Reapply r183721, reverted in r183776, with a fix for a bug in the former (we

were lacking ExprWithCleanups nodes in some cases where the new approach to
lifetime extension needed them).

Original commit message:

Rework IR emission for lifetime-extended temporaries. Instead of trying to walk
into the expression and dig out a single lifetime-extended entity and manually
pull its cleanup outside the expression, instead keep a list of the cleanups
which we'll need to emit when we get to the end of the full-expression. Also
emit those cleanups early, as EH-only cleanups, to cover the case that the
full-expression does not terminate normally. This allows IR generation to
properly model temporary lifetime when multiple temporaries are extended by the
same declaration.

We have a pre-existing bug where an exception thrown from a temporary's
destructor does not clean up lifetime-extended temporaries created in the same
expression and extended to automatic storage duration; that is not fixed by
this patch.

llvm-svn: 183859

1 files changed, 47 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 080c471..7bbf788 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -241,6 +241,18 @@ public:
   llvm::DenseMap<const VarDecl *, llvm::Value *> NRVOFlags;
 
   EHScopeStack EHStack;
+  llvm::SmallVector<char, 256> LifetimeExtendedCleanupStack;
+
+  /// Header for data within LifetimeExtendedCleanupStack.
+  struct LifetimeExtendedCleanupHeader {
+    /// The size of the following cleanup object.
+    size_t Size : 29;
+    /// The kind of cleanup to push: a value from the CleanupKind enumeration.
+    unsigned Kind : 3;
+
+    size_t getSize() const { return Size; }
+    CleanupKind getKind() const { return static_cast<CleanupKind>(Kind); }
+  };
 
   /// i32s containing the indexes of the cleanup destinations.
   llvm::AllocaInst *NormalCleanupDest;
@@ -376,6 +388,23 @@ public:
     initFullExprCleanup();
   }
 
+  /// \brief Queue a cleanup to be pushed after finishing the current
+  /// full-expression.
+  template <class T, class A0, class A1, class A2, class A3>
+  void pushCleanupAfterFullExpr(CleanupKind Kind, A0 a0, A1 a1, A2 a2, A3 a3) {
+    assert(!isInConditionalBranch() && "can't defer conditional cleanup");
+
+    LifetimeExtendedCleanupHeader Header = { sizeof(T), Kind };
+
+    size_t OldSize = LifetimeExtendedCleanupStack.size();
+    LifetimeExtendedCleanupStack.resize(
+        LifetimeExtendedCleanupStack.size() + sizeof(Header) + Header.Size);
+
+    char *Buffer = &LifetimeExtendedCleanupStack[OldSize];
+    new (Buffer) LifetimeExtendedCleanupHeader(Header);
+    new (Buffer + sizeof(Header)) T(a0, a1, a2, a3);
+  }
+
   /// Set up the last cleaup that was pushed as a conditional
   /// full-expression cleanup.
   void initFullExprCleanup();
@@ -421,6 +450,7 @@ public:
   /// will be executed once the scope is exited.
   class RunCleanupsScope {
     EHScopeStack::stable_iterator CleanupStackDepth;
+    size_t LifetimeExtendedCleanupStackSize;
     bool OldDidCallStackSave;
   protected:
     bool PerformCleanup;
@@ -438,6 +468,8 @@ public:
       : PerformCleanup(true), CGF(CGF)
     {
       CleanupStackDepth = CGF.EHStack.stable_begin();
+      LifetimeExtendedCleanupStackSize =
+          CGF.LifetimeExtendedCleanupStack.size();
       OldDidCallStackSave = CGF.DidCallStackSave;
       CGF.DidCallStackSave = false;
     }
@@ -447,7 +479,8 @@ public:
     ~RunCleanupsScope() {
       if (PerformCleanup) {
         CGF.DidCallStackSave = OldDidCallStackSave;
-        CGF.PopCleanupBlocks(CleanupStackDepth);
+        CGF.PopCleanupBlocks(CleanupStackDepth,
+                             LifetimeExtendedCleanupStackSize);
       }
     }
 
@@ -461,7 +494,8 @@ public:
     void ForceCleanup() {
       assert(PerformCleanup && "Already forced cleanup");
       CGF.DidCallStackSave = OldDidCallStackSave;
-      CGF.PopCleanupBlocks(CleanupStackDepth);
+      CGF.PopCleanupBlocks(CleanupStackDepth,
+                           LifetimeExtendedCleanupStackSize);
       PerformCleanup = false;
     }
   };
@@ -513,10 +547,16 @@ public:
   };
 
 
-  /// PopCleanupBlocks - Takes the old cleanup stack size and emits
-  /// the cleanup blocks that have been added.
+  /// \brief Takes the old cleanup stack size and emits the cleanup blocks
+  /// that have been added.
   void PopCleanupBlocks(EHScopeStack::stable_iterator OldCleanupStackSize);
 
+  /// \brief Takes the old cleanup stack size and emits the cleanup blocks
+  /// that have been added, then adds all lifetime-extended cleanups from
+  /// the given position to the stack.
+  void PopCleanupBlocks(EHScopeStack::stable_iterator OldCleanupStackSize,
+                        size_t OldLifetimeExtendedStackSize);
+
   void ResolveBranchFixups(llvm::BasicBlock *Target);
 
   /// The given basic block lies in the current EH scope, but may be a
@@ -988,6 +1028,9 @@ public:
                      llvm::Value *addr, QualType type);
   void pushDestroy(CleanupKind kind, llvm::Value *addr, QualType type,
                    Destroyer *destroyer, bool useEHCleanupForArray);
+  void pushLifetimeExtendedDestroy(CleanupKind kind, llvm::Value *addr,
+                                   QualType type, Destroyer *destroyer,
+                                   bool useEHCleanupForArray);
   void emitDestroy(llvm::Value *addr, QualType type, Destroyer *destroyer,
                    bool useEHCleanupForArray);
   llvm::Function *generateDestroyHelper(llvm::Constant *addr,