[CGP] Add support for sinking operands to their users, if they are free.

[fhahn]

Summary

This patch improves code generation for some AArch64 ACLE intrinsics. It adds
support to CGP to duplicate and sink operands to their user, if they can be
folded into a target instruction, like zexts and sub into usubl. It adds a
TargetLowering hook shouldSinkOperands, which looks at the operands of
instructions to see if sinking is profitable.

I decided to add a new target hook, as for the sinking to be profitable,
at least on AArch64, we have to look at multiple operands of an
instruction, instead of looking at the users of a zext for example.

The sinking is done in CGP, because it works around an instruction
selection limitation. If instruction selection is not limited to a
single basic block, this patch should not be needed any longer.

Alternatively this could be done in the LoopSink pass, which tries to
undo LICM for instructions in blocks that are not executed frequently.

Note that we do not force the operands to sink to have a single user,
because we duplicate them before sinking. Therefore this is only
desirable if they really can be done for free. Additionally we could
consider the impact on live ranges later on.

This should fix https://bugs.llvm.org/show_bug.cgi?id=40025.

As for performance, we have internal code that uses intrinsics and can
be speed up by 10% by this change.

I would appreciate any feedback, especially related to where to best put
the target hook.

[fhahn]

Adding Simon and Sanjay in case this might be useful for X86 as well.

[samparker]

Hi Florian,

I've had a case where I have wanted to do this, so it looks useful to me! CGP seems like a reasonable place to perform this too and I think TargetLowering is an aptly named place to include the hook.

cheers,

llvm/lib/CodeGen/CodeGenPrepare.cpp

5984

Is this order of ops enforced?

5991

This doesn't need to larger than OpsToSink, same goes for MaybeDead.

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

8292

I'm assuming cast is all you need, otherwise you're missing a nullptr check.

[spatel]

We already have various sinking transforms in CGP, so this is the right approach IMO. I do wonder if we could adapt the existing (cmp/and-mask/etc) sinking that we already have in CGP to use this hook as a refinement, but that can be a follow-up of this patch.

I'm not sure yet if/how we'd use this with x86 shuffles, but there's always hope. :)
You might be interested in looking at some recent DAGCombiner and x86 patches that are motivated by narrowing the width of vector ops and shuffles:
D55126
D55866
D56604
D56875
D57156
D57336

[fhahn]

Address Sam's comments. Thanks!

[fhahn]

llvm/lib/CodeGen/CodeGenPrepare.cpp

5984

Do you mean enforced as in by an assertion? Not at the moment. I think we would could check it with OrderedInstructions, if you think it would be beneficial.

[samparker]

LGTM with one comment.

llvm/lib/CodeGen/CodeGenPrepare.cpp

5984

It's okay, I hadn't noticed that you've added this requirement in the documentation.

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

8292

the same for below.

[fhahn]

Thanks Sam! I plan to commit this early next week, unless there are additional comments.

[fhahn]

In D57377#1377221, @spatel wrote:

We already have various sinking transforms in CGP, so this is the right approach IMO. I do wonder if we could adapt the existing (cmp/and-mask/etc) sinking that we already have in CGP to use this hook as a refinement, but that can be a follow-up of this patch.

Thanks, I'll take a look at that as a follow-up.

I'm not sure yet if/how we'd use this with x86 shuffles, but there's always hope. :)

It is not really related to shuffles, but rather to any operations that could be done for free with a target instruction.

You might be interested in looking at some recent DAGCombiner and x86 patches that are motivated by narrowing the width of vector ops and shuffles:
D55126
D55866
D56604
D56875
D57156
D57336

Great, those look quite useful!

llvm/include/llvm/CodeGen/TargetLowering.h

public:
   }
 
   /// Return true if sign-extension from FromTy to ToTy is cheaper than
   /// zero-extension.
   virtual bool isSExtCheaperThanZExt(EVT FromTy, EVT ToTy) const {
     return false;
   }
 
