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25 * \file brw_wm_vector_splitting.cpp
27 * If a vector is only ever referenced by its components, then
28 * split those components out to individual variables so they can be
29 * handled normally by other optimization passes.
31 * This skips vectors in uniforms and varyings, which need to be
32 * accessible as vectors for their access by the GL. Also, vector
33 * results of non-variable-derefs in assignments aren't handled
34 * because to do so we would have to store the vector result to a
35 * temporary in order to unload each channel, and to do so would just
36 * loop us back to where we started. For the 965, this is exactly the
37 * behavior we want for the results of texture lookups, but probably not for
41 #include "main/core.h"
42 #include "brw_context.h"
45 #include "glsl/ir_visitor.h"
46 #include "glsl/ir_rvalue_visitor.h"
47 #include "glsl/glsl_types.h"
49 static bool debug
= false;
51 class variable_entry
: public exec_node
54 variable_entry(ir_variable
*var
)
57 this->whole_vector_access
= 0;
61 ir_variable
*var
; /* The key: the variable's pointer. */
63 /** Number of times the variable is referenced, including assignments. */
64 unsigned whole_vector_access
;
66 ir_variable
*components
[4];
68 /** ralloc_parent(this->var) -- the shader's ralloc context. */
72 class ir_vector_reference_visitor
: public ir_hierarchical_visitor
{
74 ir_vector_reference_visitor(void)
76 this->mem_ctx
= ralloc_context(NULL
);
77 this->variable_list
.make_empty();
80 ~ir_vector_reference_visitor(void)
85 virtual ir_visitor_status
visit(ir_variable
*);
86 virtual ir_visitor_status
visit(ir_dereference_variable
*);
87 virtual ir_visitor_status
visit_enter(ir_swizzle
*);
88 virtual ir_visitor_status
visit_enter(ir_assignment
*);
89 virtual ir_visitor_status
visit_enter(ir_function_signature
*);
91 variable_entry
*get_variable_entry(ir_variable
*var
);
93 /* List of variable_entry */
94 exec_list variable_list
;
100 ir_vector_reference_visitor::get_variable_entry(ir_variable
*var
)
104 if (!var
->type
->is_vector())
107 switch (var
->data
.mode
) {
109 case ir_var_shader_in
:
110 case ir_var_shader_out
:
111 case ir_var_system_value
:
112 case ir_var_function_in
:
113 case ir_var_function_out
:
114 case ir_var_function_inout
:
115 /* Can't split varyings or uniforms. Function in/outs won't get split
120 case ir_var_temporary
:
124 foreach_in_list(variable_entry
, entry
, &variable_list
) {
125 if (entry
->var
== var
)
129 variable_entry
*entry
= new(mem_ctx
) variable_entry(var
);
130 this->variable_list
.push_tail(entry
);
136 ir_vector_reference_visitor::visit(ir_variable
*ir
)
138 /* Make sure splitting looks at splitting this variable */
139 (void)this->get_variable_entry(ir
);
141 return visit_continue
;
145 ir_vector_reference_visitor::visit(ir_dereference_variable
*ir
)
147 ir_variable
*const var
= ir
->var
;
148 variable_entry
*entry
= this->get_variable_entry(var
);
151 entry
->whole_vector_access
++;
153 return visit_continue
;
157 ir_vector_reference_visitor::visit_enter(ir_swizzle
*ir
)
159 /* Don't descend into a vector ir_dereference_variable below. */
160 if (ir
->val
->as_dereference_variable() && ir
->type
->is_scalar())
161 return visit_continue_with_parent
;
163 return visit_continue
;
167 ir_vector_reference_visitor::visit_enter(ir_assignment
*ir
)
169 if (ir
->lhs
->as_dereference_variable() &&
170 ir
->rhs
->as_dereference_variable() &&
172 /* We'll split copies of a vector to copies of channels, so don't
173 * descend to the ir_dereference_variables.
175 return visit_continue_with_parent
;
177 if (ir
->lhs
->as_dereference_variable() &&
178 is_power_of_two(ir
->write_mask
) &&
180 /* If we're writing just a channel, then channel-splitting the LHS is OK.
182 ir
->rhs
->accept(this);
183 return visit_continue_with_parent
;
185 return visit_continue
;
189 ir_vector_reference_visitor::visit_enter(ir_function_signature
*ir
)
191 /* We don't want to descend into the function parameters and
192 * split them, so just accept the body here.
