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21 * DEALINGS IN THE SOFTWARE.
25 * \file lower_distance.cpp
27 * This pass accounts for the difference between the way
28 * gl_ClipDistance is declared in standard GLSL (as an array of
29 * floats), and the way it is frequently implemented in hardware (as
30 * a pair of vec4s, with four clip distances packed into each).
32 * The declaration of gl_ClipDistance is replaced with a declaration
33 * of gl_ClipDistanceMESA, and any references to gl_ClipDistance are
34 * translated to refer to gl_ClipDistanceMESA with the appropriate
35 * swizzling of array indices. For instance:
41 * gl_ClipDistanceMESA[i>>2][i&3]
43 * Since some hardware may not internally represent gl_ClipDistance as a pair
44 * of vec4's, this lowering pass is optional. To enable it, set the
45 * LowerCombinedClipCullDistance flag in gl_shader_compiler_options to true.
48 #include "main/macros.h"
49 #include "glsl_symbol_table.h"
50 #include "ir_rvalue_visitor.h"
52 #include "program/prog_instruction.h" /* For WRITEMASK_* */
54 #define GLSL_CLIP_VAR_NAME "gl_ClipDistanceMESA"
58 class lower_distance_visitor
: public ir_rvalue_visitor
{
60 explicit lower_distance_visitor(gl_shader_stage shader_stage
,
61 const char *in_name
, int total_size
,
63 : progress(false), old_distance_out_var(NULL
),
64 old_distance_in_var(NULL
), new_distance_out_var(NULL
),
65 new_distance_in_var(NULL
), shader_stage(shader_stage
),
66 in_name(in_name
), total_size(total_size
), offset(offset
)
70 explicit lower_distance_visitor(gl_shader_stage shader_stage
,
72 const lower_distance_visitor
*orig
,
75 old_distance_out_var(NULL
),
76 old_distance_in_var(NULL
),
77 new_distance_out_var(orig
->new_distance_out_var
),
78 new_distance_in_var(orig
->new_distance_in_var
),
79 shader_stage(shader_stage
),
81 total_size(orig
->total_size
),
86 virtual ir_visitor_status
visit(ir_variable
*);
87 void create_indices(ir_rvalue
*, ir_rvalue
*&, ir_rvalue
*&);
88 bool is_distance_vec8(ir_rvalue
*ir
);
89 ir_rvalue
*lower_distance_vec8(ir_rvalue
*ir
);
90 virtual ir_visitor_status
visit_leave(ir_assignment
*);
91 void visit_new_assignment(ir_assignment
*ir
);
92 virtual ir_visitor_status
visit_leave(ir_call
*);
94 virtual void handle_rvalue(ir_rvalue
**rvalue
);
96 void fix_lhs(ir_assignment
*);
101 * Pointer to the declaration of gl_ClipDistance, if found.
105 * - the in_var is for geometry and both tessellation shader inputs only.
107 * - since gl_ClipDistance is available in tessellation control,
108 * tessellation evaluation and geometry shaders as both an input
109 * and an output, it's possible for both old_distance_out_var
110 * and old_distance_in_var to be non-null.
112 ir_variable
*old_distance_out_var
;
113 ir_variable
*old_distance_in_var
;
116 * Pointer to the newly-created gl_ClipDistanceMESA variable.
118 ir_variable
*new_distance_out_var
;
119 ir_variable
*new_distance_in_var
;
122 * Type of shader we are compiling (e.g. MESA_SHADER_VERTEX)
124 const gl_shader_stage shader_stage
;
130 } /* anonymous namespace */
133 * Replace any declaration of 'in_name' as an array of floats with a
134 * declaration of gl_ClipDistanceMESA as an array of vec4's.
