/*
* 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_clip_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
* LowerClipDistance flag in gl_shader_compiler_options to true.
*/
#include "ir_hierarchical_visitor.h"
#include "ir.h"
class lower_clip_distance_visitor : public ir_hierarchical_visitor {
public:
lower_clip_distance_visitor()
: progress(false), old_clip_distance_var(NULL),
new_clip_distance_var(NULL)
{
}
virtual ir_visitor_status visit(ir_variable *);
void create_indices(ir_rvalue*, ir_rvalue *&, ir_rvalue *&);
virtual ir_visitor_status visit_leave(ir_dereference_array *);
virtual ir_visitor_status visit_leave(ir_assignment *);
void visit_new_assignment(ir_assignment *ir);
virtual ir_visitor_status visit_leave(ir_call *);
bool progress;
/**
* Pointer to the declaration of gl_ClipDistance, if found.
*/
ir_variable *old_clip_distance_var;
/**
* Pointer to the newly-created gl_ClipDistanceMESA variable.
*/
ir_variable *new_clip_distance_var;
};
/**
* 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_clip_distance_visitor::visit(ir_variable *ir)
{
/* No point in looking for the declaration of gl_ClipDistance if
* we've already found it.
*/
if (this->old_clip_distance_var)
return visit_continue;
if (ir->name && strcmp(ir->name, "gl_ClipDistance") == 0) {
this->progress = true;
this->old_clip_distance_var = ir;
assert (ir->type->is_array());
assert (ir->type->element_type() == 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 */
this->new_clip_distance_var = ir->clone(ralloc_parent(ir), NULL);
/* And change the properties that we need to change */
this->new_clip_distance_var->name
= ralloc_strdup(this->new_clip_distance_var, "gl_ClipDistanceMESA");
this->new_clip_distance_var->type
= glsl_type::get_array_instance(glsl_type::vec4_type, new_size);
this->new_clip_distance_var->max_array_access = ir->max_array_access / 4;
ir->replace_with(this->new_clip_distance_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_clip_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, "clip_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 clip_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 clip_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));
}
}
/**
* Replace any expression that indexes into the gl_ClipDistance array with an
* expression that indexes into one of the vec4's in gl_ClipDistanceMESA and
* accesses the appropriate component.
*/
ir_visitor_status
lower_clip_distance_visitor::visit_leave(ir_dereference_array *ir)
{
/* If the gl_ClipDistance var hasn't been declared yet, then
* there's no way this deref can refer to it.
*/
if (!this->old_clip_distance_var)
return visit_continue;
ir_dereference_variable *old_var_ref = ir->array->as_dereference_variable();
if (old_var_ref && old_var_ref->var == this->old_clip_distance_var) {
this->progress = true;
ir_rvalue *array_index;
ir_rvalue *swizzle_index;
this->create_indices(ir->array_index, array_index, swizzle_index);
void *mem_ctx = ralloc_parent(ir);
ir->array = new(mem_ctx) ir_dereference_array(
this->new_clip_distance_var, array_index);
ir->array_index = swizzle_index;
}
return visit_continue;
}
/**
* Replace any assignment having 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.
*/
ir_visitor_status
lower_clip_distance_visitor::visit_leave(ir_assignment *ir)
{
ir_dereference_variable *lhs_var = ir->lhs->as_dereference_variable();
ir_dereference_variable *rhs_var = ir->rhs->as_dereference_variable();
if ((lhs_var && lhs_var->var == this->old_clip_distance_var)
|| (rhs_var && rhs_var->var == this->old_clip_distance_var)) {
/* LHS or RHS of the assignment is the entire gl_ClipDistance 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 only safe if the LHS and RHS are
* side-effect free. Fortunately, we know that they are, because the
* only kind of rvalue that can have side effects is an ir_call, and
* ir_calls only appear (a) as a statement on their own, or (b) as the
* RHS of an assignment that stores the result of the call in a
* temporary variable.
*/
void *ctx = ralloc_parent(ir);
int array_size = this->old_clip_distance_var->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));
new_lhs->accept(this);
ir_dereference_array *new_rhs = new(ctx) ir_dereference_array(
ir->rhs->clone(ctx, NULL), new(ctx) ir_constant(i));
new_rhs->accept(this);
this->base_ir->insert_before(
new(ctx) ir_assignment(new_lhs, new_rhs));
}
ir->remove();
}
return visit_continue;
}
/**
* 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_clip_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 gl_ClipDistance 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.
*/
ir_visitor_status
lower_clip_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;
ir_dereference_variable *deref = actual_param->as_dereference_variable();
if (deref && deref->var == this->old_clip_distance_var) {
/* User is trying to pass the whole 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->mode == ir_var_in
|| formal_param->mode == ir_var_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),
new(ctx) ir_dereference_variable(old_clip_distance_var));
this->base_ir->insert_before(new_assignment);
this->visit_new_assignment(new_assignment);
}
if (formal_param->mode == ir_var_out
|| formal_param->mode == ir_var_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(
new(ctx) ir_dereference_variable(old_clip_distance_var),
new(ctx) ir_dereference_variable(temp_clip_distance));
this->base_ir->insert_after(new_assignment);
this->visit_new_assignment(new_assignment);
}
}
}
return visit_continue;
}
bool
lower_clip_distance(exec_list *instructions)
{
lower_clip_distance_visitor v;
visit_list_elements(&v, instructions);
return v.progress;
}