194 visit_list_elements(this, &ir
->body
);
195 return visit_continue_with_parent
;
198 class ir_vector_splitting_visitor
: public ir_rvalue_visitor
{
200 ir_vector_splitting_visitor(exec_list
*vars
)
202 this->variable_list
= vars
;
205 virtual ir_visitor_status
visit_leave(ir_assignment
*);
207 void handle_rvalue(ir_rvalue
**rvalue
);
208 variable_entry
*get_splitting_entry(ir_variable
*var
);
210 exec_list
*variable_list
;
214 ir_vector_splitting_visitor::get_splitting_entry(ir_variable
*var
)
218 if (!var
->type
->is_vector())
221 foreach_in_list(variable_entry
, entry
, variable_list
) {
222 if (entry
->var
== var
) {
231 ir_vector_splitting_visitor::handle_rvalue(ir_rvalue
**rvalue
)
236 ir_swizzle
*swiz
= (*rvalue
)->as_swizzle();
237 if (!swiz
|| !swiz
->type
->is_scalar())
240 ir_dereference_variable
*deref_var
= swiz
->val
->as_dereference_variable();
244 variable_entry
*entry
= get_splitting_entry(deref_var
->var
);
248 ir_variable
*var
= entry
->components
[swiz
->mask
.x
];
249 *rvalue
= new(entry
->mem_ctx
) ir_dereference_variable(var
);
253 ir_vector_splitting_visitor::visit_leave(ir_assignment
*ir
)
255 ir_dereference_variable
*lhs_deref
= ir
->lhs
->as_dereference_variable();
256 ir_dereference_variable
*rhs_deref
= ir
->rhs
->as_dereference_variable();
257 variable_entry
*lhs
= lhs_deref
? get_splitting_entry(lhs_deref
->var
) : NULL
;
258 variable_entry
*rhs
= rhs_deref
? get_splitting_entry(rhs_deref
->var
) : NULL
;
260 if (lhs_deref
&& rhs_deref
&& (lhs
|| rhs
) && !ir
->condition
) {
261 unsigned int rhs_chan
= 0;
263 /* Straight assignment of vector variables. */
264 for (unsigned int i
= 0; i
< ir
->lhs
->type
->vector_elements
; i
++) {
265 ir_dereference
*new_lhs
;
267 void *mem_ctx
= lhs
? lhs
->mem_ctx
: rhs
->mem_ctx
;
268 unsigned int writemask
;
270 if (!(ir
->write_mask
& (1 << i
)))
274 new_lhs
= new(mem_ctx
) ir_dereference_variable(lhs
->components
[i
]);
277 new_lhs
= ir
->lhs
->clone(mem_ctx
, NULL
);
283 new(mem_ctx
) ir_dereference_variable(rhs
->components
[rhs_chan
]);
285 new_rhs
= new(mem_ctx
) ir_swizzle(ir
->rhs
->clone(mem_ctx
, NULL
),
286 rhs_chan
, 0, 0, 0, 1);
289 ir
->insert_before(new(mem_ctx
) ir_assignment(new_lhs
,
297 void *mem_ctx
= lhs
->mem_ctx
;
300 switch (ir
->write_mask
) {
315 unreachable("not reached: non-channelwise dereference of LHS.");
318 ir
->lhs
= new(mem_ctx
) ir_dereference_variable(lhs
->components
[elem
]);
319 ir
->write_mask
= (1 << 0);
321 handle_rvalue(&ir
->rhs
);
323 handle_rvalue(&ir
->rhs
);
326 handle_rvalue(&ir
->condition
);
328 return visit_continue
;
332 brw_do_vector_splitting(exec_list
*instructions
)
334 ir_vector_reference_visitor refs
;
336 visit_list_elements(&refs
, instructions
);
338 /* Trim out variables we can't split. */
339 foreach_in_list_safe(variable_entry
, entry
, &refs
.variable_list
) {
341 fprintf(stderr
, "vector %s@%p: whole_access %d\n",
342 entry
->var
->name
, (void *) entry
->var
,
343 entry
->whole_vector_access
);
346 if (entry
->whole_vector_access
) {
351 if (refs
.variable_list
.is_empty())
354 void *mem_ctx
= ralloc_context(NULL
);
356 /* Replace the decls of the vectors to be split with their split
359 foreach_in_list(variable_entry
, entry
, &refs
.variable_list
) {
360 const struct glsl_type
*type
;
361 type
= glsl_type::get_instance(entry
->var
->type
->base_type
, 1, 1);
363 entry
->mem_ctx
= ralloc_parent(entry
->var
);
365 for (unsigned int i
= 0; i
< entry
->var
->type
->vector_elements
; i
++) {
366 const char *name
= ralloc_asprintf(mem_ctx
, "%s_%c",
370 entry
->components
[i
] = new(entry
->mem_ctx
) ir_variable(type
, name
,
372 entry
->var
->insert_before(entry
->components
[i
]);
375 entry
->var
->remove();
378 ir_vector_splitting_visitor
split(&refs
.variable_list
);
379 visit_list_elements(&split
, instructions
);
381 ralloc_free(mem_ctx
);