[PM/AA] Remove the AliasDebugger pass.

[chandlerc]

Summary

This debugger was designed to catch places where the old update API was
failing to be used correctly. As I've removed the update API, it no
longer serves any purpose. We can introduce new debugging aid passes
around any future work w.r.t. updating AAs.

Note that I've updated the documentation here, but really I need to
rewrite the documentation to carefully spell out the ideas around
stateful AA and how things are changing in the AA world. However, I'm
hoping to do that as a follow-up to the refactoring of the AA
infrastructure to work in both old and new pass managers so that I can
write the documentation specific to that world.

[hfinkel]

LGTM.

docs/AliasAnalysis.rst

 There is no way for transform passes to declare that they preserve
 ``AliasAnalysis`` implementations. The ``AliasAnalysis`` interface includes
 ``deleteValue`` and ``copyValue`` methods which are intended to allow a pass to
 keep an AliasAnalysis consistent, however there's no way for a pass to declare
 in its ``getAnalysisUsage`` that it does so. Some passes attempt to use
 ``AU.addPreserved<AliasAnalysis>``, however this doesn't actually have any
 effect.
 
-``AliasAnalysisCounter`` (``-count-aa``) and ``AliasDebugger`` (``-debug-aa``)
-are implemented as ``ModulePass`` classes, so if your alias analysis uses
-``FunctionPass``, it won't be able to use these utilities. If you try to use
-them, the pass manager will silently route alias analysis queries directly to
-``BasicAliasAnalysis`` instead.
+``AliasAnalysisCounter`` (``-count-aa``) are implemented as ``ModulePass``
+classes, so if your alias analysis uses ``FunctionPass``, it won't be able to
+use these utilities. If you try to use them, the pass manager will silently
+route alias analysis queries directly to ``BasicAliasAnalysis`` instead.
 
 Similarly, the ``opt -p`` option introduces ``ModulePass`` passes between each
 pass, which prevents the use of ``FunctionPass`` alias analysis passes.
 
 The ``AliasAnalysis`` API does have functions for notifying implementations when
 values are deleted or copied, however these aren't sufficient. There are many
 other ways that LLVM IR can be modified which could be relevant to
 ``AliasAnalysis`` implementations which can not be expressed.

include/llvm/Analysis/Passes.h

namespace llvm {
   //
   // createGlobalsModRefPass - This pass provides alias and mod/ref info for
   // global values that do not have their addresses taken.
   //
   Pass *createGlobalsModRefPass();
 
   //===--------------------------------------------------------------------===//
   //
-  // createAliasDebugger - This pass helps debug clients of AA
-  //
-  Pass *createAliasDebugger();
-
-  //===--------------------------------------------------------------------===//
-  //
   // createAliasAnalysisCounterPass - This pass counts alias queries and how the
   // alias analysis implementation responds.
   //
   ModulePass *createAliasAnalysisCounterPass();
 
   //===--------------------------------------------------------------------===//
   //
   // createAAEvalPass - This pass implements a simple N^2 alias analysis

include/llvm/InitializePasses.h

 void initializeTarget(PassRegistry&);
 
 void initializeAAEvalPass(PassRegistry&);
 void initializeAddDiscriminatorsPass(PassRegistry&);
 void initializeADCEPass(PassRegistry&);
 void initializeBDCEPass(PassRegistry&);
 void initializeAliasAnalysisAnalysisGroup(PassRegistry&);
 void initializeAliasAnalysisCounterPass(PassRegistry&);
-void initializeAliasDebuggerPass(PassRegistry&);
 void initializeAliasSetPrinterPass(PassRegistry&);
 void initializeAlwaysInlinerPass(PassRegistry&);
 void initializeArgPromotionPass(PassRegistry&);
 void initializeAtomicExpandPass(PassRegistry&);
 void initializeSampleProfileLoaderPass(PassRegistry&);
 void initializeAlignmentFromAssumptionsPass(PassRegistry&);
 void initializeBarrierNoopPass(PassRegistry&);
 void initializeBasicAliasAnalysisPass(PassRegistry&);

include/llvm/LinkAllPasses.h

ForcePassLinking() {
       // to know that getenv() never returns -1, this will do the job.
       if (std::getenv("bar") != (char*) -1)
         return;
 
       (void) llvm::createAAEvalPass();
       (void) llvm::createAggressiveDCEPass();
       (void) llvm::createBitTrackingDCEPass();
       (void) llvm::createAliasAnalysisCounterPass();
-      (void) llvm::createAliasDebugger();
       (void) llvm::createArgumentPromotionPass();
       (void) llvm::createAlignmentFromAssumptionsPass();
       (void) llvm::createBasicAliasAnalysisPass();
       (void) llvm::createLibCallAliasAnalysisPass(nullptr);
       (void) llvm::createScalarEvolutionAliasAnalysisPass();
       (void) llvm::createTypeBasedAliasAnalysisPass();
       (void) llvm::createScopedNoAliasAAPass();
       (void) llvm::createBoundsCheckingPass();

