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// SPDX-License-Identifier: GPL-3.0-or-later
#include "rcc/CodeGen/MachineCFGUpdater.h"
#include "rcc/CodeGen/MachineBasicBlock.h"
#include "rcc/CodeGen/MachineFunction.h"
#include <algorithm>
#include <cstddef>
#include <optional>
#include <utility>
#include <vector>
namespace rcc {
namespace {
[[nodiscard]] std::optional<std::size_t> findSuccessorIndex(const MachineBasicBlock &From,
const MachineBasicBlock &To) {
const auto Successors = From.successors();
for (std::size_t Index = 0; Index < Successors.size(); ++Index) {
if (Successors[Index].Block == &To)
return Index;
}
return std::nullopt;
}
} // namespace
Expected<void> MachineCFGUpdater::verifyOwnership(const MachineBasicBlock &Block) const {
if (&Block.function() != Function) {
return makeUnexpected(ErrorCode::InvalidArgument,
"CFG block belongs to another machine function");
}
return {};
}
Expected<void> MachineCFGUpdater::addSuccessor(MachineBasicBlock &From, MachineBasicBlock &To,
BranchProbability Probability) {
auto FromOwnership = verifyOwnership(From);
if (!FromOwnership)
return std::unexpected(FromOwnership.error());
auto ToOwnership = verifyOwnership(To);
if (!ToOwnership)
return std::unexpected(ToOwnership.error());
const auto Existing = findSuccessorIndex(From, To);
if (Existing) {
From.Successors[*Existing].Probability =
From.Successors[*Existing].Probability.saturatingAdd(Probability);
return {};
}
From.Successors.push_back(MachineSuccessor{&To, Probability});
if (std::ranges::find(To.Predecessors, &From) == To.Predecessors.end())
To.Predecessors.push_back(&From);
return {};
}
Expected<void> MachineCFGUpdater::removeSuccessor(MachineBasicBlock &From, MachineBasicBlock &To) {
auto FromOwnership = verifyOwnership(From);
if (!FromOwnership)
return std::unexpected(FromOwnership.error());
auto ToOwnership = verifyOwnership(To);
if (!ToOwnership)
return std::unexpected(ToOwnership.error());
const auto Successor = findSuccessorIndex(From, To);
if (!Successor) {
return makeUnexpected(ErrorCode::InvalidArgument, "CFG successor edge is not present");
}
From.Successors.erase(From.Successors.begin() + static_cast<std::ptrdiff_t>(*Successor));
const auto Predecessor = std::ranges::find(To.Predecessors, &From);
if (Predecessor == To.Predecessors.end()) {
return makeUnexpected(ErrorCode::VerificationError,
"CFG successor has no reciprocal predecessor");
}
To.Predecessors.erase(Predecessor);
return {};
}
Expected<void> MachineCFGUpdater::replaceSuccessor(MachineBasicBlock &From,
MachineBasicBlock &OldTarget,
MachineBasicBlock &NewTarget) {
auto FromOwnership = verifyOwnership(From);
if (!FromOwnership)
return std::unexpected(FromOwnership.error());
auto OldOwnership = verifyOwnership(OldTarget);
if (!OldOwnership)
return std::unexpected(OldOwnership.error());
auto NewOwnership = verifyOwnership(NewTarget);
if (!NewOwnership)
return std::unexpected(NewOwnership.error());
if (&OldTarget == &NewTarget)
return {};
const auto Existing = findSuccessorIndex(From, OldTarget);
if (!Existing) {
return makeUnexpected(ErrorCode::InvalidArgument, "replaced CFG successor edge is not present");
}
const BranchProbability Probability = From.Successors[*Existing].Probability;
auto RemoveResult = removeSuccessor(From, OldTarget);
if (!RemoveResult)
return std::unexpected(RemoveResult.error());
auto AddResult = addSuccessor(From, NewTarget, Probability);
if (!AddResult) {
auto RestoreResult = addSuccessor(From, OldTarget, Probability);
if (!RestoreResult) {
return makeUnexpected(ErrorCode::InternalError,
"failed to restore CFG edge after replacement failure");
}
return std::unexpected(AddResult.error());
}
return {};
}
Expected<void> MachineCFGUpdater::updateBranchProbability(MachineBasicBlock &From,
MachineBasicBlock &To,
BranchProbability Probability) {
auto FromOwnership = verifyOwnership(From);
if (!FromOwnership)
return std::unexpected(FromOwnership.error());
auto ToOwnership = verifyOwnership(To);
if (!ToOwnership)
return std::unexpected(ToOwnership.error());
const auto Successor = findSuccessorIndex(From, To);
if (!Successor) {
return makeUnexpected(ErrorCode::InvalidArgument, "updated CFG successor edge is not present");
}
From.Successors[*Successor].Probability = Probability;
return {};
}
Expected<void> MachineCFGUpdater::transferSuccessors(MachineBasicBlock &From,
MachineBasicBlock &To) {
auto FromOwnership = verifyOwnership(From);
if (!FromOwnership)
return std::unexpected(FromOwnership.error());
auto ToOwnership = verifyOwnership(To);
if (!ToOwnership)
return std::unexpected(ToOwnership.error());
if (&From == &To)
return {};
const std::vector<MachineSuccessor> Successors = From.Successors;
for (const MachineSuccessor &Successor : Successors) {
auto RemoveResult = removeSuccessor(From, *Successor.Block);
if (!RemoveResult)
return std::unexpected(RemoveResult.error());
auto AddResult = addSuccessor(To, *Successor.Block, Successor.Probability);
if (!AddResult)
return std::unexpected(AddResult.error());
}
return {};
}
Expected<void> MachineCFGUpdater::disconnectBlock(MachineBasicBlock &Block) {
auto Ownership = verifyOwnership(Block);
if (!Ownership)
return std::unexpected(Ownership.error());
const std::vector<MachineSuccessor> Successors = Block.Successors;
for (const MachineSuccessor &Successor : Successors) {
auto Result = removeSuccessor(Block, *Successor.Block);
if (!Result)
return std::unexpected(Result.error());
}
const std::vector<MachineBasicBlock *> Predecessors = Block.Predecessors;
for (MachineBasicBlock *Predecessor : Predecessors) {
auto Result = removeSuccessor(*Predecessor, Block);
if (!Result)
return std::unexpected(Result.error());
}
return {};
}
} // namespace rcc
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