Subzero: Removed unnecessary global access checks

src/IceASanInstrumentation.cpp

 //===- subzero/src/IceASanInstrumentation.cpp - ASan ------------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 114 matching lines @@
         &NewGlobals, RzRight, RelocOffsetArray(0)));
     RzSizes->addInitializer(VariableDeclaration::DataInitializer::create(
         &NewGlobals, sizeToByteVec(RzLeftSize)));
     RzSizes->addInitializer(VariableDeclaration::DataInitializer::create(
         &NewGlobals, sizeToByteVec(RzRightSize)));
 
     NewGlobals.push_back(RzLeft);
     NewGlobals.push_back(Global);
     NewGlobals.push_back(RzRight);
     RzGlobalsNum += 2;
+
+    GlobalSizes.insert({Global->getName(), Global->getNumBytes()});
   }
 
   // Replace old list of globals, without messing up arena allocators
   Globals.clear();
   Globals.merge(&NewGlobals);
   DidProcessGlobals = true;
 
   // Log the new set of globals
   if (BuildDefs::dump() && (getFlags().getVerbose() & IceV_GlobalInit)) {
     OstreamLocker _(Ctx);
@@ skipping 145 matching lines @@
                    typeWidthInBytes(Instr->getData()->getType()), Func);
 }
 
 void ASanInstrumentation::instrumentAccess(LoweringContext &Context,
                                            Operand *Op, SizeT Size,
                                            Constant *CheckFunc) {
   VarSizeMap::iterator LocalSize = ICE_TLS_GET_FIELD(LocalVars)->find(Op);
   if (LocalSize != ICE_TLS_GET_FIELD(LocalVars)->end() &&
       LocalSize->second >= Size)
     return;
+  if (isOkGlobalAccess(Op, Size))
+    return;
   constexpr SizeT NumArgs = 2;
   constexpr Variable *Void = nullptr;
   constexpr bool NoTailCall = false;
   auto *Call = InstCall::create(Context.getNode()->getCfg(), NumArgs, Void,
                                 CheckFunc, NoTailCall);
   Call->addArg(Op);
   Call->addArg(ConstantInteger32::create(Ctx, IceType_i32, Size));
   // play games to insert the call before the access instruction
   InstList::iterator Next = Context.getNext();
   Context.setInsertPoint(Context.getCur());
   Context.insert(Call);
   Context.setNext(Next);
 }
 
+// TODO(tlively): Trace back load and store addresses to find their real offsets
+bool ASanInstrumentation::isOkGlobalAccess(Operand *Op, SizeT Size) {
+  auto *Reloc = llvm::dyn_cast<ConstantRelocatable>(Op);
+  if (Reloc == nullptr)
+    return false;
+  RelocOffsetT Offset = Reloc->getOffset();
+  GlobalSizeMap::iterator GlobalSize = GlobalSizes.find(Reloc->getName());
+  return GlobalSize != GlobalSizes.end() && GlobalSize->second - Offset >= Size;
+}
+
 void ASanInstrumentation::instrumentRet(LoweringContext &Context, InstRet *) {
   Cfg *Func = Context.getNode()->getCfg();
   InstList::iterator Next = Context.getNext();
   Context.setInsertPoint(Context.getCur());
   for (InstCall *RzUnpoison : *ICE_TLS_GET_FIELD(LocalDtors)) {
     SizeT NumArgs = RzUnpoison->getNumArgs();
     Variable *Dest = RzUnpoison->getDest();
     Operand *CallTarget = RzUnpoison->getCallTarget();
     bool HasTailCall = RzUnpoison->isTailcall();
     bool IsTargetHelperCall = RzUnpoison->isTargetHelperCall();
@@ skipping 23 matching lines @@
   Call->addArg(Ctx->getConstantSym(0, Ctx->getGlobalString(RzSizesName)));
 }
 
 // TODO(tlively): make this more efficient with swap idiom
 void ASanInstrumentation::finishFunc(Cfg *) {
   ICE_TLS_GET_FIELD(LocalVars)->clear();
   ICE_TLS_GET_FIELD(LocalDtors)->clear();
 }
 
 } // end of namespace Ice