[NFC][loop-idiom] Rename Stores to IgnoredInsts; Fix a typo

[zhuhan0]

Summary

When dealing with memmove, we also add the load instruction to the ignored
instructions list passed to mayLoopAccessLocation. Renaming "Stores" to
"IgnoredInsts" to be more precise.

[yurai007]

llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

1444–1445

Out of the scope but maybe it's good opportunity to change it to something like "new call has been formed"?

[hoy]

LGTM.

[zhuhan0]

Address comment.

llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

bool LoopIdiomRecognize::processLoopMemCpy(MemCpyInst *MCI,
   if (StoreStrideValue.getBitWidth() > 64 || LoadStrideValue.getBitWidth() > 64)
     return false;
 
   if (SizeInBytes != StoreStrideValue && SizeInBytes != -StoreStrideValue) {
     ORE.emit([&]() {
       return OptimizationRemarkMissed(DEBUG_TYPE, "SizeStrideUnequal", MCI)
              << ore::NV("Inst", "memcpy") << " in "
              << ore::NV("Function", MCI->getFunction())
-             << " function will not be hoised: "
+             << " function will not be hoisted: "
              << ore::NV("Reason", "memcpy size is not equal to stride");
     });
     return false;
   }
 
   int64_t StoreStrideInt = StoreStrideValue.getSExtValue();
   int64_t LoadStrideInt = LoadStrideValue.getSExtValue();
   // Check if the load stride matches the store stride.

 
 /// mayLoopAccessLocation - Return true if the specified loop might access the
 /// specified pointer location, which is a loop-strided access.  The 'Access'
 /// argument specifies what the verboten forms of access are (read or write).
 static bool
 mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L,
                       const SCEV *BECount, const SCEV *StoreSizeSCEV,
                       AliasAnalysis &AA,
-                      SmallPtrSetImpl<Instruction *> &IgnoredStores) {
+                      SmallPtrSetImpl<Instruction *> &IgnoredInsts) {
   // Get the location that may be stored across the loop.  Since the access is
   // strided positively through memory, we say that the modified location starts
   // at the pointer and has infinite size.
   LocationSize AccessSize = LocationSize::afterPointer();
 
   // If the loop iterates a fixed number of times, we can refine the access size
   // to be exactly the size of the memset, which is (BECount+1)*StoreSize
   const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount);
   const SCEVConstant *ConstSize = dyn_cast<SCEVConstant>(StoreSizeSCEV);
   if (BECst && ConstSize)
     AccessSize = LocationSize::precise((BECst->getValue()->getZExtValue() + 1) *
                                        ConstSize->getValue()->getZExtValue());
 
   // TODO: For this to be really effective, we have to dive into the pointer
   // operand in the store.  Store to &A[i] of 100 will always return may alias
   // with store of &A[100], we need to StoreLoc to be "A" with size of 100,
   // which will then no-alias a store to &A[100].
   MemoryLocation StoreLoc(Ptr, AccessSize);
 
   for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
        ++BI)
     for (Instruction &I : **BI)
-      if (IgnoredStores.count(&I) == 0 &&
+      if (IgnoredInsts.count(&I) == 0 &&
           isModOrRefSet(
               intersectModRef(AA.getModRefInfo(&I, StoreLoc), Access)))
         return true;
   return false;
 }
 
 // If we have a negative stride, Start refers to the end of the memory location
 // we're trying to memset.  Therefore, we need to recompute the base pointer,
bool LoopIdiomRecognize::processLoopStoreOfLoopLoad(
   // changed the IR, even if we later clean up these added instructions. There
   // may be structural differences e.g. in the order of use lists not accounted
   // for in just a textual dump of the IR. This is written as a variable, even
   // though statically all the places this dominates could be replaced with
   // 'true', with the hope that anyone trying to be clever / "more precise" with
   // the return value will read this comment, and leave them alone.
   Changed = true;
 
-  SmallPtrSet<Instruction *, 2> Stores;
-  Stores.insert(TheStore);
+  SmallPtrSet<Instruction *, 2> IgnoredInsts;
+  IgnoredInsts.insert(TheStore);
 
   bool IsMemCpy = isa<MemCpyInst>(TheStore);
   const StringRef InstRemark = IsMemCpy ? "memcpy" : "load and store";
 
   bool UseMemMove =
       mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop, BECount,
-                            StoreSizeSCEV, *AA, Stores);
+                            StoreSizeSCEV, *AA, IgnoredInsts);
   if (UseMemMove) {
-    Stores.insert(TheLoad);
+    IgnoredInsts.insert(TheLoad);
     if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop,
-                              BECount, StoreSizeSCEV, *AA, Stores)) {
+                              BECount, StoreSizeSCEV, *AA, IgnoredInsts)) {
       ORE.emit([&]() {
         return OptimizationRemarkMissed(DEBUG_TYPE, "LoopMayAccessStore",
                                         TheStore)
                << ore::NV("Inst", InstRemark) << " in "
                << ore::NV("Function", TheStore->getFunction())
                << " function will not be hoisted: "
                << ore::NV("Reason", "The loop may access store location");
       });
       return Changed;
     }
-    Stores.erase(TheLoad);
+    IgnoredInsts.erase(TheLoad);
   }
 
   const SCEV *LdStart = LoadEv->getStart();
   unsigned LdAS = SourcePtr->getType()->getPointerAddressSpace();
 
   // Handle negative strided loops.
   if (IsNegStride)
     LdStart =
         getStartForNegStride(LdStart, BECount, IntIdxTy, StoreSizeSCEV, SE);
 
   // For a memcpy, we have to make sure that the input array is not being
   // mutated by the loop.
   Value *LoadBasePtr = Expander.expandCodeFor(
       LdStart, Builder.getInt8PtrTy(LdAS), Preheader->getTerminator());
 
   // If the store is a memcpy instruction, we must check if it will write to
   // the load memory locations. So remove it from the ignored stores.
   if (IsMemCpy)
-    Stores.erase(TheStore);
+    IgnoredInsts.erase(TheStore);
   if (mayLoopAccessLocation(LoadBasePtr, ModRefInfo::Mod, CurLoop, BECount,
-                            StoreSizeSCEV, *AA, Stores)) {
+                            StoreSizeSCEV, *AA, IgnoredInsts)) {
     ORE.emit([&]() {
       return OptimizationRemarkMissed(DEBUG_TYPE, "LoopMayAccessLoad", TheLoad)
              << ore::NV("Inst", InstRemark) << " in "
              << ore::NV("Function", TheStore->getFunction())
              << " function will not be hoisted: "
              << ore::NV("Reason", "The loop may access load location");
     });
     return Changed;
ORE.emit([&]() {
     return OptimizationRemark(DEBUG_TYPE, "ProcessLoopStoreOfLoopLoad",
                               NewCall->getDebugLoc(), Preheader)
            << "Formed a call to "
            << ore::NV("NewFunction", NewCall->getCalledFunction())
            << "() intrinsic from " << ore::NV("Inst", InstRemark)
            << " instruction in " << ore::NV("Function", TheStore->getFunction())
            << " function";
   });
 
-  // Okay, the memcpy has been formed.  Zap the original store and anything that
-  // feeds into it.
+  // Okay, a new call to memcpy/memmove has been formed.  Zap the original store
+  // and anything that feeds into it.
   if (MSSAU)
     MSSAU->removeMemoryAccess(TheStore, true);
   deleteDeadInstruction(TheStore);
   if (MSSAU && VerifyMemorySSA)
     MSSAU->getMemorySSA()->verifyMemorySSA();
   if (UseMemMove)
     ++NumMemMove;
   else