[CodeGen] Remove RCC fallthrough normalization

1 files changed, 0 insertions, 163 deletions

diff --git a/backend/lib/CodeGen/MachineFallthrough.cpp b/backend/lib/CodeGen/MachineFallthrough.cpp
deleted file mode 100644
index 3619155..0000000
--- a/backend/lib/CodeGen/MachineFallthrough.cpp
+++ /dev/null
@@ -1,163 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-
-#include "rcc/CodeGen/MachineFallthrough.h"
-
-#include "rcc/CodeGen/LivePhysRegs.h"
-#include "rcc/CodeGen/LiveVariables.h"
-#include "rcc/CodeGen/MachineBasicBlock.h"
-#include "rcc/CodeGen/MachineFunction.h"
-#include "rcc/CodeGen/MachineFunctionCloner.h"
-#include "rcc/CodeGen/TargetDescription.h"
-#include "rcc/CodeGen/TargetInstrInfo.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 = {MachineFunctionAnalysisManager::id<LiveVariablesAnalysis>()},
-        .VerificationStage = PipelineStage::RegisterAllocated,
-    };
-    Value.ThreadSafety = PassThreadSafety::ThreadSafe;
-    Value.DeclaredChanges = {MachinePassChange::Instructions, MachinePassChange::Operands};
-    return Value;
-  }();
-  return Contract;
-}
-
-[[nodiscard]] Expected<std::vector<MachineBasicBlock *>>
-normalizeFallthroughs(MachineFunction &Function, const TargetDescription &Target,
-                      const TargetInstrInfo &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.insertBranch(*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.insertBranch(*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,
-                                                        MachineFunctionAnalysisManager &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(withErrorContext(Trial.error(), "fallthrough setup failed: "));
-  MachineFunctionAnalysisManager 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(withErrorContext(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