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//===- Scalarizer.cpp - Scalarize vector operations -----------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This pass converts vector operations into scalar operations, in order
// to expose optimization opportunities on the individual scalar operations.
// It is mainly intended for targets that do not have vector units, but it
// may also be useful for revectorizing code to different vector widths.
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Options.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/Scalarizer.h"
#include <cassert>
#include <cstdint>
#include <iterator>
#include <map>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "scalarizer"
// This is disabled by default because having separate loads and stores
// makes it more likely that the -combiner-alias-analysis limits will be
// reached.
static cl::opt<bool>
ScalarizeLoadStore("scalarize-load-store", cl::init(false), cl::Hidden,
cl::desc("Allow the scalarizer pass to scalarize loads and store"));
namespace {
// Used to store the scattered form of a vector.
using ValueVector = SmallVector<Value *, 8>;
// Used to map a vector Value to its scattered form. We use std::map
// because we want iterators to persist across insertion and because the
// values are relatively large.
using ScatterMap = std::map<Value *, ValueVector>;
// Lists Instructions that have been replaced with scalar implementations,
// along with a pointer to their scattered forms.
using GatherList = SmallVector<std::pair<Instruction *, ValueVector *>, 16>;
// Provides a very limited vector-like interface for lazily accessing one
// component of a scattered vector or vector pointer.
class Scatterer {
Scatterer() = default;
// Scatter V into Size components. If new instructions are needed,
// insert them before BBI in BB. If Cache is nonnull, use it to cache
// the results.
Scatterer(BasicBlock *bb, BasicBlock::iterator bbi, Value *v,
ValueVector *cachePtr = nullptr);
// Return component I, creating a new Value for it if necessary.
Value *operator[](unsigned I);
// Return the number of components.
unsigned size() const { return Size; }
BasicBlock *BB;
BasicBlock::iterator BBI;
Value *V;
ValueVector *CachePtr;
PointerType *PtrTy;
ValueVector Tmp;
unsigned Size;
// FCmpSpliiter(FCI)(Builder, X, Y, Name) uses Builder to create an FCmp
// called Name that compares X and Y in the same way as FCI.
struct FCmpSplitter {
FCmpSplitter(FCmpInst &fci) : FCI(fci) {}
Value *operator()(IRBuilder<> &Builder, Value *Op0, Value *Op1,
const Twine &Name) const {
return Builder.CreateFCmp(FCI.getPredicate(), Op0, Op1, Name);
FCmpInst &FCI;
// ICmpSpliiter(ICI)(Builder, X, Y, Name) uses Builder to create an ICmp
// called Name that compares X and Y in the same way as ICI.
struct ICmpSplitter {
ICmpSplitter(ICmpInst &ici) : ICI(ici) {}
Value *operator()(IRBuilder<> &Builder, Value *Op0, Value *Op1,
const Twine &Name) const {
return Builder.CreateICmp(ICI.getPredicate(), Op0, Op1, Name);
ICmpInst &ICI;
// UnarySpliiter(UO)(Builder, X, Name) uses Builder to create
// a unary operator like UO called Name with operand X.
struct UnarySplitter {
UnarySplitter(UnaryOperator &uo) : UO(uo) {}
Value *operator()(IRBuilder<> &Builder, Value *Op, const Twine &Name) const {
return Builder.CreateUnOp(UO.getOpcode(), Op, Name);
UnaryOperator &UO;
// BinarySpliiter(BO)(Builder, X, Y, Name) uses Builder to create
// a binary operator like BO called Name with operands X and Y.
struct BinarySplitter {
BinarySplitter(BinaryOperator &bo) : BO(bo) {}
Value *operator()(IRBuilder<> &Builder, Value *Op0, Value *Op1,
const Twine &Name) const {
return Builder.CreateBinOp(BO.getOpcode(), Op0, Op1, Name);
BinaryOperator &BO;
// Information about a load or store that we're scalarizing.
struct VectorLayout {
VectorLayout() = default;
// Return the alignment of element I.
uint64_t getElemAlign(unsigned I) {
return MinAlign(VecAlign, I * ElemSize);
// The type of the vector.
VectorType *VecTy = nullptr;
// The type of each element.
