--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/lib/ARCMigrate/TransEmptyStatementsAndDealloc.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,249 @@
+//===-- TransEmptyStatementsAndDealloc.cpp - Transformations to ARC mode --===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// removeEmptyStatementsAndDealloc:
+//
+// Removes empty statements that are leftovers from previous transformations.
+// e.g for
+//
+//  [x retain];
+//
+// removeRetainReleaseDealloc will leave an empty ";" that removeEmptyStatements
+// will remove.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Transforms.h"
+#include "Internals.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/Basic/SourceManager.h"
+
+using namespace clang;
+using namespace arcmt;
+using namespace trans;
+
+static bool isEmptyARCMTMacroStatement(NullStmt *S,
+                                       std::vector<SourceLocation> &MacroLocs,
+                                       ASTContext &Ctx) {
+  if (!S->hasLeadingEmptyMacro())
+    return false;
+
+  SourceLocation SemiLoc = S->getSemiLoc();
+  if (SemiLoc.isInvalid() || SemiLoc.isMacroID())
+    return false;
+
+  if (MacroLocs.empty())
+    return false;
+
+  SourceManager &SM = Ctx.getSourceManager();
+  std::vector<SourceLocation>::iterator I = llvm::upper_bound(
+      MacroLocs, SemiLoc, BeforeThanCompare<SourceLocation>(SM));
+  --I;
+  SourceLocation
+      AfterMacroLoc = I->getLocWithOffset(getARCMTMacroName().size());
+  assert(AfterMacroLoc.isFileID());
+
+  if (AfterMacroLoc == SemiLoc)
+    return true;
+
+  int RelOffs = 0;
+  if (!SM.isInSameSLocAddrSpace(AfterMacroLoc, SemiLoc, &RelOffs))
+    return false;
+  if (RelOffs < 0)
+    return false;
+
+  // We make the reasonable assumption that a semicolon after 100 characters
+  // means that it is not the next token after our macro. If this assumption
+  // fails it is not critical, we will just fail to clear out, e.g., an empty
+  // 'if'.
+  if (RelOffs - getARCMTMacroName().size() > 100)
+    return false;
+
+  SourceLocation AfterMacroSemiLoc = findSemiAfterLocation(AfterMacroLoc, Ctx);
+  return AfterMacroSemiLoc == SemiLoc;
+}
+
+namespace {
+
+/// Returns true if the statement became empty due to previous
+/// transformations.
+class EmptyChecker : public StmtVisitor<EmptyChecker, bool> {
+  ASTContext &Ctx;
+  std::vector<SourceLocation> &MacroLocs;
+
+public:
+  EmptyChecker(ASTContext &ctx, std::vector<SourceLocation> &macroLocs)
+    : Ctx(ctx), MacroLocs(macroLocs) { }
+
+  bool VisitNullStmt(NullStmt *S) {
+    return isEmptyARCMTMacroStatement(S, MacroLocs, Ctx);
+  }
+  bool VisitCompoundStmt(CompoundStmt *S) {
+    if (S->body_empty())
+      return false; // was already empty, not because of transformations.
