[LAA] refactor program logic (NFC)

Implement NFC improvements spotted during a cursory reading of
LoopAccessAnalysis.

Author: artagnon

llvm/lib/Analysis/LoopAccessAnalysis.cpp

@@ -394,9 +394,9 @@ void RuntimePointerChecking::generateChecks(
 
 bool RuntimePointerChecking::needsChecking(
     const RuntimeCheckingPtrGroup &M, const RuntimeCheckingPtrGroup &N) const {
-  for (unsigned I = 0, EI = M.Members.size(); EI != I; ++I)
-    for (unsigned J = 0, EJ = N.Members.size(); EJ != J; ++J)
-      if (needsChecking(M.Members[I], N.Members[J]))
+  for (auto &I : M.Members)
+    for (auto &J : N.Members)
+      if (needsChecking(I, J))
         return true;
   return false;
 }
@@ -410,9 +410,7 @@ static const SCEV *getMinFromExprs(const SCEV *I, const SCEV *J,
 
   if (!C)
     return nullptr;
-  if (C->getValue()->isNegative())
-    return J;
-  return I;
+  return C->getValue()->isNegative() ? J : I;
 }
 
 bool RuntimeCheckingPtrGroup::addPointer(unsigned Index,
@@ -510,8 +508,8 @@ void RuntimePointerChecking::groupChecks(
 
   DenseMap<Value *, SmallVector<unsigned>> PositionMap;
   for (unsigned Index = 0; Index < Pointers.size(); ++Index) {
-    auto Iter = PositionMap.insert({Pointers[Index].PointerValue, {}});
-    Iter.first->second.push_back(Index);
+    auto [It, _] = PositionMap.insert({Pointers[Index].PointerValue, {}});
+    It->second.push_back(Index);
   }
 
   // We need to keep track of what pointers we've already seen so we
@@ -610,16 +608,16 @@ void RuntimePointerChecking::printChecks(
     raw_ostream &OS, const SmallVectorImpl<RuntimePointerCheck> &Checks,
     unsigned Depth) const {
   unsigned N = 0;
-  for (const auto &Check : Checks) {
-    const auto &First = Check.first->Members, &Second = Check.second->Members;
+  for (const auto &[Check1, Check2] : Checks) {
+    const auto &First = Check1->Members, &Second = Check2->Members;
 
     OS.indent(Depth) << "Check " << N++ << ":\n";
 
-    OS.indent(Depth + 2) << "Comparing group (" << Check.first << "):\n";
+    OS.indent(Depth + 2) << "Comparing group (" << Check1 << "):\n";
     for (unsigned K = 0; K < First.size(); ++K)
       OS.indent(Depth + 2) << *Pointers[First[K]].PointerValue << "\n";
 
-    OS.indent(Depth + 2) << "Against group (" << Check.second << "):\n";
+    OS.indent(Depth + 2) << "Against group (" << Check2 << "):\n";
     for (unsigned K = 0; K < Second.size(); ++K)
       OS.indent(Depth + 2) << *Pointers[Second[K]].PointerValue << "\n";
   }
@@ -1160,8 +1158,8 @@ bool AccessAnalysis::canCheckPtrAtRT(RuntimePointerChecking &RtCheck,
     // First, count how many write and read accesses are in the alias set. Also
     // collect MemAccessInfos for later.
     SmallVector<MemAccessInfo, 4> AccessInfos;
-    for (const Value *Ptr_ : ASPointers) {
-      Value *Ptr = const_cast<Value *>(Ptr_);
+    for (const Value *ConstPtr : ASPointers) {
+      Value *Ptr = const_cast<Value *>(ConstPtr);
       bool IsWrite = Accesses.count(MemAccessInfo(Ptr, true));
       if (IsWrite)
         ++NumWritePtrChecks;
@@ -1217,9 +1215,7 @@ bool AccessAnalysis::canCheckPtrAtRT(RuntimePointerChecking &RtCheck,
       // We know that we need these checks, so we can now be more aggressive
       // and add further checks if required (overflow checks).
       CanDoAliasSetRT = true;
-      for (auto Retry : Retries) {
-        MemAccessInfo Access = Retry.first;
-        Type *AccessTy = Retry.second;
+      for (const auto &[Access, AccessTy] : Retries) {
         if (!createCheckForAccess(RtCheck, Access, AccessTy, StridesMap,
                                   DepSetId, TheLoop, RunningDepId, ASId,
                                   ShouldCheckWrap, /*Assume=*/true)) {
@@ -1291,12 +1287,11 @@ void AccessAnalysis::processMemAccesses() {
   LLVM_DEBUG(dbgs() << "  AST: "; AST.dump());
   LLVM_DEBUG(dbgs() << "LAA:   Accesses(" << Accesses.size() << "):\n");
   LLVM_DEBUG({
-    for (auto A : Accesses)
-      dbgs() << "\t" << *A.first.getPointer() << " ("
-             << (A.first.getInt()
-                     ? "write"
-                     : (ReadOnlyPtr.count(A.first.getPointer()) ? "read-only"
-                                                                : "read"))
+    for (const auto &[A, _] : Accesses)
+      dbgs() << "\t" << *A.getPointer() << " ("
+             << (A.getInt() ? "write"
+                            : (ReadOnlyPtr.count(A.getPointer()) ? "read-only"
+                                                                 : "read"))
              << ")\n";
   });
 