Type *ElemTy = nullptr;
// The alignment of the vector.
uint64_t VecAlign = 0;
// The size of each element.
uint64_t ElemSize = 0;
class ScalarizerVisitor : public InstVisitor<ScalarizerVisitor, bool> {
ScalarizerVisitor(unsigned ParallelLoopAccessMDKind)
: ParallelLoopAccessMDKind(ParallelLoopAccessMDKind) {
bool visit(Function &F);
// InstVisitor methods. They return true if the instruction was scalarized,
// false if nothing changed.
bool visitInstruction(Instruction &I) { return false; }
bool visitSelectInst(SelectInst &SI);
bool visitICmpInst(ICmpInst &ICI);
bool visitFCmpInst(FCmpInst &FCI);
bool visitUnaryOperator(UnaryOperator &UO);
bool visitBinaryOperator(BinaryOperator &BO);
bool visitGetElementPtrInst(GetElementPtrInst &GEPI);
bool visitCastInst(CastInst &CI);
bool visitBitCastInst(BitCastInst &BCI);
bool visitShuffleVectorInst(ShuffleVectorInst &SVI);
bool visitPHINode(PHINode &PHI);
bool visitLoadInst(LoadInst &LI);
bool visitStoreInst(StoreInst &SI);
bool visitCallInst(CallInst &ICI);
Scatterer scatter(Instruction *Point, Value *V);
void gather(Instruction *Op, const ValueVector &CV);
bool canTransferMetadata(unsigned Kind);
void transferMetadataAndIRFlags(Instruction *Op, const ValueVector &CV);
bool getVectorLayout(Type *Ty, unsigned Alignment, VectorLayout &Layout,
const DataLayout &DL);
bool finish();
template<typename T> bool splitUnary(Instruction &, const T &);
template<typename T> bool splitBinary(Instruction &, const T &);
bool splitCall(CallInst &CI);
ScatterMap Scattered;
GatherList Gathered;
unsigned ParallelLoopAccessMDKind;
class ScalarizerLegacyPass : public FunctionPass {
static char ID;
ScalarizerLegacyPass() : FunctionPass(ID) {
bool runOnFunction(Function &F) override;
} // end anonymous namespace
char ScalarizerLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(ScalarizerLegacyPass, "scalarizer",
"Scalarize vector operations", false, false)
INITIALIZE_PASS_END(ScalarizerLegacyPass, "scalarizer",
"Scalarize vector operations", false, false)
Scatterer::Scatterer(BasicBlock *bb, BasicBlock::iterator bbi, Value *v,
ValueVector *cachePtr)
: BB(bb), BBI(bbi), V(v), CachePtr(cachePtr) {
Type *Ty = V->getType();
PtrTy = dyn_cast<PointerType>(Ty);
if (PtrTy)
Ty = PtrTy->getElementType();
Size = Ty->getVectorNumElements();
if (!CachePtr)
Tmp.resize(Size, nullptr);
else if (CachePtr->empty())
CachePtr->resize(Size, nullptr);
assert(Size == CachePtr->size() && "Inconsistent vector sizes");
// Return component I, creating a new Value for it if necessary.
Value *Scatterer::operator[](unsigned I) {
ValueVector &CV = (CachePtr ? *CachePtr : Tmp);
// Try to reuse a previous value.
if (CV[I])
return CV[I];
IRBuilder<> Builder(BB, BBI);
if (PtrTy) {
Type *ElTy = PtrTy->getElementType()->getVectorElementType();
if (!CV[0]) {
Type *NewPtrTy = PointerType::get(ElTy, PtrTy->getAddressSpace());
CV[0] = Builder.CreateBitCast(V, NewPtrTy, V->getName() + ".i0");
if (I != 0)
CV[I] = Builder.CreateConstGEP1_32(ElTy, CV[0], I,
V->getName() + ".i" + Twine(I));
} else {
// Search through a chain of InsertElementInsts looking for element I.
