[cfi] Fixed non-determinism in codegen due to DenseSet iteration order

[mgrang]

This will fix the following unit tests which failed in the reverse iteration buildbot (http://lab.llvm.org:8011/builders/reverse-iteration/builds/23/steps/check_all/logs/stdio)

LLVM :: Transforms/CrossDSOCFI/basic.ll
LLVM :: Transforms/CrossDSOCFI/cfi_functions.ll

[mgrang]

Do you think using SetVector instead of DenseSet will impact compile-time? The other option we have is to add the TypeIds into a SmallVector and sort it before iteration.

[eugenis]

LGTM, thanks!

lib/Transforms/IPO/CrossDSOCFI.cpp

 //===-- CrossDSOCFI.cpp - Externalize this module's CFI checks ------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass exports all llvm.bitset's found in the module in the form of a
 // __cfi_check function, which can be used to verify cross-DSO call targets.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/IPO/CrossDSOCFI.h"
-#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
ConstantInt *CrossDSOCFI::extractNumericTypeId(MDNode *MD) {
 
   return C;
 }
 
 /// buildCFICheck - emits __cfi_check for the current module.
 void CrossDSOCFI::buildCFICheck(Module &M) {
   // FIXME: verify that __cfi_check ends up near the end of the code section,
   // but before the jump slots created in LowerTypeTests.
-  llvm::DenseSet<uint64_t> TypeIds;
+  SetVector<uint64_t> TypeIds;
   SmallVector<MDNode *, 2> Types;
   for (GlobalObject &GO : M.global_objects()) {
     Types.clear();
     GO.getMetadata(LLVMContext::MD_type, Types);
     for (MDNode *Type : Types) {
       // Sanity check. GO must not be a function declaration.
       assert(!isa<Function>(&GO) || !cast<Function>(&GO)->isDeclaration());