[NFC][SLP] Cleanup: Replace Value* operand with Instruction* in `vectorizeRootInstruction()` and `vectorizeHorReduction()`

[vporpo]

Summary

This makes it explicit that these functions work with instructions, and avoids
calling them if the operand is not an instruction.

[ABataev]

LG with a nit

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

14550

Just if (Root &&...

[vporpo]

Addressed comments

[ABataev]

LG

llvm/include/llvm/Transforms/Vectorize/SLPVectorizer.h

private:
 
   /// Vectorize the index computations of the getelementptr instructions
   /// collected in GEPs.
   bool vectorizeGEPIndices(BasicBlock *BB, slpvectorizer::BoUpSLP &R);
 
   /// Try to find horizontal reduction or otherwise, collect instructions
   /// for postponed vectorization attempts.
   /// \a P if not null designates phi node the reduction is fed into
-  /// (with reduction operators \a V or one of its operands, in a basic block
+  /// (with reduction operators \a Root or one of its operands, in a basic block
   /// \a BB).
   /// \returns true if a horizontal reduction was matched and reduced.
   /// \returns false if \a V is null or not an instruction,
   /// or a horizontal reduction was not matched or not possible.
-  bool vectorizeHorReduction(PHINode *P, Value *V, BasicBlock *BB,
+  bool vectorizeHorReduction(PHINode *P, Instruction *Root, BasicBlock *BB,
                              slpvectorizer::BoUpSLP &R,
                              TargetTransformInfo *TTI,
                              SmallVectorImpl<WeakTrackingVH> &PostponedInsts);
 
   /// Make an attempt to vectorize reduction and then try to vectorize
   /// postponed binary operations.
   /// \returns true on any successfull vectorization.
-  bool vectorizeRootInstruction(PHINode *P, Value *V, BasicBlock *BB,
+  bool vectorizeRootInstruction(PHINode *P, Instruction *Root, BasicBlock *BB,
                                 slpvectorizer::BoUpSLP &R,
                                 TargetTransformInfo *TTI);
 
   /// Try to vectorize trees that start at insertvalue instructions.
   bool vectorizeInsertValueInst(InsertValueInst *IVI, BasicBlock *BB,
                                 slpvectorizer::BoUpSLP &R);
 
   /// Try to vectorize trees that start at insertelement instructions.

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

static bool findBuildAggregate(Instruction *LastInsertInst,
   llvm::erase_value(BuildVectorOpds, nullptr);
   llvm::erase_value(InsertElts, nullptr);
   if (BuildVectorOpds.size() >= 2)
     return true;
 
   return false;
 }
 
-/// Try and get a reduction value from a phi node.
+/// Try and get a reduction instruction from a phi node.
 ///
 /// Given a phi node \p P in a block \p ParentBB, consider possible reductions
 /// if they come from either \p ParentBB or a containing loop latch.
 ///
 /// \returns A candidate reduction value if possible, or \code nullptr \endcode
 /// if not possible.
-static Value *getReductionValue(const DominatorTree *DT, PHINode *P,
+static Instruction *getReductionInstr(const DominatorTree *DT, PHINode *P,
                                       BasicBlock *ParentBB, LoopInfo *LI) {
   // There are situations where the reduction value is not dominated by the
   // reduction phi. Vectorizing such cases has been reported to cause
   // miscompiles. See PR25787.
   auto DominatedReduxValue = [&](Value *R) {
     return isa<Instruction>(R) &&
            DT->dominates(P->getParent(), cast<Instruction>(R)->getParent());
   };
 
-  Value *Rdx = nullptr;
+  Instruction *Rdx = nullptr;
 
   // Return the incoming value if it comes from the same BB as the phi node.
   if (P->getIncomingBlock(0) == ParentBB) {
-    Rdx = P->getIncomingValue(0);
+    Rdx = dyn_cast<Instruction>(P->getIncomingValue(0));
   } else if (P->getIncomingBlock(1) == ParentBB) {
-    Rdx = P->getIncomingValue(1);
+    Rdx = dyn_cast<Instruction>(P->getIncomingValue(1));
   }
 
   if (Rdx && DominatedReduxValue(Rdx))
     return Rdx;
 
   // Otherwise, check whether we have a loop latch to look at.
   Loop *BBL = LI->getLoopFor(ParentBB);
   if (!BBL)
     return nullptr;
   BasicBlock *BBLatch = BBL->getLoopLatch();
   if (!BBLatch)
     return nullptr;
 
   // There is a loop latch, return the incoming value if it comes from
   // that. This reduction pattern occasionally turns up.
   if (P->getIncomingBlock(0) == BBLatch) {
-    Rdx = P->getIncomingValue(0);
+    Rdx = dyn_cast<Instruction>(P->getIncomingValue(0));
   } else if (P->getIncomingBlock(1) == BBLatch) {
-    Rdx = P->getIncomingValue(1);
+    Rdx = dyn_cast<Instruction>(P->getIncomingValue(1));
   }
 
   if (Rdx && DominatedReduxValue(Rdx))
     return Rdx;
 
   return nullptr;
 }
 
static Instruction *tryGetScondaryReductionRoot(PHINode *Phi,
   if (LHS == Phi)
     return dyn_cast<Instruction>(RHS);
   if (RHS == Phi)
     return dyn_cast<Instruction>(LHS);
   return nullptr;
 }
 
