir_variable *var = (ir_variable *) hash_table_find(temps, ir->var);
+
+	    assert(var != NULL);
+	    ir->var = var;
+	    return visit_continue;
+	 }
+
+	 ir_variable *const existing =
+	    this->symbols->get_variable(ir->var->name);
+	 if (existing != NULL)
+	    ir->var = existing;
+	 else {
+	    ir_variable *copy = ir->var->clone(this->target, NULL);
+
+	    this->symbols->add_variable(copy);
+	    this->instructions->push_head(copy);
+	    ir->var = copy;
+	 }
+
+	 return visit_continue;
+      }
+
+   private:
+      struct gl_shader *target;
+      glsl_symbol_table *symbols;
+      exec_list *instructions;
+      hash_table *temps;
+   };
+
+   remap_visitor v(target, temps);
+
+   inst->accept(&v);
+}
+
+
+/**
+ * Move non-declarations from one instruction stream to another
+ *
+ * The intended usage pattern of this function is to pass the pointer to the
+ * head sentinel of a list (i.e., a pointer to the list cast to an \c exec_node
+ * pointer) for \c last and \c false for \c make_copies on the first
+ * call.  Successive calls pass the return value of the previous call for
+ * \c last and \c true for \c make_copies.
+ *
+ * \param instructions Source instruction stream
+ * \param last         Instruction after which new instructions should be
+ *                     inserted in the target instruction stream
+ * \param make_copies  Flag selecting whether instructions in \c instructions
+ *                     should be copied (via \c ir_instruction::clone) into the
+ *                     target list or moved.
+ *
+ * \return
+ * The new "last" instruction in the target instruction stream.  This pointer
+ * is suitable for use as the \c last parameter of a later call to this
+ * function.
+ */
+exec_node *
+move_non_declarations(exec_list *instructions, exec_node *last,
+		      bool make_copies, gl_shader *target)
+{
+   hash_table *temps = NULL;
+
+   if (make_copies)
+      temps = hash_table_ctor(0, hash_table_pointer_hash,
+			      hash_table_pointer_compare);
+
+   foreach_list_safe(node, instructions) {
+      ir_instruction *inst = (ir_instruction *) node;
+
+      if (inst->as_function())
+	 continue;
+
+      ir_variable *var = inst->as_variable();
+      if ((var != NULL) && (var->mode != ir_var_temporary))
+	 continue;
+
+      assert(inst->as_assignment()
+	     || ((var != NULL) && (var->mode == ir_var_temporary)));
+
+      if (make_copies) {
+	 inst = inst->clone(target, NULL);
+
+	 if (var != NULL)
+	    hash_table_insert(temps, inst, var);
+	 else
+	    remap_variables(inst, target, temps);
+      } else {
+	 inst->remove();
+      }
+
+      last->insert_after(inst);
+      last = inst;
+   }
+
+   if (make_copies)
+      hash_table_dtor(temps);
+
+   return last;
+}
+
+/**
+ * Get the function signature for main from a shader
+ */
+static ir_function_signature *
+get_main_function_signature(gl_shader *sh)
+{
+   ir_function *const f = sh->symbols->get_function("main");
+   if (f != NULL) {
+      exec_list void_parameters;
+
+      /* Look for the 'void main()' signature and ensure that it's defined.
+       * This keeps the linker from accidentally pick a shader that just
+       * contains a prototype for main.
+       *
+       * We don't have to check for multiple definitions of main (in multiple
+       * shaders) because that would have already been caught above.
+       */
+      ir_function_signature *sig = f->matching_signature(&void_parameters);
+      if ((sig != NULL) && sig->is_defined) {
+	 return sig;
+      }
+   }
+
+   return NULL;
+}
+
+
+/**
+ * Combine a group of shaders for a single stage to generate a linked shader
+ *
+ * \note
+ * If this function is supplied a single shader, it is cloned, and the new
+ * shader is returned.
+ */
+static struct gl_shader *
+link_intrastage_shaders(void *mem_ctx,
+			struct gl_context *ctx,
+			struct gl_shader_program *prog,
+			struct gl_shader **shader_list,
+			unsigned num_shaders)
+{
+   /* Check that global variables defined in multiple shaders are consistent.
