glsl: rename lower_clip_distance to lower_distance.

This just renames the file in anticipation of adding cull lowering,
and renames the internals.

Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

1 files changed, 574 insertions, 0 deletions

diff --git a/src/compiler/glsl/lower_distance.cpp b/src/compiler/glsl/lower_distance.cpp
new file mode 100644
index 0000000..301afe4
--- /dev/null
+++ b/src/compiler/glsl/lower_distance.cpp
@@ -0,0 +1,574 @@
+/*
+ * Copyright © 2011 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 lower_distance.cpp
+ *
+ * This pass accounts for the difference between the way
+ * gl_ClipDistance is declared in standard GLSL (as an array of
+ * floats), and the way it is frequently implemented in hardware (as
+ * a pair of vec4s, with four clip distances packed into each).
+ *
+ * The declaration of gl_ClipDistance is replaced with a declaration
+ * of gl_ClipDistanceMESA, and any references to gl_ClipDistance are
+ * translated to refer to gl_ClipDistanceMESA with the appropriate
+ * swizzling of array indices.  For instance:
+ *
+ *   gl_ClipDistance[i]
+ *
+ * is translated into:
+ *
+ *   gl_ClipDistanceMESA[i>>2][i&3]
+ *
+ * Since some hardware may not internally represent gl_ClipDistance as a pair
+ * of vec4's, this lowering pass is optional.  To enable it, set the
+ * LowerCombinedClipCullDistance 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_distance_visitor : public ir_rvalue_visitor {
+public:
+   explicit lower_distance_visitor(gl_shader_stage shader_stage)
+      : progress(false), old_distance_out_var(NULL),
+        old_distance_in_var(NULL), new_distance_out_var(NULL),
+        new_distance_in_var(NULL), shader_stage(shader_stage)
+   {
+   }
+
+   virtual ir_visitor_status visit(ir_variable *);
+   void create_indices(ir_rvalue*, ir_rvalue *&, ir_rvalue *&);
+   bool is_distance_vec8(ir_rvalue *ir);
+   ir_rvalue *lower_distance_vec8(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_ClipDistance, if found.
+    *
+    * Note:
+    *
+    * - the in_var is for geometry and both tessellation shader inputs only.
+    *
+    * - since gl_ClipDistance is available in tessellation control,
+    *   tessellation evaluation and geometry shaders as both an input
+    *   and an output, it's possible for both old_distance_out_var
+    *   and old_distance_in_var to be non-null.
+    */
+   ir_variable *old_distance_out_var;
+   ir_variable *old_distance_in_var;
+
+   /**
+    * Pointer to the newly-created gl_ClipDistanceMESA variable.
+    */
+   ir_variable *new_distance_out_var;
+   ir_variable *new_distance_in_var;
+
+   /**
+    * Type of shader we are compiling (e.g. MESA_SHADER_VERTEX)
+    */
+   const gl_shader_stage shader_stage;
+};
+
+} /* anonymous namespace */
+
+/**
+ * Replace any declaration of gl_ClipDistance as an array of floats with a
+ * declaration of gl_ClipDistanceMESA as an array of vec4's.
+ */
+ir_visitor_status
+lower_distance_visitor::visit(ir_variable *ir)
+{
+   ir_variable **old_var;
+   ir_variable **new_var;
+
+   if (!ir->name || strcmp(ir->name, "gl_ClipDistance") != 0)
+      return visit_continue;
+   assert (ir->type->is_array());
+
+   if (ir->data.mode == ir_var_shader_out) {
+      if (this->old_distance_out_var)
+         return visit_continue;
+      old_var = &old_distance_out_var;
+      new_var = &new_distance_out_var;
+   } else if (ir->data.mode == ir_var_shader_in) {
+      if (this->old_distance_in_var)
+         return visit_continue;
+      old_var = &old_distance_in_var;
+      new_var = &new_distance_in_var;
+   } else {
+      unreachable("not reached");
+   }
+
+   this->progress = true;
+
+   if (!ir->type->fields.array->is_array()) {
+      /* gl_ClipDistance (used for vertex, tessellation evaluation and
+       * geometry output, and fragment input).