137 lower_distance_visitor::visit(ir_variable
*ir
)
139 ir_variable
**old_var
;
140 ir_variable
**new_var
;
142 if (!ir
->name
|| strcmp(ir
->name
, in_name
) != 0)
143 return visit_continue
;
144 assert (ir
->type
->is_array());
146 if (ir
->data
.mode
== ir_var_shader_out
) {
147 if (this->old_distance_out_var
)
148 return visit_continue
;
149 old_var
= &old_distance_out_var
;
150 new_var
= &new_distance_out_var
;
151 } else if (ir
->data
.mode
== ir_var_shader_in
) {
152 if (this->old_distance_in_var
)
153 return visit_continue
;
154 old_var
= &old_distance_in_var
;
155 new_var
= &new_distance_in_var
;
157 unreachable("not reached");
160 this->progress
= true;
165 unsigned new_size
= (total_size
+ 3) / 4;
167 /* Clone the old var so that we inherit all of its properties */
168 *new_var
= ir
->clone(ralloc_parent(ir
), NULL
);
169 (*new_var
)->name
= ralloc_strdup(*new_var
, GLSL_CLIP_VAR_NAME
);
170 (*new_var
)->data
.max_array_access
= new_size
- 1;
171 (*new_var
)->data
.location
= VARYING_SLOT_CLIP_DIST0
;
173 if (!ir
->type
->fields
.array
->is_array()) {
174 /* gl_ClipDistance (used for vertex, tessellation evaluation and
175 * geometry output, and fragment input).
177 assert((ir
->data
.mode
== ir_var_shader_in
&&
178 this->shader_stage
== MESA_SHADER_FRAGMENT
) ||
179 (ir
->data
.mode
== ir_var_shader_out
&&
180 (this->shader_stage
== MESA_SHADER_VERTEX
||
181 this->shader_stage
== MESA_SHADER_TESS_EVAL
||
182 this->shader_stage
== MESA_SHADER_GEOMETRY
)));
184 assert (ir
->type
->fields
.array
== glsl_type::float_type
);
186 /* And change the properties that we need to change */
187 (*new_var
)->type
= glsl_type::get_array_instance(glsl_type::vec4_type
,
190 /* 2D gl_ClipDistance (used for tessellation control, tessellation
191 * evaluation and geometry input, and tessellation control output).
193 assert((ir
->data
.mode
== ir_var_shader_in
&&
194 (this->shader_stage
== MESA_SHADER_GEOMETRY
||
195 this->shader_stage
== MESA_SHADER_TESS_EVAL
)) ||
196 this->shader_stage
== MESA_SHADER_TESS_CTRL
);
198 assert (ir
->type
->fields
.array
->fields
.array
== glsl_type::float_type
);
200 /* And change the properties that we need to change */
201 (*new_var
)->type
= glsl_type::get_array_instance(
202 glsl_type::get_array_instance(glsl_type::vec4_type
,
204 ir
->type
->array_size());
206 ir
->replace_with(*new_var
);
211 return visit_continue
;
216 * Create the necessary GLSL rvalues to index into gl_ClipDistanceMESA based
217 * on the rvalue previously used to index into gl_ClipDistance.
219 * \param array_index Selects one of the vec4's in gl_ClipDistanceMESA
220 * \param swizzle_index Selects a component within the vec4 selected by
224 lower_distance_visitor::create_indices(ir_rvalue
*old_index
,
225 ir_rvalue
*&array_index
,
226 ir_rvalue
*&swizzle_index
)
228 void *ctx
= ralloc_parent(old_index
);
230 /* Make sure old_index is a signed int so that the bitwise "shift" and
231 * "and" operations below type check properly.
233 if (old_index
->type
!= glsl_type::int_type
) {
234 assert (old_index
->type
== glsl_type::uint_type
);
235 old_index
= new(ctx
) ir_expression(ir_unop_u2i
, old_index
);
238 ir_constant
*old_index_constant
= old_index
->constant_expression_value();
239 if (old_index_constant
) {
240 /* gl_ClipDistance is being accessed via a constant index. Don't bother
241 * creating expressions to calculate the lowered indices. Just create
244 int const_val
= old_index_constant
->get_int_component(0) + offset
;
245 array_index
= new(ctx
) ir_constant(const_val
/ 4);
246 swizzle_index
= new(ctx
) ir_constant(const_val
% 4);
248 /* Create a variable to hold the value of old_index (so that we
249 * don't compute it twice).
