[Lifetime] Add lifetime markers for C++ lifetime-extended temporaries

[timshen]

Summary

Use pushCleanupAfterFullExpr to add lifetime.end markers for
lifetime-extended temporaries, similar to the way destructor calls get
generated.

It does not change the AST representation. It doesn't generate normal temporary
lifetime markers, since normal temporaries appear in substantially different
places, which could be done in a separate patch.

[timshen]

Abandon this change, since D20498 and D20499 handle all temporaries.

lib/CodeGen/CGCleanup.cpp

 }
 
 
 void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
   char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size));
   bool IsNormalCleanup = Kind & NormalCleanup;
   bool IsEHCleanup = Kind & EHCleanup;
   bool IsActive = !(Kind & InactiveCleanup);
+  bool IsLifetimeMarker = Kind & LifetimeMarker;
   EHCleanupScope *Scope =
     new (Buffer) EHCleanupScope(IsNormalCleanup,
                                 IsEHCleanup,
                                 IsActive,
                                 Size,
                                 BranchFixups.size(),
                                 InnermostNormalCleanup,
                                 InnermostEHScope);
   if (IsNormalCleanup)
     InnermostNormalCleanup = stable_begin();
   if (IsEHCleanup)
     InnermostEHScope = stable_begin();
+  if (IsLifetimeMarker)
+    Scope->setLifetimeMarker();
 
   return Scope->getCleanupBuffer();
 }
 
 void EHScopeStack::popCleanup() {
   assert(!empty() && "popping exception stack when not empty");
 
   assert(isa<EHCleanupScope>(*begin()));

lib/CodeGen/CGDecl.cpp

void Emit(CodeGenFunction &CGF, Flags flags) override {
         CGF.Builder.CreateBitCast(Addr, CGF.ConvertType(ArgTy));
 
       CallArgList Args;
       Args.add(RValue::get(Arg),
                CGF.getContext().getPointerType(Var.getType()));
       CGF.EmitCall(FnInfo, CleanupFn, ReturnValueSlot(), Args);
     }
   };
-
-  /// A cleanup to call @llvm.lifetime.end.
-  class CallLifetimeEnd final : public EHScopeStack::Cleanup {
-    llvm::Value *Addr;
-    llvm::Value *Size;
-  public:
-    CallLifetimeEnd(Address addr, llvm::Value *size)
-      : Addr(addr.getPointer()), Size(size) {}
-
-    void Emit(CodeGenFunction &CGF, Flags flags) override {
-      CGF.EmitLifetimeEnd(Size, Addr);
-    }
-  };
 } // end anonymous namespace
 
 /// EmitAutoVarWithLifetime - Does the setup required for an automatic
 /// variable with lifetime.
 static void EmitAutoVarWithLifetime(CodeGenFunction &CGF, const VarDecl &var,
                                     Address addr,
                                     Qualifiers::ObjCLifetime lifetime) {
   switch (lifetime) {

 /// \param alignment the alignment of the address
 /// \param capturedByInit true if the variable is a __block variable
 ///   whose address is potentially changed by the initializer
 void CodeGenFunction::EmitExprAsInit(const Expr *init, const ValueDecl *D,
                                      LValue lvalue, bool capturedByInit) {
   QualType type = D->getType();
 
   if (type->isReferenceType()) {
+    // It is a lifetime-extension. Ensure that there is a RunCleanupsScope for
+    // the delayed CallLifetimeEnd in EmitMaterializeTemporaryExpr.
+    Optional<RunCleanupsScope> Cleanup;
+    // Create this scope only when there is a MaterializeTemporaryExpr that is
+    // not guarded by an ExprWithCleanups.
+    if (dyn_cast<MaterializeTemporaryExpr>(init))
+      Cleanup.emplace(*this);
+
     RValue rvalue = EmitReferenceBindingToExpr(init);
     if (capturedByInit)
       drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
     EmitStoreThroughLValue(rvalue, lvalue, true);
     return;
   }
   switch (getEvaluationKind(type)) {
   case TEK_Scalar:
void CodeGenFunction::EmitAutoVarCleanups(const AutoVarEmission &emission) {
   // If we don't have an insertion point, we're done.  Sema prevents
   // us from jumping into any of these scopes anyway.
   if (!HaveInsertPoint()) return;
 
   const VarDecl &D = *emission.Variable;
 
   // Make sure we call @llvm.lifetime.end.  This needs to happen
   // *last*, so the cleanup needs to be pushed *first*.
-  if (emission.useLifetimeMarkers()) {
-    EHStack.pushCleanup<CallLifetimeEnd>(NormalAndEHCleanup,
+  if (emission.useLifetimeMarkers())
+    EHStack.pushCleanup<CallLifetimeEnd>(NormalEHLifetimeMarker,
                                          emission.getAllocatedAddress(),
                                          emission.getSizeForLifetimeMarkers());
-    EHCleanupScope &cleanup = cast<EHCleanupScope>(*EHStack.begin());
-    cleanup.setLifetimeMarker();
-  }
 
