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llvm-project/polly/lib/Analysis/ScopBuilder.cpp

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//===- ScopBuilder.cpp ---------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Create a polyhedral description for a static control flow region.
//
// The pass creates a polyhedral description of the Scops detected by the SCoP
// detection derived from their LLVM-IR code.
//
//===----------------------------------------------------------------------===//
#include "polly/ScopBuilder.h"
#include "polly/Options.h"
#include "polly/Support/GICHelper.h"
#include "polly/Support/SCEVValidator.h"
#include "polly/Support/VirtualInstruction.h"
#include "llvm/Analysis/RegionIterator.h"
#include "llvm/IR/DiagnosticInfo.h"
using namespace llvm;
using namespace polly;
#define DEBUG_TYPE "polly-scops"
STATISTIC(ScopFound, "Number of valid Scops");
STATISTIC(RichScopFound, "Number of Scops containing a loop");
STATISTIC(InfeasibleScops,
"Number of SCoPs with statically infeasible context.");
static cl::opt<bool> ModelReadOnlyScalars(
"polly-analyze-read-only-scalars",
cl::desc("Model read-only scalar values in the scop description"),
cl::Hidden, cl::ZeroOrMore, cl::init(true), cl::cat(PollyCategory));
static cl::opt<bool> UnprofitableScalarAccs(
"polly-unprofitable-scalar-accs",
cl::desc("Count statements with scalar accesses as not optimizable"),
cl::Hidden, cl::init(false), cl::cat(PollyCategory));
static cl::opt<bool> DetectFortranArrays(
"polly-detect-fortran-arrays",
cl::desc("Detect Fortran arrays and use this for code generation"),
cl::Hidden, cl::init(false), cl::cat(PollyCategory));
void ScopBuilder::buildPHIAccesses(ScopStmt *PHIStmt, PHINode *PHI,
Region *NonAffineSubRegion,
bool IsExitBlock) {
// PHI nodes that are in the exit block of the region, hence if IsExitBlock is
// true, are not modeled as ordinary PHI nodes as they are not part of the
// region. However, we model the operands in the predecessor blocks that are
// part of the region as regular scalar accesses.
// If we can synthesize a PHI we can skip it, however only if it is in
// the region. If it is not it can only be in the exit block of the region.
// In this case we model the operands but not the PHI itself.
auto *Scope = LI.getLoopFor(PHI->getParent());
if (!IsExitBlock && canSynthesize(PHI, *scop, &SE, Scope))
return;
// PHI nodes are modeled as if they had been demoted prior to the SCoP
// detection. Hence, the PHI is a load of a new memory location in which the
// incoming value was written at the end of the incoming basic block.
bool OnlyNonAffineSubRegionOperands = true;
for (unsigned u = 0; u < PHI->getNumIncomingValues(); u++) {
Value *Op = PHI->getIncomingValue(u);
BasicBlock *OpBB = PHI->getIncomingBlock(u);
ScopStmt *OpStmt = scop->getLastStmtFor(OpBB);
// Do not build PHI dependences inside a non-affine subregion, but make
// sure that the necessary scalar values are still made available.
if (NonAffineSubRegion && NonAffineSubRegion->contains(OpBB)) {
auto *OpInst = dyn_cast<Instruction>(Op);
if (!OpInst || !NonAffineSubRegion->contains(OpInst))
ensureValueRead(Op, OpStmt);
continue;
}
OnlyNonAffineSubRegionOperands = false;
ensurePHIWrite(PHI, OpStmt, OpBB, Op, IsExitBlock);
}
if (!OnlyNonAffineSubRegionOperands && !IsExitBlock) {
addPHIReadAccess(PHIStmt, PHI);
}
}
void ScopBuilder::buildScalarDependences(ScopStmt *UserStmt,
Instruction *Inst) {
assert(!isa<PHINode>(Inst));
// Pull-in required operands.
for (Use &Op : Inst->operands())
ensureValueRead(Op.get(), UserStmt);
}
void ScopBuilder::buildEscapingDependences(Instruction *Inst) {
// Check for uses of this instruction outside the scop. Because we do not
// iterate over such instructions and therefore did not "ensure" the existence
// of a write, we must determine such use here.
for (Use &U : Inst->uses()) {
Instruction *UI = dyn_cast<Instruction>(U.getUser());
if (!UI)
continue;
BasicBlock *UseParent = getUseBlock(U);
BasicBlock *UserParent = UI->getParent();
// An escaping value is either used by an instruction not within the scop,
// or (when the scop region's exit needs to be simplified) by a PHI in the
// scop's exit block. This is because region simplification before code
// generation inserts new basic blocks before the PHI such that its incoming
// blocks are not in the scop anymore.
if (!scop->contains(UseParent) ||
(isa<PHINode>(UI) && scop->isExit(UserParent) &&
scop->hasSingleExitEdge())) {
// At least one escaping use found.
ensureValueWrite(Inst);
break;
}
}
}
/// Check that a value is a Fortran Array descriptor.