// Record other elements in the cache. The new V is still suitable
// for all uncached indices.
while (true) {
InsertElementInst *Insert = dyn_cast<InsertElementInst>(V);
if (!Insert)
ConstantInt *Idx = dyn_cast<ConstantInt>(Insert->getOperand(2));
if (!Idx)
unsigned J = Idx->getZExtValue();
V = Insert->getOperand(0);
if (I == J) {
CV[J] = Insert->getOperand(1);
return CV[J];
} else if (!CV[J]) {
// Only cache the first entry we find for each index we're not actively
// searching for. This prevents us from going too far up the chain and
// caching incorrect entries.
CV[J] = Insert->getOperand(1);
CV[I] = Builder.CreateExtractElement(V, Builder.getInt32(I),
V->getName() + ".i" + Twine(I));
return CV[I];
bool ScalarizerLegacyPass::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
Module &M = *F.getParent();
unsigned ParallelLoopAccessMDKind =
ScalarizerVisitor Impl(ParallelLoopAccessMDKind);
return Impl.visit(F);
FunctionPass *llvm::createScalarizerPass() {
return new ScalarizerLegacyPass();
bool ScalarizerVisitor::visit(Function &F) {
assert(Gathered.empty() && Scattered.empty());
// To ensure we replace gathered components correctly we need to do an ordered
// traversal of the basic blocks in the function.
ReversePostOrderTraversal<BasicBlock *> RPOT(&F.getEntryBlock());
for (BasicBlock *BB : RPOT) {
for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) {
Instruction *I = &*II;
bool Done = InstVisitor::visit(I);
if (Done && I->getType()->isVoidTy())
return finish();
// Return a scattered form of V that can be accessed by Point. V must be a
// vector or a pointer to a vector.
Scatterer ScalarizerVisitor::scatter(Instruction *Point, Value *V) {
if (Argument *VArg = dyn_cast<Argument>(V)) {
// Put the scattered form of arguments in the entry block,
// so that it can be used everywhere.
Function *F = VArg->getParent();
BasicBlock *BB = &F->getEntryBlock();
return Scatterer(BB, BB->begin(), V, &Scattered[V]);
if (Instruction *VOp = dyn_cast<Instruction>(V)) {
// Put the scattered form of an instruction directly after the
// instruction.
BasicBlock *BB = VOp->getParent();
return Scatterer(BB, std::next(BasicBlock::iterator(VOp)),
V, &Scattered[V]);
// In the fallback case, just put the scattered before Point and
// keep the result local to Point.
return Scatterer(Point->getParent(), Point->getIterator(), V);
// Replace Op with the gathered form of the components in CV. Defer the
// deletion of Op and creation of the gathered form to the end of the pass,
// so that we can avoid creating the gathered form if all uses of Op are
// replaced with uses of CV.
void ScalarizerVisitor::gather(Instruction *Op, const ValueVector &CV) {
// Since we're not deleting Op yet, stub out its operands, so that it
// doesn't make anything live unnecessarily.
for (unsigned I = 0, E = Op->getNumOperands(); I != E; ++I)
Op->setOperand(I, UndefValue::get(Op->getOperand(I)->getType()));
transferMetadataAndIRFlags(Op, CV);
// If we already have a scattered form of Op (created from ExtractElements
// of Op itself), replace them with the new form.
ValueVector &SV = Scattered[Op];
if (!SV.empty()) {
for (unsigned I = 0, E = SV.size(); I != E; ++I) {
Value *V = SV[I];
if (V == nullptr)
Instruction *Old = cast<Instruction>(V);
SV = CV;
Gathered.push_back(GatherList::value_type(Op, &SV));
// Return true if it is safe to transfer the given metadata tag from
// vector to scalar instructions.
bool ScalarizerVisitor::canTransferMetadata(unsigned Tag) {
return (Tag == LLVMContext::MD_tbaa
|| Tag == LLVMContext::MD_fpmath
|| Tag == LLVMContext::MD_tbaa_struct
|| Tag == LLVMContext::MD_invariant_load
|| Tag == LLVMContext::MD_alias_scope
|| Tag == LLVMContext::MD_noalias
|| Tag == ParallelLoopAccessMDKind
|| Tag == LLVMContext::MD_access_group);
// Transfer metadata from Op to the instructions in CV if it is known
// to be safe to do so.
void ScalarizerVisitor::transferMetadataAndIRFlags(Instruction *Op,
const ValueVector &CV) {
SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
for (unsigned I = 0, E = CV.size(); I != E; ++I) {
if (Instruction *New = dyn_cast<Instruction>(CV[I])) {
for (const auto &MD : MDs)
if (canTransferMetadata(MD.first))
New->setMetadata(MD.first, MD.second);
if (Op->getDebugLoc() && !New->getDebugLoc())
// Try to fill in Layout from Ty, returning true on success. Alignment is
// the alignment of the vector, or 0 if the ABI default should be used.
bool ScalarizerVisitor::getVectorLayout(Type *Ty, unsigned Alignment,
VectorLayout &Layout, const DataLayout &DL) {
// Make sure we're dealing with a vector.