   // Check the type for a cleanup.
   if (QualType::DestructionKind dtorKind = D.getType().isDestructedType())
     emitAutoVarTypeCleanup(emission, dtorKind);
 
   // In GC mode, honor objc_precise_lifetime.
   if (getLangOpts().getGC() != LangOptions::NonGC &&
       D.hasAttr<ObjCPreciseLifetimeAttr>()) {

lib/CodeGen/CGExpr.cpp

 //===--- CGExpr.cpp - Emit LLVM Code from Expressions ---------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This contains code to emit Expr nodes as LLVM code.
 //
 //===----------------------------------------------------------------------===//
 
-#include "CodeGenFunction.h"
 #include "CGCXXABI.h"
 #include "CGCall.h"
+#include "CGCleanup.h"
 #include "CGDebugInfo.h"
 #include "CGObjCRuntime.h"
 #include "CGOpenMPRuntime.h"
 #include "CGRecordLayout.h"
+#include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/Frontend/CodeGenOptions.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/StringExtras.h"
if (auto *Var = dyn_cast<llvm::GlobalVariable>(Object.getPointer())) {
     // If the temporary is a global and has a constant initializer or is a
     // constant temporary that we promoted to a global, we may have already
     // initialized it.
     if (!Var->hasInitializer()) {
       Var->setInitializer(CGM.EmitNullConstant(E->getType()));
       EmitAnyExprToMem(E, Object, Qualifiers(), /*IsInit*/true);
     }
   } else {
+    llvm::Value *Size = nullptr;
+    // Only handle lifetime extended objects.
+    // TODO: Handle normal temporaries.
+    if (M->getStorageDuration() == SD_Automatic)
+      Size = EmitLifetimeStart(
+          CGM.getDataLayout().getTypeAllocSize(Object.getElementType()),
+          Object.getPointer());
+
     EmitAnyExprToMem(E, Object, Qualifiers(), /*IsInit*/true);
+
+    if (Size)
+      pushCleanupAfterFullExpr<CallLifetimeEnd>(NormalEHLifetimeMarker, Object,
+                                                Size);
   }
   pushTemporaryCleanup(*this, M, E, Object);
 
   // Perform derived-to-base casts and/or field accesses, to get from the
   // temporary object we created (and, potentially, for which we extended
   // the lifetime) to the subobject we're binding the reference to.
   for (unsigned I = Adjustments.size(); I != 0; --I) {
     SubobjectAdjustment &Adjustment = Adjustments[I-1];

lib/CodeGen/CodeGenFunction.h

public:
   llvm::DenseMap<const VarDecl *, llvm::Value *> NRVOFlags;
 
   EHScopeStack EHStack;
   llvm::SmallVector<char, 256> LifetimeExtendedCleanupStack;
   llvm::SmallVector<const JumpDest *, 2> SEHTryEpilogueStack;
 
   llvm::Instruction *CurrentFuncletPad = nullptr;
 
+  class CallLifetimeEnd final : public EHScopeStack::Cleanup {
+    llvm::Value *Addr;
+    llvm::Value *Size;
+
+  public:
+    CallLifetimeEnd(Address addr, llvm::Value *size)
+        : Addr(addr.getPointer()), Size(size) {}
+
+    void Emit(CodeGenFunction &CGF, Flags flags) override {
+      CGF.EmitLifetimeEnd(Size, Addr);
+    }
+  };
+
   /// Header for data within LifetimeExtendedCleanupStack.
   struct LifetimeExtendedCleanupHeader {
     /// The size of the following cleanup object.
     unsigned Size;
     /// The kind of cleanup to push: a value from the CleanupKind enumeration.
     CleanupKind Kind;
 
     size_t getSize() const { return Size; }

lib/CodeGen/EHScopeStack.h

enum CleanupKind : unsigned {
   /// control flow (falling off the end of the scope, return, goto, ...).
   NormalCleanup = 0x2,
 
   NormalAndEHCleanup = EHCleanup | NormalCleanup,
 
   InactiveCleanup = 0x4,
   InactiveEHCleanup = EHCleanup | InactiveCleanup,
   InactiveNormalCleanup = NormalCleanup | InactiveCleanup,
-  InactiveNormalAndEHCleanup = NormalAndEHCleanup | InactiveCleanup
+  InactiveNormalAndEHCleanup = NormalAndEHCleanup | InactiveCleanup,
+
+  LifetimeMarker = 0x8,
+  NormalEHLifetimeMarker = LifetimeMarker | NormalAndEHCleanup,
 };
 