///
/// We check if V has the following structure:
/// %"struct.array1_real(kind=8)" = type { i8*, i<zz>, i<zz>,
/// [<num> x %struct.descriptor_dimension] }
///
///
/// %struct.descriptor_dimension = type { i<zz>, i<zz>, i<zz> }
///
/// 1. V's type name starts with "struct.array"
/// 2. V's type has layout as shown.
/// 3. Final member of V's type has name "struct.descriptor_dimension",
/// 4. "struct.descriptor_dimension" has layout as shown.
/// 5. Consistent use of i<zz> where <zz> is some fixed integer number.
///
/// We are interested in such types since this is the code that dragonegg
/// generates for Fortran array descriptors.
///
/// @param V the Value to be checked.
///
/// @returns True if V is a Fortran array descriptor, False otherwise.
bool isFortranArrayDescriptor(Value *V) {
PointerType *PTy = dyn_cast<PointerType>(V->getType());
if (!PTy)
return false;
Type *Ty = PTy->getElementType();
assert(Ty && "Ty expected to be initialized");
auto *StructArrTy = dyn_cast<StructType>(Ty);
if (!(StructArrTy && StructArrTy->hasName()))
return false;
if (!StructArrTy->getName().startswith("struct.array"))
return false;
if (StructArrTy->getNumElements() != 4)
return false;
const ArrayRef<Type *> ArrMemberTys = StructArrTy->elements();
// i8* match
if (ArrMemberTys[0] != Type::getInt8PtrTy(V->getContext()))
return false;
// Get a reference to the int type and check that all the members
// share the same int type
Type *IntTy = ArrMemberTys[1];
if (ArrMemberTys[2] != IntTy)
return false;
// type: [<num> x %struct.descriptor_dimension]
ArrayType *DescriptorDimArrayTy = dyn_cast<ArrayType>(ArrMemberTys[3]);
if (!DescriptorDimArrayTy)
return false;
// type: %struct.descriptor_dimension := type { ixx, ixx, ixx }
StructType *DescriptorDimTy =
dyn_cast<StructType>(DescriptorDimArrayTy->getElementType());
if (!(DescriptorDimTy && DescriptorDimTy->hasName()))
return false;
if (DescriptorDimTy->getName() != "struct.descriptor_dimension")
return false;
if (DescriptorDimTy->getNumElements() != 3)
return false;
for (auto MemberTy : DescriptorDimTy->elements()) {
if (MemberTy != IntTy)
return false;
}
return true;
}
Value *ScopBuilder::findFADAllocationVisible(MemAccInst Inst) {
// match: 4.1 & 4.2 store/load
if (!isa<LoadInst>(Inst) && !isa<StoreInst>(Inst))
return nullptr;
// match: 4
if (Inst.getAlignment() != 8)
return nullptr;
Value *Address = Inst.getPointerOperand();
const BitCastInst *Bitcast = nullptr;
// [match: 3]
if (auto *Slot = dyn_cast<GetElementPtrInst>(Address)) {
Value *TypedMem = Slot->getPointerOperand();
// match: 2
Bitcast = dyn_cast<BitCastInst>(TypedMem);
} else {
// match: 2
Bitcast = dyn_cast<BitCastInst>(Address);
}
if (!Bitcast)
return nullptr;
auto *MallocMem = Bitcast->getOperand(0);
// match: 1
auto *MallocCall = dyn_cast<CallInst>(MallocMem);
if (!MallocCall)
return nullptr;
Function *MallocFn = MallocCall->getCalledFunction();
if (!(MallocFn && MallocFn->hasName() && MallocFn->getName() == "malloc"))
return nullptr;
// Find all uses the malloc'd memory.
// We are looking for a "store" into a struct with the type being the Fortran
// descriptor type
for (auto user : MallocMem->users()) {
/// match: 5
auto *MallocStore = dyn_cast<StoreInst>(user);
if (!MallocStore)
continue;
auto *DescriptorGEP =
dyn_cast<GEPOperator>(MallocStore->getPointerOperand());
if (!DescriptorGEP)
continue;
// match: 5
auto DescriptorType =
dyn_cast<StructType>(DescriptorGEP->getSourceElementType());
if (!(DescriptorType && DescriptorType->hasName()))
continue;
Value *Descriptor = dyn_cast<Value>(DescriptorGEP->getPointerOperand());
if (!Descriptor)
continue;
if (!isFortranArrayDescriptor(Descriptor))
continue;
return Descriptor;
}
return nullptr;
}
Value *ScopBuilder::findFADAllocationInvisible(MemAccInst Inst) {
// match: 3
if (!isa<LoadInst>(Inst) && !isa<StoreInst>(Inst))
return nullptr;
Value *Slot = Inst.getPointerOperand();
LoadInst *MemLoad = nullptr;
// [match: 2]
if (auto *SlotGEP = dyn_cast<GetElementPtrInst>(Slot)) {
// match: 1
MemLoad = dyn_cast<LoadInst>(SlotGEP->getPointerOperand());
} else {
// match: 1
MemLoad = dyn_cast<LoadInst>(Slot);
}
if (!MemLoad)
return nullptr;
auto *BitcastOperator =
dyn_cast<BitCastOperator>(MemLoad->getPointerOperand());
if (!BitcastOperator)
return nullptr;
Value *Descriptor = dyn_cast<Value>(BitcastOperator->getOperand(0));
if (!Descriptor)
return nullptr;
if (!isFortranArrayDescriptor(Descriptor))
return nullptr;
return Descriptor;
}
bool ScopBuilder::buildAccessMultiDimFixed(MemAccInst Inst, ScopStmt *Stmt) {
Value *Val = Inst.getValueOperand();
Type *ElementType = Val->getType();
Value *Address = Inst.getPointerOperand();
const SCEV *AccessFunction =
SE.getSCEVAtScope(Address, LI.getLoopFor(Inst->getParent()));
const SCEVUnknown *BasePointer =
dyn_cast<SCEVUnknown>(SE.getPointerBase(AccessFunction));
enum MemoryAccess::AccessType AccType =
isa<LoadInst>(Inst) ? MemoryAccess::READ : MemoryAccess::MUST_WRITE;
if (auto *BitCast = dyn_cast<BitCastInst>(Address)) {
auto *Src = BitCast->getOperand(0);
auto *SrcTy = Src->getType();
auto *DstTy = BitCast->getType();
// Do not try to delinearize non-sized (opaque) pointers.
