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25 #include "brw_vec4_live_variables.h"
30 /** @file brw_vec4_cse.cpp
32 * Support for local common subexpression elimination.
34 * See Muchnick's Advanced Compiler Design and Implementation, section
39 struct aeb_entry
: public exec_node
{
40 /** The instruction that generates the expression value. */
41 vec4_instruction
*generator
;
43 /** The temporary where the value is stored. */
49 is_expression(const vec4_instruction
*const inst
)
51 switch (inst
->opcode
) {
65 case SHADER_OPCODE_MULH
:
75 case VEC4_OPCODE_UNPACK_UNIFORM
:
76 case SHADER_OPCODE_FIND_LIVE_CHANNEL
:
77 case SHADER_OPCODE_BROADCAST
:
79 case SHADER_OPCODE_RCP
:
80 case SHADER_OPCODE_RSQ
:
81 case SHADER_OPCODE_SQRT
:
82 case SHADER_OPCODE_EXP2
:
83 case SHADER_OPCODE_LOG2
:
84 case SHADER_OPCODE_POW
:
85 case SHADER_OPCODE_INT_QUOTIENT
:
86 case SHADER_OPCODE_INT_REMAINDER
:
87 case SHADER_OPCODE_SIN
:
88 case SHADER_OPCODE_COS
:
89 return inst
->mlen
== 0;
96 operands_match(const vec4_instruction
*a
, const vec4_instruction
*b
)
98 const src_reg
*xs
= a
->src
;
99 const src_reg
*ys
= b
->src
;
101 if (a
->opcode
== BRW_OPCODE_MAD
) {
102 return xs
[0].equals(ys
[0]) &&
103 ((xs
[1].equals(ys
[1]) && xs
[2].equals(ys
[2])) ||
104 (xs
[2].equals(ys
[1]) && xs
[1].equals(ys
[2])));
105 } else if (!a
->is_commutative()) {
106 return xs
[0].equals(ys
[0]) && xs
[1].equals(ys
[1]) && xs
[2].equals(ys
[2]);
108 return (xs
[0].equals(ys
[0]) && xs
[1].equals(ys
[1])) ||
109 (xs
[1].equals(ys
[0]) && xs
[0].equals(ys
[1]));
114 instructions_match(vec4_instruction
*a
, vec4_instruction
*b
)
116 return a
->opcode
== b
->opcode
&&
117 a
->saturate
== b
->saturate
&&
118 a
->predicate
== b
->predicate
&&
119 a
->predicate_inverse
== b
->predicate_inverse
&&
120 a
->conditional_mod
== b
->conditional_mod
&&
121 a
->flag_subreg
== b
->flag_subreg
&&
122 a
->dst
.type
== b
->dst
.type
&&
123 a
->offset
== b
->offset
&&
124 a
->mlen
== b
->mlen
&&
125 a
->base_mrf
== b
->base_mrf
&&
126 a
->header_size
== b
->header_size
&&
127 a
->shadow_compare
== b
->shadow_compare
&&
128 a
->dst
.writemask
== b
->dst
.writemask
&&
129 a
->force_writemask_all
== b
->force_writemask_all
&&
130 a
->regs_written
== b
->regs_written
&&
131 operands_match(a
, b
);
135 vec4_visitor::opt_cse_local(bblock_t
*block
)
137 bool progress
= false;
140 void *cse_ctx
= ralloc_context(NULL
);
142 int ip
= block
->start_ip
;
143 foreach_inst_in_block (vec4_instruction
, inst
, block
) {
144 /* Skip some cases. */
145 if (is_expression(inst
) && !inst
->predicate
&& inst
->mlen
== 0 &&
146 (inst
->dst
.file
!= HW_REG
|| inst
->dst
.is_null()))
150 foreach_in_list_use_after(aeb_entry
, entry
, &aeb
) {
151 /* Match current instruction's expression against those in AEB. */
152 if (!(entry
->generator
->dst
.is_null() && !inst
->dst
.is_null()) &&
153 instructions_match(inst
, entry
->generator
)) {
161 if (inst
->opcode
!= BRW_OPCODE_MOV
||
162 (inst
->opcode
== BRW_OPCODE_MOV
&&
163 inst
->src
[0].file
== IMM
&&
164 inst
->src
[0].type
== BRW_REGISTER_TYPE_VF
)) {
165 /* Our first sighting of this expression. Create an entry. */
166 aeb_entry
*entry
= ralloc(cse_ctx
, aeb_entry
);
167 entry
->tmp
= src_reg(); /* file will be BAD_FILE */
168 entry
->generator
= inst
;
169 aeb
.push_tail(entry
);
172 /* This is at least our second sighting of this expression.
173 * If we don't have a temporary already, make one.
175 bool no_existing_temp
= entry
->tmp
.file
== BAD_FILE
;
176 if (no_existing_temp
&& !entry
->generator
->dst
.is_null()) {
177 entry
->tmp
= retype(src_reg(GRF
, alloc
.allocate(
178 entry
->generator
->regs_written
),
179 NULL
), inst
->dst
.type
);
181 for (unsigned i
= 0; i
< entry
->generator
->regs_written
; ++i
) {
182 vec4_instruction
*copy
= MOV(offset(entry
->generator
->dst
, i
),
183 offset(entry
->tmp
, i
));
184 copy
->force_writemask_all
=
185 entry
->generator
->force_writemask_all
;
186 entry
->generator
->insert_after(block
, copy
);
189 entry
->generator
->dst
= dst_reg(entry
->tmp
);
193 if (!inst
->dst
.is_null()) {
194 assert(inst
->dst
.type
== entry
->tmp
.type
);
196 for (unsigned i
= 0; i
< inst
->regs_written
; ++i
) {
197 vec4_instruction
*copy
= MOV(offset(inst
->dst
, i
),
198 offset(entry
->tmp
, i
));
199 copy
->force_writemask_all
= inst
->force_writemask_all
;
200 inst
->insert_before(block
, copy
);
204 /* Set our iterator so that next time through the loop inst->next
205 * will get the instruction in the basic block after the one we've
208 vec4_instruction
*prev
= (vec4_instruction
*)inst
->prev
;
215 foreach_in_list_safe(aeb_entry
, entry
, &aeb
) {
216 /* Kill all AEB entries that write a different value to or read from
217 * the flag register if we just wrote it.
219 if (inst
->writes_flag()) {
220 if (entry
->generator
->reads_flag() ||
221 (entry
->generator
->writes_flag() &&
222 !instructions_match(inst
, entry
->generator
))) {
229 for (int i
= 0; i
< 3; i
++) {
230 src_reg
*src
= &entry
->generator
->src
[i
];
232 /* Kill all AEB entries that use the destination we just
235 if (inst
->dst
.file
== entry
->generator
->src
[i
].file
&&
236 inst
->dst
.reg
== entry
->generator
->src
[i
].reg
) {
242 /* Kill any AEB entries using registers that don't get reused any
243 * more -- a sure sign they'll fail operands_match().
245 if (src
->file
== GRF
) {
246 if (var_range_end(var_from_reg(alloc
, *src
), 4) < ip
) {
258 ralloc_free(cse_ctx
);
264 vec4_visitor::opt_cse()
266 bool progress
= false;
268 calculate_live_intervals();
270 foreach_block (block
, cfg
) {
271 progress
= opt_cse_local(block
) || progress
;
275 invalidate_live_intervals();