+       */
+      assert((ir->data.mode == ir_var_shader_in &&
+              this->shader_stage == MESA_SHADER_FRAGMENT) ||
+             (ir->data.mode == ir_var_shader_out &&
+              (this->shader_stage == MESA_SHADER_VERTEX ||
+               this->shader_stage == MESA_SHADER_TESS_EVAL ||
+               this->shader_stage == MESA_SHADER_GEOMETRY)));
+
+      *old_var = ir;
+      assert (ir->type->fields.array == glsl_type::float_type);
+      unsigned new_size = (ir->type->array_size() + 3) / 4;
+
+      /* Clone the old var so that we inherit all of its properties */
+      *new_var = ir->clone(ralloc_parent(ir), NULL);
+
+      /* And change the properties that we need to change */
+      (*new_var)->name = ralloc_strdup(*new_var, "gl_ClipDistanceMESA");
+      (*new_var)->type = glsl_type::get_array_instance(glsl_type::vec4_type,
+                                                       new_size);
+      (*new_var)->data.max_array_access = ir->data.max_array_access / 4;
+
+      ir->replace_with(*new_var);
+   } else {
+      /* 2D gl_ClipDistance (used for tessellation control, tessellation
+       * evaluation and geometry input, and tessellation control output).
+       */
+      assert((ir->data.mode == ir_var_shader_in &&
+              (this->shader_stage == MESA_SHADER_GEOMETRY ||
+               this->shader_stage == MESA_SHADER_TESS_EVAL)) ||
+             this->shader_stage == MESA_SHADER_TESS_CTRL);
+
+      *old_var = ir;
+      assert (ir->type->fields.array->fields.array == glsl_type::float_type);
+      unsigned new_size = (ir->type->fields.array->array_size() + 3) / 4;
+
+      /* Clone the old var so that we inherit all of its properties */
+      *new_var = ir->clone(ralloc_parent(ir), NULL);
+
+      /* And change the properties that we need to change */
+      (*new_var)->name = ralloc_strdup(*new_var, "gl_ClipDistanceMESA");
+      (*new_var)->type = glsl_type::get_array_instance(
+         glsl_type::get_array_instance(glsl_type::vec4_type,
+            new_size),
+         ir->type->array_size());
+      (*new_var)->data.max_array_access = ir->data.max_array_access / 4;
+
+      ir->replace_with(*new_var);
+   }
+
+   return visit_continue;
+}
+
+
+/**
+ * Create the necessary GLSL rvalues to index into gl_ClipDistanceMESA based
+ * on the rvalue previously used to index into gl_ClipDistance.
+ *
+ * \param array_index Selects one of the vec4's in gl_ClipDistanceMESA
+ * \param swizzle_index Selects a component within the vec4 selected by
+ *        array_index.
+ */
+void
+lower_distance_visitor::create_indices(ir_rvalue *old_index,
+                                            ir_rvalue *&array_index,
+                                            ir_rvalue *&swizzle_index)
+{
+   void *ctx = ralloc_parent(old_index);
+
+   /* Make sure old_index is a signed int so that the bitwise "shift" and
+    * "and" operations below type check properly.
+    */
+   if (old_index->type != glsl_type::int_type) {
+      assert (old_index->type == glsl_type::uint_type);
+      old_index = new(ctx) ir_expression(ir_unop_u2i, old_index);
+   }
+
+   ir_constant *old_index_constant = old_index->constant_expression_value();
+   if (old_index_constant) {
+      /* gl_ClipDistance is being accessed via a constant index.  Don't bother
+       * creating expressions to calculate the lowered indices.  Just create
+       * constants.
+       */
+      int const_val = old_index_constant->get_int_component(0);
+      array_index = new(ctx) ir_constant(const_val / 4);
+      swizzle_index = new(ctx) ir_constant(const_val % 4);
+   } else {
+      /* Create a variable to hold the value of old_index (so that we
+       * don't compute it twice).
+       */
+      ir_variable *old_index_var = new(ctx) ir_variable(
+         glsl_type::int_type, "distance_index", ir_var_temporary);
+      this->base_ir->insert_before(old_index_var);
+      this->base_ir->insert_before(new(ctx) ir_assignment(
+         new(ctx) ir_dereference_variable(old_index_var), old_index));
+
+      /* Create the expression distance_index / 4.  Do this as a bit
+       * shift because that's likely to be more efficient.
