[PM] refactoring of LoopAccessInfo /NFC

[davidxl]

Summary

LoopAccessInfo will be the result type managed by a loop analysis pass. The result type needs to define move constructors so that result objects can be passed from analysis pass to the analysis manager/cache.

This refactoring makes it easier to define move constructors for LoopAccessInfo.

[davide]

David, this one sounds reasonable to me. Adam?

[anemet]

LGTM too with the change below.

include/llvm/Analysis/LoopAccessAnalysis.h

617–623

Please add a comment saying that these are pointers to facilitate the move ctor.

[silvas]

include/llvm/Analysis/LoopAccessAnalysis.h

617–623

This might not be relevant, but FYI there is a gotcha with MSVC 2013 where it can't synthesize a move ctor. Just a heads up in case there are bot problems with this patch.

This caused me problems when porting JumpThreading. See http://reviews.llvm.org/rL272607 in particular the manually defined move constructor with the comment "// Hack for MSVC 2013 which seems like it can't synthesize this.".

The fix there is based on the earlier r216244 that gave insight into the problem.

[davidxl]

Ok -- I plan to explicitly define move ctors in the second stage change.

thanks,

David

include/llvm/Analysis/LoopAccessAnalysis.h

LoopAccessInfo(Loop *L, ScalarEvolution *SE, const DataLayout &DL,
                  const TargetLibraryInfo *TLI, AliasAnalysis *AA,
                  DominatorTree *DT, LoopInfo *LI);
 
   /// Return true we can analyze the memory accesses in the loop and there are
   /// no memory dependence cycles.
   bool canVectorizeMemory() const { return CanVecMem; }
 
   const RuntimePointerChecking *getRuntimePointerChecking() const {
-    return &PtrRtChecking;
+    return PtrRtChecking.get();
   }
 
   /// \brief Number of memchecks required to prove independence of otherwise
   /// may-alias pointers.
   unsigned getNumRuntimePointerChecks() const {
-    return PtrRtChecking.getNumberOfChecks();
+    return PtrRtChecking->getNumberOfChecks();
   }
 
   /// Return true if the block BB needs to be predicated in order for the loop
   /// to be vectorized.
   static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop,
                                     DominatorTree *DT);
 
   /// Returns true if the value V is uniform within the loop.
addRuntimeChecks(Instruction *Loc,
                        &PointerChecks) const;
 
   /// \brief The diagnostics report generated for the analysis.  E.g. why we
   /// couldn't analyze the loop.
   const Optional<LoopAccessReport> &getReport() const { return Report; }
 
   /// \brief the Memory Dependence Checker which can determine the
   /// loop-independent and loop-carried dependences between memory accesses.
-  const MemoryDepChecker &getDepChecker() const { return DepChecker; }
+  const MemoryDepChecker &getDepChecker() const { return *DepChecker; }
 
   /// \brief Return the list of instructions that use \p Ptr to read or write
   /// memory.
   SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
                                                          bool isWrite) const {
-    return DepChecker.getInstructionsForAccess(Ptr, isWrite);
+    return DepChecker->getInstructionsForAccess(Ptr, isWrite);
   }
 
   /// \brief If an access has a symbolic strides, this maps the pointer value to
   /// the stride symbol.
   const ValueToValueMap &getSymbolicStrides() const { return SymbolicStrides; }
 
   /// \brief Pointer has a symbolic stride.
   bool hasStride(Value *V) const { return StrideSet.count(V); }
private:
   void emitAnalysis(LoopAccessReport &Message);
 
   /// \brief Collect memory access with loop invariant strides.
   ///
   /// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop
   /// invariant.
   void collectStridedAccess(Value *LoadOrStoreInst);
 
   /// We need to check that all of the pointers in this list are disjoint
   /// at runtime.
-  RuntimePointerChecking PtrRtChecking;
+  std::unique_ptr<RuntimePointerChecking> PtrRtChecking;
 
   /// \brief the Memory Dependence Checker which can determine the
   /// loop-independent and loop-carried dependences between memory accesses.
-  MemoryDepChecker DepChecker;
+  std::unique_ptr<MemoryDepChecker> DepChecker;
 
   Loop *TheLoop;
   const DataLayout &DL;
   const TargetLibraryInfo *TLI;
   AliasAnalysis *AA;
   DominatorTree *DT;
   LoopInfo *LI;
 

lib/Analysis/LoopAccessAnalysis.cpp

   // Holds the Load and Store instructions.
   SmallVector<LoadInst *, 16> Loads;
   SmallVector<StoreInst *, 16> Stores;
 
   // Holds all the different accesses in the loop.
   unsigned NumReads = 0;
   unsigned NumReadWrites = 0;
 
-  PtrRtChecking.Pointers.clear();
-  PtrRtChecking.Need = false;
+  PtrRtChecking->Pointers.clear();
+  PtrRtChecking->Need = false;
 
   const bool IsAnnotatedParallel = TheLoop->isAnnotatedParallel();
 
