lib/SILOptimizer/Mandatory/RawSILInstLowering.cpp

//===--- RawSILInstLowering.cpp -------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#include "MandatoryOptUtils.h"
#include "swift/SIL/SILBuilder.h"
#include "swift/SIL/SILFunction.h"
#include "swift/SIL/SILInstruction.h"
#include "swift/SILOptimizer/PassManager/Passes.h"
#include "swift/SILOptimizer/PassManager/Transforms.h"

using namespace swift;

/// lowerRawSILOperations - There are a variety of raw-sil instructions like
/// 'assign' that are only used by this pass.  Now that definite initialization
/// checking is done, remove them.
static bool lowerRawSILOperations(SILFunction &Fn) {
  bool Changed = false;
  for (auto &BB : Fn) {
    auto I = BB.begin(), E = BB.end();
    while (I != E) {
      SILInstruction *Inst = &*I;
      ++I;

      // Unprocessed assigns just lower into assignments, not initializations.
      if (auto *AI = dyn_cast<AssignInst>(Inst)) {
        SILBuilderWithScope B(AI);
        lowerAssignInstruction(B, AI,
                               PartialInitializationKind::IsNotInitialization);
        // Assign lowering may split the block. If it did,
        // reset our iteration range to the block after the insertion.
        if (B.getInsertionBB() != &BB)
          I = E;
        Changed = true;
        continue;
      }

      // mark_uninitialized just becomes a noop, resolving to its operand.
      if (auto *MUI = dyn_cast<MarkUninitializedInst>(Inst)) {
        MUI->replaceAllUsesWith(MUI->getOperand());
        MUI->eraseFromParent();
        Changed = true;
        continue;
      }

      // mark_function_escape just gets zapped.
      if (isa<MarkFunctionEscapeInst>(Inst)) {
        Inst->eraseFromParent();
        Changed = true;
        continue;
      }
    }
  }
  return Changed;
}

//===----------------------------------------------------------------------===//
//                            Top Level Entrypoint
//===----------------------------------------------------------------------===//

namespace {

class RawSILInstLowering : public SILFunctionTransform {
  void run() override {
    // Do not try to relower raw instructions in canonical SIL. There won't be
    // any there.
    if (getFunction()->wasDeserializedCanonical()) {
      return;
    }

    // Lower raw-sil only instructions used by this pass, like "assign".
    if (lowerRawSILOperations(*getFunction()))
      invalidateAnalysis(SILAnalysis::InvalidationKind::FunctionBody);
  }
};

} // end anonymous namespace

SILTransform *swift::createRawSILInstLowering() {
  return new RawSILInstLowering();
}