+    */
+   if (!cross_validate_globals(prog, shader_list, num_shaders, false))
+      return NULL;
+
+   /* Check that there is only a single definition of each function signature
+    * across all shaders.
+    */
+   for (unsigned i = 0; i < (num_shaders - 1); i++) {
+      foreach_list(node, shader_list[i]->ir) {
+	 ir_function *const f = ((ir_instruction *) node)->as_function();
+
+	 if (f == NULL)
+	    continue;
+
+	 for (unsigned j = i + 1; j < num_shaders; j++) {
+	    ir_function *const other =
+	       shader_list[j]->symbols->get_function(f->name);
+
+	    /* If the other shader has no function (and therefore no function
+	     * signatures) with the same name, skip to the next shader.
+	     */
+	    if (other == NULL)
+	       continue;
+
+	    foreach_iter (exec_list_iterator, iter, *f) {
+	       ir_function_signature *sig =
+		  (ir_function_signature *) iter.get();
+
+	       if (!sig->is_defined || sig->is_builtin)
+		  continue;
+
+	       ir_function_signature *other_sig =
+		  other->exact_matching_signature(& sig->parameters);
+
+	       if ((other_sig != NULL) && other_sig->is_defined
+		   && !other_sig->is_builtin) {
+		  linker_error_printf(prog,
+				      "function `%s' is multiply defined",
+				      f->name);
+		  return NULL;
+	       }
+	    }
+	 }
+      }
+   }
+
+   /* Find the shader that defines main, and make a clone of it.
+    *
+    * Starting with the clone, search for undefined references.  If one is
+    * found, find the shader that defines it.  Clone the reference and add
+    * it to the shader.  Repeat until there are no undefined references or
+    * until a reference cannot be resolved.
+    */
+   gl_shader *main = NULL;
+   for (unsigned i = 0; i < num_shaders; i++) {
+      if (get_main_function_signature(shader_list[i]) != NULL) {
+	 main = shader_list[i];
+	 break;
+      }
+   }
+
+   if (main == NULL) {
+      linker_error_printf(prog, "%s shader lacks `main'\n",
+			  (shader_list[0]->Type == GL_VERTEX_SHADER)
+			  ? "vertex" : "fragment");
+      return NULL;
+   }
+
+   gl_shader *linked = ctx->Driver.NewShader(NULL, 0, main->Type);
+   linked->ir = new(linked) exec_list;
+   clone_ir_list(mem_ctx, linked->ir, main->ir);
+
+   populate_symbol_table(linked);
+
+   /* The a pointer to the main function in the final linked shader (i.e., the
+    * copy of the original shader that contained the main function).
+    */
+   ir_function_signature *const main_sig = get_main_function_signature(linked);
+
+   /* Move any instructions other than variable declarations or function
+    * declarations into main.
+    */
+   exec_node *insertion_point =
+      move_non_declarations(linked->ir, (exec_node *) &main_sig->body, false,
+			    linked);
+
+   for (unsigned i = 0; i < num_shaders; i++) {
+      if (shader_list[i] == main)
+	 continue;
+
+      insertion_point = move_non_declarations(shader_list[i]->ir,
+					      insertion_point, true, linked);
+   }
+
+   /* Resolve initializers for global variables in the linked shader.
+    */
+   unsigned num_linking_shaders = num_shaders;
+   for (unsigned i = 0; i < num_shaders; i++)
+      num_linking_shaders += shader_list[i]->num_builtins_to_link;
+
+   gl_shader **linking_shaders =
+      (gl_shader **) calloc(num_linking_shaders, sizeof(gl_shader *));
+
+   memcpy(linking_shaders, shader_list,
+	  sizeof(linking_shaders[0]) * num_shaders);
+
+   unsigned idx = num_shaders;
+   for (unsigned i = 0; i < num_shaders; i++) {
+      memcpy(&linking_shaders[idx], shader_list[i]->builtins_to_link,
+	     sizeof(linking_shaders[0]) * shader_list[i]->num_builtins_to_link);
+      idx += shader_list[i]->num_builtins_to_link;
+   }
+
+   assert(idx == num_linking_shaders);
+
+   if (!link_function_calls(prog, linked, linking_shaders,
+			    num_linking_shaders)) {
+      ctx->Driver.DeleteShader(ctx, linked);
+      linked = NULL;
+   }
+
+   free(linking_shaders);
+
+   /* Make a pass over all variable declarations to ensure that arrays with
+    * unspecified sizes have a size specified.  The size is inferred from the
+    * max_array_access field.