+  /// Return true if sinking I's operands to the same basic block as I is
+  /// profitable, e.g. because the operands can be folded into a target
+  /// instruction during instruction selection. After calling the function
+  /// \p Ops contains the Uses to sink ordered by dominance (dominating users
+  /// come first).
+  virtual bool shouldSinkOperands(Instruction *I,
+                                  SmallVectorImpl<Use *> &Ops) const {
+    return false;
+  }
+
   /// Return true if the target supplies and combines to a paired load
   /// two loaded values of type LoadedType next to each other in memory.
   /// RequiredAlignment gives the minimal alignment constraints that must be met
   /// to be able to select this paired load.
   ///
   /// This information is *not* used to generate actual paired loads, but it is
   /// used to generate a sequence of loads that is easier to combine into a
   /// paired load.

llvm/lib/CodeGen/CodeGenPrepare.cpp

private:
     bool splitLargeGEPOffsets();
     bool performAddressTypePromotion(
         Instruction *&Inst,
         bool AllowPromotionWithoutCommonHeader,
         bool HasPromoted, TypePromotionTransaction &TPT,
         SmallVectorImpl<Instruction *> &SpeculativelyMovedExts);
     bool splitBranchCondition(Function &F);
     bool simplifyOffsetableRelocate(Instruction &I);
+
+    bool tryToSinkFreeOperands(Instruction *I);
   };
 
 } // end anonymous namespace
 
 char CodeGenPrepare::ID = 0;
 
 INITIALIZE_PASS_BEGIN(CodeGenPrepare, DEBUG_TYPE,
                       "Optimize for code generation", false, false)
case Intrinsic::aarch64_stxr: {
         return false;
       // Sink a zext feeding stlxr/stxr before it, so it can be folded into it.
       ExtVal->moveBefore(CI);
       // Mark this instruction as "inserted by CGP", so that other
       // optimizations don't touch it.
       InsertedInsts.insert(ExtVal);
       return true;
     }
+
     case Intrinsic::launder_invariant_group:
     case Intrinsic::strip_invariant_group: {
       Value *ArgVal = II->getArgOperand(0);
       auto it = LargeOffsetGEPMap.find(II);
       if (it != LargeOffsetGEPMap.end()) {
           // Merge entries in LargeOffsetGEPMap to reflect the RAUW.
           // Make sure not to have to deal with iterator invalidation
           // after possibly adding ArgVal to LargeOffsetGEPMap.
bool CodeGenPrepare::optimizeShuffleVectorInst(ShuffleVectorInst *SVI) {
   if (SVI->use_empty()) {
     SVI->eraseFromParent();
     MadeChange = true;
   }
 
   return MadeChange;
 }
 
+bool CodeGenPrepare::tryToSinkFreeOperands(Instruction *I) {
+  // If the operands of I can be folded into a target instruction together with
+  // I, duplicate and sink them.
+  SmallVector<Use *, 4> OpsToSink;
+  if (!TLI || !TLI->shouldSinkOperands(I, OpsToSink))
+    return false;
+
+  // OpsToSink can contain multiple uses in a use chain (e.g.
+  // (%u1 with %u1 = shufflevector), (%u2 with %u2 = zext %u1)). The dominating
+  // uses must come first, which means they are sunk first, temporarily creating
+  // invalid IR. This will be fixed once their dominated users are sunk and
+  // updated.
+  BasicBlock *TargetBB = I->getParent();
+  bool Changed = false;
+  SmallVector<Use *, 4> ToReplace;
+  for (Use *U : OpsToSink) {
+    auto *UI = cast<Instruction>(U->get());
+    if (UI->getParent() == TargetBB || isa<PHINode>(UI))
+      continue;
+    ToReplace.push_back(U);
+  }
+
+  SmallPtrSet<Instruction *, 4> MaybeDead;
+  for (Use *U : ToReplace) {
+    auto *UI = cast<Instruction>(U->get());
+    Instruction *NI = UI->clone();
+    MaybeDead.insert(UI);
+    LLVM_DEBUG(dbgs() << "Sinking " << *UI << " to user " << *I << "\n");
+    NI->insertBefore(I);
+    InsertedInsts.insert(NI);
+    U->set(NI);
+    Changed = true;
+  }
+
+  // Remove instructions that are dead after sinking.
+  for (auto *I : MaybeDead)
+    if (!I->hasNUsesOrMore(1))
+      I->eraseFromParent();
+
+  return Changed;
+}
+
 bool CodeGenPrepare::optimizeSwitchInst(SwitchInst *SI) {
   if (!TLI || !DL)
     return false;
 
