Revert r182909.

PR/16177


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182919 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombine.h

@@ -234,7 +234,6 @@ private:
   bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
   Value *EmitGEPOffset(User *GEP);
   Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
-  Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
 
 public:
   // InsertNewInstBefore - insert an instruction New before instruction Old

lib/Transforms/InstCombine/InstCombineVectorOps.cpp

@@ -494,241 +494,6 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
   return 0;
 }
 
-/// Return true if we can evaluate the specified expression tree if the vector
-/// elements were shuffled in a different order.
-static bool CanEvaluateShuffled(Value *V, ArrayRef<int> Mask,
-                                unsigned Depth = 100) {
-  // We can always reorder the elements of a constant.
-  if (isa<Constant>(V))
-    return true;
-
-  // We won't reorder vector arguments. No IPO here.
-  Instruction *I = dyn_cast<Instruction>(V);
-  if (!I) return false;
-
-  // Two users may expect different orders of the elements. Don't try it.
-  if (!I->hasOneUse())
-    return false;
-
-  if (Depth == 0) return false;
-
-  switch (I->getOpcode()) {
-    case Instruction::Add:
-    case Instruction::FAdd:
-    case Instruction::Sub:
-    case Instruction::FSub:
-    case Instruction::Mul:
-    case Instruction::FMul:
-    case Instruction::UDiv:
-    case Instruction::SDiv:
-    case Instruction::FDiv:
-    case Instruction::URem:
-    case Instruction::SRem:
-    case Instruction::FRem:
-    case Instruction::Shl:
-    case Instruction::LShr:
-    case Instruction::AShr:
-    case Instruction::And:
-    case Instruction::Or:
-    case Instruction::Xor:
-    case Instruction::ICmp:
-    case Instruction::FCmp:
-    case Instruction::Trunc:
-    case Instruction::ZExt:
-    case Instruction::SExt:
-    case Instruction::FPToUI:
-    case Instruction::FPToSI:
-    case Instruction::UIToFP:
-    case Instruction::SIToFP:
-    case Instruction::FPTrunc:
-    case Instruction::FPExt:
-    case Instruction::GetElementPtr: {
-      for (int i = 0, e = I->getNumOperands(); i != e; ++i) {
-        if (!CanEvaluateShuffled(I->getOperand(i), Mask, Depth-1))
-          return false;
-      }
-      return true;
-    }
-    case Instruction::InsertElement: {
-      ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(2));
-      if (!CI) return false;
-      int ElementNumber = CI->getLimitedValue();
-
-      // Verify that 'CI' does not occur twice in Mask. A single 'insertelement'
-      // can't put an element into multiple indices.
-      bool SeenOnce = false;
-      for (int i = 0, e = Mask.size(); i != e; ++i) {
-        if (Mask[i] == ElementNumber) {
-          if (SeenOnce)
-            return false;
-          SeenOnce = true;
-        }
-      }
-      return CanEvaluateShuffled(I->getOperand(0), Mask, Depth-1);
-    }
-  }
-  return false;
-}
-
-/// Rebuild a new instruction just like 'I' but with the new operands given.
-/// In the event of type mismatch, the type of the operands is correct.
-static Value *BuildNew(Instruction *I, ArrayRef<Value*> NewOps) {
-  // We don't want to use the IRBuilder here because we want the replacement
-  // instructions to appear next to 'I', not the builder's insertion point.
-  switch (I->getOpcode()) {
-    case Instruction::Add:
-    case Instruction::FAdd:
-    case Instruction::Sub:
-    case Instruction::FSub:
-    case Instruction::Mul:
-    case Instruction::FMul:
-    case Instruction::UDiv:
-    case Instruction::SDiv:
-    case Instruction::FDiv:
-    case Instruction::URem:
-    case Instruction::SRem:
-    case Instruction::FRem:
-    case Instruction::Shl:
-    case Instruction::LShr:
-    case Instruction::AShr:
-    case Instruction::And:
-    case Instruction::Or:
-    case Instruction::Xor: {
-      BinaryOperator *BO = cast<BinaryOperator>(I);
-      assert(NewOps.size() == 2 && "binary operator with #ops != 2");
-      BinaryOperator *New =
-          BinaryOperator::Create(cast<BinaryOperator>(I)->getOpcode(),
-                                 NewOps[0], NewOps[1], "", BO);
-      if (isa<OverflowingBinaryOperator>(BO)) {
-        New->setHasNoUnsignedWrap(BO->hasNoUnsignedWrap());
-        New->setHasNoSignedWrap(BO->hasNoSignedWrap());
-      }
-      if (isa<PossiblyExactOperator>(BO)) {
-        New->setIsExact(BO->isExact());
-      }
-      return New;
-    }
-    case Instruction::ICmp:
-      assert(NewOps.size() == 2 && "icmp with #ops != 2");