+    */
+   if (linked != NULL) {
+      class array_sizing_visitor : public ir_hierarchical_visitor {
+      public:
+	 virtual ir_visitor_status visit(ir_variable *var)
+	 {
+	    if (var->type->is_array() && (var->type->length == 0)) {
+	       const glsl_type *type =
+		  glsl_type::get_array_instance(var->type->fields.array,
+						var->max_array_access);
+
+	       assert(type != NULL);
+	       var->type = type;
+	    }
+
+	    return visit_continue;
+	 }
+      } v;
+
+      v.run(linked->ir);
+   }
+
+   return linked;
+}
+
+
+struct uniform_node {
+   exec_node link;
+   struct gl_uniform *u;
+   unsigned slots;
+};
+
+/**
+ * Update the sizes of linked shader uniform arrays to the maximum
+ * array index used.
+ *
+ * From page 81 (page 95 of the PDF) of the OpenGL 2.1 spec:
+ *
+ *     If one or more elements of an array are active,
+ *     GetActiveUniform will return the name of the array in name,
+ *     subject to the restrictions listed above. The type of the array
+ *     is returned in type. The size parameter contains the highest
+ *     array element index used, plus one. The compiler or linker
+ *     determines the highest index used.  There will be only one
+ *     active uniform reported by the GL per uniform array.
+
+ */
+static void
+update_array_sizes(struct gl_shader_program *prog)
+{
+   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {
+	 if (prog->_LinkedShaders[i] == NULL)
+	    continue;
+
+      foreach_list(node, prog->_LinkedShaders[i]->ir) {
+	 ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+	 if ((var == NULL) || (var->mode != ir_var_uniform &&
+			       var->mode != ir_var_in &&
+			       var->mode != ir_var_out) ||
+	     !var->type->is_array())
+	    continue;
+
+	 unsigned int size = var->max_array_access;
+	 for (unsigned j = 0; j < MESA_SHADER_TYPES; j++) {
+	       if (prog->_LinkedShaders[j] == NULL)
+		  continue;
+
+	    foreach_list(node2, prog->_LinkedShaders[j]->ir) {
+	       ir_variable *other_var = ((ir_instruction *) node2)->as_variable();
+	       if (!other_var)
+		  continue;
+
+	       if (strcmp(var->name, other_var->name) == 0 &&
+		   other_var->max_array_access > size) {
+		  size = other_var->max_array_access;
+	       }
+	    }
+	 }
+
+	 if (size + 1 != var->type->fields.array->length) {
+	    var->type = glsl_type::get_array_instance(var->type->fields.array,
+						      size + 1);
+	    /* FINISHME: We should update the types of array
+	     * dereferences of this variable now.
+	     */
+	 }
+      }
+   }
+}
+
+static void
+add_uniform(void *mem_ctx, exec_list *uniforms, struct hash_table *ht,
+	    const char *name, const glsl_type *type, GLenum shader_type,
+	    unsigned *next_shader_pos, unsigned *total_uniforms)
+{
+   if (type->is_record()) {
+      for (unsigned int i = 0; i < type->length; i++) {
+	 const glsl_type *field_type = type->fields.structure[i].type;
+	 char *field_name = talloc_asprintf(mem_ctx, "%s.%s", name,
+					    type->fields.structure[i].name);
+
+	 add_uniform(mem_ctx, uniforms, ht, field_name, field_type,
+		     shader_type, next_shader_pos, total_uniforms);
+      }
+   } else {
+      uniform_node *n = (uniform_node *) hash_table_find(ht, name);
+      unsigned int vec4_slots;
+      const glsl_type *array_elem_type = NULL;
+
+      if (type->is_array()) {
+	 array_elem_type = type->fields.array;
+	 /* Array of structures. */
+	 if (array_elem_type->is_record()) {
+	    for (unsigned int i = 0; i < type->length; i++) {
+	       char *elem_name = talloc_asprintf(mem_ctx, "%s[%d]", name, i);
+	       add_uniform(mem_ctx, uniforms, ht, elem_name, array_elem_type,
+			   shader_type, next_shader_pos, total_uniforms);
+	    }
+	    return;
+	 }
+      }
+
+      /* Fix the storage size of samplers at 1 vec4 each. Be sure to pad out
+       * vectors to vec4 slots.