Layout.VecTy = dyn_cast<VectorType>(Ty);
if (!Layout.VecTy)
return false;
// Check that we're dealing with full-byte elements.
Layout.ElemTy = Layout.VecTy->getElementType();
if (!DL.typeSizeEqualsStoreSize(Layout.ElemTy))
return false;
if (Alignment)
Layout.VecAlign = Alignment;
Layout.VecAlign = DL.getABITypeAlignment(Layout.VecTy);
Layout.ElemSize = DL.getTypeStoreSize(Layout.ElemTy);
return true;
// Scalarize one-operand instruction I, using Split(Builder, X, Name)
// to create an instruction like I with operand X and name Name.
template<typename Splitter>
bool ScalarizerVisitor::splitUnary(Instruction &I, const Splitter &Split) {
VectorType *VT = dyn_cast<VectorType>(I.getType());
if (!VT)
return false;
unsigned NumElems = VT->getNumElements();
IRBuilder<> Builder(&I);
Scatterer Op = scatter(&I, I.getOperand(0));
assert(Op.size() == NumElems && "Mismatched unary operation");
ValueVector Res;
for (unsigned Elem = 0; Elem < NumElems; ++Elem)
Res[Elem] = Split(Builder, Op[Elem], I.getName() + ".i" + Twine(Elem));
gather(&I, Res);
return true;
// Scalarize two-operand instruction I, using Split(Builder, X, Y, Name)
// to create an instruction like I with operands X and Y and name Name.
template<typename Splitter>
bool ScalarizerVisitor::splitBinary(Instruction &I, const Splitter &Split) {
VectorType *VT = dyn_cast<VectorType>(I.getType());
if (!VT)
return false;
unsigned NumElems = VT->getNumElements();
IRBuilder<> Builder(&I);
Scatterer Op0 = scatter(&I, I.getOperand(0));
Scatterer Op1 = scatter(&I, I.getOperand(1));
assert(Op0.size() == NumElems && "Mismatched binary operation");
assert(Op1.size() == NumElems && "Mismatched binary operation");
ValueVector Res;
for (unsigned Elem = 0; Elem < NumElems; ++Elem)
Res[Elem] = Split(Builder, Op0[Elem], Op1[Elem],
I.getName() + ".i" + Twine(Elem));
gather(&I, Res);
return true;
static bool isTriviallyScalariable(Intrinsic::ID ID) {
return isTriviallyVectorizable(ID);
// All of the current scalarizable intrinsics only have one mangled type.
static Function *getScalarIntrinsicDeclaration(Module *M,
Intrinsic::ID ID,
VectorType *Ty) {
return Intrinsic::getDeclaration(M, ID, { Ty->getScalarType() });
/// If a call to a vector typed intrinsic function, split into a scalar call per
/// element if possible for the intrinsic.
bool ScalarizerVisitor::splitCall(CallInst &CI) {
VectorType *VT = dyn_cast<VectorType>(CI.getType());
if (!VT)
return false;
Function *F = CI.getCalledFunction();
if (!F)
return false;
Intrinsic::ID ID = F->getIntrinsicID();
if (ID == Intrinsic::not_intrinsic || !isTriviallyScalariable(ID))
return false;
unsigned NumElems = VT->getNumElements();
unsigned NumArgs = CI.getNumArgOperands();
ValueVector ScalarOperands(NumArgs);
SmallVector<Scatterer, 8> Scattered(NumArgs);
// Assumes that any vector type has the same number of elements as the return
// vector type, which is true for all current intrinsics.