251 ir_variable
*old_index_var
= new(ctx
) ir_variable(
252 glsl_type::int_type
, "distance_index", ir_var_temporary
);
253 this->base_ir
->insert_before(old_index_var
);
254 this->base_ir
->insert_before(new(ctx
) ir_assignment(
255 new(ctx
) ir_dereference_variable(old_index_var
), old_index
));
257 /* Create the expression distance_index / 4. Do this as a bit
258 * shift because that's likely to be more efficient.
260 array_index
= new(ctx
) ir_expression(
262 new(ctx
) ir_expression(ir_binop_add
,
263 new(ctx
) ir_dereference_variable(old_index_var
),
264 new(ctx
) ir_constant(offset
)),
265 new(ctx
) ir_constant(2));
267 /* Create the expression distance_index % 4. Do this as a bitwise
268 * AND because that's likely to be more efficient.
270 swizzle_index
= new(ctx
) ir_expression(
272 new(ctx
) ir_expression(ir_binop_add
,
273 new(ctx
) ir_dereference_variable(old_index_var
),
274 new(ctx
) ir_constant(offset
)),
275 new(ctx
) ir_constant(3));
281 * Determine whether the given rvalue describes an array of 8 floats that
282 * needs to be lowered to an array of 2 vec4's; that is, determine whether it
283 * matches one of the following patterns:
285 * - gl_ClipDistance (if gl_ClipDistance is 1D)
286 * - gl_ClipDistance[i] (if gl_ClipDistance is 2D)
289 lower_distance_visitor::is_distance_vec8(ir_rvalue
*ir
)
291 /* Note that geometry shaders contain gl_ClipDistance both as an input
292 * (which is a 2D array) and an output (which is a 1D array), so it's
293 * possible for both this->old_distance_out_var and
294 * this->old_distance_in_var to be non-NULL in the same shader.
297 if (!ir
->type
->is_array())
299 if (ir
->type
->fields
.array
!= glsl_type::float_type
)
302 if (this->old_distance_out_var
) {
303 if (ir
->variable_referenced() == this->old_distance_out_var
)
306 if (this->old_distance_in_var
) {
307 assert(this->shader_stage
== MESA_SHADER_TESS_CTRL
||
308 this->shader_stage
== MESA_SHADER_TESS_EVAL
||
309 this->shader_stage
== MESA_SHADER_GEOMETRY
||
310 this->shader_stage
== MESA_SHADER_FRAGMENT
);
312 if (ir
->variable_referenced() == this->old_distance_in_var
)
320 * If the given ir satisfies is_distance_vec8(), return new ir
321 * representing its lowered equivalent. That is, map:
323 * - gl_ClipDistance => gl_ClipDistanceMESA (if gl_ClipDistance is 1D)
324 * - gl_ClipDistance[i] => gl_ClipDistanceMESA[i] (if gl_ClipDistance is 2D)
326 * Otherwise return NULL.
329 lower_distance_visitor::lower_distance_vec8(ir_rvalue
*ir
)
331 if (!ir
->type
->is_array())
333 if (ir
->type
->fields
.array
!= glsl_type::float_type
)
336 ir_variable
**new_var
= NULL
;
337 if (this->old_distance_out_var
) {
338 if (ir
->variable_referenced() == this->old_distance_out_var
)
339 new_var
= &this->new_distance_out_var
;
341 if (this->old_distance_in_var
) {
342 if (ir
->variable_referenced() == this->old_distance_in_var
)
343 new_var
= &this->new_distance_in_var
;
348 if (ir
->as_dereference_variable()) {
349 return new(ralloc_parent(ir
)) ir_dereference_variable(*new_var
);
351 ir_dereference_array
*array_ref
= ir
->as_dereference_array();
353 assert(array_ref
->array
->as_dereference_variable());
355 return new(ralloc_parent(ir
))
356 ir_dereference_array(*new_var
, array_ref
->array_index
);
362 lower_distance_visitor::handle_rvalue(ir_rvalue
**rv
)
367 ir_dereference_array
*const array_deref
= (*rv
)->as_dereference_array();
368 if (array_deref
== NULL
)
371 /* Replace any expression that indexes one of the floats in gl_ClipDistance
372 * with an expression that indexes into one of the vec4's in
373 * gl_ClipDistanceMESA and accesses the appropriate component.
