glsl: lower gl_TessLevel* from float[n] to vecn.

Similar to gl_ClipDistance -> gl_ClipDistanceMESA

v2: - renamed is_mesa_var to lowered_builtin_array_variable
    - moved LowerTessLevel into gl_constants
    - cosmetic changes in lower_tess_level.cpp

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/Makefile.sources

@@ -154,6 +154,7 @@ LIBGLSL_FILES = \
 	lower_packed_varyings.cpp \
 	lower_named_interface_blocks.cpp \
 	lower_packing_builtins.cpp \
+	lower_tess_level.cpp \
 	lower_texture_projection.cpp \
 	lower_variable_index_to_cond_assign.cpp \
 	lower_vec_index_to_cond_assign.cpp \

src/glsl/ir_optimization.h

@@ -132,6 +132,7 @@ bool optimize_split_arrays(exec_list *instructions, bool linked);
 bool lower_offset_arrays(exec_list *instructions);
 void optimize_dead_builtin_variables(exec_list *instructions,
                                      enum ir_variable_mode other);
+bool lower_tess_level(gl_shader *shader);
 
 bool lower_vertex_id(gl_shader *shader);
 

src/glsl/link_varyings.cpp

@@ -328,7 +328,7 @@ tfeedback_decl::init(struct gl_context *ctx, const void *mem_ctx,
 
    this->location = -1;
    this->orig_name = input;
-   this->is_clip_distance_mesa = false;
+   this->lowered_builtin_array_variable = none;
    this->skip_components = 0;
    this->next_buffer_separator = false;
    this->matched_candidate = NULL;
@@ -377,8 +377,15 @@ tfeedback_decl::init(struct gl_context *ctx, const void *mem_ctx,
     */
    if (ctx->Const.ShaderCompilerOptions[MESA_SHADER_VERTEX].LowerClipDistance &&
        strcmp(this->var_name, "gl_ClipDistance") == 0) {
-      this->is_clip_distance_mesa = true;
+      this->lowered_builtin_array_variable = clip_distance;
    }
+
+   if (ctx->Const.LowerTessLevel &&
+       (strcmp(this->var_name, "gl_TessLevelOuter") == 0))
+      this->lowered_builtin_array_variable = tess_level_outer;
+   if (ctx->Const.LowerTessLevel &&
+       (strcmp(this->var_name, "gl_TessLevelInner") == 0))
+      this->lowered_builtin_array_variable = tess_level_inner;
 }
 
 
@@ -425,9 +432,22 @@ tfeedback_decl::assign_location(struct gl_context *ctx,
          this->matched_candidate->type->fields.array->matrix_columns;
       const unsigned vector_elements =
          this->matched_candidate->type->fields.array->vector_elements;
-      unsigned actual_array_size = this->is_clip_distance_mesa ?
-         prog->LastClipDistanceArraySize :
-         this->matched_candidate->type->array_size();
+      unsigned actual_array_size;
+      switch (this->lowered_builtin_array_variable) {
+      case clip_distance:
+         actual_array_size = prog->LastClipDistanceArraySize;
+         break;
+      case tess_level_outer:
+         actual_array_size = 4;
+         break;
+      case tess_level_inner:
+         actual_array_size = 2;
+         break;
+      case none:
+      default:
+         actual_array_size = this->matched_candidate->type->array_size();
+         break;
+      }
 