   Value *Cond = SI->getCondition();
   Type *OldType = Cond->getType();
   LLVMContext &Context = Cond->getContext();
   MVT RegType = TLI->getRegisterType(Context, TLI->getValueType(*DL, OldType));
if (GEPI->hasAllZeroIndices()) {
       return true;
     }
     if (tryUnmergingGEPsAcrossIndirectBr(GEPI, TTI)) {
       return true;
     }
     return false;
   }
 
+  if (tryToSinkFreeOperands(I))
+    return true;
+
   if (CallInst *CI = dyn_cast<CallInst>(I))
     return optimizeCallInst(CI, ModifiedDT);
 
   if (SelectInst *SI = dyn_cast<SelectInst>(I))
     return optimizeSelectInst(SI);
 
   if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I))
     return optimizeShuffleVectorInst(SVI);

llvm/lib/Target/AArch64/AArch64ISelLowering.h

public:
   bool isTruncateFree(EVT VT1, EVT VT2) const override;
 
   bool isProfitableToHoist(Instruction *I) const override;
 
   bool isZExtFree(Type *Ty1, Type *Ty2) const override;
   bool isZExtFree(EVT VT1, EVT VT2) const override;
   bool isZExtFree(SDValue Val, EVT VT2) const override;
 
+  bool shouldSinkOperands(Instruction *I,
+                          SmallVectorImpl<Use *> &Ops) const override;
+
   bool hasPairedLoad(EVT LoadedType, unsigned &RequiredAligment) const override;
 
   unsigned getMaxSupportedInterleaveFactor() const override { return 4; }
 
   bool lowerInterleavedLoad(LoadInst *LI,
                             ArrayRef<ShuffleVectorInst *> Shuffles,
                             ArrayRef<unsigned> Indices,
                             unsigned Factor) const override;

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/OperandTraits.h"
+#include "llvm/IR/PatternMatch.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Use.h"
 #include "llvm/IR/Value.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"

 #include <cstdlib>
 #include <iterator>
 #include <limits>
 #include <tuple>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
+using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "aarch64-lower"
 
 STATISTIC(NumTailCalls, "Number of tail calls");
 STATISTIC(NumShiftInserts, "Number of vector shift inserts");
 STATISTIC(NumOptimizedImms, "Number of times immediates were optimized");
 
 static cl::opt<bool>
for (const Use &U : Ext->uses()) {
     }
 
     // At this point we can use the bfm family, so this extension is free
     // for that use.
   }
   return true;
 }
 
