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// SPDX-License-Identifier: GPL-3.0-or-later
#include "rcc/CodeGen/MachineFallthrough.h"
#include "rcc/CodeGen/MachineBasicBlock.h"
#include "rcc/CodeGen/MachineFunction.h"
#include "rcc/CodeGen/MachineFunctionCloner.h"
#include "rcc/CodeGen/MachineLiveness.h"
#include "rcc/CodeGen/MachineLivenessRepair.h"
#include "rcc/CodeGen/TargetBranchInfo.h"
#include "rcc/CodeGen/TargetDescription.h"
#include <optional>
#include <string>
#include <utility>
#include <vector>
namespace rcc {
namespace {
[[nodiscard]] const MachinePassContract &fallthroughContract() {
static const MachinePassContract Contract = [] {
MachinePassContract Value{
.Name = "machine-fallthrough-normalization",
.Requires = {MachineFunctionProperty::Selected, MachineFunctionProperty::NoPHIs,
MachineFunctionProperty::NoVRegs, MachineFunctionProperty::TracksLiveness},
.Sets = {},
.Clears = {},
.RequiredAnalyses = {MachineAnalysisManager::id<LiveVariablesAnalysis>()},
.VerificationStage = PipelineStage::RegisterAllocated,
};
Value.ThreadSafety = PassThreadSafety::ThreadSafe;
Value.DeclaredChanges = {MachinePassChange::Instructions, MachinePassChange::Operands};
return Value;
}();
return Contract;
}
[[nodiscard]] Error prefixedError(const Error &Failure, std::string Prefix) {
Prefix.append(Failure.message());
return Error(Failure.code(), std::move(Prefix));
}
[[nodiscard]] Expected<std::vector<MachineBasicBlock *>>
normalizeFallthroughs(MachineFunction &Function, const TargetDescription &Target,
const TargetBranchInfo &Info) {
std::vector<MachineBasicBlock *> ChangedBlocks;
for (MachineBasicBlock *Block = Function.firstBlock(); Block != nullptr; Block = Block->next()) {
MachineBasicBlock *LayoutSuccessor = Block->next();
if (LayoutSuccessor == nullptr)
continue;
auto Analysis = Info.analyzeBranch(*Block, Function, Target);
if (!Analysis)
return std::unexpected(Analysis.error());
if (Analysis->HasUnanalyzableTerminator)
continue;
bool Changed = false;
if (Analysis->Conditional != nullptr && Analysis->Unconditional != nullptr &&
Analysis->FalseTarget == LayoutSuccessor) {
auto Removed = Info.removeBranch(*Analysis->Unconditional, Function, Target);
if (!Removed)
return std::unexpected(Removed.error());
Changed = true;
} else if (Analysis->Conditional != nullptr && Analysis->Unconditional != nullptr &&
Analysis->TrueTarget == LayoutSuccessor && Analysis->FalseTarget != nullptr) {
auto Reversed = Info.reverseBranchCondition(*Analysis->Conditional, *Analysis->FalseTarget,
Function, Target);
if (!Reversed)
return std::unexpected(Reversed.error());
auto Removed = Info.removeBranch(*Analysis->Unconditional, Function, Target);
if (!Removed)
return std::unexpected(Removed.error());
Changed = true;
} else if (Analysis->Conditional != nullptr && Analysis->Unconditional == nullptr &&
Analysis->FalseTarget == LayoutSuccessor) {
continue;
} else if (Analysis->Conditional != nullptr && Analysis->Unconditional == nullptr &&
Analysis->TrueTarget == LayoutSuccessor && Analysis->FalseTarget != nullptr) {
auto Reversed = Info.reverseBranchCondition(*Analysis->Conditional, *Analysis->FalseTarget,
Function, Target);
if (!Reversed)
return std::unexpected(Reversed.error());
Changed = true;
} else if (Analysis->Conditional != nullptr && Analysis->Unconditional == nullptr &&
Analysis->FalseTarget != nullptr) {
auto Inserted =
Info.insertUnconditionalBranch(*Block, *Analysis->FalseTarget, Function, Target);
if (!Inserted)
return std::unexpected(Inserted.error());
Changed = true;
} else if (Analysis->Conditional == nullptr && Analysis->Unconditional != nullptr &&
Analysis->TrueTarget == LayoutSuccessor) {
auto Removed = Info.removeBranch(*Analysis->Unconditional, Function, Target);
if (!Removed)
return std::unexpected(Removed.error());
Changed = true;
} else if (Analysis->Conditional == nullptr && Analysis->Unconditional == nullptr &&
Block->successors().size() == 1 &&
Block->successors().front().Block != LayoutSuccessor) {
MachineBasicBlock *Successor = Block->successors().front().Block;
if (Successor == nullptr) {
return makeUnexpected(ErrorCode::VerificationError,
"fallthrough normalization encountered a null successor");
}
auto Inserted = Info.insertUnconditionalBranch(*Block, *Successor, Function, Target);
if (!Inserted)
return std::unexpected(Inserted.error());
Changed = true;
}
if (Changed)
ChangedBlocks.push_back(Block);
}
return ChangedBlocks;
}
} // namespace
const MachinePassContract &MachineFallthroughPass::contract() const noexcept {
return fallthroughContract();
}
Expected<MachinePassResult> MachineFallthroughPass::run(MachineFunction &Function,
const TargetDescription &Target,
MachineAnalysisManager &Analyses) {
if (!Function.properties().containsAll(contract().Requires)) {
return makeUnexpected(ErrorCode::VerificationError,
"fallthrough normalization requires allocated tracked-liveness MIR");
}
auto Trial = cloneMachineFunction(
Function, Target,
MachineFunctionCloneOptions{.NewStableID = Function.stableID(), .NewName = std::nullopt});
if (!Trial)
return std::unexpected(prefixedError(Trial.error(), "fallthrough setup failed: "));
MachineAnalysisManager TrialAnalyses;
auto TrialLiveness =
TrialAnalyses.getResult<LiveVariablesAnalysis>(*Trial->ClonedFunction, Target);
if (!TrialLiveness)
return std::unexpected(TrialLiveness.error());
auto TrialChanged = normalizeFallthroughs(*Trial->ClonedFunction, Target, *Info);
if (!TrialChanged)
return std::unexpected(TrialChanged.error());
auto TrialRepair = repairPostRAMachineBlockLiveness(*TrialChanged, Target, **TrialLiveness);
if (!TrialRepair)
return std::unexpected(TrialRepair.error());
auto Liveness = Analyses.getResult<LiveVariablesAnalysis>(Function, Target);
if (!Liveness)
return std::unexpected(Liveness.error());
auto ChangedBlocks = normalizeFallthroughs(Function, Target, *Info);
if (!ChangedBlocks) {
return std::unexpected(prefixedError(ChangedBlocks.error(),
"fallthrough diverged after a successful preflight: "));
}
auto Repaired = repairPostRAMachineBlockLiveness(*ChangedBlocks, Target, **Liveness);
if (!Repaired)
return std::unexpected(Repaired.error());
MachinePassResult Result;
Result.Changed = !ChangedBlocks->empty() || *Repaired;
if (Result.Changed) {
Result.Changes = {MachinePassChange::Instructions, MachinePassChange::Operands};
Result.Preserved.preserve<LiveVariablesAnalysis>();
} else {
Result.Preserved = PreservedAnalyses::all();
}
return Result;
}
} // namespace rcc
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