375 ir_rvalue
*lowered_vec8
=
376 this->lower_distance_vec8(array_deref
->array
);
377 if (lowered_vec8
!= NULL
) {
378 this->progress
= true;
379 ir_rvalue
*array_index
;
380 ir_rvalue
*swizzle_index
;
381 this->create_indices(array_deref
->array_index
, array_index
, swizzle_index
);
382 void *mem_ctx
= ralloc_parent(array_deref
);
384 ir_dereference_array
*const new_array_deref
=
385 new(mem_ctx
) ir_dereference_array(lowered_vec8
, array_index
);
387 ir_expression
*const expr
=
388 new(mem_ctx
) ir_expression(ir_binop_vector_extract
,
397 lower_distance_visitor::fix_lhs(ir_assignment
*ir
)
399 if (ir
->lhs
->ir_type
== ir_type_expression
) {
400 void *mem_ctx
= ralloc_parent(ir
);
401 ir_expression
*const expr
= (ir_expression
*) ir
->lhs
;
403 /* The expression must be of the form:
405 * (vector_extract gl_ClipDistanceMESA[i], j).
407 assert(expr
->operation
== ir_binop_vector_extract
);
408 assert(expr
->operands
[0]->ir_type
== ir_type_dereference_array
);
409 assert(expr
->operands
[0]->type
== glsl_type::vec4_type
);
411 ir_dereference
*const new_lhs
= (ir_dereference
*) expr
->operands
[0];
412 ir
->rhs
= new(mem_ctx
) ir_expression(ir_triop_vector_insert
,
413 glsl_type::vec4_type
,
414 new_lhs
->clone(mem_ctx
, NULL
),
417 ir
->set_lhs(new_lhs
);
418 ir
->write_mask
= WRITEMASK_XYZW
;
423 * Replace any assignment having the 1D gl_ClipDistance (undereferenced) as
424 * its LHS or RHS with a sequence of assignments, one for each component of
425 * the array. Each of these assignments is lowered to refer to
426 * gl_ClipDistanceMESA as appropriate.
428 * We need to do a similar replacement for 2D gl_ClipDistance, however since
429 * it's an input, the only case we need to address is where a 1D slice of it
430 * is the entire RHS of an assignment, e.g.:
432 * foo = gl_in[i].gl_ClipDistance
435 lower_distance_visitor::visit_leave(ir_assignment
*ir
)
437 /* First invoke the base class visitor. This causes handle_rvalue() to be
438 * called on ir->rhs and ir->condition.
440 ir_rvalue_visitor::visit_leave(ir
);
442 if (this->is_distance_vec8(ir
->lhs
) ||
443 this->is_distance_vec8(ir
->rhs
)) {
444 /* LHS or RHS of the assignment is the entire 1D gl_ClipDistance array
445 * (or a 1D slice of a 2D gl_ClipDistance input array). Since we are
446 * reshaping gl_ClipDistance from an array of floats to an array of
447 * vec4's, this isn't going to work as a bulk assignment anymore, so
448 * unroll it to element-by-element assignments and lower each of them.
450 * Note: to unroll into element-by-element assignments, we need to make
451 * clones of the LHS and RHS. This is safe because expressions and
452 * l-values are side-effect free.
454 void *ctx
= ralloc_parent(ir
);
455 int array_size
= ir
->lhs
->type
->array_size();
456 for (int i
= 0; i
< array_size
; ++i
) {
457 ir_dereference_array
*new_lhs
= new(ctx
) ir_dereference_array(
458 ir
->lhs
->clone(ctx
, NULL
), new(ctx
) ir_constant(i
));
459 ir_dereference_array
*new_rhs
= new(ctx
) ir_dereference_array(
460 ir
->rhs
->clone(ctx
, NULL
), new(ctx
) ir_constant(i
));
461 this->handle_rvalue((ir_rvalue
**) &new_rhs
);
463 /* Handle the LHS after creating the new assignment. This must
464 * happen in this order because handle_rvalue may replace the old LHS
465 * with an ir_expression of ir_binop_vector_extract. Since this is
466 * not a valide l-value, this will cause an assertion in the
467 * ir_assignment constructor to fail.