if ((SrcTy->isPointerTy() && !SrcTy->getPointerElementType()->isSized()) ||
(DstTy->isPointerTy() && !DstTy->getPointerElementType()->isSized())) {
return false;
}
if (SrcTy->isPointerTy() && DstTy->isPointerTy() &&
DL.getTypeAllocSize(SrcTy->getPointerElementType()) ==
DL.getTypeAllocSize(DstTy->getPointerElementType()))
Address = Src;
}
auto *GEP = dyn_cast<GetElementPtrInst>(Address);
if (!GEP)
return false;
std::vector<const SCEV *> Subscripts;
std::vector<int> Sizes;
std::tie(Subscripts, Sizes) = getIndexExpressionsFromGEP(GEP, SE);
auto *BasePtr = GEP->getOperand(0);
if (auto *BasePtrCast = dyn_cast<BitCastInst>(BasePtr))
BasePtr = BasePtrCast->getOperand(0);
// Check for identical base pointers to ensure that we do not miss index
// offsets that have been added before this GEP is applied.
if (BasePtr != BasePointer->getValue())
return false;
std::vector<const SCEV *> SizesSCEV;
const InvariantLoadsSetTy &ScopRIL = scop->getRequiredInvariantLoads();
Loop *SurroundingLoop = Stmt->getSurroundingLoop();
for (auto *Subscript : Subscripts) {
InvariantLoadsSetTy AccessILS;
if (!isAffineExpr(&scop->getRegion(), SurroundingLoop, Subscript, SE,
&AccessILS))
return false;
for (LoadInst *LInst : AccessILS)
if (!ScopRIL.count(LInst))
return false;
}
if (Sizes.empty())
return false;
SizesSCEV.push_back(nullptr);
for (auto V : Sizes)
SizesSCEV.push_back(SE.getSCEV(
ConstantInt::get(IntegerType::getInt64Ty(BasePtr->getContext()), V)));
addArrayAccess(Stmt, Inst, AccType, BasePointer->getValue(), ElementType,
true, Subscripts, SizesSCEV, Val);
return true;
}
bool ScopBuilder::buildAccessMultiDimParam(MemAccInst Inst, ScopStmt *Stmt) {
if (!PollyDelinearize)
return false;
Value *Address = Inst.getPointerOperand();
Value *Val = Inst.getValueOperand();
Type *ElementType = Val->getType();
unsigned ElementSize = DL.getTypeAllocSize(ElementType);
enum MemoryAccess::AccessType AccType =
isa<LoadInst>(Inst) ? MemoryAccess::READ : MemoryAccess::MUST_WRITE;
const SCEV *AccessFunction =
SE.getSCEVAtScope(Address, LI.getLoopFor(Inst->getParent()));
const SCEVUnknown *BasePointer =
dyn_cast<SCEVUnknown>(SE.getPointerBase(AccessFunction));
assert(BasePointer && "Could not find base pointer");
auto &InsnToMemAcc = scop->getInsnToMemAccMap();
auto AccItr = InsnToMemAcc.find(Inst);
if (AccItr == InsnToMemAcc.end())
return false;
std::vector<const SCEV *> Sizes = {nullptr};
Sizes.insert(Sizes.end(), AccItr->second.Shape->DelinearizedSizes.begin(),
AccItr->second.Shape->DelinearizedSizes.end());
// In case only the element size is contained in the 'Sizes' array, the
// access does not access a real multi-dimensional array. Hence, we allow
// the normal single-dimensional access construction to handle this.
if (Sizes.size() == 1)
return false;
// Remove the element size. This information is already provided by the
// ElementSize parameter. In case the element size of this access and the
// element size used for delinearization differs the delinearization is
// incorrect. Hence, we invalidate the scop.