+       */
+      array_index = new(ctx) ir_expression(
+         ir_binop_rshift, new(ctx) ir_dereference_variable(old_index_var),
+         new(ctx) ir_constant(2));
+
+      /* Create the expression distance_index % 4.  Do this as a bitwise
+       * AND because that's likely to be more efficient.
+       */
+      swizzle_index = new(ctx) ir_expression(
+         ir_binop_bit_and, new(ctx) ir_dereference_variable(old_index_var),
+         new(ctx) ir_constant(3));
+   }
+}
+
+
+/**
+ * Determine whether the given rvalue describes an array of 8 floats that
+ * needs to be lowered to an array of 2 vec4's; that is, determine whether it
+ * matches one of the following patterns:
+ *
+ * - gl_ClipDistance (if gl_ClipDistance is 1D)
+ * - gl_ClipDistance[i] (if gl_ClipDistance is 2D)
+ */
+bool
+lower_distance_visitor::is_distance_vec8(ir_rvalue *ir)
+{
+   /* Note that geometry shaders contain gl_ClipDistance both as an input
+    * (which is a 2D array) and an output (which is a 1D array), so it's
+    * possible for both this->old_distance_out_var and
+    * this->old_distance_in_var to be non-NULL in the same shader.
+    */
+
+   if (!ir->type->is_array())
+      return false;
+   if (ir->type->fields.array != glsl_type::float_type)
+      return false;
+
+   if (this->old_distance_out_var) {
+      if (ir->variable_referenced() == this->old_distance_out_var)
+         return true;
+   }
+   if (this->old_distance_in_var) {
+      assert(this->shader_stage == MESA_SHADER_TESS_CTRL ||
+             this->shader_stage == MESA_SHADER_TESS_EVAL ||
+             this->shader_stage == MESA_SHADER_GEOMETRY ||
+             this->shader_stage == MESA_SHADER_FRAGMENT);
+
+      if (ir->variable_referenced() == this->old_distance_in_var)
+         return true;
+   }
+   return false;
+}
+
+
+/**
+ * If the given ir satisfies is_distance_vec8(), return new ir
+ * representing its lowered equivalent.  That is, map:
+ *
+ * - gl_ClipDistance    => gl_ClipDistanceMESA    (if gl_ClipDistance is 1D)
+ * - gl_ClipDistance[i] => gl_ClipDistanceMESA[i] (if gl_ClipDistance is 2D)
+ *
+ * Otherwise return NULL.
+ */
+ir_rvalue *
+lower_distance_visitor::lower_distance_vec8(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_distance_out_var) {
+      if (ir->variable_referenced() == this->old_distance_out_var)
+         new_var = &this->new_distance_out_var;
+   }
+   if (this->old_distance_in_var) {
+      if (ir->variable_referenced() == this->old_distance_in_var)
+         new_var = &this->new_distance_in_var;
+   }
+   if (new_var == NULL)
+      return NULL;
+
+   if (ir->as_dereference_variable()) {
+      return new(ralloc_parent(ir)) ir_dereference_variable(*new_var);
+   } else {
+      ir_dereference_array *array_ref = ir->as_dereference_array();
+      assert(array_ref);
+      assert(array_ref->array->as_dereference_variable());
+
+      return new(ralloc_parent(ir))
+         ir_dereference_array(*new_var, array_ref->array_index);
+   }
+}
+
+
+void
+lower_distance_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_ClipDistance
+    * with an expression that indexes into one of the vec4's in
+    * gl_ClipDistanceMESA and accesses the appropriate component.