 /// A stack of scopes which respond to exceptions, including cleanups
 /// and catch blocks.
 class EHScopeStack {
 public:
   /* Should switch to alignof(uint64_t) instead of 8, when EHCleanupScope can */
   enum { ScopeStackAlignment = 8 };

test/CodeGen/lifetime-extended-temporaries.cpp

+// RUN: %clang_cc1 %s -std=c++11 -O1 -DWITH_DTOR -triple x86_64 -emit-llvm -o - | FileCheck -check-prefix=CHECK-DTOR %s
+// RUN: %clang_cc1 %s -std=c++11 -O1 -triple x86_64 -emit-llvm -o - | FileCheck -check-prefix=CHECK-NO-DTOR %s
+
+struct A {
+  A();
+#ifdef WITH_DTOR
+  ~A();
+#endif
+  char a[1024];
+  operator bool() const;
+};
+
+template <typename T>
+void Foo(T &&);
+
+template <typename T>
+void Bar(T &&);
+
+template <typename T>
+T Baz();
+
+void Test1() {
+  // CHECK-DTOR-LABEL: Test1
+  // CHECK-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR:[0-9]+]])
+  // CHECK-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR:[^ ]+]])
+  // CHECK-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-DTOR: call void @_ZN1AD1Ev(%struct.A* nonnull %[[VAR]])
+  // CHECK-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR]])
+  // CHECK-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR:[0-9]+]])
+  // CHECK-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR:[^ ]+]])
+  // CHECK-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-DTOR: call void @_ZN1AD1Ev(%struct.A* nonnull %[[VAR]])
+  // CHECK-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR]])
+  // CHECK-DTOR: }
+
+  // CHECK-NO-DTOR-LABEL: Test1
+  // CHECK-NO-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR:[0-9]+]])
+  // CHECK-NO-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR:[^ ]+]])
+  // CHECK-NO-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-NO-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR]])
+  // CHECK-NO-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR:[0-9]+]])
+  // CHECK-NO-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR:[^ ]+]])
+  // CHECK-NO-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-NO-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR]])
+  // CHECK-NO-DTOR: }
+  {
+    const A &a = A{};
+    Foo(a);
+  }
+  {
+    const A &a = A{};
+    Foo(a);
+  }
+}
+
+void Test2() {
+  // CHECK-DTOR-LABEL: Test2
+  // CHECK-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR1:[0-9]+]])
+  // CHECK-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR1:[^ ]+]])
+  // CHECK-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR2:[0-9]+]])
+  // CHECK-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR2:[^ ]+]])
+  // CHECK-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-DTOR: call void @_ZN1AD1Ev(%struct.A* nonnull %[[VAR2]])
+  // CHECK-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR2]])
+  // CHECK-DTOR: call void @_ZN1AD1Ev(%struct.A* nonnull %[[VAR1]])
+  // CHECK-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR1]])
+  // CHECK-DTOR: }
+
+  // CHECK-NO-DTOR-LABEL: Test2
+  // CHECK-NO-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR1:[0-9]+]])
+  // CHECK-NO-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR1:[^ ]+]])
+  // CHECK-NO-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-NO-DTOR: call void @llvm.lifetime.start(i64 1024, i8* %[[ADDR2:[0-9]+]])
+  // CHECK-NO-DTOR: call void @_ZN1AC1Ev(%struct.A* nonnull %[[VAR2:[^ ]+]])
+  // CHECK-NO-DTOR: call void @_Z3FooIRK1AEvOT_
+  // CHECK-NO-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR2]])
+  // CHECK-NO-DTOR: call void @llvm.lifetime.end(i64 1024, i8* %[[ADDR1]])
+  // CHECK-NO-DTOR: }
+  const A &a = A{};
+  Foo(a);
+  const A &b = A{};
+  Foo(b);
+}
+
+void Test3() {
+  // CHECK-DTOR-LABEL: Test3
+  // CHECK-DTOR: entry:
+  // CHECK-DTOR: call void @llvm.lifetime.start
+  // CHECK-DTOR: call void @llvm.lifetime.start
+  // CHECK-DTOR: if.then:
+  // CHECK-DTOR: call void @llvm.lifetime.end
+  // CHECK-DTOR: cleanup{{.*}}:
+  // CHECK-DTOR: call void @llvm.lifetime.end
+  // CHECK-DTOR: cleanup{{.*}}:
+  // CHECK-DTOR: call void @llvm.lifetime.end
+  // CHECK-DTOR: }
+  const A &a = A{};
+  if (const A &b = A(a)) {
+    Foo(b);
+    return;
+  }
+  Bar(a);
+}
+
+void Test4() {
+  // CHECK-DTOR-LABEL: Test4
+  // CHECK-DTOR: entry:
+  // CHECK-DTOR: call void @llvm.lifetime.start
+  // CHECK-DTOR: for.cond.cleanup:
+  // CHECK-DTOR: call void @llvm.lifetime.end
+  // CHECK-DTOR: for.body:
+  // CHECK-DTOR: }
+  for (const A &a = A{}; a;) {
+    Foo(a);
+  }
+}
+
+int Test5() {
+  // CHECK-DTOR-LABEL: Test5
+  // CHECK-DTOR: call void @llvm.lifetime.start
+  // CHECK-DTOR: call i32 @_Z3BazIiET_v()
+  // CHECK-DTOR: store
+  // CHECK-DTOR: call void @_Z3FooIRKiEvOT_
+  // CHECK-DTOR: load
+  // CHECK-DTOR: call void @llvm.lifetime.end
+  // CHECK-DTOR: }
+  const int &a = Baz<int>();
+  Foo(a);
+  return a;
+}