+/// Check if both Op1 and Op2 are shufflevector extracts of either the lower
+/// or upper half of the vector elements.
+static bool areExtractShuffleVectors(Value *Op1, Value *Op2) {
+  auto areTypesHalfed = [](Value *FullV, Value *HalfV) {
+    auto *FullVT = cast<VectorType>(FullV->getType());
+    auto *HalfVT = cast<VectorType>(HalfV->getType());
+    return FullVT->getBitWidth() == 2 * HalfVT->getBitWidth();
+  };
+
+  auto extractHalf = [](Value *FullV, Value *HalfV) {
+    auto *FullVT = dyn_cast<VectorType>(FullV->getType());
+    auto *HalfVT = dyn_cast<VectorType>(HalfV->getType());
+    return FullVT->getNumElements() == 2 * HalfVT->getNumElements();
+  };
+
+  Constant *M1, *M2;
+  Value *S1Op1, *S2Op1;
+  if (!match(Op1, m_ShuffleVector(m_Value(S1Op1), m_Undef(), m_Constant(M1))) ||
+      !match(Op2, m_ShuffleVector(m_Value(S2Op1), m_Undef(), m_Constant(M2))))
+    return false;
+
+  // Check that the operands are half as wide as the result and we extract
+  // half of the elements of the input vectors.
+  if (!areTypesHalfed(S1Op1, Op1) || !areTypesHalfed(S2Op1, Op2) ||
+      !extractHalf(S1Op1, Op1) || !extractHalf(S2Op1, Op2))
+    return false;
+
+  // Check the mask extracts either the lower or upper half of vector
+  // elements.
+  int M1Start = -1;
+  int M2Start = -1;
+  int NumElements = cast<VectorType>(Op1->getType())->getNumElements() * 2;
+  if (!ShuffleVectorInst::isExtractSubvectorMask(M1, NumElements, M1Start) ||
+      !ShuffleVectorInst::isExtractSubvectorMask(M2, NumElements, M2Start) ||
+      M1Start != M2Start || (M1Start != 0 && M2Start != (NumElements / 2)))
+    return false;
+
+  return true;
+}
+
+/// Check if Ext1 and Ext2 are extends of the same type, doubling the bitwidth
+/// of the vector elements.
+static bool areExtractExts(Value *Ext1, Value *Ext2) {
+  auto areExtDoubled = [](Instruction *Ext) {
+    return Ext->getType()->getScalarSizeInBits() ==
+           2 * Ext->getOperand(0)->getType()->getScalarSizeInBits();
+  };
+
+  if (!match(Ext1, m_ZExtOrSExt(m_Value())) ||
+      !match(Ext2, m_ZExtOrSExt(m_Value())) ||
+      !areExtDoubled(cast<Instruction>(Ext1)) ||
+      !areExtDoubled(cast<Instruction>(Ext2)))
+    return false;
+
+  return true;
+}
+
+/// Check if sinking \p I's operands to I's basic block is profitable, because
+/// the operands can be folded into a target instruction, e.g.
+/// shufflevectors extracts and/or sext/zext can be folded into (u,s)subl(2).
+bool AArch64TargetLowering::shouldSinkOperands(
+    Instruction *I, SmallVectorImpl<Use *> &Ops) const {
+  if (!I->getType()->isVectorTy())
+    return false;
+
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+    switch (II->getIntrinsicID()) {
+    case Intrinsic::aarch64_neon_umull:
+      if (!areExtractShuffleVectors(II->getOperand(0), II->getOperand(1)))
+        return false;
+      Ops.push_back(&II->getOperandUse(0));
+      Ops.push_back(&II->getOperandUse(1));
+      return true;
+    default:
+      return false;
+    }
+  }
+
+  switch (I->getOpcode()) {
+  case Instruction::Sub:
+  case Instruction::Add: {
+    if (!areExtractExts(I->getOperand(0), I->getOperand(1)))
+      return false;
+
+    // If the exts' operands extract either the lower or upper elements, we
+    // can sink them too.
+    auto Ext1 = cast<Instruction>(I->getOperand(0));
+    auto Ext2 = cast<Instruction>(I->getOperand(1));
+    if (areExtractShuffleVectors(Ext1, Ext2)) {
+      Ops.push_back(&Ext1->getOperandUse(0));
+      Ops.push_back(&Ext2->getOperandUse(0));
+    }
+
+    Ops.push_back(&I->getOperandUse(0));
+    Ops.push_back(&I->getOperandUse(1));
+
+    return true;
+  }
+  default:
+    return false;
+  }
+  return false;
+}
+
 bool AArch64TargetLowering::hasPairedLoad(EVT LoadedType,
                                           unsigned &RequiredAligment) const {
   if (!LoadedType.isSimple() ||
       (!LoadedType.isInteger() && !LoadedType.isFloatingPoint()))
     return false;
   // Cyclone supports unaligned accesses.
   RequiredAligment = 0;
   unsigned NumBits = LoadedType.getSizeInBits();