+    */
+   ir_rvalue *lowered_vec8 =
+      this->lower_distance_vec8(array_deref->array);
+   if (lowered_vec8 != NULL) {
+      this->progress = true;
+      ir_rvalue *array_index;
+      ir_rvalue *swizzle_index;
+      this->create_indices(array_deref->array_index, array_index, swizzle_index);
+      void *mem_ctx = ralloc_parent(array_deref);
+
+      ir_dereference_array *const new_array_deref =
+         new(mem_ctx) ir_dereference_array(lowered_vec8, array_index);
+
+      ir_expression *const expr =
+         new(mem_ctx) ir_expression(ir_binop_vector_extract,
+                                    new_array_deref,
+                                    swizzle_index);
+
+      *rv = expr;
+   }
+}
+
+void
+lower_distance_visitor::fix_lhs(ir_assignment *ir)
+{
+   if (ir->lhs->ir_type == ir_type_expression) {
+      void *mem_ctx = ralloc_parent(ir);
+      ir_expression *const expr = (ir_expression *) ir->lhs;
+
+      /* The expression must be of the form:
+       *
+       *     (vector_extract gl_ClipDistanceMESA[i], j).
+       */
+      assert(expr->operation == ir_binop_vector_extract);
+      assert(expr->operands[0]->ir_type == ir_type_dereference_array);
+      assert(expr->operands[0]->type == glsl_type::vec4_type);
+
+      ir_dereference *const new_lhs = (ir_dereference *) expr->operands[0];
+      ir->rhs = new(mem_ctx) ir_expression(ir_triop_vector_insert,
+					   glsl_type::vec4_type,
+					   new_lhs->clone(mem_ctx, NULL),
+					   ir->rhs,
+					   expr->operands[1]);
+      ir->set_lhs(new_lhs);
+      ir->write_mask = WRITEMASK_XYZW;
+   }
+}
+
+/**
+ * Replace any assignment having the 1D gl_ClipDistance (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_ClipDistanceMESA as appropriate.
+ *
+ * We need to do a similar replacement for 2D gl_ClipDistance, however since
+ * it's an input, the only case we need to address is where a 1D slice of it
+ * is the entire RHS of an assignment, e.g.:
+ *
+ *     foo = gl_in[i].gl_ClipDistance
+ */
+ir_visitor_status
+lower_distance_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_distance_vec8(ir->lhs) ||
+       this->is_distance_vec8(ir->rhs)) {
+      /* LHS or RHS of the assignment is the entire 1D gl_ClipDistance array
+       * (or a 1D slice of a 2D gl_ClipDistance input array).  Since we are
+       * reshaping gl_ClipDistance from an array of floats to an array of
+       * vec4's, 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_distance_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 1D gl_ClipDistance 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_ClipDistance.  Each of these
+ * assignments is then lowered to refer to gl_ClipDistanceMESA.
+ *
+ * We need to do a similar replacement for 2D gl_ClipDistance, however since
+ * it's an input, the only case we need to address is where a 1D slice of it
+ * is passed as an "in" parameter to an ir_call, e.g.:
+ *
+ *     foo(gl_in[i].gl_ClipDistance)
+ */
+ir_visitor_status
+lower_distance_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_distance_vec8(actual_param)) {
+         /* User is trying to pass the whole 1D gl_ClipDistance array (or a 1D
+          * slice of a 2D gl_ClipDistance array) to a function call.  Since we
+          * are reshaping gl_ClipDistance from an array of floats to an array
+          * of vec4's, this isn't going to work anymore, so use a temporary
+          * array instead.
+          */
+         ir_variable *temp_clip_distance = new(ctx) ir_variable(
+            actual_param->type, "temp_clip_distance", ir_var_temporary);
+         this->base_ir->insert_before(temp_clip_distance);
+         actual_param->replace_with(
+            new(ctx) ir_dereference_variable(temp_clip_distance));
+         if (formal_param->data.mode == ir_var_function_in
+             || formal_param->data.mode == ir_var_function_inout) {
+            /* Copy from gl_ClipDistance 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_clip_distance),
+               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_ClipDistance 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_clip_distance));
+            this->base_ir->insert_after(new_assignment);
+            this->visit_new_assignment(new_assignment);
+         }
+      }
+   }
+
+   return rvalue_visit(ir);
+}
+
+
+bool
+lower_clip_distance(gl_shader *shader)
+{
+   lower_distance_visitor v(shader->Stage);
+
+   visit_list_elements(&v, shader->ir);
+
+   if (v.new_distance_out_var)
+      shader->symbols->add_variable(v.new_distance_out_var);
+   if (v.new_distance_in_var)
+      shader->symbols->add_variable(v.new_distance_in_var);
+
+   return v.progress;
+}