+    for (auto *I : S->body())
+      if (!Visit(I))
+        return false;
+    return true;
+  }
+  bool VisitIfStmt(IfStmt *S) {
+    if (S->getConditionVariable())
+      return false;
+    Expr *condE = S->getCond();
+    if (!condE)
+      return false;
+    if (hasSideEffects(condE, Ctx))
+      return false;
+    if (!S->getThen() || !Visit(S->getThen()))
+      return false;
+    return !S->getElse() || Visit(S->getElse());
+  }
+  bool VisitWhileStmt(WhileStmt *S) {
+    if (S->getConditionVariable())
+      return false;
+    Expr *condE = S->getCond();
+    if (!condE)
+      return false;
+    if (hasSideEffects(condE, Ctx))
+      return false;
+    if (!S->getBody())
+      return false;
+    return Visit(S->getBody());
+  }
+  bool VisitDoStmt(DoStmt *S) {
+    Expr *condE = S->getCond();
+    if (!condE)
+      return false;
+    if (hasSideEffects(condE, Ctx))
+      return false;
+    if (!S->getBody())
+      return false;
+    return Visit(S->getBody());
+  }
+  bool VisitObjCForCollectionStmt(ObjCForCollectionStmt *S) {
+    Expr *Exp = S->getCollection();
+    if (!Exp)
+      return false;
+    if (hasSideEffects(Exp, Ctx))
+      return false;
+    if (!S->getBody())
+      return false;
+    return Visit(S->getBody());
+  }
+  bool VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S) {
+    if (!S->getSubStmt())
+      return false;
+    return Visit(S->getSubStmt());
+  }
+};
+
+class EmptyStatementsRemover :
+                            public RecursiveASTVisitor<EmptyStatementsRemover> {
+  MigrationPass &Pass;
+
+public:
+  EmptyStatementsRemover(MigrationPass &pass) : Pass(pass) { }
+
+  bool TraverseStmtExpr(StmtExpr *E) {
+    CompoundStmt *S = E->getSubStmt();
+    for (CompoundStmt::body_iterator
+           I = S->body_begin(), E = S->body_end(); I != E; ++I) {
+      if (I != E - 1)
+        check(*I);
+      TraverseStmt(*I);
+    }
+    return true;
+  }
+
+  bool VisitCompoundStmt(CompoundStmt *S) {
+    for (auto *I : S->body())
+      check(I);
+    return true;
+  }
+
+  ASTContext &getContext() { return Pass.Ctx; }
+
+private:
+  void check(Stmt *S) {
+    if (!S) return;
+    if (EmptyChecker(Pass.Ctx, Pass.ARCMTMacroLocs).Visit(S)) {
+      Transaction Trans(Pass.TA);
+      Pass.TA.removeStmt(S);
+    }
+  }
+};
+
+} // anonymous namespace
+
+static bool isBodyEmpty(CompoundStmt *body, ASTContext &Ctx,
+                        std::vector<SourceLocation> &MacroLocs) {
+  for (auto *I : body->body())
+    if (!EmptyChecker(Ctx, MacroLocs).Visit(I))
+      return false;
+
+  return true;
+}
+
+static void cleanupDeallocOrFinalize(MigrationPass &pass) {
+  ASTContext &Ctx = pass.Ctx;
+  TransformActions &TA = pass.TA;
+  DeclContext *DC = Ctx.getTranslationUnitDecl();
+  Selector FinalizeSel =
+      Ctx.Selectors.getNullarySelector(&pass.Ctx.Idents.get("finalize"));
+
+  typedef DeclContext::specific_decl_iterator<ObjCImplementationDecl>
+    impl_iterator;
+  for (impl_iterator I = impl_iterator(DC->decls_begin()),
+                     E = impl_iterator(DC->decls_end()); I != E; ++I) {
+    ObjCMethodDecl *DeallocM = nullptr;
+    ObjCMethodDecl *FinalizeM = nullptr;
+    for (auto *MD : I->instance_methods()) {
+      if (!MD->hasBody())
+        continue;
+
+      if (MD->getMethodFamily() == OMF_dealloc) {
+        DeallocM = MD;
+      } else if (MD->isInstanceMethod() && MD->getSelector() == FinalizeSel) {
+        FinalizeM = MD;
+      }
+    }
+
+    if (DeallocM) {
+      if (isBodyEmpty(DeallocM->getCompoundBody(), Ctx, pass.ARCMTMacroLocs)) {
+        Transaction Trans(TA);
+        TA.remove(DeallocM->getSourceRange());
+      }
+
+      if (FinalizeM) {
+        Transaction Trans(TA);
+        TA.remove(FinalizeM->getSourceRange());
+      }
+
+    } else if (FinalizeM) {
+      if (isBodyEmpty(FinalizeM->getCompoundBody(), Ctx, pass.ARCMTMacroLocs)) {
+        Transaction Trans(TA);
+        TA.remove(FinalizeM->getSourceRange());
+      } else {
+        Transaction Trans(TA);
+        TA.replaceText(FinalizeM->getSelectorStartLoc(), "finalize", "dealloc");
+      }
+    }
+  }
+}
+
+void trans::removeEmptyStatementsAndDeallocFinalize(MigrationPass &pass) {
+  EmptyStatementsRemover(pass).TraverseDecl(pass.Ctx.getTranslationUnitDecl());
+
+  cleanupDeallocOrFinalize(pass);
+
+  for (unsigned i = 0, e = pass.ARCMTMacroLocs.size(); i != e; ++i) {
+    Transaction Trans(pass.TA);
+    pass.TA.remove(pass.ARCMTMacroLocs[i]);
+  }
+}