Emit lifetime.start / lifetime.end markers for unnamed temporary objects.

This will give more information to the optimizers so that they can reuse stack slots.

llvm-svn: 213379

1 files changed, 20 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 3692b02..285ef63 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -990,6 +990,23 @@ private:
   void EmitOpenCLKernelMetadata(const FunctionDecl *FD, 
                                 llvm::Function *Fn);
 
+  /// Should we use the LLVM lifetime intrinsics for a local variable of the
+  /// given size in bytes ?
+  bool shouldUseLifetimeMarkers(unsigned Size) const;
+
+  /// A cleanup to call @llvm.lifetime.end.
+  class CallLifetimeEnd : public EHScopeStack::Cleanup {
+    llvm::Value *Addr;
+    llvm::Value *Size;
+  public:
+    CallLifetimeEnd(llvm::Value *addr, llvm::Value *size)
+      : Addr(addr), Size(size) {}
+
+    void Emit(CodeGenFunction &CGF, Flags flags) override {
+      CGF.EmitLifetimeEnd(Size, Addr);
+    }
+  };
+
 public:
   CodeGenFunction(CodeGenModule &cgm, bool suppressNewContext=false);
   ~CodeGenFunction();
@@ -1673,6 +1690,9 @@ public:
   void EmitCXXTemporary(const CXXTemporary *Temporary, QualType TempType,
                         llvm::Value *Ptr);
 
+  void EmitLifetimeStart(llvm::Value *Size, llvm::Value *Addr);
+  void EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr);
+
   llvm::Value *EmitCXXNewExpr(const CXXNewExpr *E);
   void EmitCXXDeleteExpr(const CXXDeleteExpr *E);