//
// TODO: Handle delinearization with differing element sizes.
auto DelinearizedSize =
cast<SCEVConstant>(Sizes.back())->getAPInt().getSExtValue();
Sizes.pop_back();
if (ElementSize != DelinearizedSize)
scop->invalidate(DELINEARIZATION, Inst->getDebugLoc());
addArrayAccess(Stmt, Inst, AccType, BasePointer->getValue(), ElementType,
true, AccItr->second.DelinearizedSubscripts, Sizes, Val);
return true;
}
bool ScopBuilder::buildAccessMemIntrinsic(MemAccInst Inst, ScopStmt *Stmt) {
auto *MemIntr = dyn_cast_or_null<MemIntrinsic>(Inst);
if (MemIntr == nullptr)
return false;
auto *L = LI.getLoopFor(Inst->getParent());
auto *LengthVal = SE.getSCEVAtScope(MemIntr->getLength(), L);
assert(LengthVal);
// Check if the length val is actually affine or if we overapproximate it
InvariantLoadsSetTy AccessILS;
const InvariantLoadsSetTy &ScopRIL = scop->getRequiredInvariantLoads();
Loop *SurroundingLoop = Stmt->getSurroundingLoop();
bool LengthIsAffine = isAffineExpr(&scop->getRegion(), SurroundingLoop,
LengthVal, SE, &AccessILS);
for (LoadInst *LInst : AccessILS)
if (!ScopRIL.count(LInst))
LengthIsAffine = false;
if (!LengthIsAffine)
LengthVal = nullptr;
auto *DestPtrVal = MemIntr->getDest();
assert(DestPtrVal);
auto *DestAccFunc = SE.getSCEVAtScope(DestPtrVal, L);
assert(DestAccFunc);
// Ignore accesses to "NULL".
// TODO: We could use this to optimize the region further, e.g., intersect
// the context with
// isl_set_complement(isl_set_params(getDomain()))
// as we know it would be undefined to execute this instruction anyway.
if (DestAccFunc->isZero())
return true;
auto *DestPtrSCEV = dyn_cast<SCEVUnknown>(SE.getPointerBase(DestAccFunc));
assert(DestPtrSCEV);
DestAccFunc = SE.getMinusSCEV(DestAccFunc, DestPtrSCEV);
addArrayAccess(Stmt, Inst, MemoryAccess::MUST_WRITE, DestPtrSCEV->getValue(),
IntegerType::getInt8Ty(DestPtrVal->getContext()),
LengthIsAffine, {DestAccFunc, LengthVal}, {nullptr},
Inst.getValueOperand());
auto *MemTrans = dyn_cast<MemTransferInst>(MemIntr);
if (!MemTrans)
return true;
auto *SrcPtrVal = MemTrans->getSource();
assert(SrcPtrVal);
auto *SrcAccFunc = SE.getSCEVAtScope(SrcPtrVal, L);
assert(SrcAccFunc);
// Ignore accesses to "NULL".
// TODO: See above TODO
if (SrcAccFunc->isZero())
return true;
auto *SrcPtrSCEV = dyn_cast<SCEVUnknown>(SE.getPointerBase(SrcAccFunc));
assert(SrcPtrSCEV);
SrcAccFunc = SE.getMinusSCEV(SrcAccFunc, SrcPtrSCEV);
addArrayAccess(Stmt, Inst, MemoryAccess::READ, SrcPtrSCEV->getValue(),
IntegerType::getInt8Ty(SrcPtrVal->getContext()),
LengthIsAffine, {SrcAccFunc, LengthVal}, {nullptr},
Inst.getValueOperand());
return true;
}
bool ScopBuilder::buildAccessCallInst(MemAccInst Inst, ScopStmt *Stmt) {
auto *CI = dyn_cast_or_null<CallInst>(Inst);
if (CI == nullptr)
return false;
if (CI->doesNotAccessMemory() || isIgnoredIntrinsic(CI))
return true;
bool ReadOnly = false;
auto *AF = SE.getConstant(IntegerType::getInt64Ty(CI->getContext()), 0);
auto *CalledFunction = CI->getCalledFunction();
switch (AA.getModRefBehavior(CalledFunction)) {
case FMRB_UnknownModRefBehavior:
llvm_unreachable("Unknown mod ref behaviour cannot be represented.");
case FMRB_DoesNotAccessMemory:
return true;
case FMRB_DoesNotReadMemory:
case FMRB_OnlyAccessesInaccessibleMem:
case FMRB_OnlyAccessesInaccessibleOrArgMem:
return false;
case FMRB_OnlyReadsMemory:
GlobalReads.emplace_back(Stmt, CI);
return true;
case FMRB_OnlyReadsArgumentPointees:
ReadOnly = true;
// Fall through
case FMRB_OnlyAccessesArgumentPointees:
auto AccType = ReadOnly ? MemoryAccess::READ : MemoryAccess::MAY_WRITE;
Loop *L = LI.getLoopFor(Inst->getParent());
for (const auto &Arg : CI->arg_operands()) {
if (!Arg->getType()->isPointerTy())
continue;
auto *ArgSCEV = SE.getSCEVAtScope(Arg, L);
if (ArgSCEV->isZero())
continue;
auto *ArgBasePtr = cast<SCEVUnknown>(SE.getPointerBase(ArgSCEV));
addArrayAccess(Stmt, Inst, AccType, ArgBasePtr->getValue(),
ArgBasePtr->getType(), false, {AF}, {nullptr}, CI);
}
return true;
}
return true;
}
void ScopBuilder::buildAccessSingleDim(MemAccInst Inst, ScopStmt *Stmt) {
Value *Address = Inst.getPointerOperand();
Value *Val = Inst.getValueOperand();
Type *ElementType = Val->getType();
enum MemoryAccess::AccessType AccType =
isa<LoadInst>(Inst) ? MemoryAccess::READ : MemoryAccess::MUST_WRITE;
const SCEV *AccessFunction =
SE.getSCEVAtScope(Address, LI.getLoopFor(Inst->getParent()));
const SCEVUnknown *BasePointer =
dyn_cast<SCEVUnknown>(SE.getPointerBase(AccessFunction));
assert(BasePointer && "Could not find base pointer");
AccessFunction = SE.getMinusSCEV(AccessFunction, BasePointer);
// Check if the access depends on a loop contained in a non-affine subregion.