+       */
+      if (type->is_array()) {
+	 if (array_elem_type->is_sampler())
+	    vec4_slots = type->length;
+	 else
+	    vec4_slots = type->length * array_elem_type->matrix_columns;
+      } else if (type->is_sampler()) {
+	 vec4_slots = 1;
+      } else {
+	 vec4_slots = type->matrix_columns;
+      }
+
+      if (n == NULL) {
+	 n = (uniform_node *) calloc(1, sizeof(struct uniform_node));
+	 n->u = (gl_uniform *) calloc(1, sizeof(struct gl_uniform));
+	 n->slots = vec4_slots;
+
+	 n->u->Name = strdup(name);
+	 n->u->Type = type;
+	 n->u->VertPos = -1;
+	 n->u->FragPos = -1;
+	 n->u->GeomPos = -1;
+	 (*total_uniforms)++;
+
+	 hash_table_insert(ht, n, name);
+	 uniforms->push_tail(& n->link);
+      }
+
+      switch (shader_type) {
+      case GL_VERTEX_SHADER:
+	 n->u->VertPos = *next_shader_pos;
+	 break;
+      case GL_FRAGMENT_SHADER:
+	 n->u->FragPos = *next_shader_pos;
+	 break;
+      case GL_GEOMETRY_SHADER:
+	 n->u->GeomPos = *next_shader_pos;
+	 break;
+      }
+
+      (*next_shader_pos) += vec4_slots;
+   }
+}
+
+void
+assign_uniform_locations(struct gl_shader_program *prog)
+{
+   /* */
+   exec_list uniforms;
+   unsigned total_uniforms = 0;
+   hash_table *ht = hash_table_ctor(32, hash_table_string_hash,
+				    hash_table_string_compare);
+   void *mem_ctx = talloc_new(NULL);
+
+   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {
+      if (prog->_LinkedShaders[i] == NULL)
+	 continue;
+
+      unsigned next_position = 0;
+
+      foreach_list(node, prog->_LinkedShaders[i]->ir) {
+	 ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+	 if ((var == NULL) || (var->mode != ir_var_uniform))
+	    continue;
+
+	 if (strncmp(var->name, "gl_", 3) == 0) {
+	    /* At the moment, we don't allocate uniform locations for
+	     * builtin uniforms.  It's permitted by spec, and we'll
+	     * likely switch to doing that at some point, but not yet.
+	     */
+	    continue;
+	 }
+
+	 var->location = next_position;
+	 add_uniform(mem_ctx, &uniforms, ht, var->name, var->type,
+		     prog->_LinkedShaders[i]->Type,
+		     &next_position, &total_uniforms);
+      }
+   }
+
+   talloc_free(mem_ctx);
+
+   gl_uniform_list *ul = (gl_uniform_list *)
+      calloc(1, sizeof(gl_uniform_list));
+
+   ul->Size = total_uniforms;
+   ul->NumUniforms = total_uniforms;
+   ul->Uniforms = (gl_uniform *) calloc(total_uniforms, sizeof(gl_uniform));
+
+   unsigned idx = 0;
+   uniform_node *next;
+   for (uniform_node *node = (uniform_node *) uniforms.head
+	   ; node->link.next != NULL
+	   ; node = next) {
+      next = (uniform_node *) node->link.next;
+
+      node->link.remove();
+      memcpy(&ul->Uniforms[idx], node->u, sizeof(gl_uniform));
+      idx++;
+
+      free(node->u);
+      free(node);
+   }
+
+   hash_table_dtor(ht);
+
+   prog->Uniforms = ul;
+}
+
+
+/**
+ * Find a contiguous set of available bits in a bitmask
+ *
+ * \param used_mask     Bits representing used (1) and unused (0) locations
+ * \param needed_count  Number of contiguous bits needed.
