IPO: Add use-list-order verifier

Add a -verify-use-list-order pass, which shuffles use-list order, writes
to bitcode, reads back, and verifies that the (shuffled) order matches.

  - The utility functions live in lib/IR/UseListOrder.cpp.

  - Moved (and renamed) the command-line option to enable writing
    use-lists, so that this pass can return early if the use-list orders
    aren't being serialized.

It's not clear that this pass is the right direction long-term (perhaps
a separate tool instead?), but short-term it's a great way to test the
use-list order prototype.  I've added an XFAIL-ed testcase that I'm
hoping to get working pretty quickly.

This is part of PR5680.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213945 91177308-0d34-0410-b5e6-96231b3b80d8

Author: dexonsmith

include/llvm/IR/UseListOrder.h

@@ -0,0 +1,42 @@
+//===- llvm/IR/UseListOrder.h - LLVM Use List Order functions ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file has functions to modify the use-list order and to verify that it
+// doesn't change after serialization.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_USELISTORDER_H
+#define LLVM_IR_USELISTORDER_H
+
+namespace llvm {
+
+class Module;
+
+/// \brief Whether to preserve use-list ordering.
+bool shouldPreserveBitcodeUseListOrder();
+
+/// \brief Shuffle all use-lists in a module.
+///
+/// Adds \c SeedOffset to the default seed for the random number generator.
+void shuffleUseLists(Module &M, unsigned SeedOffset = 0);
+
+/// \brief Verify use-list order after serializing to bitcode.
+///
+/// \return \c true if there are no errors.
+bool verifyBitcodeUseListOrder(const Module &M);
+
+/// \brief Verify use-list order after serializing to assembly.
+///
+/// \return \c true if there are no errors.
+bool verifyAssemblyUseListOrder(const Module &M);
+
+} // end namespace llvm
+
+#endif

include/llvm/InitializePasses.h

@@ -268,6 +268,7 @@ void initializeUnifyFunctionExitNodesPass(PassRegistry&);
 void initializeUnreachableBlockElimPass(PassRegistry&);
 void initializeUnreachableMachineBlockElimPass(PassRegistry&);
 void initializeVerifierLegacyPassPass(PassRegistry&);
+void initializeVerifyUseListOrderPass(PassRegistry&);
 void initializeVirtRegMapPass(PassRegistry&);
 void initializeVirtRegRewriterPass(PassRegistry&);
 void initializeInstSimplifierPass(PassRegistry&);

include/llvm/LinkAllPasses.h

@@ -161,6 +161,7 @@ namespace {
       (void) llvm::createPartiallyInlineLibCallsPass();
       (void) llvm::createScalarizerPass();
       (void) llvm::createSeparateConstOffsetFromGEPPass();
+      (void) llvm::createVerifyUseListOrderPass();
 
       (void)new llvm::IntervalPartition();
       (void)new llvm::FindUsedTypes();

include/llvm/Transforms/IPO.h

@@ -118,6 +118,11 @@ ModulePass *createInternalizePass(ArrayRef<const char *> ExportList);
 /// createInternalizePass - Same as above, but with an empty exportList.
 ModulePass *createInternalizePass();
 
+/// \brief Verify that use-list order doesn't change after shuffling.
+///
+/// \note This is a transformation, since the use-list order changes.
+ModulePass *createVerifyUseListOrderPass();
+
 //===----------------------------------------------------------------------===//
 /// createDeadArgEliminationPass - This pass removes arguments from functions
 /// which are not used by the body of the function.

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -22,6 +22,7 @@
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
+#include "llvm/IR/UseListOrder.h"
 #include "llvm/IR/ValueSymbolTable.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -32,12 +33,6 @@
 #include <map>
 using namespace llvm;
 
-static cl::opt<bool>
-EnablePreserveUseListOrdering("enable-bc-uselist-preserve",
-                              cl::desc("Turn on experimental support for "
-                                       "use-list order preservation."),
-                              cl::init(false), cl::Hidden);
-
 /// These are manifest constants used by the bitcode writer. They do not need to
 /// be kept in sync with the reader, but need to be consistent within this file.
 enum {
@@ -1975,7 +1970,7 @@ static void WriteModule(const Module *M, BitstreamWriter &Stream) {
   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
 
   // Emit use-lists.
-  if (EnablePreserveUseListOrdering)
+  if (shouldPreserveBitcodeUseListOrder())
     WriteModuleUseLists(M, VE, Stream);
 
   // Emit function bodies.

lib/IR/CMakeLists.txt

@@ -39,6 +39,7 @@ add_llvm_library(LLVMCore
   Type.cpp
   TypeFinder.cpp
   Use.cpp
+  UseListOrder.cpp
   User.cpp
   Value.cpp
   ValueSymbolTable.cpp