lib/Analysis/AliasDebugger.cpp

-//===- AliasDebugger.cpp - Simple Alias Analysis Use Checker --------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This simple pass checks alias analysis users to ensure that if they
-// create a new value, they do not query AA without informing it of the value.
-// It acts as a shim over any other AA pass you want.
-//
-// Yes keeping track of every value in the program is expensive, but this is 
-// a debugging pass.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Analysis/Passes.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Pass.h"
-#include <set>
-using namespace llvm;
-
-namespace {
-  
-  class AliasDebugger : public ModulePass, public AliasAnalysis {
-
-    //What we do is simple.  Keep track of every value the AA could
-    //know about, and verify that queries are one of those.
-    //A query to a value that didn't exist when the AA was created
-    //means someone forgot to update the AA when creating new values
-
-    std::set<const Value*> Vals;
-    
-  public:
-    static char ID; // Class identification, replacement for typeinfo
-    AliasDebugger() : ModulePass(ID) {
-      initializeAliasDebuggerPass(*PassRegistry::getPassRegistry());
-    }
-
-    bool runOnModule(Module &M) override {
-      InitializeAliasAnalysis(this, &M.getDataLayout()); // set up super class
-
-      for(Module::global_iterator I = M.global_begin(),
-            E = M.global_end(); I != E; ++I) {
-        Vals.insert(&*I);
-        for (User::const_op_iterator OI = I->op_begin(),
-             OE = I->op_end(); OI != OE; ++OI)
-          Vals.insert(*OI);
-      }
-
-      for(Module::iterator I = M.begin(),
-            E = M.end(); I != E; ++I){
-        Vals.insert(&*I);
-        if(!I->isDeclaration()) {
-          for (Function::arg_iterator AI = I->arg_begin(), AE = I->arg_end();
-               AI != AE; ++AI) 
-            Vals.insert(&*AI);     
-          for (Function::const_iterator FI = I->begin(), FE = I->end();
-               FI != FE; ++FI) 
-            for (BasicBlock::const_iterator BI = FI->begin(), BE = FI->end();
-                 BI != BE; ++BI) {
-              Vals.insert(&*BI);
-              for (User::const_op_iterator OI = BI->op_begin(),
-                   OE = BI->op_end(); OI != OE; ++OI)
-                Vals.insert(*OI);
-            }
-        }
-        
-      }
-      return false;
-    }
-
-    void getAnalysisUsage(AnalysisUsage &AU) const override {
-      AliasAnalysis::getAnalysisUsage(AU);
-      AU.setPreservesAll();                         // Does not transform code
-    }
-
-    /// getAdjustedAnalysisPointer - This method is used when a pass implements
-    /// an analysis interface through multiple inheritance.  If needed, it
-    /// should override this to adjust the this pointer as needed for the
-    /// specified pass info.
-    void *getAdjustedAnalysisPointer(AnalysisID PI) override {
-      if (PI == &AliasAnalysis::ID)
-        return (AliasAnalysis*)this;
-      return this;
-    }
-    
-    //------------------------------------------------
-    // Implement the AliasAnalysis API
-    //
-    AliasResult alias(const MemoryLocation &LocA,
-                      const MemoryLocation &LocB) override {
-      assert(Vals.find(LocA.Ptr) != Vals.end() &&
-             "Never seen value in AA before");
-      assert(Vals.find(LocB.Ptr) != Vals.end() &&
-             "Never seen value in AA before");
-      return AliasAnalysis::alias(LocA, LocB);
-    }
-
-    ModRefInfo getModRefInfo(ImmutableCallSite CS,
-                             const MemoryLocation &Loc) override {
-      assert(Vals.find(Loc.Ptr) != Vals.end() && "Never seen value in AA before");
-      return AliasAnalysis::getModRefInfo(CS, Loc);
-    }
-
-    ModRefInfo getModRefInfo(ImmutableCallSite CS1,
-                             ImmutableCallSite CS2) override {
-      return AliasAnalysis::getModRefInfo(CS1,CS2);
-    }
-
-    bool pointsToConstantMemory(const MemoryLocation &Loc,
-                                bool OrLocal) override {
-      assert(Vals.find(Loc.Ptr) != Vals.end() && "Never seen value in AA before");
-      return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
-    }
-  };
-}
-
-char AliasDebugger::ID = 0;
-INITIALIZE_AG_PASS(AliasDebugger, AliasAnalysis, "debug-aa",
-                   "AA use debugger", false, true, false)
-
-Pass *llvm::createAliasDebugger() { return new AliasDebugger(); }
-

lib/Analysis/Analysis.cpp

 
 using namespace llvm;
 
 /// initializeAnalysis - Initialize all passes linked into the Analysis library.
 void llvm::initializeAnalysis(PassRegistry &Registry) {
   initializeAliasAnalysisAnalysisGroup(Registry);
   initializeAliasAnalysisCounterPass(Registry);
   initializeAAEvalPass(Registry);
-  initializeAliasDebuggerPass(Registry);
   initializeAliasSetPrinterPass(Registry);
   initializeNoAAPass(Registry);
   initializeBasicAliasAnalysisPass(Registry);
   initializeBlockFrequencyInfoWrapperPassPass(Registry);
   initializeBranchProbabilityInfoWrapperPassPass(Registry);
   initializeCostModelAnalysisPass(Registry);
   initializeCFGViewerPass(Registry);
   initializeCFGPrinterPass(Registry);

lib/Analysis/CMakeLists.txt

 add_llvm_library(LLVMAnalysis
   AliasAnalysis.cpp
   AliasAnalysisCounter.cpp
   AliasAnalysisEvaluator.cpp
-  AliasDebugger.cpp
   AliasSetTracker.cpp
   Analysis.cpp
   AssumptionCache.cpp
   BasicAliasAnalysis.cpp
   BlockFrequencyInfo.cpp
   BlockFrequencyInfoImpl.cpp
   BranchProbabilityInfo.cpp
   CFG.cpp