+ *
+ * \return
+ * Base location of the available bits on success or -1 on failure.
+ */
+int
+find_available_slots(unsigned used_mask, unsigned needed_count)
+{
+   unsigned needed_mask = (1 << needed_count) - 1;
+   const int max_bit_to_test = (8 * sizeof(used_mask)) - needed_count;
+
+   /* The comparison to 32 is redundant, but without it GCC emits "warning:
+    * cannot optimize possibly infinite loops" for the loop below.
+    */
+   if ((needed_count == 0) || (max_bit_to_test < 0) || (max_bit_to_test > 32))
+      return -1;
+
+   for (int i = 0; i <= max_bit_to_test; i++) {
+      if ((needed_mask & ~used_mask) == needed_mask)
+	 return i;
+
+      needed_mask <<= 1;
+   }
+
+   return -1;
+}
+
+
+bool
+assign_attribute_locations(gl_shader_program *prog, unsigned max_attribute_index)
+{
+   /* Mark invalid attribute locations as being used.
+    */
+   unsigned used_locations = (max_attribute_index >= 32)
+      ? ~0 : ~((1 << max_attribute_index) - 1);
+
+   gl_shader *const sh = prog->_LinkedShaders[0];
+   assert(sh->Type == GL_VERTEX_SHADER);
+
+   /* Operate in a total of four passes.
+    *
+    * 1. Invalidate the location assignments for all vertex shader inputs.
+    *
+    * 2. Assign locations for inputs that have user-defined (via
+    *    glBindVertexAttribLocation) locatoins.
+    *
+    * 3. Sort the attributes without assigned locations by number of slots
+    *    required in decreasing order.  Fragmentation caused by attribute
+    *    locations assigned by the application may prevent large attributes
+    *    from having enough contiguous space.
+    *
+    * 4. Assign locations to any inputs without assigned locations.
+    */
+
+   invalidate_variable_locations(sh, ir_var_in, VERT_ATTRIB_GENERIC0);
+
+   if (prog->Attributes != NULL) {
+      for (unsigned i = 0; i < prog->Attributes->NumParameters; i++) {
+	 ir_variable *const var =
+	    sh->symbols->get_variable(prog->Attributes->Parameters[i].Name);
+
+	 /* Note: attributes that occupy multiple slots, such as arrays or
+	  * matrices, may appear in the attrib array multiple times.
+	  */
+	 if ((var == NULL) || (var->location != -1))
+	    continue;
+
+	 /* From page 61 of the OpenGL 4.0 spec:
+	  *
+	  *     "LinkProgram will fail if the attribute bindings assigned by
+	  *     BindAttribLocation do not leave not enough space to assign a
+	  *     location for an active matrix attribute or an active attribute
+	  *     array, both of which require multiple contiguous generic
+	  *     attributes."
+	  *
+	  * Previous versions of the spec contain similar language but omit the
+	  * bit about attribute arrays.
+	  *
+	  * Page 61 of the OpenGL 4.0 spec also says:
+	  *
+	  *     "It is possible for an application to bind more than one
+	  *     attribute name to the same location. This is referred to as
+	  *     aliasing. This will only work if only one of the aliased
+	  *     attributes is active in the executable program, or if no path
+	  *     through the shader consumes more than one attribute of a set
+	  *     of attributes aliased to the same location. A link error can
+	  *     occur if the linker determines that every path through the
+	  *     shader consumes multiple aliased attributes, but
+	  *     implementations are not required to generate an error in this
+	  *     case."
+	  *
+	  * These two paragraphs are either somewhat contradictory, or I don't
+	  * fully understand one or both of them.
+	  */
+	 /* FINISHME: The code as currently written does not support attribute
+	  * FINISHME: location aliasing (see comment above).
+	  */
+	 const int attr = prog->Attributes->Parameters[i].StateIndexes[0];
+	 const unsigned slots = count_attribute_slots(var->type);
+
+	 /* Mask representing the contiguous slots that will be used by this
+	  * attribute.
+	  */
+	 const unsigned use_mask = (1 << slots) - 1;
+
+	 /* Generate a link error if the set of bits requested for this
+	  * attribute overlaps any previously allocated bits.