@@ -1325,16 +1320,16 @@ void AccessAnalysis::processMemAccesses() {
       bool UseDeferred = SetIteration > 0;
       PtrAccessMap &S = UseDeferred ? DeferredAccesses : Accesses;
 
-      for (const Value *Ptr_ : ASPointers) {
-        Value *Ptr = const_cast<Value *>(Ptr_);
+      for (const Value *ConstPtr : ASPointers) {
+        Value *Ptr = const_cast<Value *>(ConstPtr);
 
         // For a single memory access in AliasSetTracker, Accesses may contain
         // both read and write, and they both need to be handled for CheckDeps.
-        for (const auto &AC : S) {
-          if (AC.first.getPointer() != Ptr)
+        for (const auto &[AC, _] : S) {
+          if (AC.getPointer() != Ptr)
             continue;
 
-          bool IsWrite = AC.first.getInt();
+          bool IsWrite = AC.getInt();
 
           // If we're using the deferred access set, then it contains only
           // reads.
@@ -1866,10 +1861,7 @@ static bool isSafeDependenceDistance(const DataLayout &DL, ScalarEvolution &SE,
   // (If so, then we have proven (**) because |Dist| >= -1*Dist)
   const SCEV *NegDist = SE.getNegativeSCEV(CastedDist);
   Minus = SE.getMinusSCEV(NegDist, CastedProduct);
-  if (SE.isKnownPositive(Minus))
-    return true;
-
-  return false;
+  return SE.isKnownPositive(Minus);
 }
 
 /// Check the dependence for two accesses with the same stride \p Stride.
@@ -2043,7 +2035,7 @@ MemoryDepChecker::Dependence::DepType MemoryDepChecker::isDependent(
   if (isa<SCEVCouldNotCompute>(Dist)) {
     // TODO: Relax requirement that there is a common stride to retry with
     // non-constant distance dependencies.
-    FoundNonConstantDistanceDependence |= !!CommonStride;
+    FoundNonConstantDistanceDependence |= CommonStride.has_value();
     LLVM_DEBUG(dbgs() << "LAA: Dependence because of uncomputable distance.\n");
     return Dependence::Unknown;
   }
@@ -2082,14 +2074,12 @@ MemoryDepChecker::Dependence::DepType MemoryDepChecker::isDependent(
   // Negative distances are not plausible dependencies.
   if (SE.isKnownNonPositive(Dist)) {
     if (SE.isKnownNonNegative(Dist)) {
-      if (HasSameSize) {
+      if (HasSameSize)
         // Write to the same location with the same size.
         return Dependence::Forward;
-      } else {
-        LLVM_DEBUG(dbgs() << "LAA: possibly zero dependence difference but "
-                             "different type sizes\n");
-        return Dependence::Unknown;
-      }
+      LLVM_DEBUG(dbgs() << "LAA: possibly zero dependence difference but "
+                           "different type sizes\n");
+      return Dependence::Unknown;
     }
 
     bool IsTrueDataDependence = (AIsWrite && !BIsWrite);
@@ -2335,7 +2325,7 @@ bool MemoryDepChecker::areDepsSafe(
           }
         ++OI;
       }
-      AI++;
+      ++AI;
     }
   }
 
@@ -2344,8 +2334,8 @@ bool MemoryDepChecker::areDepsSafe(
 }
 
 SmallVector<Instruction *, 4>
-MemoryDepChecker::getInstructionsForAccess(Value *Ptr, bool isWrite) const {
-  MemAccessInfo Access(Ptr, isWrite);
+MemoryDepChecker::getInstructionsForAccess(Value *Ptr, bool IsWrite) const {
+  MemAccessInfo Access(Ptr, IsWrite);
   auto &IndexVector = Accesses.find(Access)->second;
 