       if (this->is_subscripted) {
          /* Check array bounds. */
@@ -438,7 +458,7 @@ tfeedback_decl::assign_location(struct gl_context *ctx,
                          actual_array_size);
             return false;
          }
-         unsigned array_elem_size = this->is_clip_distance_mesa ?
+         unsigned array_elem_size = this->lowered_builtin_array_variable ?
             1 : vector_elements * matrix_cols;
          fine_location += array_elem_size * this->array_subscript;
          this->size = 1;
@@ -447,7 +467,7 @@ tfeedback_decl::assign_location(struct gl_context *ctx,
       }
       this->vector_elements = vector_elements;
       this->matrix_columns = matrix_cols;
-      if (this->is_clip_distance_mesa)
+      if (this->lowered_builtin_array_variable)
          this->type = GL_FLOAT;
       else
          this->type = this->matched_candidate->type->fields.array->gl_type;
@@ -570,8 +590,21 @@ const tfeedback_candidate *
 tfeedback_decl::find_candidate(gl_shader_program *prog,
                                hash_table *tfeedback_candidates)
 {
-   const char *name = this->is_clip_distance_mesa
-      ? "gl_ClipDistanceMESA" : this->var_name;
+   const char *name = this->var_name;
+   switch (this->lowered_builtin_array_variable) {
+   case none:
+      name = this->var_name;
+      break;
+   case clip_distance:
+      name = "gl_ClipDistanceMESA";
+      break;
+   case tess_level_outer:
+      name = "gl_TessLevelOuterMESA";
+      break;
+   case tess_level_inner:
+      name = "gl_TessLevelInnerMESA";
+      break;
+   }
    this->matched_candidate = (const tfeedback_candidate *)
       hash_table_find(tfeedback_candidates, name);
    if (!this->matched_candidate) {

src/glsl/link_varyings.h

@@ -128,7 +128,7 @@ public:
     */
    unsigned num_components() const
    {
-      if (this->is_clip_distance_mesa)
+      if (this->lowered_builtin_array_variable)
          return this->size;
       else
          return this->vector_elements * this->matrix_columns * this->size;
@@ -161,10 +161,15 @@ private:
    unsigned array_subscript;
 
    /**
-    * True if the variable is gl_ClipDistance and the driver lowers
-    * gl_ClipDistance to gl_ClipDistanceMESA.
+    * Non-zero if the variable is gl_ClipDistance, glTessLevelOuter or
+    * gl_TessLevelInner and the driver lowers it to gl_*MESA.
     */
-   bool is_clip_distance_mesa;
+   enum {
+      none,
+      clip_distance,
+      tess_level_outer,
+      tess_level_inner,
+   } lowered_builtin_array_variable;
 
    /**
     * The vertex shader output location that the linker assigned for this

src/glsl/linker.cpp

@@ -3324,6 +3324,10 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
          lower_clip_distance(prog->_LinkedShaders[i]);
       }
 
+      if (ctx->Const.LowerTessLevel) {
+         lower_tess_level(prog->_LinkedShaders[i]);
+      }
+
       while (do_common_optimization(prog->_LinkedShaders[i]->ir, true, false,
                                     &ctx->Const.ShaderCompilerOptions[i],
                                     ctx->Const.NativeIntegers))