bool isVariantInNonAffineLoop = false;
SetVector<const Loop *> Loops;
findLoops(AccessFunction, Loops);
for (const Loop *L : Loops)
if (Stmt->contains(L)) {
isVariantInNonAffineLoop = true;
break;
}
InvariantLoadsSetTy AccessILS;
Loop *SurroundingLoop = Stmt->getSurroundingLoop();
bool IsAffine = !isVariantInNonAffineLoop &&
isAffineExpr(&scop->getRegion(), SurroundingLoop,
AccessFunction, SE, &AccessILS);
const InvariantLoadsSetTy &ScopRIL = scop->getRequiredInvariantLoads();
for (LoadInst *LInst : AccessILS)
if (!ScopRIL.count(LInst))
IsAffine = false;
if (!IsAffine && AccType == MemoryAccess::MUST_WRITE)
AccType = MemoryAccess::MAY_WRITE;
addArrayAccess(Stmt, Inst, AccType, BasePointer->getValue(), ElementType,
IsAffine, {AccessFunction}, {nullptr}, Val);
}
void ScopBuilder::buildMemoryAccess(MemAccInst Inst, ScopStmt *Stmt) {
if (buildAccessMemIntrinsic(Inst, Stmt))
return;
if (buildAccessCallInst(Inst, Stmt))
return;
if (buildAccessMultiDimFixed(Inst, Stmt))
return;
if (buildAccessMultiDimParam(Inst, Stmt))
return;
buildAccessSingleDim(Inst, Stmt);
}
void ScopBuilder::buildAccessFunctions() {
for (auto &Stmt : *scop) {
if (Stmt.isBlockStmt()) {
buildAccessFunctions(&Stmt, *Stmt.getBasicBlock());
continue;
}
Region *R = Stmt.getRegion();
for (BasicBlock *BB : R->blocks())
buildAccessFunctions(&Stmt, *BB, R);
}
}
void ScopBuilder::buildStmts(Region &SR) {
if (scop->isNonAffineSubRegion(&SR)) {
Loop *SurroundingLoop =
getFirstNonBoxedLoopFor(SR.getEntry(), LI, scop->getBoxedLoops());
scop->addScopStmt(&SR, SurroundingLoop);
return;
}
for (auto I = SR.element_begin(), E = SR.element_end(); I != E; ++I)
if (I->isSubRegion())
buildStmts(*I->getNodeAs<Region>());
else {
std::vector<Instruction *> Instructions;
for (Instruction &Inst : *I->getNodeAs<BasicBlock>()) {
Loop *L = LI.getLoopFor(Inst.getParent());
if (!isa<TerminatorInst>(&Inst) && !isIgnoredIntrinsic(&Inst) &&
!canSynthesize(&Inst, *scop, &SE, L))
Instructions.push_back(&Inst);
}
Loop *SurroundingLoop = LI.getLoopFor(I->getNodeAs<BasicBlock>());
scop->addScopStmt(I->getNodeAs<BasicBlock>(), SurroundingLoop,
Instructions);
}
}
void ScopBuilder::buildAccessFunctions(ScopStmt *Stmt, BasicBlock &BB,
Region *NonAffineSubRegion,
bool IsExitBlock) {
assert(
!Stmt == IsExitBlock &&
"The exit BB is the only one that cannot be represented by a statement");
assert(IsExitBlock || Stmt->contains(&BB));
// We do not build access functions for error blocks, as they may contain
// instructions we can not model.
if (isErrorBlock(BB, scop->getRegion(), LI, DT) && !IsExitBlock)
return;
for (Instruction &Inst : BB) {
PHINode *PHI = dyn_cast<PHINode>(&Inst);
if (PHI)
buildPHIAccesses(Stmt, PHI, NonAffineSubRegion, IsExitBlock);
// For the exit block we stop modeling after the last PHI node.