 bool SLPVectorizerPass::vectorizeHorReduction(
-    PHINode *P, Value *V, BasicBlock *BB, BoUpSLP &R, TargetTransformInfo *TTI,
+    PHINode *P, Instruction *Root, BasicBlock *BB, BoUpSLP &R, TargetTransformInfo *TTI,
     SmallVectorImpl<WeakTrackingVH> &PostponedInsts) {
   if (!ShouldVectorizeHor)
     return false;
-
-  auto *Root = dyn_cast_or_null<Instruction>(V);
-  if (!Root)
-    return false;
-
   if (!isa<BinaryOperator>(Root))
     P = nullptr;
 
   if (Root->getParent() != BB || isa<PHINode>(Root))
     return false;
   // Start analysis starting from Root instruction. If horizontal reduction is
   // found, try to vectorize it. If it is not a horizontal reduction or
   // vectorization is not possible or not effective, and currently analyzed
if (++Level < RecursionMaxDepth)
             // separately.
             if (!isa<PHINode, CmpInst, InsertElementInst, InsertValueInst>(I) &&
                 !R.isDeleted(I) && I->getParent() == BB)
               Stack.emplace(I, Level);
   }
   return Res;
 }
 
-bool SLPVectorizerPass::vectorizeRootInstruction(PHINode *P, Value *V,
+bool SLPVectorizerPass::vectorizeRootInstruction(PHINode *P, Instruction *Root,
                                                  BasicBlock *BB, BoUpSLP &R,
                                                  TargetTransformInfo *TTI) {
   SmallVector<WeakTrackingVH> PostponedInsts;
-  bool Res = vectorizeHorReduction(P, V, BB, R, TTI, PostponedInsts);
+  bool Res = vectorizeHorReduction(P, Root, BB, R, TTI, PostponedInsts);
   Res |= tryToVectorize(PostponedInsts, R);
   return Res;
 }
 
 bool SLPVectorizerPass::tryToVectorize(ArrayRef<WeakTrackingVH> Insts,
                                        BoUpSLP &R) {
   bool Res = false;
   for (Value *V : Insts)
bool SLPVectorizerPass::vectorizeSimpleInstructions(InstSetVector &Instructions,
   OpsChanged |= tryToVectorize(PostponedInsts, R);
 
   if (AtTerminator) {
     // Try to find reductions first.
     for (Instruction *I : PostponedCmps) {
       if (R.isDeleted(I))
         continue;
       for (Value *Op : I->operands())
-        OpsChanged |= vectorizeRootInstruction(nullptr, Op, BB, R, TTI);
+        if (auto *RootOp = dyn_cast<Instruction>(Op))
+          OpsChanged |= vectorizeRootInstruction(nullptr, RootOp, BB, R, TTI);
     }
     // Try to vectorize operands as vector bundles.
     for (Instruction *I : PostponedCmps) {
       if (R.isDeleted(I))
         continue;
       OpsChanged |= tryToVectorize(I, R);
     }
     // Try to vectorize list of compares.
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
     if (isa<DbgInfoIntrinsic>(it))
       continue;
 
     // Try to vectorize reductions that use PHINodes.
     if (PHINode *P = dyn_cast<PHINode>(it)) {
       // Check that the PHI is a reduction PHI.
       if (P->getNumIncomingValues() == 2) {
         // Try to match and vectorize a horizontal reduction.
-        if (vectorizeRootInstruction(P, getReductionValue(DT, P, BB, LI), BB, R,
-                                     TTI)) {
+        Instruction *Root = getReductionInstr(DT, P, BB, LI);
+        if (Root && vectorizeRootInstruction(P, Root, BB, R, TTI)) {
           Changed = true;
           it = BB->begin();
           e = BB->end();
           continue;
         }
       }
       // Try to vectorize the incoming values of the PHI, to catch reductions
       // that feed into PHIs.
       for (unsigned I = 0, E = P->getNumIncomingValues(); I != E; I++) {
         // Skip if the incoming block is the current BB for now. Also, bypass
         // unreachable IR for efficiency and to avoid crashing.
         // TODO: Collect the skipped incoming values and try to vectorize them
         // after processing BB.
         if (BB == P->getIncomingBlock(I) ||
             !DT->isReachableFromEntry(P->getIncomingBlock(I)))
           continue;
 
         // Postponed instructions should not be vectorized here, delay their
         // vectorization.
         if (auto *PI = dyn_cast<Instruction>(P->getIncomingValue(I));
             PI && !PostProcessInstructions.contains(PI))
-          Changed |= vectorizeRootInstruction(nullptr, P->getIncomingValue(I),
+          Changed |= vectorizeRootInstruction(nullptr, PI,
                                               P->getIncomingBlock(I), R, TTI);
       }
       continue;
     }
 
     // Ran into an instruction without users, like terminator, or function call
     // with ignored return value, store. Ignore unused instructions (basing on
     // instruction type, except for CallInst and InvokeInst).
if (it->use_empty() &&
       }
       if (TryToVectorizeRoot) {
         for (auto *V : it->operand_values()) {
           // Postponed instructions should not be vectorized here, delay their
           // vectorization.
           if (auto *VI = dyn_cast<Instruction>(V);
               VI && !PostProcessInstructions.contains(VI))
             // Try to match and vectorize a horizontal reduction.
-            OpsChanged |= vectorizeRootInstruction(nullptr, V, BB, R, TTI);
+            OpsChanged |= vectorizeRootInstruction(nullptr, VI, BB, R, TTI);
         }
       }
       // Start vectorization of post-process list of instructions from the
       // top-tree instructions to try to vectorize as many instructions as
       // possible.
       OpsChanged |= vectorizeSimpleInstructions(PostProcessInstructions, BB, R,
                                                 it->isTerminator());
       if (OpsChanged) {