src/glsl/lower_tess_level.cpp

@@ -0,0 +1,459 @@
+/*
+ * Copyright © 2014 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
+
+ *
+ * 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 lower_tess_level.cpp
+ *
+ * This pass accounts for the difference between the way gl_TessLevelOuter
+ * and gl_TessLevelInner is declared in standard GLSL (as an array of
+ * floats), and the way it is frequently implemented in hardware (as a vec4
+ * and vec2).
+ *
+ * The declaration of gl_TessLevel* is replaced with a declaration
+ * of gl_TessLevel*MESA, and any references to gl_TessLevel* are
+ * translated to refer to gl_TessLevel*MESA with the appropriate
+ * swizzling of array indices.  For instance:
+ *
+ *   gl_TessLevelOuter[i]
+ *
+ * is translated into:
+ *
+ *   gl_TessLevelOuterMESA[i]
+ *
+ * Since some hardware may not internally represent gl_TessLevel* as a pair
+ * of vec4's, this lowering pass is optional.  To enable it, set the
+ * LowerTessLevel flag in gl_shader_compiler_options to true.
+ */
+
+#include "glsl_symbol_table.h"
+#include "ir_rvalue_visitor.h"
+#include "ir.h"
+#include "program/prog_instruction.h" /* For WRITEMASK_* */
+
+namespace {
+
+class lower_tess_level_visitor : public ir_rvalue_visitor {
+public:
+   explicit lower_tess_level_visitor(gl_shader_stage shader_stage)
+      : progress(false), old_tess_level_outer_var(NULL),
+        old_tess_level_inner_var(NULL), new_tess_level_outer_var(NULL),
+        new_tess_level_inner_var(NULL), shader_stage(shader_stage)
+   {
+   }
+
+   virtual ir_visitor_status visit(ir_variable *);
+   bool is_tess_level_array(ir_rvalue *ir);
+   ir_rvalue *lower_tess_level_array(ir_rvalue *ir);
+   virtual ir_visitor_status visit_leave(ir_assignment *);
+   void visit_new_assignment(ir_assignment *ir);
+   virtual ir_visitor_status visit_leave(ir_call *);
+
+   virtual void handle_rvalue(ir_rvalue **rvalue);
+
+   void fix_lhs(ir_assignment *);
+
+   bool progress;
+
+   /**
+    * Pointer to the declaration of gl_TessLevel*, if found.
+    */
+   ir_variable *old_tess_level_outer_var;
+   ir_variable *old_tess_level_inner_var;
+
+   /**
+    * Pointer to the newly-created gl_TessLevel*MESA variables.
+    */
+   ir_variable *new_tess_level_outer_var;
+   ir_variable *new_tess_level_inner_var;
+
+   /**
+    * Type of shader we are compiling (e.g. MESA_SHADER_TESS_CTRL)
+    */
+   const gl_shader_stage shader_stage;
+};
+
+} /* anonymous namespace */
+
+/**
+ * Replace any declaration of gl_TessLevel* as an array of floats with a
+ * declaration of gl_TessLevel*MESA as a vec4.
+ */
+ir_visitor_status
+lower_tess_level_visitor::visit(ir_variable *ir)
+{
+   if ((!ir->name) ||
+       ((strcmp(ir->name, "gl_TessLevelInner") != 0) &&
+        (strcmp(ir->name, "gl_TessLevelOuter") != 0)))
+      return visit_continue;
+
+   assert (ir->type->is_array());
+
+   if (strcmp(ir->name, "gl_TessLevelOuter") == 0) {
+      if (this->old_tess_level_outer_var)
+         return visit_continue;
+
+      old_tess_level_outer_var = ir;
+      assert(ir->type->fields.array == glsl_type::float_type);
+
+      /* Clone the old var so that we inherit all of its properties */
+      new_tess_level_outer_var = ir->clone(ralloc_parent(ir), NULL);
+
+      /* And change the properties that we need to change */
+      new_tess_level_outer_var->name = ralloc_strdup(new_tess_level_outer_var,
+                                                "gl_TessLevelOuterMESA");
+      new_tess_level_outer_var->type = glsl_type::vec4_type;
+      new_tess_level_outer_var->data.max_array_access = 0;
+
+      ir->replace_with(new_tess_level_outer_var);
+   } else if (strcmp(ir->name, "gl_TessLevelInner") == 0) {
+      if (this->old_tess_level_inner_var)
+         return visit_continue;
+
+      old_tess_level_inner_var = ir;
+      assert(ir->type->fields.array == glsl_type::float_type);
+
+      /* Clone the old var so that we inherit all of its properties */
