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25 * @file brw_vec4_copy_propagation.cpp
27 * Implements tracking of values copied between registers, and
28 * optimizations based on that: copy propagation and constant
34 #include "main/macros.h"
40 is_direct_copy(vec4_instruction
*inst
)
42 return (inst
->opcode
== BRW_OPCODE_MOV
&&
44 inst
->dst
.file
== GRF
&&
47 !inst
->src
[0].reladdr
&&
48 inst
->dst
.type
== inst
->src
[0].type
);
52 is_dominated_by_previous_instruction(vec4_instruction
*inst
)
54 return (inst
->opcode
!= BRW_OPCODE_DO
&&
55 inst
->opcode
!= BRW_OPCODE_WHILE
&&
56 inst
->opcode
!= BRW_OPCODE_ELSE
&&
57 inst
->opcode
!= BRW_OPCODE_ENDIF
);
61 try_constant_propagation(vec4_instruction
*inst
, int arg
, src_reg
*values
[4])
63 /* For constant propagation, we only handle the same constant
64 * across all 4 channels. Some day, we should handle the 8-bit
65 * float vector format, which would let us constant propagate
68 src_reg value
= *values
[0];
69 for (int i
= 1; i
< 4; i
++) {
70 if (!value
.equals(values
[i
]))
74 if (value
.file
!= IMM
)
77 if (inst
->src
[arg
].abs
) {
78 if (value
.type
== BRW_REGISTER_TYPE_F
) {
79 value
.imm
.f
= fabs(value
.imm
.f
);
80 } else if (value
.type
== BRW_REGISTER_TYPE_D
) {
82 value
.imm
.i
= -value
.imm
.i
;
86 if (inst
->src
[arg
].negate
) {
87 if (value
.type
== BRW_REGISTER_TYPE_F
)
88 value
.imm
.f
= -value
.imm
.f
;
90 value
.imm
.u
= -value
.imm
.u
;
93 switch (inst
->opcode
) {
95 inst
->src
[arg
] = value
;
102 case BRW_OPCODE_SUBB
:
104 inst
->src
[arg
] = value
;
109 case BRW_OPCODE_MACH
:
115 case BRW_OPCODE_ADDC
:
117 inst
->src
[arg
] = value
;
119 } else if (arg
== 0 && inst
->src
[1].file
!= IMM
) {
120 /* Fit this constant in by commuting the operands. Exception: we
121 * can't do this for 32-bit integer MUL/MACH because it's asymmetric.
123 if ((inst
->opcode
== BRW_OPCODE_MUL
||
124 inst
->opcode
== BRW_OPCODE_MACH
) &&
125 (inst
->src
[1].type
== BRW_REGISTER_TYPE_D
||
126 inst
->src
[1].type
== BRW_REGISTER_TYPE_UD
))
128 inst
->src
[0] = inst
->src
[1];
129 inst
->src
[1] = value
;
136 inst
->src
[arg
] = value
;
138 } else if (arg
== 0 && inst
->src
[1].file
!= IMM
) {
141 new_cmod
= brw_swap_cmod(inst
->conditional_mod
);
142 if (new_cmod
!= ~0u) {
143 /* Fit this constant in by swapping the operands and
146 inst
->src
[0] = inst
->src
[1];
147 inst
->src
[1] = value
;
148 inst
->conditional_mod
= new_cmod
;
156 inst
->src
[arg
] = value
;
158 } else if (arg
== 0 && inst
->src
[1].file
!= IMM
) {
159 inst
->src
[0] = inst
->src
[1];
160 inst
->src
[1] = value
;
162 /* If this was predicated, flipping operands means
163 * we also need to flip the predicate.
165 if (inst
->conditional_mod
== BRW_CONDITIONAL_NONE
) {
166 inst
->predicate_inverse
= !inst
->predicate_inverse
;
180 vec4_visitor::try_copy_propagation(vec4_instruction
*inst
, int arg
,
183 /* For constant propagation, we only handle the same constant
184 * across all 4 channels. Some day, we should handle the 8-bit
185 * float vector format, which would let us constant propagate
188 src_reg value
= *values
[0];
189 for (int i
= 1; i
< 4; i
++) {
190 /* This is equals() except we don't care about the swizzle. */
191 if (value
.file
!= values
[i
]->file
||
192 value
.reg
!= values
[i
]->reg
||
193 value
.reg_offset
!= values
[i
]->reg_offset
||
194 value
.type
!= values
[i
]->type
||
195 value
.negate
!= values
[i
]->negate
||
196 value
.abs
!= values
[i
]->abs
) {
201 /* Compute the swizzle of the original register by swizzling the
202 * component loaded from each value according to the swizzle of
203 * operand we're going to change.