   // For each block.
   for (Loop::block_iterator bb = TheLoop->block_begin(),
        be = TheLoop->block_end(); bb != be; ++bb) {
 
     // Scan the BB and collect legal loads and stores.

           emitAnalysis(LoopAccessReport(Ld)
                        << "read with atomic ordering or volatile read");
           DEBUG(dbgs() << "LAA: Found a non-simple load.\n");
           CanVecMem = false;
           return;
         }
         NumLoads++;
         Loads.push_back(Ld);
-        DepChecker.addAccess(Ld);
+        DepChecker->addAccess(Ld);
         if (EnableMemAccessVersioning)
           collectStridedAccess(Ld);
         continue;
       }
 
       // Save 'store' instructions. Abort if other instructions write to memory.
       if (it->mayWriteToMemory()) {
         StoreInst *St = dyn_cast<StoreInst>(it);
         if (!St) {
           emitAnalysis(LoopAccessReport(&*it) <<
                        "instruction cannot be vectorized");
           CanVecMem = false;
           return;
         }
         if (!St->isSimple() && !IsAnnotatedParallel) {
           emitAnalysis(LoopAccessReport(St)
                        << "write with atomic ordering or volatile write");
           DEBUG(dbgs() << "LAA: Found a non-simple store.\n");
           CanVecMem = false;
           return;
         }
         NumStores++;
         Stores.push_back(St);
-        DepChecker.addAccess(St);
+        DepChecker->addAccess(St);
         if (EnableMemAccessVersioning)
           collectStridedAccess(St);
       }
     } // Next instr.
   } // Next block.
 
   // Now we have two lists that hold the loads and the stores.
   // Next, we find the pointers that they use.

   }
 
   // Build dependence sets and check whether we need a runtime pointer bounds
   // check.
   Accesses.buildDependenceSets();
 
   // Find pointers with computable bounds. We are going to use this information
   // to place a runtime bound check.
-  bool CanDoRTIfNeeded = Accesses.canCheckPtrAtRT(PtrRtChecking, PSE.getSE(),
+  bool CanDoRTIfNeeded = Accesses.canCheckPtrAtRT(*PtrRtChecking, PSE.getSE(),
                                                   TheLoop, SymbolicStrides);
   if (!CanDoRTIfNeeded) {
     emitAnalysis(LoopAccessReport() << "cannot identify array bounds");
     DEBUG(dbgs() << "LAA: We can't vectorize because we can't find "
                  << "the array bounds.\n");
     CanVecMem = false;
     return;
   }
 
   DEBUG(dbgs() << "LAA: We can perform a memory runtime check if needed.\n");
 
   CanVecMem = true;
   if (Accesses.isDependencyCheckNeeded()) {
     DEBUG(dbgs() << "LAA: Checking memory dependencies\n");
-    CanVecMem = DepChecker.areDepsSafe(
+    CanVecMem = DepChecker->areDepsSafe(
         DependentAccesses, Accesses.getDependenciesToCheck(), SymbolicStrides);
-    MaxSafeDepDistBytes = DepChecker.getMaxSafeDepDistBytes();
+    MaxSafeDepDistBytes = DepChecker->getMaxSafeDepDistBytes();
 
-    if (!CanVecMem && DepChecker.shouldRetryWithRuntimeCheck()) {
+    if (!CanVecMem && DepChecker->shouldRetryWithRuntimeCheck()) {
       DEBUG(dbgs() << "LAA: Retrying with memory checks\n");
 
       // Clear the dependency checks. We assume they are not needed.
-      Accesses.resetDepChecks(DepChecker);
+      Accesses.resetDepChecks(*DepChecker);
 
-      PtrRtChecking.reset();
-      PtrRtChecking.Need = true;
+      PtrRtChecking->reset();
+      PtrRtChecking->Need = true;
 
       auto *SE = PSE.getSE();
-      CanDoRTIfNeeded = Accesses.canCheckPtrAtRT(PtrRtChecking, SE, TheLoop,
+      CanDoRTIfNeeded = Accesses.canCheckPtrAtRT(*PtrRtChecking, SE, TheLoop,
                                                  SymbolicStrides, true);
 
       // Check that we found the bounds for the pointer.
       if (!CanDoRTIfNeeded) {
         emitAnalysis(LoopAccessReport()
                      << "cannot check memory dependencies at runtime");
         DEBUG(dbgs() << "LAA: Can't vectorize with memory checks\n");
         CanVecMem = false;
         return;
       }
 