469 * If this occurs, replace the mangled LHS with a dereference of the
470 * vector, and replace the RHS with an ir_triop_vector_insert.
472 ir_assignment
*const assign
= new(ctx
) ir_assignment(new_lhs
, new_rhs
);
473 this->handle_rvalue((ir_rvalue
**) &assign
->lhs
);
474 this->fix_lhs(assign
);
476 this->base_ir
->insert_before(assign
);
480 return visit_continue
;
483 /* Handle the LHS as if it were an r-value. Normally
484 * rvalue_visit(ir_assignment *) only visits the RHS, but we need to lower
485 * expressions in the LHS as well.
487 * This may cause the LHS to get replaced with an ir_expression of
488 * ir_binop_vector_extract. If this occurs, replace it with a dereference
489 * of the vector, and replace the RHS with an ir_triop_vector_insert.
491 handle_rvalue((ir_rvalue
**)&ir
->lhs
);
494 return rvalue_visit(ir
);
499 * Set up base_ir properly and call visit_leave() on a newly created
500 * ir_assignment node. This is used in cases where we have to insert an
501 * ir_assignment in a place where we know the hierarchical visitor won't see
505 lower_distance_visitor::visit_new_assignment(ir_assignment
*ir
)
507 ir_instruction
*old_base_ir
= this->base_ir
;
510 this->base_ir
= old_base_ir
;
515 * If a 1D gl_ClipDistance variable appears as an argument in an ir_call
516 * expression, replace it with a temporary variable, and make sure the ir_call
517 * is preceded and/or followed by assignments that copy the contents of the
518 * temporary variable to and/or from gl_ClipDistance. Each of these
519 * assignments is then lowered to refer to gl_ClipDistanceMESA.
521 * We need to do a similar replacement for 2D gl_ClipDistance, however since
522 * it's an input, the only case we need to address is where a 1D slice of it
523 * is passed as an "in" parameter to an ir_call, e.g.:
525 * foo(gl_in[i].gl_ClipDistance)
528 lower_distance_visitor::visit_leave(ir_call
*ir
)
530 void *ctx
= ralloc_parent(ir
);
532 const exec_node
*formal_param_node
= ir
->callee
->parameters
.get_head_raw();
533 const exec_node
*actual_param_node
= ir
->actual_parameters
.get_head_raw();
534 while (!actual_param_node
->is_tail_sentinel()) {
535 ir_variable
*formal_param
= (ir_variable
*) formal_param_node
;
536 ir_rvalue
*actual_param
= (ir_rvalue
*) actual_param_node
;
538 /* Advance formal_param_node and actual_param_node now so that we can
539 * safely replace actual_param with another node, if necessary, below.
541 formal_param_node
= formal_param_node
->next
;
542 actual_param_node
= actual_param_node
->next
;
544 if (this->is_distance_vec8(actual_param
)) {
545 /* User is trying to pass the whole 1D gl_ClipDistance array (or a 1D
546 * slice of a 2D gl_ClipDistance array) to a function call. Since we
547 * are reshaping gl_ClipDistance from an array of floats to an array
548 * of vec4's, this isn't going to work anymore, so use a temporary
551 ir_variable
*temp_clip_distance
= new(ctx
) ir_variable(
552 actual_param
->type
, "temp_clip_distance", ir_var_temporary
);
553 this->base_ir
->insert_before(temp_clip_distance
);
554 actual_param
->replace_with(
555 new(ctx
) ir_dereference_variable(temp_clip_distance
));
556 if (formal_param
->data
.mode
== ir_var_function_in
557 || formal_param
->data
.mode
== ir_var_function_inout
) {
558 /* Copy from gl_ClipDistance to the temporary before the call.