+      new_tess_level_inner_var = ir->clone(ralloc_parent(ir), NULL);
+
+      /* And change the properties that we need to change */
+      new_tess_level_inner_var->name = ralloc_strdup(new_tess_level_inner_var,
+                                                "gl_TessLevelInnerMESA");
+      new_tess_level_inner_var->type = glsl_type::vec2_type;
+      new_tess_level_inner_var->data.max_array_access = 0;
+
+      ir->replace_with(new_tess_level_inner_var);
+   } else {
+      assert(0);
+   }
+
+   this->progress = true;
+
+   return visit_continue;
+}
+
+
+/**
+ * Determine whether the given rvalue describes an array of floats that
+ * needs to be lowered to a vec4; that is, determine whether it
+ * matches one of the following patterns:
+ *
+ * - gl_TessLevelOuter
+ * - gl_TessLevelInner
+ */
+bool
+lower_tess_level_visitor::is_tess_level_array(ir_rvalue *ir)
+{
+   if (!ir->type->is_array())
+      return false;
+   if (ir->type->fields.array != glsl_type::float_type)
+      return false;
+
+   if (this->old_tess_level_outer_var) {
+      if (ir->variable_referenced() == this->old_tess_level_outer_var)
+         return true;
+   }
+   if (this->old_tess_level_inner_var) {
+      if (ir->variable_referenced() == this->old_tess_level_inner_var)
+         return true;
+   }
+   return false;
+}
+
+
+/**
+ * If the given ir satisfies is_tess_level_array(), return new ir
+ * representing its lowered equivalent.  That is, map:
+ *
+ * - gl_TessLevelOuter => gl_TessLevelOuterMESA
+ * - gl_TessLevelInner => gl_TessLevelInnerMESA
+ *
+ * Otherwise return NULL.
+ */
+ir_rvalue *
+lower_tess_level_visitor::lower_tess_level_array(ir_rvalue *ir)
+{
+   if (!ir->type->is_array())
+      return NULL;
+   if (ir->type->fields.array != glsl_type::float_type)
+      return NULL;
+
+   ir_variable **new_var = NULL;
+
+   if (this->old_tess_level_outer_var) {
+      if (ir->variable_referenced() == this->old_tess_level_outer_var)
+         new_var = &this->new_tess_level_outer_var;
+   }
+   if (this->old_tess_level_inner_var) {
+      if (ir->variable_referenced() == this->old_tess_level_inner_var)
+         new_var = &this->new_tess_level_inner_var;
+   }
+
+   if (new_var == NULL)
+      return NULL;
+
+   assert(ir->as_dereference_variable());
+   return new(ralloc_parent(ir)) ir_dereference_variable(*new_var);
+}
+
+
+void
+lower_tess_level_visitor::handle_rvalue(ir_rvalue **rv)
+{
+   if (*rv == NULL)
+      return;
+
+   ir_dereference_array *const array_deref = (*rv)->as_dereference_array();
+   if (array_deref == NULL)
+      return;
+
+   /* Replace any expression that indexes one of the floats in gl_TessLevel*
+    * with an expression that indexes into one of the vec4's
+    * gl_TessLevel*MESA and accesses the appropriate component.
+    */
+   ir_rvalue *lowered_vec4 =
+      this->lower_tess_level_array(array_deref->array);
+   if (lowered_vec4 != NULL) {
+      this->progress = true;
+      void *mem_ctx = ralloc_parent(array_deref);
+
+      ir_expression *const expr =
+         new(mem_ctx) ir_expression(ir_binop_vector_extract,
+                                    lowered_vec4,
+                                    array_deref->array_index);
+
+      *rv = expr;
+   }
+}
+
+void
+lower_tess_level_visitor::fix_lhs(ir_assignment *ir)
+{
+   if (ir->lhs->ir_type != ir_type_expression)
+      return;
+   void *mem_ctx = ralloc_parent(ir);
+   ir_expression *const expr = (ir_expression *) ir->lhs;
+
+   /* The expression must be of the form:
+    *
+    *     (vector_extract gl_TessLevel*MESA, j).
+    */
+   assert(expr->operation == ir_binop_vector_extract);
+   assert(expr->operands[0]->ir_type == ir_type_dereference_variable);
+   assert((expr->operands[0]->type == glsl_type::vec4_type) ||
+          (expr->operands[0]->type == glsl_type::vec2_type));
+
+   ir_dereference *const new_lhs = (ir_dereference *) expr->operands[0];
+
+   ir_constant *old_index_constant = expr->operands[1]->constant_expression_value();