206 for (int i
= 0; i
< 4; i
++) {
207 s
[i
] = BRW_GET_SWZ(values
[i
]->swizzle
,
208 BRW_GET_SWZ(inst
->src
[arg
].swizzle
, i
));
210 value
.swizzle
= BRW_SWIZZLE4(s
[0], s
[1], s
[2], s
[3]);
212 if (value
.file
!= UNIFORM
&&
217 if (inst
->src
[arg
].abs
) {
218 value
.negate
= false;
221 if (inst
->src
[arg
].negate
)
222 value
.negate
= !value
.negate
;
224 bool has_source_modifiers
= value
.negate
|| value
.abs
;
226 /* gen6 math and gen7+ SENDs from GRFs ignore source modifiers on
229 if ((has_source_modifiers
|| value
.file
== UNIFORM
||
230 value
.swizzle
!= BRW_SWIZZLE_XYZW
) && !can_do_source_mods(inst
))
233 if (has_source_modifiers
&& value
.type
!= inst
->src
[arg
].type
)
236 bool is_3src_inst
= (inst
->opcode
== BRW_OPCODE_LRP
||
237 inst
->opcode
== BRW_OPCODE_MAD
||
238 inst
->opcode
== BRW_OPCODE_BFE
||
239 inst
->opcode
== BRW_OPCODE_BFI2
);
240 if (is_3src_inst
&& value
.file
== UNIFORM
)
243 if (inst
->is_send_from_grf())
246 /* We can't copy-propagate a UD negation into a condmod
247 * instruction, because the condmod ends up looking at the 33-bit
248 * signed accumulator value instead of the 32-bit value we wanted
250 if (inst
->conditional_mod
&&
252 value
.type
== BRW_REGISTER_TYPE_UD
)
255 /* Don't report progress if this is a noop. */
256 if (value
.equals(&inst
->src
[arg
]))
259 value
.type
= inst
->src
[arg
].type
;
260 inst
->src
[arg
] = value
;
265 vec4_visitor::opt_copy_propagation()
267 bool progress
= false;
268 src_reg
*cur_value
[virtual_grf_reg_count
][4];
270 memset(&cur_value
, 0, sizeof(cur_value
));
272 foreach_list(node
, &this->instructions
) {
273 vec4_instruction
*inst
= (vec4_instruction
*)node
;
275 /* This pass only works on basic blocks. If there's flow
276 * control, throw out all our information and start from
279 * This should really be fixed by using a structure like in
280 * src/glsl/opt_copy_propagation.cpp to track available copies.
282 if (!is_dominated_by_previous_instruction(inst
)) {
283 memset(cur_value
, 0, sizeof(cur_value
));
287 /* For each source arg, see if each component comes from a copy
288 * from the same type file (IMM, GRF, UNIFORM), and try
289 * optimizing out access to the copy result
291 for (int i
= 2; i
>= 0; i
--) {
292 /* Copied values end up in GRFs, and we don't track reladdr
295 if (inst
->src
[i
].file
!= GRF
||
296 inst
->src
[i
].reladdr
)
299 int reg
= (virtual_grf_reg_map
[inst
->src
[i
].reg
] +
300 inst
->src
[i
].reg_offset
);
302 /* Find the regs that each swizzle component came from.
306 for (c
= 0; c
< 4; c
++) {
307 values
[c
] = cur_value
[reg
][BRW_GET_SWZ(inst
->src
[i
].swizzle
, c
)];
309 /* If there's no available copy for this channel, bail.
310 * We could be more aggressive here -- some channels might
311 * not get used based on the destination writemask.
316 /* We'll only be able to copy propagate if the sources are
317 * all from the same file -- there's no ability to swizzle
318 * 0 or 1 constants in with source registers like in i915.
320 if (c
> 0 && values
[c
- 1]->file
!= values
[c
]->file
)
327 if (try_constant_propagation(inst
, i
, values
) ||
328 try_copy_propagation(inst
, i
, values
))
332 /* Track available source registers. */
333 if (inst
->dst
.file
== GRF
) {
335 virtual_grf_reg_map
[inst
->dst
.reg
] + inst
->dst
.reg_offset
;
337 /* Update our destination's current channel values. For a direct copy,
338 * the value is the newly propagated source. Otherwise, we don't know
339 * the new value, so clear it.
341 bool direct_copy
= is_direct_copy(inst
);
342 for (int i
= 0; i
< 4; i
++) {
343 if (inst
->dst
.writemask
& (1 << i
)) {
344 cur_value
[reg
][i
] = direct_copy
? &inst
->src
[0] : NULL
;
348 /* Clear the records for any registers whose current value came from
349 * our destination's updated channels, as the two are no longer equal.
351 if (inst
->dst
.reladdr
)
352 memset(cur_value
, 0, sizeof(cur_value
));
354 for (int i
= 0; i
< virtual_grf_reg_count
; i
++) {
355 for (int j
= 0; j
< 4; j
++) {
356 if (inst
->dst
.writemask
& (1 << j
) &&
358 cur_value
[i
][j
]->file
== GRF
&&
359 cur_value
[i
][j
]->reg
== inst
->dst
.reg
&&
360 cur_value
[i
][j
]->reg_offset
== inst
->dst
.reg_offset
) {
361 cur_value
[i
][j
] = NULL
;
370 invalidate_live_intervals();
375 } /* namespace brw */