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// SPDX-License-Identifier: GPL-3.0-or-later
#include "rcc/CodeGen/LivePhysRegs.h"
#include "rcc/CodeGen/MachineBasicBlock.h"
#include "rcc/CodeGen/MachineFunction.h"
#include "rcc/CodeGen/MachineInstr.h"
#include "rcc/CodeGen/MachineOperand.h"
#include "rcc/CodeGen/RegisterMask.h"
#include "rcc/CodeGen/TargetDescription.h"
#include "rcc/CodeGen/TargetRegisterInfo.h"
#include <algorithm>
#include <cstddef>
#include <ranges>
#include <vector>
namespace rcc {
namespace {
struct OperandFlagUpdate final {
MachineOperand *Operand = nullptr;
RegisterOperandFlags Flags;
};
[[nodiscard]] bool intersects(const LiveRegUnits &Live,
const std::vector<PhysicalUnitAccess> &Units) noexcept {
return std::ranges::any_of(Units, [&Live](const PhysicalUnitAccess &Unit) {
return Live.intersects(Unit.Unit, Unit.Lanes);
});
}
void addUnits(LiveRegUnits &Live, const std::vector<PhysicalUnitAccess> &Units) {
for (const PhysicalUnitAccess &Unit : Units)
Live.add(Unit.Unit, Unit.Lanes);
}
void removeUnits(LiveRegUnits &Live, const std::vector<PhysicalUnitAccess> &Units) {
for (const PhysicalUnitAccess &Unit : Units)
Live.remove(Unit.Unit, Unit.Lanes);
}
[[nodiscard]] OperandFlagUpdate &getFlagUpdate(std::vector<OperandFlagUpdate> &Updates,
MachineOperand &Operand) {
const auto Position = std::ranges::find_if(
Updates, [&Operand](const OperandFlagUpdate &Update) { return Update.Operand == &Operand; });
if (Position != Updates.end())
return *Position;
Updates.push_back({&Operand, Operand.registerFlags()});
return Updates.back();
}
[[nodiscard]] Expected<std::vector<OperandFlagUpdate>>
buildBlockLivenessRepairPlan(MachineBasicBlock &Block, const TargetDescription &Target,
const MachineBlockLiveness &Boundary) {
LiveRegUnits Live = Boundary.PhysicalLiveOut;
std::vector<OperandFlagUpdate> Updates;
for (MachineInstr *Instruction = Block.lastInstruction(); Instruction != nullptr;
Instruction = Instruction->previous()) {
for (const MachineOperand &Operand : Instruction->operands()) {
const auto *Mask = Operand.getIf<LiveOutRegisterMaskOperand>();
if (Mask == nullptr)
continue;
if (!Mask->Mask) {
return makeUnexpected(ErrorCode::VerificationError,
"post-RA liveness repair encountered a null live-out mask");
}
for (const PhysicalRegisterDesc &Register : Target.registers().physicalRegisters()) {
if (Mask->Mask->preserves(Register.Reg))
addPhysicalRegister(Live, Register);
}
}
for (std::size_t Index = 0; Index < Instruction->operandCount(); ++Index) {
MachineOperand *Operand = Instruction->operandAt(Index);
if (Operand == nullptr || !Operand->isRegister())
continue;
OperandFlagUpdate &Update = getFlagUpdate(Updates, *Operand);
Update.Flags.clear(RegisterOperandFlag::Dead);
if (!Operand->isDef())
continue;
const Register *Reg = Operand->getIf<Register>();
if (Reg == nullptr || Reg->isNoRegister())
continue;
auto Units = physicalOperandUnits(*Operand, Target);
if (!Units)
return std::unexpected(Units.error());
if (!intersects(Live, *Units))
Update.Flags.set(RegisterOperandFlag::Dead);
}
for (const MachineOperand &Operand : Instruction->operands()) {
if (Operand.isRegister() && Operand.isDef()) {
const Register *Reg = Operand.getIf<Register>();
if (Reg == nullptr || Reg->isNoRegister())
continue;
auto Units = physicalOperandUnits(Operand, Target);
if (!Units)
return std::unexpected(Units.error());
removeUnits(Live, *Units);
continue;
}
const auto *Mask = Operand.getIf<RegisterMaskOperand>();
if (Mask == nullptr)
continue;
if (!Mask->Mask) {
return makeUnexpected(ErrorCode::VerificationError,
"post-RA liveness repair encountered a null register mask");
}
LiveRegUnits Clobbers;
for (const PhysicalRegisterDesc &Register : Target.registers().physicalRegisters()) {
if (Mask->Mask->clobbers(Register.Reg))
addPhysicalRegister(Clobbers, Register);
}
Live.subtract(Clobbers);
}
for (std::size_t Index = 0; Index < Instruction->operandCount(); ++Index) {
MachineOperand *Operand = Instruction->operandAt(Index);
if (Operand == nullptr || !Operand->isRegister())
continue;
OperandFlagUpdate &Update = getFlagUpdate(Updates, *Operand);
Update.Flags.clear(RegisterOperandFlag::Kill);
if (!Operand->isUse() || Operand->isDebugUse() ||
Operand->registerFlags().has(RegisterOperandFlag::Undef)) {
continue;
}
const Register *Reg = Operand->getIf<Register>();
if (Reg == nullptr || Reg->isNoRegister())
continue;
if (isReservedPhysicalRegister(*Reg, Block.function(), Target))
continue;
auto Units = physicalOperandUnits(*Operand, Target);
if (!Units)
return std::unexpected(Units.error());
if (!intersects(Live, *Units))
Update.Flags.set(RegisterOperandFlag::Kill);
addUnits(Live, *Units);
}
}
if (Live != Boundary.PhysicalLiveIn) {
return makeUnexpected(ErrorCode::InternalError,
"post-RA local liveness repair changed the block boundary");
}
return Updates;
}
} // namespace
Expected<bool> repairPostRAMachineBlockLiveness(std::span<MachineBasicBlock *const> Blocks,
const TargetDescription &Target,
const LiveVariablesAnalysis::Result &Liveness) {
std::vector<OperandFlagUpdate> Updates;
for (MachineBasicBlock *Block : Blocks) {
const MachineBlockLiveness *Boundary = Liveness.block(*Block);
if (Boundary == nullptr) {
return makeUnexpected(ErrorCode::InternalError,
"post-RA scheduler lost a block liveness boundary");
}
auto BlockUpdates = buildBlockLivenessRepairPlan(*Block, Target, *Boundary);
if (!BlockUpdates)
return std::unexpected(BlockUpdates.error());
Updates.insert(Updates.end(), BlockUpdates->begin(), BlockUpdates->end());
}
bool Changed = false;
for (const OperandFlagUpdate &Update : Updates) {
Changed |= Update.Operand->registerFlags() != Update.Flags;
auto Applied = Update.Operand->setRegisterFlags(Update.Flags);
if (!Applied)
return std::unexpected(Applied.error());
}
return Changed;
}
} // namespace rcc
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