+   if (!old_index_constant) {
+      ir->rhs = new(mem_ctx) ir_expression(ir_triop_vector_insert,
+                                           expr->operands[0]->type,
+                                           new_lhs->clone(mem_ctx, NULL),
+                                           ir->rhs,
+                                           expr->operands[1]);
+   }
+   ir->set_lhs(new_lhs);
+
+   if (old_index_constant) {
+      /* gl_TessLevel* is being accessed via a constant index.  Don't bother
+       * creating a vector insert op. Just use a write mask.
+       */
+      ir->write_mask = 1 << old_index_constant->get_int_component(0);
+   } else {
+      ir->write_mask = (1 << expr->operands[0]->type->vector_elements) - 1;
+   }
+}
+
+/**
+ * Replace any assignment having a gl_TessLevel* (undereferenced) as
+ * its LHS or RHS with a sequence of assignments, one for each component of
+ * the array.  Each of these assignments is lowered to refer to
+ * gl_TessLevel*MESA as appropriate.
+ */
+ir_visitor_status
+lower_tess_level_visitor::visit_leave(ir_assignment *ir)
+{
+   /* First invoke the base class visitor.  This causes handle_rvalue() to be
+    * called on ir->rhs and ir->condition.
+    */
+   ir_rvalue_visitor::visit_leave(ir);
+
+   if (this->is_tess_level_array(ir->lhs) ||
+       this->is_tess_level_array(ir->rhs)) {
+      /* LHS or RHS of the assignment is the entire gl_TessLevel* array.
+       * Since we are
+       * reshaping gl_TessLevel* from an array of floats to a
+       * vec4, this isn't going to work as a bulk assignment anymore, so
+       * unroll it to element-by-element assignments and lower each of them.
+       *
+       * Note: to unroll into element-by-element assignments, we need to make
+       * clones of the LHS and RHS.  This is safe because expressions and
+       * l-values are side-effect free.
+       */
+      void *ctx = ralloc_parent(ir);
+      int array_size = ir->lhs->type->array_size();
+      for (int i = 0; i < array_size; ++i) {
+         ir_dereference_array *new_lhs = new(ctx) ir_dereference_array(
+            ir->lhs->clone(ctx, NULL), new(ctx) ir_constant(i));
+         ir_dereference_array *new_rhs = new(ctx) ir_dereference_array(
+            ir->rhs->clone(ctx, NULL), new(ctx) ir_constant(i));
+         this->handle_rvalue((ir_rvalue **) &new_rhs);
+
+         /* Handle the LHS after creating the new assignment.  This must
+          * happen in this order because handle_rvalue may replace the old LHS
+          * with an ir_expression of ir_binop_vector_extract.  Since this is
+          * not a valide l-value, this will cause an assertion in the
+          * ir_assignment constructor to fail.
+          *
+          * If this occurs, replace the mangled LHS with a dereference of the
+          * vector, and replace the RHS with an ir_triop_vector_insert.
+          */
+         ir_assignment *const assign = new(ctx) ir_assignment(new_lhs, new_rhs);
+         this->handle_rvalue((ir_rvalue **) &assign->lhs);
+         this->fix_lhs(assign);
+
+         this->base_ir->insert_before(assign);
+      }
+      ir->remove();
+
+      return visit_continue;
+   }
+
+   /* Handle the LHS as if it were an r-value.  Normally
+    * rvalue_visit(ir_assignment *) only visits the RHS, but we need to lower
+    * expressions in the LHS as well.
+    *
+    * This may cause the LHS to get replaced with an ir_expression of
+    * ir_binop_vector_extract.  If this occurs, replace it with a dereference
+    * of the vector, and replace the RHS with an ir_triop_vector_insert.
+    */
+   handle_rvalue((ir_rvalue **)&ir->lhs);
+   this->fix_lhs(ir);
+
+   return rvalue_visit(ir);
+}
+
+
+/**
+ * Set up base_ir properly and call visit_leave() on a newly created
+ * ir_assignment node.  This is used in cases where we have to insert an
+ * ir_assignment in a place where we know the hierarchical visitor won't see
+ * it.
+ */
+void
+lower_tess_level_visitor::visit_new_assignment(ir_assignment *ir)