   SmallVector<Instruction *, 4> Insts;
@@ -2656,7 +2646,7 @@ void LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
                                SymbolicStrides, UncomputablePtr, false);
   if (!CanDoRTIfNeeded) {
     auto *I = dyn_cast_or_null<Instruction>(UncomputablePtr);
-    recordAnalysis("CantIdentifyArrayBounds", I) 
+    recordAnalysis("CantIdentifyArrayBounds", I)
         << "cannot identify array bounds";
     LLVM_DEBUG(dbgs() << "LAA: We can't vectorize because we can't find "
                       << "the array bounds.\n");
@@ -2721,13 +2711,14 @@ void LoopAccessInfo::analyzeLoop(AAResults *AA, LoopInfo *LI,
 }
 
 void LoopAccessInfo::emitUnsafeDependenceRemark() {
-  auto Deps = getDepChecker().getDependences();
+  const auto *Deps = getDepChecker().getDependences();
   if (!Deps)
     return;
-  auto Found = llvm::find_if(*Deps, [](const MemoryDepChecker::Dependence &D) {
-    return MemoryDepChecker::Dependence::isSafeForVectorization(D.Type) !=
-           MemoryDepChecker::VectorizationSafetyStatus::Safe;
-  });
+  const auto *Found =
+      llvm::find_if(*Deps, [](const MemoryDepChecker::Dependence &D) {
+        return MemoryDepChecker::Dependence::isSafeForVectorization(D.Type) !=
+               MemoryDepChecker::VectorizationSafetyStatus::Safe;
+      });
   if (Found == Deps->end())
     return;
   MemoryDepChecker::Dependence Dep = *Found;
@@ -2866,9 +2857,9 @@ static Value *stripGetElementPtr(Value *Ptr, ScalarEvolution *SE, Loop *Lp) {
 
   // Check that all of the gep indices are uniform except for our induction
   // operand.
-  for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i)
-    if (i != InductionOperand &&
-        !SE->isLoopInvariant(SE->getSCEV(GEP->getOperand(i)), Lp))
+  for (unsigned I = 0, E = GEP->getNumOperands(); I != E; ++I)
+    if (I != InductionOperand &&
+        !SE->isLoopInvariant(SE->getSCEV(GEP->getOperand(I)), Lp))
       return Ptr;
   return GEP->getOperand(InductionOperand);
 }
@@ -3050,11 +3041,10 @@ LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
   if (TTI) {
     TypeSize FixedWidth =
         TTI->getRegisterBitWidth(TargetTransformInfo::RGK_FixedWidthVector);
-    if (FixedWidth.isNonZero()) {
+    if (FixedWidth.isNonZero())
       // Scale the vector width by 2 as rough estimate to also consider
       // interleaving.
       MaxTargetVectorWidthInBits = FixedWidth.getFixedValue() * 2;
-    }
 
     TypeSize ScalableWidth =
         TTI->getRegisterBitWidth(TargetTransformInfo::RGK_ScalableVector);
@@ -3064,9 +3054,8 @@ LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
   DepChecker =
       std::make_unique<MemoryDepChecker>(*PSE, L, MaxTargetVectorWidthInBits);
   PtrRtChecking = std::make_unique<RuntimePointerChecking>(*DepChecker, SE);
-  if (canAnalyzeLoop()) {
+  if (canAnalyzeLoop())
     analyzeLoop(AA, LI, TLI, DT);
-  }
 }
 
 void LoopAccessInfo::print(raw_ostream &OS, unsigned Depth) const {
@@ -3118,13 +3107,13 @@ void LoopAccessInfo::print(raw_ostream &OS, unsigned Depth) const {
 }
 
 const LoopAccessInfo &LoopAccessInfoManager::getInfo(Loop &L) {
-  auto I = LoopAccessInfoMap.insert({&L, nullptr});
+  auto [It, Inserted] = LoopAccessInfoMap.insert({&L, nullptr});
 
-  if (I.second)
-    I.first->second =
+  if (Inserted)
+    It->second =
         std::make_unique<LoopAccessInfo>(&L, &SE, TTI, TLI, &AA, &DT, &LI);
 
-  return *I.first->second;
+  return *It->second;
 }
 
 bool LoopAccessInfoManager::invalidate(