for (unsigned I = 0; I != NumArgs; ++I) {
Value *OpI = CI.getOperand(I);
if (OpI->getType()->isVectorTy()) {
Scattered[I] = scatter(&CI, OpI);
assert(Scattered[I].size() == NumElems && "mismatched call operands");
} else {
ScalarOperands[I] = OpI;
ValueVector Res(NumElems);
ValueVector ScalarCallOps(NumArgs);
Function *NewIntrin = getScalarIntrinsicDeclaration(F->getParent(), ID, VT);
IRBuilder<> Builder(&CI);
// Perform actual scalarization, taking care to preserve any scalar operands.
for (unsigned Elem = 0; Elem < NumElems; ++Elem) {
for (unsigned J = 0; J != NumArgs; ++J) {
if (hasVectorInstrinsicScalarOpd(ID, J))
Res[Elem] = Builder.CreateCall(NewIntrin, ScalarCallOps,
CI.getName() + ".i" + Twine(Elem));
gather(&CI, Res);
return true;
bool ScalarizerVisitor::visitSelectInst(SelectInst &SI) {
VectorType *VT = dyn_cast<VectorType>(SI.getType());
if (!VT)
return false;
unsigned NumElems = VT->getNumElements();
IRBuilder<> Builder(&SI);
Scatterer Op1 = scatter(&SI, SI.getOperand(1));
Scatterer Op2 = scatter(&SI, SI.getOperand(2));
assert(Op1.size() == NumElems && "Mismatched select");
assert(Op2.size() == NumElems && "Mismatched select");
ValueVector Res;
if (SI.getOperand(0)->getType()->isVectorTy()) {
Scatterer Op0 = scatter(&SI, SI.getOperand(0));
assert(Op0.size() == NumElems && "Mismatched select");
for (unsigned I = 0; I < NumElems; ++I)
Res[I] = Builder.CreateSelect(Op0[I], Op1[I], Op2[I],
SI.getName() + ".i" + Twine(I));
} else {
Value *Op0 = SI.getOperand(0);
for (unsigned I = 0; I < NumElems; ++I)
Res[I] = Builder.CreateSelect(Op0, Op1[I], Op2[I],
SI.getName() + ".i" + Twine(I));
gather(&SI, Res);
return true;
bool ScalarizerVisitor::visitICmpInst(ICmpInst &ICI) {
return splitBinary(ICI, ICmpSplitter(ICI));
bool ScalarizerVisitor::visitFCmpInst(FCmpInst &FCI) {
return splitBinary(FCI, FCmpSplitter(FCI));
bool ScalarizerVisitor::visitUnaryOperator(UnaryOperator &UO) {
return splitUnary(UO, UnarySplitter(UO));
bool ScalarizerVisitor::visitBinaryOperator(BinaryOperator &BO) {
return splitBinary(BO, BinarySplitter(BO));
bool ScalarizerVisitor::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
VectorType *VT = dyn_cast<VectorType>(GEPI.getType());
if (!VT)
return false;
IRBuilder<> Builder(&GEPI);
unsigned NumElems = VT->getNumElements();
unsigned NumIndices = GEPI.getNumIndices();
// The base pointer might be scalar even if it's a vector GEP. In those cases,
// splat the pointer into a vector value, and scatter that vector.
Value *Op0 = GEPI.getOperand(0);
if (!Op0->getType()->isVectorTy())
Op0 = Builder.CreateVectorSplat(NumElems, Op0);
Scatterer Base = scatter(&GEPI, Op0);
SmallVector<Scatterer, 8> Ops;
for (unsigned I = 0; I < NumIndices; ++I) {
Value *Op = GEPI.getOperand(I + 1);
// The indices might be scalars even if it's a vector GEP. In those cases,
// splat the scalar into a vector value, and scatter that vector.
