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aco: consider how definitions fixed to operands can change register demand

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Usually the register demand before an instruction would be considered part
of the previous instruction, since it's not greater than the register
demand for that previous instruction. Except, it can be greater in the
case of an definition fixed to a non-killed operand: the RA needs to
reserve space between the two instructions for the definition (containing
a copy of the operand).

fossil-db (navi21):
Totals from 5 (0.00% of 135636) affected shaders:
PreVGPRs: 35 -> 40 (+14.29%)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/8807
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22446>
This commit is contained in:
Rhys Perry 2023-04-12 16:00:10 +01:00 • committed by Marge Bot
parent 446d0dd658
commit fab911858c
1 changed files with 27 additions and 0 deletions
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27
src/amd/compiler/aco_live_var_analysis.cpp
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@ -50,6 +50,20 @@ get_live_changes(aco_ptr<Instruction>& instr)
return changes;
}
void
handle_def_fixed_to_op(RegisterDemand* demand, RegisterDemand demand_before, Instruction* instr,
int op_idx)
{
/* Usually the register demand before an instruction would be considered part of the previous
* instruction, since it's not greater than the register demand for that previous instruction.
* Except, it can be greater in the case of an definition fixed to a non-killed operand: the RA
* needs to reserve space between the two instructions for the definition (containing a copy of
* the operand).
*/
demand_before += instr->definitions[0].getTemp();
demand->update(demand_before);
}
RegisterDemand
get_temp_registers(aco_ptr<Instruction>& instr)
{
@ -67,6 +81,13 @@ get_temp_registers(aco_ptr<Instruction>& instr)
temp_registers += op.getTemp();
}
int op_idx = get_op_fixed_to_def(instr.get());
if (op_idx != -1 && !instr->operands[op_idx].isKill()) {
RegisterDemand before_instr;
before_instr -= get_live_changes(instr);
handle_def_fixed_to_op(&temp_registers, before_instr, instr.get(), op_idx);
}
return temp_registers;
}
@ -183,6 +204,12 @@ process_live_temps_per_block(Program* program, live& lives, Block* block, unsign
}
}
int op_idx = get_op_fixed_to_def(insn);
if (op_idx != -1 && !insn->operands[op_idx].isKill()) {
RegisterDemand before_instr = new_demand;
handle_def_fixed_to_op(&register_demand[idx], before_instr, insn, op_idx);
}
block_register_demand.update(register_demand[idx]);
}