if (!PHI && IsExitBlock)
break;
if (auto MemInst = MemAccInst::dyn_cast(Inst)) {
assert(Stmt && "Cannot build access function in non-existing statement");
buildMemoryAccess(MemInst, Stmt);
}
if (isIgnoredIntrinsic(&Inst))
continue;
// PHI nodes have already been modeled above and TerminatorInsts that are
// not part of a non-affine subregion are fully modeled and regenerated
// from the polyhedral domains. Hence, they do not need to be modeled as
// explicit data dependences.
if (!PHI && (!isa<TerminatorInst>(&Inst) || NonAffineSubRegion))
buildScalarDependences(Stmt, &Inst);
if (!IsExitBlock)
buildEscapingDependences(&Inst);
}
}
MemoryAccess *ScopBuilder::addMemoryAccess(
ScopStmt *Stmt, Instruction *Inst, MemoryAccess::AccessType AccType,
Value *BaseAddress, Type *ElementType, bool Affine, Value *AccessValue,
ArrayRef<const SCEV *> Subscripts, ArrayRef<const SCEV *> Sizes,
MemoryKind Kind) {
bool isKnownMustAccess = false;
// Accesses in single-basic block statements are always executed.
if (Stmt->isBlockStmt())
isKnownMustAccess = true;
if (Stmt->isRegionStmt()) {
// Accesses that dominate the exit block of a non-affine region are always
// executed. In non-affine regions there may exist MemoryKind::Values that
// do not dominate the exit. MemoryKind::Values will always dominate the
// exit and MemoryKind::PHIs only if there is at most one PHI_WRITE in the
// non-affine region.
if (Inst && DT.dominates(Inst->getParent(), Stmt->getRegion()->getExit()))
isKnownMustAccess = true;
}
// Non-affine PHI writes do not "happen" at a particular instruction, but
// after exiting the statement. Therefore they are guaranteed to execute and
// overwrite the old value.
if (Kind == MemoryKind::PHI || Kind == MemoryKind::ExitPHI)
isKnownMustAccess = true;
if (!isKnownMustAccess && AccType == MemoryAccess::MUST_WRITE)
AccType = MemoryAccess::MAY_WRITE;
auto *Access = new MemoryAccess(Stmt, Inst, AccType, BaseAddress, ElementType,
Affine, Subscripts, Sizes, AccessValue, Kind);
scop->addAccessFunction(Access);
Stmt->addAccess(Access);
return Access;
}
void ScopBuilder::addArrayAccess(ScopStmt *Stmt, MemAccInst MemAccInst,
MemoryAccess::AccessType AccType,
Value *BaseAddress, Type *ElementType,
bool IsAffine,
ArrayRef<const SCEV *> Subscripts,
ArrayRef<const SCEV *> Sizes,
Value *AccessValue) {
ArrayBasePointers.insert(BaseAddress);
auto *MemAccess = addMemoryAccess(Stmt, MemAccInst, AccType, BaseAddress,
ElementType, IsAffine, AccessValue,
Subscripts, Sizes, MemoryKind::Array);
if (!DetectFortranArrays)
return;
if (Value *FAD = findFADAllocationInvisible(MemAccInst))
MemAccess->setFortranArrayDescriptor(FAD);
else if (Value *FAD = findFADAllocationVisible(MemAccInst))
MemAccess->setFortranArrayDescriptor(FAD);
}
void ScopBuilder::ensureValueWrite(Instruction *Inst) {
// Find the statement that defines the value of Inst. That statement has to
// write the value to make it available to those statements that read it.
ScopStmt *Stmt = scop->getStmtFor(Inst);
// It is possible that the value is synthesizable within a loop (such that it
// is not part of any statement), but not after the loop (where you need the
// number of loop round-trips to synthesize it). In LCSSA-form a PHI node will
// avoid this. In case the IR has no such PHI, use the last statement (where
// the value is synthesizable) to write the value.
if (!Stmt)
Stmt = scop->getLastStmtFor(Inst->getParent());
// Inst not defined within this SCoP.
if (!Stmt)
return;
// Do not process further if the instruction is already written.
if (Stmt->lookupValueWriteOf(Inst))
return;
addMemoryAccess(Stmt, Inst, MemoryAccess::MUST_WRITE, Inst, Inst->getType(),
true, Inst, ArrayRef<const SCEV *>(),
ArrayRef<const SCEV *>(), MemoryKind::Value);
}
void ScopBuilder::ensureValueRead(Value *V, ScopStmt *UserStmt) {
auto *Scope = UserStmt->getSurroundingLoop();
auto VUse = VirtualUse::create(scop.get(), UserStmt, Scope, V, false);
switch (VUse.getKind()) {
case VirtualUse::Constant:
case VirtualUse::Block:
case VirtualUse::Synthesizable:
case VirtualUse::Hoisted:
case VirtualUse::Intra:
// Uses of these kinds do not need a MemoryAccess.
break;
case VirtualUse::ReadOnly:
// Add MemoryAccess for invariant values only if requested.