+	  */
+	 if ((~(use_mask << attr) & used_locations) != used_locations) {
+	    linker_error_printf(prog,
+				"insufficient contiguous attribute locations "
+				"available for vertex shader input `%s'",
+				var->name);
+	    return false;
+	 }
+
+	 var->location = VERT_ATTRIB_GENERIC0 + attr;
+	 used_locations |= (use_mask << attr);
+      }
+   }
+
+   /* Temporary storage for the set of attributes that need locations assigned.
+    */
+   struct temp_attr {
+      unsigned slots;
+      ir_variable *var;
+
+      /* Used below in the call to qsort. */
+      static int compare(const void *a, const void *b)
+      {
+	 const temp_attr *const l = (const temp_attr *) a;
+	 const temp_attr *const r = (const temp_attr *) b;
+
+	 /* Reversed because we want a descending order sort below. */
+	 return r->slots - l->slots;
+      }
+   } to_assign[16];
+
+   unsigned num_attr = 0;
+
+   foreach_list(node, sh->ir) {
+      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+      if ((var == NULL) || (var->mode != ir_var_in))
+	 continue;
+
+      if (var->explicit_location) {
+	 const unsigned slots = count_attribute_slots(var->type);
+	 const unsigned use_mask = (1 << slots) - 1;
+	 const int attr = var->location - VERT_ATTRIB_GENERIC0;
+
+	 if ((var->location >= (int)(max_attribute_index + VERT_ATTRIB_GENERIC0))
+	     || (var->location < 0)) {
+	    linker_error_printf(prog,
+				"invalid explicit location %d specified for "
+				"`%s'\n",
+				(var->location < 0) ? var->location : attr,
+				var->name);
+	    return false;
+	 } else if (var->location >= VERT_ATTRIB_GENERIC0) {
+	    used_locations |= (use_mask << attr);
+	 }
+      }
+
+      /* The location was explicitly assigned, nothing to do here.
+       */
+      if (var->location != -1)
+	 continue;
+
+      to_assign[num_attr].slots = count_attribute_slots(var->type);
+      to_assign[num_attr].var = var;
+      num_attr++;
+   }
+
+   /* If all of the attributes were assigned locations by the application (or
+    * are built-in attributes with fixed locations), return early.  This should
+    * be the common case.
+    */
+   if (num_attr == 0)
+      return true;
+
+   qsort(to_assign, num_attr, sizeof(to_assign[0]), temp_attr::compare);
+
+   /* VERT_ATTRIB_GENERIC0 is a psdueo-alias for VERT_ATTRIB_POS.  It can only
+    * be explicitly assigned by via glBindAttribLocation.  Mark it as reserved
+    * to prevent it from being automatically allocated below.
+    */
+   find_deref_visitor find("gl_Vertex");
+   find.run(sh->ir);
+   if (find.variable_found())
+      used_locations |= (1 << 0);
+
+   for (unsigned i = 0; i < num_attr; i++) {
+      /* Mask representing the contiguous slots that will be used by this
+       * attribute.
+       */
+      const unsigned use_mask = (1 << to_assign[i].slots) - 1;
+
+      int location = find_available_slots(used_locations, to_assign[i].slots);
+
+      if (location < 0) {
+	 linker_error_printf(prog,
+			     "insufficient contiguous attribute locations "
+			     "available for vertex shader input `%s'",
+			     to_assign[i].var->name);
+	 return false;
+      }
+
+      to_assign[i].var->location = VERT_ATTRIB_GENERIC0 + location;
+      used_locations |= (use_mask << location);
+   }
+
+   return true;
+}
+
+
+/**
+ * Demote shader inputs and outputs that are not used in other stages
+ */
+void
+demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)
+{
+   foreach_list(node, sh->ir) {
+      ir_variable *const var = ((ir_instruction *) node)->as_variable();
+
+      if ((var == NULL) || (var->mode != int(mode)))
+	 continue;
+
+      /* A shader 'in' or 'out' variable is only really an input or output if
+       * its value is used by other shader stages.  This will cause the variable
+       * to have a location assigned.