-      return new ICmpInst(I, cast<ICmpInst>(I)->getPredicate(),
-                          NewOps[0], NewOps[1]);
-    case Instruction::FCmp:
-      assert(NewOps.size() == 2 && "fcmp with #ops != 2");
-      return new FCmpInst(I, cast<FCmpInst>(I)->getPredicate(),
-                          NewOps[0], NewOps[1]);
-    case Instruction::Trunc:
-    case Instruction::ZExt:
-    case Instruction::SExt:
-    case Instruction::FPToUI:
-    case Instruction::FPToSI:
-    case Instruction::UIToFP:
-    case Instruction::SIToFP:
-    case Instruction::FPTrunc:
-    case Instruction::FPExt: {
-      // It's possible that the mask has a different number of elements from
-      // the original cast. We recompute the destination type to match the mask.
-      Type *DestTy =
-          VectorType::get(I->getType()->getScalarType(),
-                          NewOps[0]->getType()->getVectorNumElements());
-      assert(NewOps.size() == 1 && "cast with #ops != 1");
-      return CastInst::Create(cast<CastInst>(I)->getOpcode(), NewOps[0], DestTy,
-                              "", I);
-    }
-    case Instruction::GetElementPtr: {
-      Value *Ptr = NewOps[0];
-      ArrayRef<Value*> Idx = NewOps.slice(1);
-      GetElementPtrInst *GEP = GetElementPtrInst::Create(Ptr, Idx, "", I);
-      GEP->setIsInBounds(cast<GetElementPtrInst>(I)->isInBounds());
-      return GEP;
-    }
-  }
-  llvm_unreachable("failed to rebuild vector instructions");
-}
-
-Value *
-InstCombiner::EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask) {
-  // Mask.size() does not need to be equal to the number of vector elements.
-
-  assert(V->getType()->isVectorTy() && "can't reorder non-vector elements");
-  if (isa<UndefValue>(V)) {
-    return UndefValue::get(VectorType::get(V->getType()->getScalarType(),
-                                           Mask.size()));
-  }
-  if (isa<ConstantAggregateZero>(V)) {
-    return ConstantAggregateZero::get(
-               VectorType::get(V->getType()->getScalarType(),
-                               Mask.size()));
-  }
-  if (Constant *C = dyn_cast<Constant>(V)) {
-    SmallVector<Constant *, 16> MaskValues;
-    for (int i = 0, e = Mask.size(); i != e; ++i) {
-      if (Mask[i] == -1)
-        MaskValues.push_back(UndefValue::get(Builder->getInt32Ty()));
-      else
-        MaskValues.push_back(Builder->getInt32(Mask[i]));
-    }
-    return ConstantExpr::getShuffleVector(C, UndefValue::get(C->getType()),
-                                          ConstantVector::get(MaskValues));
-  }
-
-  Instruction *I = cast<Instruction>(V);
-  switch (I->getOpcode()) {
-    case Instruction::Add:
-    case Instruction::FAdd:
-    case Instruction::Sub:
-    case Instruction::FSub:
-    case Instruction::Mul:
-    case Instruction::FMul:
-    case Instruction::UDiv:
-    case Instruction::SDiv:
-    case Instruction::FDiv:
-    case Instruction::URem:
-    case Instruction::SRem:
-    case Instruction::FRem:
-    case Instruction::Shl:
-    case Instruction::LShr:
-    case Instruction::AShr:
-    case Instruction::And:
-    case Instruction::Or:
-    case Instruction::Xor:
-    case Instruction::ICmp:
-    case Instruction::FCmp:
-    case Instruction::Trunc:
-    case Instruction::ZExt:
-    case Instruction::SExt:
-    case Instruction::FPToUI:
-    case Instruction::FPToSI:
-    case Instruction::UIToFP:
-    case Instruction::SIToFP:
-    case Instruction::FPTrunc:
-    case Instruction::FPExt:
-    case Instruction::Select:
-    case Instruction::GetElementPtr: {
-      SmallVector<Value*, 8> NewOps;
-      bool NeedsRebuild = (Mask.size() != I->getType()->getVectorNumElements());
-      for (int i = 0, e = I->getNumOperands(); i != e; ++i) {
-        Value *V = EvaluateInDifferentElementOrder(I->getOperand(i), Mask);
-        NewOps.push_back(V);
-        NeedsRebuild |= (V != I->getOperand(i));
-      }
-      if (NeedsRebuild) {
-        return BuildNew(I, NewOps);
-      }
-      return I;
-    }
-    case Instruction::InsertElement: {
-      uint32_t Element = cast<ConstantInt>(I->getOperand(2))->getLimitedValue();
-      if (Element >= Mask.size()) {
-        // Such instructions are valid and exhibit undefined behaviour.
-        return UndefValue::get(I->getType());
-      }
-      Value *V = EvaluateInDifferentElementOrder(I->getOperand(0), Mask);
-      return InsertElementInst::Create(V, I->getOperand(1),
-                                       Builder->getInt32(Mask[Element]), "", I);
-    }
-  }
-  llvm_unreachable("failed to reorder elements of vector instruction!");
-}
 
 Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   Value *LHS = SVI.getOperand(0);
@@ -809,16 +574,6 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
     if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
   }
 
-  if (isa<UndefValue>(RHS) &&
-      // This isn't necessary for correctness, but the comment block below
-      // claims that there are cases where folding two shuffles into one would
-      // cause worse codegen on some targets.
-      !isa<ShuffleVectorInst>(LHS) &&
-      CanEvaluateShuffled(LHS, Mask)) {
-    Value *V = EvaluateInDifferentElementOrder(LHS, Mask);
-    return ReplaceInstUsesWith(SVI, V);
-  }
-
   // If the LHS is a shufflevector itself, see if we can combine it with this
   // one without producing an unusual shuffle.
   // Cases that might be simplified:

test/Transforms/InstCombine/vec_shuffle.ll

@@ -153,15 +153,3 @@ define <8 x i8> @test12a(<8 x i8> %tmp6, <8 x i8> %tmp2) nounwind {
   ret <8 x i8> %tmp3
 }
 
-define <2 x i8> @test13(i8 %x1, i8 %x2) {
-; CHECK: @test13
-; CHECK-NEXT: insertelement {{.*}} undef, i8 %x1, i32 1
-; CHECK-NEXT: insertelement {{.*}} i8 %x2, i32 0
-; CHECK-NEXT: add {{.*}} <i8 7, i8 5>
-; CHECK-NEXT: ret
-  %A = insertelement <2 x i8> undef, i8 %x1, i32 0
-  %B = insertelement <2 x i8> %A, i8 %x2, i32 1
-  %C = add <2 x i8> %B, <i8 5, i8 7>
-  %D = shufflevector <2 x i8> %C, <2 x i8> undef, <2 x i32> <i32 1, i32 0>
-  ret <2 x i8> %D
-}