PNaCl: Add NoAlias attributes in ExpandByVal and ExpandVarArgs passes

lib/Transforms/NaCl/ExpandVarArgs.cpp

 //===- ExpandVarArgs.cpp - Expand out variable argument function calls-----===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass expands out all use of variable argument functions.
@@ skipping 185 matching lines @@
 
   // Split argument list into fixed and variable arguments.
   SmallVector<Value *, 8> FixedArgs;
   SmallVector<Value *, 8> VarArgs;
   SmallVector<Type *, 8> VarArgsTypes;
   for (unsigned I = 0; I < FuncType->getNumParams(); ++I) {
     FixedArgs.push_back(Call->getArgOperand(I));
     // AttributeSets use 1-based indexing.
     Attrs.push_back(Call->getAttributes().getParamAttributes(I + 1));
   }
+  Attrs.push_back(AttributeSet::get(*Context, FuncType->getNumParams() + 1,
+                                    Attribute::NoAlias));
   for (unsigned I = FuncType->getNumParams();
        I < Call->getNumArgOperands(); ++I) {
     Value *ArgVal = Call->getArgOperand(I);
     if (Call->getAttributes().hasAttribute(I + 1, Attribute::ByVal)) {
       // For "byval" arguments we must dereference the pointer and
       // make a copy of the struct being passed by value.
       ArgVal = CopyDebug(new LoadInst(ArgVal, "vararg_struct_copy", Call),
                          Call);
     }
     VarArgs.push_back(ArgVal);
@@ skipping 114 matching lines @@
       ExpandVarArgFunc(Func);
     }
   }
 
   return Changed;
 }
 
 ModulePass *llvm::createExpandVarArgsPass() {
   return new ExpandVarArgs();
 }