src/main/java/com/android/tools/r8/ir/conversion/IRToDexFinalizer.java

// Copyright (c) 2022, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

package com.android.tools.r8.ir.conversion;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexCode;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.bytecodemetadata.BytecodeMetadataProvider;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.optimize.CodeRewriter;
import com.android.tools.r8.ir.optimize.DeadCodeRemover;
import com.android.tools.r8.ir.optimize.PeepholeOptimizer;
import com.android.tools.r8.ir.optimize.RuntimeWorkaroundCodeRewriter;
import com.android.tools.r8.ir.regalloc.LinearScanRegisterAllocator;
import com.android.tools.r8.ir.regalloc.RegisterAllocator;
import com.android.tools.r8.logging.Log;
import com.android.tools.r8.utils.InternalOptions;
import com.android.tools.r8.utils.Timing;

public class IRToDexFinalizer extends IRFinalizer<DexCode> {

  private static final int PEEPHOLE_OPTIMIZATION_PASSES = 2;

  private final CodeRewriter codeRewriter;
  private final InternalOptions options;

  public IRToDexFinalizer(AppView<?> appView, DeadCodeRemover deadCodeRemover) {
    super(appView, deadCodeRemover);
    this.codeRewriter = deadCodeRemover.getCodeRewriter();
    this.options = appView.options();
  }

  @Override
  public DexCode finalizeCode(
      IRCode code, BytecodeMetadataProvider bytecodeMetadataProvider, Timing timing) {
    DexEncodedMethod method = code.method();
    code.traceBlocks();
    RuntimeWorkaroundCodeRewriter.workaroundNumberConversionRegisterAllocationBug(code, options);
    // Workaround massive dex2oat memory use for self-recursive methods.
    RuntimeWorkaroundCodeRewriter.workaroundDex2OatInliningIssue(appView, code);
    // Workaround MAX_INT switch issue.
    RuntimeWorkaroundCodeRewriter.workaroundSwitchMaxIntBug(code, codeRewriter, options);
    RuntimeWorkaroundCodeRewriter.workaroundDex2OatLinkedListBug(code, options);
    RuntimeWorkaroundCodeRewriter.workaroundForwardingInitializerBug(code, options);
    RuntimeWorkaroundCodeRewriter.workaroundExceptionTargetingLoopHeaderBug(code, options);
    // Perform register allocation.
    RegisterAllocator registerAllocator = performRegisterAllocation(code, method, timing);
    return new DexBuilder(code, bytecodeMetadataProvider, registerAllocator, options).build();
  }

  private RegisterAllocator performRegisterAllocation(
      IRCode code, DexEncodedMethod method, Timing timing) {
    // Always perform dead code elimination before register allocation. The register allocator
    // does not allow dead code (to make sure that we do not waste registers for unneeded values).
    assert deadCodeRemover.verifyNoDeadCode(code);
    timing.begin("Allocate registers");
    LinearScanRegisterAllocator registerAllocator = new LinearScanRegisterAllocator(appView, code);
    registerAllocator.allocateRegisters();
    timing.end();
    if (code.getConversionOptions().isPeepholeOptimizationsEnabled()) {
      timing.begin("Peephole optimize");
      for (int i = 0; i < PEEPHOLE_OPTIMIZATION_PASSES; i++) {
        CodeRewriter.collapseTrivialGotos(appView, code);
        PeepholeOptimizer.optimize(appView, code, registerAllocator);
      }
      timing.end();
    }
    timing.begin("Clean up");
    CodeRewriter.removeUnneededMovesOnExitingPaths(code, registerAllocator);
    CodeRewriter.collapseTrivialGotos(appView, code);
    timing.end();
    if (Log.ENABLED) {
      Log.debug(
          getClass(), "Final (non-SSA) flow graph for %s:\n%s", method.toSourceString(), code);
    }
    return registerAllocator;
  }
}