559 * Since we are going to insert this copy before the current
560 * instruction, we need to visit it afterwards to make sure it
563 ir_assignment
*new_assignment
= new(ctx
) ir_assignment(
564 new(ctx
) ir_dereference_variable(temp_clip_distance
),
565 actual_param
->clone(ctx
, NULL
));
566 this->base_ir
->insert_before(new_assignment
);
567 this->visit_new_assignment(new_assignment
);
569 if (formal_param
->data
.mode
== ir_var_function_out
570 || formal_param
->data
.mode
== ir_var_function_inout
) {
571 /* Copy from the temporary to gl_ClipDistance after the call.
572 * Since visit_list_elements() has already decided which
573 * instruction it's going to visit next, we need to visit
574 * afterwards to make sure it gets lowered.
576 ir_assignment
*new_assignment
= new(ctx
) ir_assignment(
577 actual_param
->clone(ctx
, NULL
),
578 new(ctx
) ir_dereference_variable(temp_clip_distance
));
579 this->base_ir
->insert_after(new_assignment
);
580 this->visit_new_assignment(new_assignment
);
585 return rvalue_visit(ir
);
589 class lower_distance_visitor_counter
: public ir_rvalue_visitor
{
591 explicit lower_distance_visitor_counter(void)
592 : in_clip_size(0), in_cull_size(0),
593 out_clip_size(0), out_cull_size(0)
597 virtual ir_visitor_status
visit(ir_variable
*);
598 virtual void handle_rvalue(ir_rvalue
**rvalue
);
608 * Count gl_ClipDistance and gl_CullDistance sizes.
611 lower_distance_visitor_counter::visit(ir_variable
*ir
)
613 int *clip_size
, *cull_size
;
616 return visit_continue
;
618 if (ir
->data
.mode
== ir_var_shader_out
) {
619 clip_size
= &out_clip_size
;
620 cull_size
= &out_cull_size
;
621 } else if (ir
->data
.mode
== ir_var_shader_in
) {
622 clip_size
= &in_clip_size
;
623 cull_size
= &in_cull_size
;
625 return visit_continue
;
627 if (ir
->type
->is_unsized_array())
628 return visit_continue
;
630 if (*clip_size
== 0) {
631 if (!strcmp(ir
->name
, "gl_ClipDistance")) {
632 if (!ir
->type
->fields
.array
->is_array())
633 *clip_size
= ir
->type
->array_size();
635 *clip_size
= ir
->type
->fields
.array
->array_size();
639 if (*cull_size
== 0) {
640 if (!strcmp(ir
->name
, "gl_CullDistance")) {
641 if (!ir
->type
->fields
.array
->is_array())
642 *cull_size
= ir
->type
->array_size();
644 *cull_size
= ir
->type
->fields
.array
->array_size();
647 return visit_continue
;
651 lower_distance_visitor_counter::handle_rvalue(ir_rvalue
**rv
)
657 lower_clip_cull_distance(struct gl_shader_program
*prog
,
658 struct gl_linked_shader
*shader
)
660 int clip_size
, cull_size
;
662 lower_distance_visitor_counter count
;
663 visit_list_elements(&count
, shader
->ir
);
665 clip_size
= MAX2(count
.in_clip_size
, count
.out_clip_size
);
666 cull_size
= MAX2(count
.in_cull_size
, count
.out_cull_size
);
668 if (clip_size
== 0 && cull_size
== 0)
671 lower_distance_visitor
v(shader
->Stage
, "gl_ClipDistance", clip_size
+ cull_size
, 0);
672 visit_list_elements(&v
, shader
->ir
);
674 lower_distance_visitor
v2(shader
->Stage
, "gl_CullDistance", &v
, clip_size
);
675 visit_list_elements(&v2
, shader
->ir
);
677 if (v2
.new_distance_out_var
)
678 shader
->symbols
->add_variable(v2
.new_distance_out_var
);
679 if (v2
.new_distance_in_var
)
680 shader
->symbols
->add_variable(v2
.new_distance_in_var
);