+{
+   ir_instruction *old_base_ir = this->base_ir;
+   this->base_ir = ir;
+   ir->accept(this);
+   this->base_ir = old_base_ir;
+}
+
+
+/**
+ * If a gl_TessLevel* variable appears as an argument in an ir_call
+ * expression, replace it with a temporary variable, and make sure the ir_call
+ * is preceded and/or followed by assignments that copy the contents of the
+ * temporary variable to and/or from gl_TessLevel*.  Each of these
+ * assignments is then lowered to refer to gl_TessLevel*MESA.
+ */
+ir_visitor_status
+lower_tess_level_visitor::visit_leave(ir_call *ir)
+{
+   void *ctx = ralloc_parent(ir);
+
+   const exec_node *formal_param_node = ir->callee->parameters.head;
+   const exec_node *actual_param_node = ir->actual_parameters.head;
+   while (!actual_param_node->is_tail_sentinel()) {
+      ir_variable *formal_param = (ir_variable *) formal_param_node;
+      ir_rvalue *actual_param = (ir_rvalue *) actual_param_node;
+
+      /* Advance formal_param_node and actual_param_node now so that we can
+       * safely replace actual_param with another node, if necessary, below.
+       */
+      formal_param_node = formal_param_node->next;
+      actual_param_node = actual_param_node->next;
+
+      if (!this->is_tess_level_array(actual_param))
+         continue;
+
+      /* User is trying to pass a whole gl_TessLevel* array to a function
+       * call.  Since we are reshaping gl_TessLevel* from an array of floats
+       * to a vec4, this isn't going to work anymore, so use a temporary
+       * array instead.
+       */
+      ir_variable *temp = new(ctx) ir_variable(
+         actual_param->type, "temp_tess_level", ir_var_temporary);
+      this->base_ir->insert_before(temp);
+      actual_param->replace_with(
+         new(ctx) ir_dereference_variable(temp));
+      if (formal_param->data.mode == ir_var_function_in
+          || formal_param->data.mode == ir_var_function_inout) {
+         /* Copy from gl_TessLevel* to the temporary before the call.
+          * Since we are going to insert this copy before the current
+          * instruction, we need to visit it afterwards to make sure it
+          * gets lowered.
+          */
+         ir_assignment *new_assignment = new(ctx) ir_assignment(
+            new(ctx) ir_dereference_variable(temp),
+            actual_param->clone(ctx, NULL));
+         this->base_ir->insert_before(new_assignment);
+         this->visit_new_assignment(new_assignment);
+      }
+      if (formal_param->data.mode == ir_var_function_out
+          || formal_param->data.mode == ir_var_function_inout) {
+         /* Copy from the temporary to gl_TessLevel* after the call.
+          * Since visit_list_elements() has already decided which
+          * instruction it's going to visit next, we need to visit
+          * afterwards to make sure it gets lowered.
+          */
+         ir_assignment *new_assignment = new(ctx) ir_assignment(
+            actual_param->clone(ctx, NULL),
+            new(ctx) ir_dereference_variable(temp));
+         this->base_ir->insert_after(new_assignment);
+         this->visit_new_assignment(new_assignment);
+      }
+   }
+
+   return rvalue_visit(ir);
+}
+
+
+bool
+lower_tess_level(gl_shader *shader)
+{
+   if ((shader->Stage != MESA_SHADER_TESS_CTRL) &&
+       (shader->Stage != MESA_SHADER_TESS_EVAL))
+      return false;
+
+   lower_tess_level_visitor v(shader->Stage);
+
+   visit_list_elements(&v, shader->ir);
+
+   if (v.new_tess_level_outer_var)
+      shader->symbols->add_variable(v.new_tess_level_outer_var);
+   if (v.new_tess_level_inner_var)
+      shader->symbols->add_variable(v.new_tess_level_inner_var);
+
+   return v.progress;
+}

src/mesa/main/mtypes.h

@@ -3758,6 +3758,7 @@ struct gl_constants
    GLuint MaxTessGenLevel;
    GLuint MaxTessPatchComponents;
    GLuint MaxTessControlTotalOutputComponents;
+   bool LowerTessLevel; /**< Lower gl_TessLevel* from float[n] to vecn? */
 };