if (!ModelReadOnlyScalars)
break;
LLVM_FALLTHROUGH;
case VirtualUse::Inter:
// Do not create another MemoryAccess for reloading the value if one already
// exists.
if (UserStmt->lookupValueReadOf(V))
break;
addMemoryAccess(UserStmt, nullptr, MemoryAccess::READ, V, V->getType(),
true, V, ArrayRef<const SCEV *>(), ArrayRef<const SCEV *>(),
MemoryKind::Value);
// Inter-statement uses need to write the value in their defining statement.
if (VUse.isInter())
ensureValueWrite(cast<Instruction>(V));
break;
}
}
void ScopBuilder::ensurePHIWrite(PHINode *PHI, ScopStmt *IncomingStmt,
BasicBlock *IncomingBlock,
Value *IncomingValue, bool IsExitBlock) {
// As the incoming block might turn out to be an error statement ensure we
// will create an exit PHI SAI object. It is needed during code generation
// and would be created later anyway.
if (IsExitBlock)
scop->getOrCreateScopArrayInfo(PHI, PHI->getType(), {},
MemoryKind::ExitPHI);
// This is possible if PHI is in the SCoP's entry block. The incoming blocks
// from outside the SCoP's region have no statement representation.
if (!IncomingStmt)
return;
// Take care for the incoming value being available in the incoming block.
// This must be done before the check for multiple PHI writes because multiple
// exiting edges from subregion each can be the effective written value of the
// subregion. As such, all of them must be made available in the subregion
// statement.
ensureValueRead(IncomingValue, IncomingStmt);
// Do not add more than one MemoryAccess per PHINode and ScopStmt.
if (MemoryAccess *Acc = IncomingStmt->lookupPHIWriteOf(PHI)) {
assert(Acc->getAccessInstruction() == PHI);
Acc->addIncoming(IncomingBlock, IncomingValue);
return;
}
MemoryAccess *Acc = addMemoryAccess(
IncomingStmt, PHI, MemoryAccess::MUST_WRITE, PHI, PHI->getType(), true,
PHI, ArrayRef<const SCEV *>(), ArrayRef<const SCEV *>(),
IsExitBlock ? MemoryKind::ExitPHI : MemoryKind::PHI);
assert(Acc);
Acc->addIncoming(IncomingBlock, IncomingValue);
}
void ScopBuilder::addPHIReadAccess(ScopStmt *PHIStmt, PHINode *PHI) {
addMemoryAccess(PHIStmt, PHI, MemoryAccess::READ, PHI, PHI->getType(), true,
PHI, ArrayRef<const SCEV *>(), ArrayRef<const SCEV *>(),
MemoryKind::PHI);
}
#ifndef NDEBUG
static void verifyUse(Scop *S, Use &Op, LoopInfo &LI) {
auto PhysUse = VirtualUse::create(S, Op, &LI, false);
auto VirtUse = VirtualUse::create(S, Op, &LI, true);
assert(PhysUse.getKind() == VirtUse.getKind());
}
/// Check the consistency of every statement's MemoryAccesses.
///
/// The check is carried out by expecting the "physical" kind of use (derived
/// from the BasicBlocks instructions resides in) to be same as the "virtual"
/// kind of use (derived from a statement's MemoryAccess).
///
/// The "physical" uses are taken by ensureValueRead to determine whether to
/// create MemoryAccesses. When done, the kind of scalar access should be the
/// same no matter which way it was derived.
///
/// The MemoryAccesses might be changed by later SCoP-modifying passes and hence
/// can intentionally influence on the kind of uses (not corresponding to the
/// "physical" anymore, hence called "virtual"). The CodeGenerator therefore has
/// to pick up the virtual uses. But here in the code generator, this has not
/// happened yet, such that virtual and physical uses are equivalent.
static void verifyUses(Scop *S, LoopInfo &LI, DominatorTree &DT) {
for (auto *BB : S->getRegion().blocks()) {
auto *Stmt = S->getStmtFor(BB);
if (!Stmt)
continue;
for (auto &Inst : *BB) {
if (isIgnoredIntrinsic(&Inst))
continue;
// Branch conditions are encoded in the statement domains.
if (isa<TerminatorInst>(&Inst) && Stmt->isBlockStmt())
continue;
// Verify all uses.
for (auto &Op : Inst.operands())
verifyUse(S, Op, LI);
// Stores do not produce values used by other statements.
if (isa<StoreInst>(Inst))
continue;
// For every value defined in the block, also check that a use of that
// value in the same statement would not be an inter-statement use. It can
// still be synthesizable or load-hoisted, but these kind of instructions
// are not directly copied in code-generation.
auto VirtDef =
VirtualUse::create(S, Stmt, Stmt->getSurroundingLoop(), &Inst, true);
assert(VirtDef.getKind() == VirtualUse::Synthesizable ||
VirtDef.getKind() == VirtualUse::Intra ||
VirtDef.getKind() == VirtualUse::Hoisted);
}
}
if (S->hasSingleExitEdge())
return;
// PHINodes in the SCoP region's exit block are also uses to be checked.