llvm/test/Transforms/CodeGenPrepare/AArch64/sink-free-instructions.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -codegenprepare -S | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown"
+
+define <8 x i16> @sink_zext(<8 x i8> %a, <8 x i8> %b, i1 %c) {
+; CHECK-LABEL: @sink_zext(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[ZB_1:%.*]] = zext <8 x i8> [[B:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[TMP0:%.*]] = zext <8 x i8> [[A:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_1]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[ZB_2:%.*]] = zext <8 x i8> [[B]] to <8 x i16>
+; CHECK-NEXT:    [[TMP1:%.*]] = zext <8 x i8> [[A]] to <8 x i16>
+; CHECK-NEXT:    [[RES_2:%.*]] = sub <8 x i16> [[TMP1]], [[ZB_2]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_2]]
+;
+entry:
+  %za = zext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %zb.1 = zext <8 x i8> %b to <8 x i16>
+  %res.1 = add <8 x i16> %za, %zb.1
+  ret <8 x i16> %res.1
+
+if.else:
+  %zb.2 = zext <8 x i8> %b to <8 x i16>
+  %res.2 = sub <8 x i16> %za, %zb.2
+  ret <8 x i16> %res.2
+}
+
+define <8 x i16> @sink_sext(<8 x i8> %a, <8 x i8> %b, i1 %c) {
+; CHECK-LABEL: @sink_sext(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[ZB_1:%.*]] = sext <8 x i8> [[B:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[TMP0:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_1]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[ZB_2:%.*]] = sext <8 x i8> [[B]] to <8 x i16>
+; CHECK-NEXT:    [[TMP1:%.*]] = sext <8 x i8> [[A]] to <8 x i16>
+; CHECK-NEXT:    [[RES_2:%.*]] = sub <8 x i16> [[TMP1]], [[ZB_2]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_2]]
+;
+entry:
+  %za = sext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %zb.1 = sext <8 x i8> %b to <8 x i16>
+  %res.1 = add <8 x i16> %za, %zb.1
+  ret <8 x i16> %res.1
+
+if.else:
+  %zb.2 = sext <8 x i8> %b to <8 x i16>
+  %res.2 = sub <8 x i16> %za, %zb.2
+  ret <8 x i16> %res.2
+}
+
+define <8 x i16> @do_not_sink_nonfree_zext(<8 x i8> %a, <8 x i8> %b, i1 %c) {
+; CHECK-LABEL: @do_not_sink_nonfree_zext(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[ZB_1:%.*]] = sext <8 x i8> [[B:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[TMP0:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_1]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[ZB_2:%.*]] = sext <8 x i8> [[B]] to <8 x i16>
+; CHECK-NEXT:    ret <8 x i16> [[ZB_2]]
+;
+entry:
+  %za = sext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %zb.1 = sext <8 x i8> %b to <8 x i16>
+  %res.1 = add <8 x i16> %za, %zb.1
+  ret <8 x i16> %res.1
+
+if.else:
+  %zb.2 = sext <8 x i8> %b to <8 x i16>
+  ret <8 x i16> %zb.2
+}
+
+define <8 x i16> @do_not_sink_nonfree_sext(<8 x i8> %a, <8 x i8> %b, i1 %c) {
+; CHECK-LABEL: @do_not_sink_nonfree_sext(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[ZB_1:%.*]] = sext <8 x i8> [[B:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[TMP0:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_1]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[ZB_2:%.*]] = sext <8 x i8> [[B]] to <8 x i16>
+; CHECK-NEXT:    ret <8 x i16> [[ZB_2]]
+;
+entry:
+  %za = sext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %zb.1 = sext <8 x i8> %b to <8 x i16>
+  %res.1 = add <8 x i16> %za, %zb.1
+  ret <8 x i16> %res.1
+
+if.else:
+  %zb.2 = sext <8 x i8> %b to <8 x i16>
+  ret <8 x i16> %zb.2
+}
+
+; The masks used are suitable for umull, sink shufflevector to users.
+define <8 x i16> @sink_shufflevector_umull(<16 x i8> %a, <16 x i8> %b) {
+; CHECK-LABEL: @sink_shufflevector_umull(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 undef, label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[B:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:    [[TMP0:%.*]] = shufflevector <16 x i8> [[A:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:    [[VMULL0:%.*]] = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> [[TMP0]], <8 x i8> [[S2]])