+       */
+      if (var->location == -1) {
+	 var->mode = ir_var_auto;
+      }
+   }
+}
+
+
+void
+assign_varying_locations(struct gl_shader_program *prog,
+			 gl_shader *producer, gl_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);
+
+      output_var->location = output_index;
+      input_var->location = input_index;
+
+      /* FINISHME: Support for "varying" records in GLSL 1.50. */
+      assert(!output_var->type->is_record());
+
+      if (output_var->type->is_array()) {
+	 const unsigned slots = output_var->type->length
+	    * output_var->type->fields.array->matrix_columns;
+
+	 output_index += slots;
+	 input_index += slots;
+      } else {
+	 const unsigned slots = output_var->type->matrix_columns;
+
+	 output_index += slots;
+	 input_index += slots;
+      }
+   }
+
+   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_printf(prog, "fragment shader varying %s not written "
+				"by vertex shader\n.", var->name);
+	    prog->LinkStatus = false;
+	 }
+
+	 /* An 'in' variable is only really a shader input if its
+	  * value is written by the previous stage.
+	  */
+	 var->mode = ir_var_auto;
+      }
+   }
+}
+
+
+void
+link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
+{
+   void *mem_ctx = talloc_init("temporary linker context");
+
+   prog->LinkStatus = false;
+   prog->Validated = false;
+   prog->_Used = false;
+
+   if (prog->InfoLog != NULL)
+      talloc_free(prog->InfoLog);
+
+   prog->InfoLog = talloc_strdup(NULL, "");
+
+   /* Separate the shaders into groups based on their type.
+    */
+   struct gl_shader **vert_shader_list;
+   unsigned num_vert_shaders = 0;
+   struct gl_shader **frag_shader_list;
+   unsigned num_frag_shaders = 0;
+
+   vert_shader_list = (struct gl_shader **)
+      calloc(2 * prog->NumShaders, sizeof(struct gl_shader *));
+   frag_shader_list =  &vert_shader_list[prog->NumShaders];
+
+   unsigned min_version = UINT_MAX;
+   unsigned max_version = 0;
+   for (unsigned i = 0; i < prog->NumShaders; i++) {
+      min_version = MIN2(min_version, prog->Shaders[i]->Version);
+      max_version = MAX2(max_version, prog->Shaders[i]->Version);
+
+      switch (prog->Shaders[i]->Type) {
+      case GL_VERTEX_SHADER:
+	 vert_shader_list[num_vert_shaders] = prog->Shaders[i];
+	 num_vert_shaders++;
+	 break;
+      case GL_FRAGMENT_SHADER:
+	 frag_shader_list[num_frag_shaders] = prog->Shaders[i];
+	 num_frag_shaders++;
+	 break;
+      case GL_GEOMETRY_SHADER:
+	 /* FINISHME: Support geometry shaders. */
+	 assert(prog->Shaders[i]->Type != GL_GEOMETRY_SHADER);
+	 break;
+      }
+   }
+
+   /* Previous to GLSL version 1.30, different compilation units could mix and
+    * match shading language versions.  With GLSL 1.30 and later, the versions
+    * of all shaders must match.
+    */
+   assert(min_version >= 100);
+   assert(max_version <= 130);
+   if ((max_version >= 130 || min_version == 100)
+       && min_version != max_version) {
+      linker_error_printf(prog, "all shaders must use same shading "
+			  "language version\n");
+      goto done;
+   }
+
+   prog->Version = max_version;
+
+   for (unsigned int i = 0; i < MESA_SHADER_TYPES; i++) {
+      if (prog->_LinkedShaders[i] != NULL)
+	 ctx->Driver.DeleteShader(ctx, prog->_LinkedShaders[i]);
+
+      prog->_LinkedShaders[i] = NULL;
+   }
+
+   /* Link all shaders for a particular stage and validate the result.
