[LAA] NFC: Rename [get]MaxSafeRegisterWidth -> [get]MaxSafeVectorWidthInBits

MaxSafeRegisterWidth is a misnomer since it actually returns the maximum
safe vector width. Register suggests it relates directly to a physical
register where it could be a vector spanning one or more physical
registers.

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D91727

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

@@ -171,7 +171,8 @@ public:
 
   MemoryDepChecker(PredicatedScalarEvolution &PSE, const Loop *L)
       : PSE(PSE), InnermostLoop(L), AccessIdx(0), MaxSafeDepDistBytes(0),
-        MaxSafeRegisterWidth(-1U), FoundNonConstantDistanceDependence(false),
+        MaxSafeVectorWidthInBits(-1U),
+        FoundNonConstantDistanceDependence(false),
         Status(VectorizationSafetyStatus::Safe), RecordDependences(true) {}
 
   /// Register the location (instructions are given increasing numbers)
@@ -210,7 +211,9 @@ public:
 
   /// Return the number of elements that are safe to operate on
   /// simultaneously, multiplied by the size of the element in bits.
-  uint64_t getMaxSafeRegisterWidth() const { return MaxSafeRegisterWidth; }
+  uint64_t getMaxSafeVectorWidthInBits() const {
+    return MaxSafeVectorWidthInBits;
+  }
 
   /// In same cases when the dependency check fails we can still
   /// vectorize the loop with a dynamic array access check.
@@ -275,7 +278,7 @@ private:
   /// operate on simultaneously, multiplied by the size of the element in bits.
   /// The size of the element is taken from the memory access that is most
   /// restrictive.
-  uint64_t MaxSafeRegisterWidth;
+  uint64_t MaxSafeVectorWidthInBits;
 
   /// If we see a non-constant dependence distance we can still try to
   /// vectorize this loop with runtime checks.

llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h

@@ -311,8 +311,8 @@ public:
 
   unsigned getMaxSafeDepDistBytes() { return LAI->getMaxSafeDepDistBytes(); }
 
-  uint64_t getMaxSafeRegisterWidth() const {
-    return LAI->getDepChecker().getMaxSafeRegisterWidth();
+  uint64_t getMaxSafeVectorWidthInBits() const {
+    return LAI->getDepChecker().getMaxSafeVectorWidthInBits();
   }
 
   bool hasStride(Value *V) { return LAI->hasStride(V); }

llvm/lib/Analysis/LoopAccessAnalysis.cpp

@@ -1654,7 +1654,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
   LLVM_DEBUG(dbgs() << "LAA: Positive distance " << Val.getSExtValue()
                     << " with max VF = " << MaxVF << '\n');
   uint64_t MaxVFInBits = MaxVF * TypeByteSize * 8;
-  MaxSafeRegisterWidth = std::min(MaxSafeRegisterWidth, MaxVFInBits);
+  MaxSafeVectorWidthInBits = std::min(MaxSafeVectorWidthInBits, MaxVFInBits);
   return Dependence::BackwardVectorizable;
 }
 

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -5369,9 +5369,9 @@ LoopVectorizationCostModel::computeFeasibleMaxVF(unsigned ConstTripCount) {
   // It is computed by MaxVF * sizeOf(type) * 8, where type is taken from
   // the memory accesses that is most restrictive (involved in the smallest
   // dependence distance).
-  unsigned MaxSafeRegisterWidth = Legal->getMaxSafeRegisterWidth();
+  unsigned MaxSafeVectorWidthInBits = Legal->getMaxSafeVectorWidthInBits();
 
-  WidestRegister = std::min(WidestRegister, MaxSafeRegisterWidth);
+  WidestRegister = std::min(WidestRegister, MaxSafeVectorWidthInBits);
 
   // Ensure MaxVF is a power of 2; the dependence distance bound may not be.
   // Note that both WidestRegister and WidestType may not be a powers of 2.