+; CHECK-NEXT:    ret <8 x i16> [[VMULL0]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[S4:%.*]] = shufflevector <16 x i8> [[B]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <16 x i8> [[A]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; CHECK-NEXT:    [[VMULL1:%.*]] = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> [[TMP1]], <8 x i8> [[S4]])
+; CHECK-NEXT:    ret <8 x i16> [[VMULL1]]
+;
+entry:
+  %s1 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %s3 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  %s2 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %vmull0 = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> %s1, <8 x i8> %s2) #3
+  ret <8 x i16> %vmull0
+
+if.else:
+  %s4 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %vmull1 = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> %s3, <8 x i8> %s4) #3
+  ret <8 x i16> %vmull1
+}
+
+; Both exts and their shufflevector operands can be sunk.
+define <8 x i16> @sink_shufflevector_ext_subadd(<16 x i8> %a, <16 x i8> %b) {
+entry:
+  %s1 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %z1 = zext <8 x i8> %s1 to <8 x i16>
+  %s3 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %z3 = sext <8 x i8> %s3 to <8 x i16>
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  %s2 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %z2 = zext <8 x i8> %s2 to <8 x i16>
+  %res1 = add <8 x i16> %z1, %z2
+  ret <8 x i16> %res1
+
+if.else:
+  %s4 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %z4 = sext <8 x i8> %s4 to <8 x i16>
+  %res2 = sub <8 x i16> %z3, %z4
+  ret <8 x i16> %res2
+}
+
+
+declare void @user1(<8 x i16>)
+
+; Both exts and their shufflevector operands can be sunk.
+define <8 x i16> @sink_shufflevector_ext_subadd_multiuse(<16 x i8> %a, <16 x i8> %b) {
+entry:
+  %s1 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %z1 = zext <8 x i8> %s1 to <8 x i16>
+  %s3 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %z3 = sext <8 x i8> %s3 to <8 x i16>
+  call void @user1(<8 x i16> %z3)
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  %s2 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %z2 = zext <8 x i8> %s2 to <8 x i16>
+  %res1 = add <8 x i16> %z1, %z2
+  ret <8 x i16> %res1
+
+if.else:
+  %s4 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %z4 = sext <8 x i8> %s4 to <8 x i16>
+  %res2 = sub <8 x i16> %z3, %z4
+  ret <8 x i16> %res2
+}
+
+
+; The masks used are not suitable for umull, do not sink.
+define <8 x i16> @no_sink_shufflevector_umull(<16 x i8> %a, <16 x i8> %b) {
+; CHECK-LABEL: @no_sink_shufflevector_umull(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[S1:%.*]] = shufflevector <16 x i8> [[A:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 1, i32 5, i32 6, i32 7>
+; CHECK-NEXT:    [[S3:%.*]] = shufflevector <16 x i8> [[A]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; CHECK-NEXT:    br i1 undef, label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[B:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:    [[VMULL0:%.*]] = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> [[S1]], <8 x i8> [[S2]])
+; CHECK-NEXT:    ret <8 x i16> [[VMULL0]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[S4:%.*]] = shufflevector <16 x i8> [[B]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 10, i32 12, i32 13, i32 14, i32 15>
+; CHECK-NEXT:    [[VMULL1:%.*]] = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> [[S3]], <8 x i8> [[S4]])
+; CHECK-NEXT:    ret <8 x i16> [[VMULL1]]
+;
+entry:
+  %s1 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 1, i32 5, i32 6, i32 7>
+  %s3 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  %s2 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %vmull0 = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> %s1, <8 x i8> %s2) #3
+  ret <8 x i16> %vmull0
+
+if.else:
+  %s4 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 10, i32 12, i32 13, i32 14, i32 15>
+  %vmull1 = tail call <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8> %s3, <8 x i8> %s4) #3
+  ret <8 x i16> %vmull1
+}
+
+
+; Function Attrs: nounwind readnone
+declare <8 x i16> @llvm.aarch64.neon.umull.v8i16(<8 x i8>, <8 x i8>) #2