+    */
+   if (num_vert_shaders > 0) {
+      gl_shader *const sh =
+	 link_intrastage_shaders(mem_ctx, ctx, prog, vert_shader_list,
+				 num_vert_shaders);
+
+      if (sh == NULL)
+	 goto done;
+
+      if (!validate_vertex_shader_executable(prog, sh))
+	 goto done;
+
+      _mesa_reference_shader(ctx, &prog->_LinkedShaders[MESA_SHADER_VERTEX],
+			     sh);
+   }
+
+   if (num_frag_shaders > 0) {
+      gl_shader *const sh =
+	 link_intrastage_shaders(mem_ctx, ctx, prog, frag_shader_list,
+				 num_frag_shaders);
+
+      if (sh == NULL)
+	 goto done;
+
+      if (!validate_fragment_shader_executable(prog, sh))
+	 goto done;
+
+      _mesa_reference_shader(ctx, &prog->_LinkedShaders[MESA_SHADER_FRAGMENT],
+			     sh);
+   }
+
+   /* Here begins the inter-stage linking phase.  Some initial validation is
+    * performed, then locations are assigned for uniforms, attributes, and
+    * varyings.
+    */
+   if (cross_validate_uniforms(prog)) {
+      unsigned prev;
+
+      for (prev = 0; prev < MESA_SHADER_TYPES; prev++) {
+	 if (prog->_LinkedShaders[prev] != NULL)
+	    break;
+      }
+
+      /* Validate the inputs of each stage with the output of the preceeding
+       * stage.
+       */
+      for (unsigned i = prev + 1; i < MESA_SHADER_TYPES; i++) {
+	 if (prog->_LinkedShaders[i] == NULL)
+	    continue;
+
+	 if (!cross_validate_outputs_to_inputs(prog,
+					       prog->_LinkedShaders[prev],
+					       prog->_LinkedShaders[i]))
+	    goto done;
+
+	 prev = i;
+      }
+
+      prog->LinkStatus = true;
+   }
+
+   /* Do common optimization before assigning storage for attributes,
+    * uniforms, and varyings.  Later optimization could possibly make
+    * some of that unused.
+    */
+   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {
+      if (prog->_LinkedShaders[i] == NULL)
+	 continue;
+
+      while (do_common_optimization(prog->_LinkedShaders[i]->ir, true, 32))
+	 ;
+   }
+
+   update_array_sizes(prog);
+
+   assign_uniform_locations(prog);
+
+   if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) {
+      /* FINISHME: The value of the max_attribute_index parameter is
+       * FINISHME: implementation dependent based on the value of
+       * FINISHME: GL_MAX_VERTEX_ATTRIBS.  GL_MAX_VERTEX_ATTRIBS must be
+       * FINISHME: at least 16, so hardcode 16 for now.
+       */
+      if (!assign_attribute_locations(prog, 16)) {
+	 prog->LinkStatus = false;
+	 goto done;
+      }
+   }
+
+   unsigned prev;
+   for (prev = 0; prev < MESA_SHADER_TYPES; prev++) {
+      if (prog->_LinkedShaders[prev] != NULL)
+	 break;
+   }
+
+   for (unsigned i = prev + 1; i < MESA_SHADER_TYPES; i++) {
+      if (prog->_LinkedShaders[i] == NULL)
+	 continue;
+
+      assign_varying_locations(prog,
+			       prog->_LinkedShaders[prev],
+			       prog->_LinkedShaders[i]);
+      prev = i;
+   }
+
+   if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) {
+      demote_shader_inputs_and_outputs(prog->_LinkedShaders[MESA_SHADER_VERTEX],
+				       ir_var_out);
+   }
+
+   if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) {
+      gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_GEOMETRY];
+
+      demote_shader_inputs_and_outputs(sh, ir_var_in);
+      demote_shader_inputs_and_outputs(sh, ir_var_inout);
+      demote_shader_inputs_and_outputs(sh, ir_var_out);
+   }
+
+   if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] != NULL) {
+      gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_FRAGMENT];
+
+      demote_shader_inputs_and_outputs(sh, ir_var_in);
+   }
+
+   /* FINISHME: Assign fragment shader output locations. */
+
+done:
+   free(vert_shader_list);
+
+   for (unsigned i = 0; i < MESA_SHADER_TYPES; i++) {
+      if (prog->_LinkedShaders[i] == NULL)
+	 continue;
+
+      /* Retain any live IR, but trash the rest. */
+      reparent_ir(prog->_LinkedShaders[i]->ir, prog->_LinkedShaders[i]->ir);
+   }
+
+   talloc_free(mem_ctx);
+}