if (!Op->getType()->isVectorTy())
Op = Builder.CreateVectorSplat(NumElems, Op);
Ops[I] = scatter(&GEPI, Op);
ValueVector Res;
for (unsigned I = 0; I < NumElems; ++I) {
SmallVector<Value *, 8> Indices;
for (unsigned J = 0; J < NumIndices; ++J)
Indices[J] = Ops[J][I];
Res[I] = Builder.CreateGEP(GEPI.getSourceElementType(), Base[I], Indices,
GEPI.getName() + ".i" + Twine(I));
if (GEPI.isInBounds())
if (GetElementPtrInst *NewGEPI = dyn_cast<GetElementPtrInst>(Res[I]))
gather(&GEPI, Res);
return true;
bool ScalarizerVisitor::visitCastInst(CastInst &CI) {
VectorType *VT = dyn_cast<VectorType>(CI.getDestTy());
if (!VT)
return false;
unsigned NumElems = VT->getNumElements();
IRBuilder<> Builder(&CI);
Scatterer Op0 = scatter(&CI, CI.getOperand(0));
assert(Op0.size() == NumElems && "Mismatched cast");
ValueVector Res;
for (unsigned I = 0; I < NumElems; ++I)
Res[I] = Builder.CreateCast(CI.getOpcode(), Op0[I], VT->getElementType(),
CI.getName() + ".i" + Twine(I));
gather(&CI, Res);
return true;
bool ScalarizerVisitor::visitBitCastInst(BitCastInst &BCI) {
VectorType *DstVT = dyn_cast<VectorType>(BCI.getDestTy());
VectorType *SrcVT = dyn_cast<VectorType>(BCI.getSrcTy());
if (!DstVT || !SrcVT)
return false;
unsigned DstNumElems = DstVT->getNumElements();
unsigned SrcNumElems = SrcVT->getNumElements();
IRBuilder<> Builder(&BCI);
Scatterer Op0 = scatter(&BCI, BCI.getOperand(0));
ValueVector Res;
if (DstNumElems == SrcNumElems) {
for (unsigned I = 0; I < DstNumElems; ++I)
Res[I] = Builder.CreateBitCast(Op0[I], DstVT->getElementType(),
BCI.getName() + ".i" + Twine(I));
} else if (DstNumElems > SrcNumElems) {
// <M x t1> -> <N*M x t2>. Convert each t1 to <N x t2> and copy the
// individual elements to the destination.
unsigned FanOut = DstNumElems / SrcNumElems;
Type *MidTy = VectorType::get(DstVT->getElementType(), FanOut);
unsigned ResI = 0;
for (unsigned Op0I = 0; Op0I < SrcNumElems; ++Op0I) {
Value *V = Op0[Op0I];
Instruction *VI;
// Look through any existing bitcasts before converting to <N x t2>.
// In the best case, the resulting conversion might be a no-op.
while ((VI = dyn_cast<Instruction>(V)) &&
VI->getOpcode() == Instruction::BitCast)
V = VI->getOperand(0);
V = Builder.CreateBitCast(V, MidTy, V->getName() + ".cast");
Scatterer Mid = scatter(&BCI, V);
for (unsigned MidI = 0; MidI < FanOut; ++MidI)
Res[ResI++] = Mid[MidI];
} else {
// <N*M x t1> -> <M x t2>. Convert each group of <N x t1> into a t2.
unsigned FanIn = SrcNumElems / DstNumElems;
Type *MidTy = VectorType::get(SrcVT->getElementType(), FanIn);
unsigned Op0I = 0;
for (unsigned ResI = 0; ResI < DstNumElems; ++ResI) {
Value *V = UndefValue::get(MidTy);
for (unsigned MidI = 0; MidI < FanIn; ++MidI)
V = Builder.CreateInsertElement(V, Op0[Op0I++], Builder.getInt32(MidI),
BCI.getName() + ".i" + Twine(ResI)
+ ".upto" + Twine(MidI));
Res[ResI] = Builder.CreateBitCast(V, DstVT->getElementType(),
BCI.getName() + ".i" + Twine(ResI));
gather(&BCI, Res);
return true;
bool ScalarizerVisitor::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
VectorType *VT = dyn_cast<VectorType>(SVI.getType());
if (!VT)
return false;
unsigned NumElems = VT->getNumElements();
Scatterer Op0 = scatter(&SVI, SVI.getOperand(0));
Scatterer Op1 = scatter(&SVI, SVI.getOperand(1));
ValueVector Res;
for (unsigned I = 0; I < NumElems; ++I) {
int Selector = SVI.getMaskValue(I);
