[LAA] Rename var used to retry with RT-checks (NFC) (#147307)

FoundNonConstantDistanceDependence is a misleading name for a variable
that determines whether we retry with runtime checks. Rename it.

Author: artagnon

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

@@ -236,8 +236,8 @@ class MemoryDepChecker {
 
   /// In same cases when the dependency check fails we can still
   /// vectorize the loop with a dynamic array access check.
-  bool shouldRetryWithRuntimeCheck() const {
-    return FoundNonConstantDistanceDependence &&
+  bool shouldRetryWithRuntimeChecks() const {
+    return ShouldRetryWithRuntimeChecks &&
            Status == VectorizationSafetyStatus::PossiblySafeWithRtChecks;
   }
 
@@ -327,9 +327,9 @@ class MemoryDepChecker {
   uint64_t MaxStoreLoadForwardSafeDistanceInBits =
       std::numeric_limits<uint64_t>::max();
 
-  /// If we see a non-constant dependence distance we can still try to
-  /// vectorize this loop with runtime checks.
-  bool FoundNonConstantDistanceDependence = false;
+  /// Whether we should try to vectorize the loop with runtime checks, if the
+  /// dependencies are not safe.
+  bool ShouldRetryWithRuntimeChecks = false;
 
   /// Result of the dependence checks, indicating whether the checked
   /// dependences are safe for vectorization, require RT checks or are known to

llvm/lib/Analysis/LoopAccessAnalysis.cpp

@@ -589,11 +589,11 @@ void RuntimePointerChecking::groupChecks(
   // dependence. Not grouping the checks for a[i] and a[i + 9000] allows
   // us to perform an accurate check in this case.
   //
-  // The above case requires that we have an UnknownDependence between
-  // accesses to the same underlying object. This cannot happen unless
-  // FoundNonConstantDistanceDependence is set, and therefore UseDependencies
-  // is also false. In this case we will use the fallback path and create
-  // separate checking groups for all pointers.
+  // In the above case, we have a non-constant distance and an Unknown
+  // dependence between accesses to the same underlying object, and could retry
+  // with runtime checks. Therefore UseDependencies is false. In this case we
+  // will use the fallback path and create separate checking groups for all
+  // pointers.
 
   // If we don't have the dependency partitions, construct a new
   // checking pointer group for each pointer. This is also required
@@ -819,7 +819,7 @@ class AccessAnalysis {
   /// perform dependency checking.
   ///
   /// Note that this can later be cleared if we retry memcheck analysis without
-  /// dependency checking (i.e. FoundNonConstantDistanceDependence).
+  /// dependency checking (i.e. ShouldRetryWithRuntimeChecks).
   bool isDependencyCheckNeeded() const { return !CheckDeps.empty(); }
 
   /// We decided that no dependence analysis would be used.  Reset the state.
@@ -896,7 +896,7 @@ class AccessAnalysis {
   ///
   /// Note that, this is different from isDependencyCheckNeeded.  When we retry
   /// memcheck analysis without dependency checking
-  /// (i.e. FoundNonConstantDistanceDependence), isDependencyCheckNeeded is
+  /// (i.e. ShouldRetryWithRuntimeChecks), isDependencyCheckNeeded is
   /// cleared while this remains set if we have potentially dependent accesses.
   bool IsRTCheckAnalysisNeeded = false;
 
@@ -2079,11 +2079,10 @@ MemoryDepChecker::getDependenceDistanceStrideAndSize(
   if (StrideAScaled == StrideBScaled)
     CommonStride = StrideAScaled;
 
-  // TODO: FoundNonConstantDistanceDependence is used as a necessary condition
-  // to consider retrying with runtime checks. Historically, we did not set it
-  // when (unscaled) strides were different but there is no inherent reason to.
+  // TODO: Historically, we didn't retry with runtime checks when (unscaled)
+  // strides were different but there is no inherent reason to.
   if (!isa<SCEVConstant>(Dist))
-    FoundNonConstantDistanceDependence |= StrideAPtrInt == StrideBPtrInt;
+    ShouldRetryWithRuntimeChecks |= StrideAPtrInt == StrideBPtrInt;
 
   // If distance is a SCEVCouldNotCompute, return Unknown immediately.
   if (isa<SCEVCouldNotCompute>(Dist)) {
@@ -2712,7 +2711,7 @@ bool LoopAccessInfo::analyzeLoop(AAResults *AA, const LoopInfo *LI,
     DepsAreSafe =
         DepChecker->areDepsSafe(DepCands, Accesses.getDependenciesToCheck());
 
-    if (!DepsAreSafe && DepChecker->shouldRetryWithRuntimeCheck()) {
+    if (!DepsAreSafe && DepChecker->shouldRetryWithRuntimeChecks()) {
       LLVM_DEBUG(dbgs() << "LAA: Retrying with memory checks\n");
 
       // Clear the dependency checks. We assume they are not needed.