Subzero. RAII NaCl Bundling.

src/IceTargetLowering.h

 //===- subzero/src/IceTargetLowering.h - Lowering interface -----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 279 matching lines @@
 
   /// Performs target-specific argument lowering.
   virtual void lowerArguments() = 0;
 
   virtual void initNodeForLowering(CfgNode *) {}
   virtual void addProlog(CfgNode *Node) = 0;
   virtual void addEpilog(CfgNode *Node) = 0;
 
   virtual ~TargetLowering() = default;
 
+private:
+  // This control variable is used by AutoBundle (RAII-style bundle
+  // locking/unlocking) to prevent nested bundles.
+  bool AutoBundling = false;
+
+  // _bundle_lock(), and _bundle_unlock(), were made private to force subtargets
+  // to use the AutoBundle helper.
+  void
+  _bundle_lock(InstBundleLock::Option BundleOption = InstBundleLock::Opt_None) {
+    Context.insert<InstBundleLock>(BundleOption);
+  }
+  void _bundle_unlock() { Context.insert<InstBundleUnlock>(); }
+
 protected:
+  /// AutoBundle provides RIAA-style bundling. Sub-targets are expected to use
+  /// it when emitting NaCl Bundles to ensure proper bundle_unlocking, and
+  /// prevent nested bundles.
+  ///
+  /// AutoBundle objects will emit a _bundle_lock during construction (but only
+  /// if sandboxed code generation was requested), and a bundle_unlock() during
+  /// destruction. By carefully scoping objects of this type, Subtargets can
+  /// ensure proper bundle emission.
+  class AutoBundle {
+    AutoBundle() = delete;
+    AutoBundle(const AutoBundle &) = delete;
+    AutoBundle &operator=(const AutoBundle &) = delete;
+
+  public:
+    explicit AutoBundle(TargetLowering *Target, InstBundleLock::Option Option =
+                                                    InstBundleLock::Opt_None);
+    ~AutoBundle();
+
+  private:
+    TargetLowering *const Target;
+    const bool NeedSandboxing;
+  };
+
   explicit TargetLowering(Cfg *Func);
   virtual void lowerAlloca(const InstAlloca *Inst) = 0;
   virtual void lowerArithmetic(const InstArithmetic *Inst) = 0;
   virtual void lowerAssign(const InstAssign *Inst) = 0;
   virtual void lowerBr(const InstBr *Inst) = 0;
   virtual void lowerCall(const InstCall *Inst) = 0;
   virtual void lowerCast(const InstCast *Inst) = 0;
   virtual void lowerFcmp(const InstFcmp *Inst) = 0;
   virtual void lowerExtractElement(const InstExtractElement *Inst) = 0;
   virtual void lowerIcmp(const InstIcmp *Inst) = 0;
@@ skipping 70 matching lines @@
                            bool UsesFramePointer);
 
   /// Sort the variables in Source based on required alignment. The variables
   /// with the largest alignment need are placed in the front of the Dest list.
   void sortVarsByAlignment(VarList &Dest, const VarList &Source) const;
 
   /// Make a call to an external helper function.
   InstCall *makeHelperCall(const IceString &Name, Variable *Dest,
                            SizeT MaxSrcs);
 
-  void
-  _bundle_lock(InstBundleLock::Option BundleOption = InstBundleLock::Opt_None) {
-    Context.insert<InstBundleLock>(BundleOption);
-  }
-  void _bundle_unlock() { Context.insert<InstBundleUnlock>(); }
   void _set_dest_redefined() { Context.getLastInserted()->setDestRedefined(); }
 
   bool shouldOptimizeMemIntrins();
 
   Cfg *Func;
   GlobalContext *Ctx;
   bool HasComputedFrame = false;
   bool CallsReturnsTwice = false;
   SizeT NextLabelNumber = 0;
   SizeT NextJumpTableNumber = 0;
@@ skipping 85 matching lines @@
   virtual void lower() {}
 
 protected:
   explicit TargetHeaderLowering(GlobalContext *Ctx) : Ctx(Ctx) {}
   GlobalContext *Ctx;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERING_H