Revert "[SLP]Reduce number of alternate instruction, where possible"

This caused assertion failures:

  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:16237:
  Value *llvm::slpvectorizer::BoUpSLP::vectorizeTree(TreeEntry *):
  Assertion `OpTE1.isSame( ArrayRef(E->Scalars).take_front(OpTE1.getVectorFactor())) && "Expected same first part of scalars."' failed.

See comment on the PR.

> Previous version was reviewed here #123360
> It is mostly the same, adjusted after graph-to-tree transformation

This reverts commit 7de895f.

Author: zmodem

llvm/include/llvm/Analysis/TargetTransformInfo.h

@@ -1771,10 +1771,6 @@ class TargetTransformInfo {
   /// scalable version of the vectorized loop.
   bool preferFixedOverScalableIfEqualCost() const;
 
-  /// \returns True if target prefers SLP vectorizer with altermate opcode
-  /// vectorization, false - otherwise.
-  bool preferAlternateOpcodeVectorization() const;
-
   /// \returns True if the target prefers reductions in loop.
   bool preferInLoopReduction(unsigned Opcode, Type *Ty) const;
 
@@ -2329,7 +2325,6 @@ class TargetTransformInfo::Concept {
   virtual bool preferInLoopReduction(unsigned Opcode, Type *Ty) const = 0;
   virtual bool preferPredicatedReductionSelect(unsigned Opcode,
                                                Type *Ty) const = 0;
-  virtual bool preferAlternateOpcodeVectorization() const = 0;
   virtual bool preferEpilogueVectorization() const = 0;
 
   virtual bool shouldExpandReduction(const IntrinsicInst *II) const = 0;
@@ -3140,9 +3135,6 @@ class TargetTransformInfo::Model final : public TargetTransformInfo::Concept {
   bool preferInLoopReduction(unsigned Opcode, Type *Ty) const override {
     return Impl.preferInLoopReduction(Opcode, Ty);
   }
-  bool preferAlternateOpcodeVectorization() const override {
-    return Impl.preferAlternateOpcodeVectorization();
-  }
   bool preferPredicatedReductionSelect(unsigned Opcode,
                                        Type *Ty) const override {
     return Impl.preferPredicatedReductionSelect(Opcode, Ty);

llvm/include/llvm/Analysis/TargetTransformInfoImpl.h

@@ -1007,7 +1007,6 @@ class TargetTransformInfoImplBase {
   bool preferFixedOverScalableIfEqualCost() const { return false; }
 
   bool preferInLoopReduction(unsigned Opcode, Type *Ty) const { return false; }
-  bool preferAlternateOpcodeVectorization() const { return true; }
 
   bool preferPredicatedReductionSelect(unsigned Opcode, Type *Ty) const {
     return false;

llvm/lib/Analysis/TargetTransformInfo.cpp

@@ -1384,10 +1384,6 @@ bool TargetTransformInfo::preferInLoopReduction(unsigned Opcode,
   return TTIImpl->preferInLoopReduction(Opcode, Ty);
 }
 
-bool TargetTransformInfo::preferAlternateOpcodeVectorization() const {
-  return TTIImpl->preferAlternateOpcodeVectorization();
-}
-
 bool TargetTransformInfo::preferPredicatedReductionSelect(unsigned Opcode,
                                                           Type *Ty) const {
   return TTIImpl->preferPredicatedReductionSelect(Opcode, Ty);

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h

@@ -125,8 +125,6 @@ class RISCVTTIImpl : public BasicTTIImplBase<RISCVTTIImpl> {
 
   unsigned getMaximumVF(unsigned ElemWidth, unsigned Opcode) const;
 
-  bool preferAlternateOpcodeVectorization() const { return false; }
-
   bool preferEpilogueVectorization() const {
     // Epilogue vectorization is usually unprofitable - tail folding or
     // a smaller VF would have been better.  This a blunt hammer - we

llvm/lib/Target/X86/X86TargetTransformInfo.h

@@ -292,7 +292,6 @@ class X86TTIImpl : public BasicTTIImplBase<X86TTIImpl> {
 
   TTI::MemCmpExpansionOptions enableMemCmpExpansion(bool OptSize,
                                                     bool IsZeroCmp) const;
-  bool preferAlternateOpcodeVectorization() const { return false; }
   bool prefersVectorizedAddressing() const;
   bool supportsEfficientVectorElementLoadStore() const;
   bool enableInterleavedAccessVectorization();