       CanVecMem = true;
     }
   }
 
   if (CanVecMem)
     DEBUG(dbgs() << "LAA: No unsafe dependent memory operations in loop.  We"
-                 << (PtrRtChecking.Need ? "" : " don't")
+                 << (PtrRtChecking->Need ? "" : " don't")
                  << " need runtime memory checks.\n");
   else {
     emitAnalysis(
         LoopAccessReport()
         << "unsafe dependent memory operations in loop. Use "
            "#pragma loop distribute(enable) to allow loop distribution "
            "to attempt to isolate the offending operations into a separate "
            "loop");

 
 std::pair<Instruction *, Instruction *> LoopAccessInfo::addRuntimeChecks(
     Instruction *Loc,
     const SmallVectorImpl<RuntimePointerChecking::PointerCheck> &PointerChecks)
     const {
   auto *SE = PSE.getSE();
   SCEVExpander Exp(*SE, DL, "induction");
   auto ExpandedChecks =
-      expandBounds(PointerChecks, TheLoop, Loc, SE, Exp, PtrRtChecking);
+      expandBounds(PointerChecks, TheLoop, Loc, SE, Exp, *PtrRtChecking);
 
   LLVMContext &Ctx = Loc->getContext();
   Instruction *FirstInst = nullptr;
   IRBuilder<> ChkBuilder(Loc);
   // Our instructions might fold to a constant.
   Value *MemoryRuntimeCheck = nullptr;
 
   for (const auto &Check : ExpandedChecks) {

                                                  ConstantInt::getTrue(Ctx));
   ChkBuilder.Insert(Check, "memcheck.conflict");
   FirstInst = getFirstInst(FirstInst, Check, Loc);
   return std::make_pair(FirstInst, Check);
 }
 
 std::pair<Instruction *, Instruction *>
 LoopAccessInfo::addRuntimeChecks(Instruction *Loc) const {
-  if (!PtrRtChecking.Need)
+  if (!PtrRtChecking->Need)
     return std::make_pair(nullptr, nullptr);
 
-  return addRuntimeChecks(Loc, PtrRtChecking.getChecks());
+  return addRuntimeChecks(Loc, PtrRtChecking->getChecks());
 }
 
 void LoopAccessInfo::collectStridedAccess(Value *MemAccess) {
   Value *Ptr = nullptr;
   if (LoadInst *LI = dyn_cast<LoadInst>(MemAccess))
     Ptr = LI->getPointerOperand();
   else if (StoreInst *SI = dyn_cast<StoreInst>(MemAccess))
     Ptr = SI->getPointerOperand();

   SymbolicStrides[Ptr] = Stride;
   StrideSet.insert(Stride);
 }
 
 LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
                                const DataLayout &DL,
                                const TargetLibraryInfo *TLI, AliasAnalysis *AA,
                                DominatorTree *DT, LoopInfo *LI)
-    : PSE(*SE, *L), PtrRtChecking(SE), DepChecker(PSE, L), TheLoop(L), DL(DL),
-      TLI(TLI), AA(AA), DT(DT), LI(LI), NumLoads(0), NumStores(0),
+    : PSE(*SE, *L),
+      PtrRtChecking(llvm::make_unique<RuntimePointerChecking>(SE)),
+      DepChecker(llvm::make_unique<MemoryDepChecker>(PSE, L)), TheLoop(L),
+      DL(DL), TLI(TLI), AA(AA), DT(DT), LI(LI), NumLoads(0), NumStores(0),
       MaxSafeDepDistBytes(-1U), CanVecMem(false),
       StoreToLoopInvariantAddress(false) {
   if (canAnalyzeLoop())
     analyzeLoop();
 }
 
 void LoopAccessInfo::print(raw_ostream &OS, unsigned Depth) const {
   if (CanVecMem) {
     OS.indent(Depth) << "Memory dependences are safe";
     if (MaxSafeDepDistBytes != -1U)
       OS << " with a maximum dependence distance of " << MaxSafeDepDistBytes
          << " bytes";
-    if (PtrRtChecking.Need)
+    if (PtrRtChecking->Need)
       OS << " with run-time checks";
     OS << "\n";
   }
 
   if (Report)
     OS.indent(Depth) << "Report: " << Report->str() << "\n";
 
-  if (auto *Dependences = DepChecker.getDependences()) {
+  if (auto *Dependences = DepChecker->getDependences()) {
     OS.indent(Depth) << "Dependences:\n";
     for (auto &Dep : *Dependences) {
-      Dep.print(OS, Depth + 2, DepChecker.getMemoryInstructions());
+      Dep.print(OS, Depth + 2, DepChecker->getMemoryInstructions());
       OS << "\n";
     }
   } else
     OS.indent(Depth) << "Too many dependences, not recorded\n";
 
   // List the pair of accesses need run-time checks to prove independence.
-  PtrRtChecking.print(OS, Depth);
+  PtrRtChecking->print(OS, Depth);
   OS << "\n";
 
   OS.indent(Depth) << "Store to invariant address was "
                    << (StoreToLoopInvariantAddress ? "" : "not ")
                    << "found in loop.\n";
 
   OS.indent(Depth) << "SCEV assumptions:\n";
   PSE.getUnionPredicate().print(OS, Depth);