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29 /** @file brw_vec4_cse.cpp
31 * Support for local common subexpression elimination.
33 * See Muchnick's Advanced Compiler Design and Implementation, section
38 struct aeb_entry
: public exec_node
{
39 /** The instruction that generates the expression value. */
40 vec4_instruction
*generator
;
42 /** The temporary where the value is stored. */
48 is_expression(const vec4_instruction
*const inst
)
50 switch (inst
->opcode
) {
73 case VEC4_OPCODE_UNPACK_UNIFORM
:
75 case SHADER_OPCODE_RCP
:
76 case SHADER_OPCODE_RSQ
:
77 case SHADER_OPCODE_SQRT
:
78 case SHADER_OPCODE_EXP2
:
79 case SHADER_OPCODE_LOG2
:
80 case SHADER_OPCODE_POW
:
81 case SHADER_OPCODE_INT_QUOTIENT
:
82 case SHADER_OPCODE_INT_REMAINDER
:
83 case SHADER_OPCODE_SIN
:
84 case SHADER_OPCODE_COS
:
85 return inst
->mlen
== 0;
92 operands_match(const vec4_instruction
*a
, const vec4_instruction
*b
)
94 const src_reg
*xs
= a
->src
;
95 const src_reg
*ys
= b
->src
;
97 if (a
->opcode
== BRW_OPCODE_MAD
) {
98 return xs
[0].equals(ys
[0]) &&
99 ((xs
[1].equals(ys
[1]) && xs
[2].equals(ys
[2])) ||
100 (xs
[2].equals(ys
[1]) && xs
[1].equals(ys
[2])));
101 } else if (!a
->is_commutative()) {
102 return xs
[0].equals(ys
[0]) && xs
[1].equals(ys
[1]) && xs
[2].equals(ys
[2]);
104 return (xs
[0].equals(ys
[0]) && xs
[1].equals(ys
[1])) ||
105 (xs
[1].equals(ys
[0]) && xs
[0].equals(ys
[1]));
110 instructions_match(vec4_instruction
*a
, vec4_instruction
*b
)
112 return a
->opcode
== b
->opcode
&&
113 a
->saturate
== b
->saturate
&&
114 a
->conditional_mod
== b
->conditional_mod
&&
115 a
->dst
.type
== b
->dst
.type
&&
116 a
->dst
.writemask
== b
->dst
.writemask
&&
117 operands_match(a
, b
);
121 vec4_visitor::opt_cse_local(bblock_t
*block
)
123 bool progress
= false;
126 void *cse_ctx
= ralloc_context(NULL
);
128 int ip
= block
->start_ip
;
129 foreach_inst_in_block (vec4_instruction
, inst
, block
) {
130 /* Skip some cases. */
131 if (is_expression(inst
) && !inst
->predicate
&& inst
->mlen
== 0 &&
132 (inst
->dst
.file
!= HW_REG
|| inst
->dst
.is_null()))
136 foreach_in_list_use_after(aeb_entry
, entry
, &aeb
) {
137 /* Match current instruction's expression against those in AEB. */
138 if (!(entry
->generator
->dst
.is_null() && !inst
->dst
.is_null()) &&
139 instructions_match(inst
, entry
->generator
)) {
147 if (inst
->opcode
!= BRW_OPCODE_MOV
||
148 (inst
->opcode
== BRW_OPCODE_MOV
&&
149 inst
->src
[0].file
== IMM
&&
150 inst
->src
[0].type
== BRW_REGISTER_TYPE_VF
)) {
151 /* Our first sighting of this expression. Create an entry. */
152 aeb_entry
*entry
= ralloc(cse_ctx
, aeb_entry
);
153 entry
->tmp
= src_reg(); /* file will be BAD_FILE */
154 entry
->generator
= inst
;
155 aeb
.push_tail(entry
);
158 /* This is at least our second sighting of this expression.
159 * If we don't have a temporary already, make one.
161 bool no_existing_temp
= entry
->tmp
.file
== BAD_FILE
;
162 if (no_existing_temp
&& !entry
->generator
->dst
.is_null()) {
163 entry
->tmp
= src_reg(this, glsl_type::float_type
);
164 entry
->tmp
.type
= inst
->dst
.type
;
165 entry
->tmp
.swizzle
= BRW_SWIZZLE_XYZW
;
167 vec4_instruction
*copy
= MOV(entry
->generator
->dst
, entry
->tmp
);
168 entry
->generator
->insert_after(block
, copy
);
169 entry
->generator
->dst
= dst_reg(entry
->tmp
);
173 if (!inst
->dst
.is_null()) {
174 assert(inst
->dst
.type
== entry
->tmp
.type
);
175 vec4_instruction
*copy
= MOV(inst
->dst
, entry
->tmp
);
176 copy
->force_writemask_all
= inst
->force_writemask_all
;
177 inst
->insert_before(block
, copy
);
180 /* Set our iterator so that next time through the loop inst->next
181 * will get the instruction in the basic block after the one we've
184 vec4_instruction
*prev
= (vec4_instruction
*)inst
->prev
;
191 foreach_in_list_safe(aeb_entry
, entry
, &aeb
) {
192 /* Kill all AEB entries that write a different value to or read from
193 * the flag register if we just wrote it.
195 if (inst
->writes_flag()) {
196 if (entry
->generator
->reads_flag() ||
197 (entry
->generator
->writes_flag() &&
198 !instructions_match(inst
, entry
->generator
))) {
205 for (int i
= 0; i
< 3; i
++) {
206 src_reg
*src
= &entry
->generator
->src
[i
];
208 /* Kill all AEB entries that use the destination we just
211 if (inst
->dst
.file
== entry
->generator
->src
[i
].file
&&
212 inst
->dst
.reg
== entry
->generator
->src
[i
].reg
) {
218 /* Kill any AEB entries using registers that don't get reused any
219 * more -- a sure sign they'll fail operands_match().
221 if (src
->file
== GRF
) {
222 assert((unsigned)(src
->reg
* 4 + 3) < (alloc
.count
* 4));
224 int last_reg_use
= MAX2(MAX2(virtual_grf_end
[src
->reg
* 4 + 0],
225 virtual_grf_end
[src
->reg
* 4 + 1]),
226 MAX2(virtual_grf_end
[src
->reg
* 4 + 2],
227 virtual_grf_end
[src
->reg
* 4 + 3]));
228 if (last_reg_use
< ip
) {
240 ralloc_free(cse_ctx
);
246 vec4_visitor::opt_cse()
248 bool progress
= false;
250 calculate_live_intervals();
252 foreach_block (block
, cfg
) {
253 progress
= opt_cse_local(block
) || progress
;
257 invalidate_live_intervals();