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i965: Improve dead control flow elimination.

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... to eliminate an ELSE instruction followed immediately by an ENDIF.

instructions in affected programs:     704 -> 700 (-0.57%)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner 2014-07-15 15:29:29 -07:00
parent 0ddc28b026
commit ac2acf04f7
1 changed files with 15 additions and 10 deletions
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25
src/mesa/drivers/dri/i965/brw_dead_control_flow.cpp
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@ -32,6 +32,7 @@
/* Look for and eliminate dead control flow:
*
* - if/endif
* . else in else/endif
* - if/else/endif
*/
bool
@ -54,24 +55,28 @@ dead_control_flow_eliminate(backend_visitor *v)
backend_instruction *if_inst = NULL, *else_inst = NULL;
backend_instruction *prev_inst = (backend_instruction *) endif_inst->prev;
if (prev_inst->opcode == BRW_OPCODE_ELSE) {
else_inst = prev_inst;
found = true;
prev_inst = (backend_instruction *) prev_inst->prev;
}
if (prev_inst->opcode == BRW_OPCODE_IF) {
if_inst = prev_inst;
found = true;
} else if (prev_inst->opcode == BRW_OPCODE_ELSE) {
else_inst = prev_inst;
prev_inst = (backend_instruction *) prev_inst->prev;
if (prev_inst->opcode == BRW_OPCODE_IF) {
if_inst = prev_inst;
found = true;
}
} else {
/* Don't remove the ENDIF if we didn't find a dead IF. */
endif_inst = NULL;
}
if (found) {
if_inst->remove();
if (if_inst)
if_inst->remove();
if (else_inst)
else_inst->remove();
endif_inst->remove();
if (endif_inst)
endif_inst->remove();
progress = true;
}
}