if (Selector < 0)
Res[I] = UndefValue::get(VT->getElementType());
else if (unsigned(Selector) < Op0.size())
Res[I] = Op0[Selector];
Res[I] = Op1[Selector - Op0.size()];
gather(&SVI, Res);
return true;
bool ScalarizerVisitor::visitPHINode(PHINode &PHI) {
VectorType *VT = dyn_cast<VectorType>(PHI.getType());
if (!VT)
return false;
unsigned NumElems = VT->getNumElements();
IRBuilder<> Builder(&PHI);
ValueVector Res;
unsigned NumOps = PHI.getNumOperands();
for (unsigned I = 0; I < NumElems; ++I)
Res[I] = Builder.CreatePHI(VT->getElementType(), NumOps,
PHI.getName() + ".i" + Twine(I));
for (unsigned I = 0; I < NumOps; ++I) {
Scatterer Op = scatter(&PHI, PHI.getIncomingValue(I));
BasicBlock *IncomingBlock = PHI.getIncomingBlock(I);
for (unsigned J = 0; J < NumElems; ++J)
cast<PHINode>(Res[J])->addIncoming(Op[J], IncomingBlock);
gather(&PHI, Res);
return true;
bool ScalarizerVisitor::visitLoadInst(LoadInst &LI) {
if (!ScalarizeLoadStore)
return false;
if (!LI.isSimple())
return false;
VectorLayout Layout;
if (!getVectorLayout(LI.getType(), LI.getAlignment(), Layout,
return false;
unsigned NumElems = Layout.VecTy->getNumElements();
IRBuilder<> Builder(&LI);
Scatterer Ptr = scatter(&LI, LI.getPointerOperand());
ValueVector Res;
for (unsigned I = 0; I < NumElems; ++I)
Res[I] = Builder.CreateAlignedLoad(Layout.VecTy->getElementType(), Ptr[I],
LI.getName() + ".i" + Twine(I));
gather(&LI, Res);
return true;
bool ScalarizerVisitor::visitStoreInst(StoreInst &SI) {
if (!ScalarizeLoadStore)
return false;
if (!SI.isSimple())
return false;
VectorLayout Layout;
Value *FullValue = SI.getValueOperand();
if (!getVectorLayout(FullValue->getType(), SI.getAlignment(), Layout,
return false;
unsigned NumElems = Layout.VecTy->getNumElements();
IRBuilder<> Builder(&SI);
Scatterer Ptr = scatter(&SI, SI.getPointerOperand());
Scatterer Val = scatter(&SI, FullValue);
ValueVector Stores;
for (unsigned I = 0; I < NumElems; ++I) {
unsigned Align = Layout.getElemAlign(I);
Stores[I] = Builder.CreateAlignedStore(Val[I], Ptr[I], Align);
transferMetadataAndIRFlags(&SI, Stores);
return true;
bool ScalarizerVisitor::visitCallInst(CallInst &CI) {
return splitCall(CI);
// Delete the instructions that we scalarized. If a full vector result
// is still needed, recreate it using InsertElements.
bool ScalarizerVisitor::finish() {
// The presence of data in Gathered or Scattered indicates changes
// made to the Function.
if (Gathered.empty() && Scattered.empty())
return false;
for (const auto &GMI : Gathered) {
Instruction *Op = GMI.first;
ValueVector &CV = *GMI.second;
if (!Op->use_empty()) {
// The value is still needed, so recreate it using a series of
// InsertElements.
Type *Ty = Op->getType();
Value *Res = UndefValue::get(Ty);
BasicBlock *BB = Op->getParent();
unsigned Count = Ty->getVectorNumElements();
IRBuilder<> Builder(Op);
if (isa<PHINode>(Op))
Builder.SetInsertPoint(BB, BB->getFirstInsertionPt());
for (unsigned I = 0; I < Count; ++I)
Res = Builder.CreateInsertElement(Res, CV[I], Builder.getInt32(I),
Op->getName() + ".upto" + Twine(I));
return true;
PreservedAnalyses ScalarizerPass::run(Function &F, FunctionAnalysisManager &AM) {
Module &M = *F.getParent();
unsigned ParallelLoopAccessMDKind =
ScalarizerVisitor Impl(ParallelLoopAccessMDKind);
bool Changed = Impl.visit(F);
return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();