[LV] Remove IVEndValues, use resume value directly from fixed phi.(NFC)

Use the IV resume/end values from the phis in the scalar header,
instead of collecting them in a map. This removes some complexity
from the code dealing with induction resume values.

Analogous to 1edd220 which did the same for reduction resume values.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -537,8 +537,8 @@ class InnerLoopVectorizer {
 
   /// Set up the values of the IVs correctly when exiting the vector loop.
   virtual void fixupIVUsers(PHINode *OrigPhi, const InductionDescriptor &II,
-                            Value *VectorTripCount, Value *EndValue,
-                            BasicBlock *MiddleBlock, VPTransformState &State);
+                            Value *VectorTripCount, BasicBlock *MiddleBlock,
+                            VPTransformState &State);
 
   /// Iteratively sink the scalarized operands of a predicated instruction into
   /// the block that was created for it.
@@ -651,10 +651,6 @@ class InnerLoopVectorizer {
   // Record whether runtime checks are added.
   bool AddedSafetyChecks = false;
 
-  // Holds the end values for each induction variable. We save the end values
-  // so we can later fix-up the external users of the induction variables.
-  DenseMap<PHINode *, Value *> IVEndValues;
-
   /// BFI and PSI are used to check for profile guided size optimizations.
   BlockFrequencyInfo *BFI;
   ProfileSummaryInfo *PSI;
@@ -766,8 +762,7 @@ class EpilogueVectorizerMainLoop : public InnerLoopAndEpilogueVectorizer {
   void printDebugTracesAtEnd() override;
 
   void fixupIVUsers(PHINode *OrigPhi, const InductionDescriptor &II,
-                    Value *VectorTripCount, Value *EndValue,
-                    BasicBlock *MiddleBlock,
+                    Value *VectorTripCount, BasicBlock *MiddleBlock,
                     VPTransformState &State) override {};
 };
 
@@ -2599,7 +2594,7 @@ PHINode *InnerLoopVectorizer::createInductionResumeValue(
   assert(VectorTripCount && "Expected valid arguments");
 
   Instruction *OldInduction = Legal->getPrimaryInduction();
-  Value *&EndValue = IVEndValues[OrigPhi];
+  Value *EndValue = nullptr;
   Value *EndValueFromAdditionalBypass = AdditionalBypass.second;
   if (OrigPhi == OldInduction) {
     // We know what the end value is.
@@ -2756,7 +2751,7 @@ InnerLoopVectorizer::createVectorizedLoopSkeleton(
 // value for the IV when arriving directly from the middle block.
 void InnerLoopVectorizer::fixupIVUsers(PHINode *OrigPhi,
                                        const InductionDescriptor &II,
-                                       Value *VectorTripCount, Value *EndValue,
+                                       Value *VectorTripCount,
                                        BasicBlock *MiddleBlock,
                                        VPTransformState &State) {
   // There are two kinds of external IV usages - those that use the value
@@ -2768,6 +2763,10 @@ void InnerLoopVectorizer::fixupIVUsers(PHINode *OrigPhi,
 
   DenseMap<Value *, Value *> MissingVals;
 
+  Value *EndValue = cast<PHINode>(OrigPhi->getIncomingValueForBlock(
+                                      OrigLoop->getLoopPreheader()))
+                        ->getIncomingValueForBlock(MiddleBlock);
+
   // An external user of the last iteration's value should see the value that
   // the remainder loop uses to initialize its own IV.
   Value *PostInc = OrigPhi->getIncomingValueForBlock(OrigLoop->getLoopLatch());
@@ -2970,8 +2969,7 @@ void InnerLoopVectorizer::fixVectorizedLoop(VPTransformState &State) {
     // Fix-up external users of the induction variables.
     for (const auto &Entry : Legal->getInductionVars())
       fixupIVUsers(Entry.first, Entry.second,
-                   getOrCreateVectorTripCount(nullptr),
-                   IVEndValues[Entry.first], LoopMiddleBlock, State);
+                   getOrCreateVectorTripCount(nullptr), LoopMiddleBlock, State);
   }
 
   for (Instruction *PI : PredicatedInstructions)