if (!S->getRegion().isTopLevelRegion()) {
for (auto &Inst : *S->getRegion().getExit()) {
if (!isa<PHINode>(Inst))
break;
for (auto &Op : Inst.operands())
verifyUse(S, Op, LI);
}
}
}
#endif
/// Return the block that is the representing block for @p RN.
static inline BasicBlock *getRegionNodeBasicBlock(RegionNode *RN) {
return RN->isSubRegion() ? RN->getNodeAs<Region>()->getEntry()
: RN->getNodeAs<BasicBlock>();
}
void ScopBuilder::buildScop(Region &R, AssumptionCache &AC) {
scop.reset(new Scop(R, SE, LI, *SD.getDetectionContext(&R)));
buildStmts(R);
buildAccessFunctions();
// In case the region does not have an exiting block we will later (during
// code generation) split the exit block. This will move potential PHI nodes
// from the current exit block into the new region exiting block. Hence, PHI
// nodes that are at this point not part of the region will be.
// To handle these PHI nodes later we will now model their operands as scalar
// accesses. Note that we do not model anything in the exit block if we have
// an exiting block in the region, as there will not be any splitting later.
if (!R.isTopLevelRegion() && !scop->hasSingleExitEdge())
buildAccessFunctions(nullptr, *R.getExit(), nullptr,
/* IsExitBlock */ true);
// Create memory accesses for global reads since all arrays are now known.
auto *AF = SE.getConstant(IntegerType::getInt64Ty(SE.getContext()), 0);
for (auto GlobalReadPair : GlobalReads) {
ScopStmt *GlobalReadStmt = GlobalReadPair.first;
Instruction *GlobalRead = GlobalReadPair.second;
for (auto *BP : ArrayBasePointers)
addArrayAccess(GlobalReadStmt, MemAccInst(GlobalRead), MemoryAccess::READ,
BP, BP->getType(), false, {AF}, {nullptr}, GlobalRead);
}
scop->buildInvariantEquivalenceClasses();
/// A map from basic blocks to their invalid domains.
DenseMap<BasicBlock *, isl_set *> InvalidDomainMap;
if (!scop->buildDomains(&R, DT, LI, InvalidDomainMap)) {
for (auto It : InvalidDomainMap)
isl_set_free(It.second);
return;
}
scop->addUserAssumptions(AC, DT, LI, InvalidDomainMap);
// Initialize the invalid domain.
for (ScopStmt &Stmt : scop->Stmts)
if (Stmt.isBlockStmt())
Stmt.setInvalidDomain(
isl_set_copy(InvalidDomainMap[Stmt.getEntryBlock()]));
else
Stmt.setInvalidDomain(
isl_set_copy(InvalidDomainMap[getRegionNodeBasicBlock(
Stmt.getRegion()->getNode())]));
for (auto It : InvalidDomainMap)
isl_set_free(It.second);
// Remove empty statements.
// Exit early in case there are no executable statements left in this scop.
scop->simplifySCoP(false);
if (scop->isEmpty())
return;
// The ScopStmts now have enough information to initialize themselves.
for (ScopStmt &Stmt : *scop)
Stmt.init(LI);
// Check early for a feasible runtime context.
if (!scop->hasFeasibleRuntimeContext())
return;
// Check early for profitability. Afterwards it cannot change anymore,
// only the runtime context could become infeasible.
if (!scop->isProfitable(UnprofitableScalarAccs)) {
scop->invalidate(PROFITABLE, DebugLoc());
return;
}
scop->buildSchedule(LI);
scop->finalizeAccesses();
scop->realignParams();
scop->addUserContext();
// After the context was fully constructed, thus all our knowledge about
// the parameters is in there, we add all recorded assumptions to the
// assumed/invalid context.
scop->addRecordedAssumptions();
scop->simplifyContexts();
if (!scop->buildAliasChecks(AA))
return;
scop->hoistInvariantLoads();
scop->canonicalizeDynamicBasePtrs();
scop->verifyInvariantLoads();
scop->simplifySCoP(true);
// Check late for a feasible runtime context because profitability did not
// change.
if (!scop->hasFeasibleRuntimeContext())
return;
#ifndef NDEBUG
verifyUses(scop.get(), LI, DT);
#endif
}
ScopBuilder::ScopBuilder(Region *R, AssumptionCache &AC, AliasAnalysis &AA,
const DataLayout &DL, DominatorTree &DT, LoopInfo &LI,
ScopDetection &SD, ScalarEvolution &SE)
: AA(AA), DL(DL), DT(DT), LI(LI), SD(SD), SE(SE) {
Function *F = R->getEntry()->getParent();
DebugLoc Beg, End;
getDebugLocations(getBBPairForRegion(R), Beg, End);
std::string Msg = "SCoP begins here.";
emitOptimizationRemarkAnalysis(F->getContext(), DEBUG_TYPE, *F, Beg, Msg);
buildScop(*R, AC);
DEBUG(scop->print(dbgs()));
if (!scop->hasFeasibleRuntimeContext()) {
InfeasibleScops++;
Msg = "SCoP ends here but was dismissed.";
scop.reset();
} else {
Msg = "SCoP ends here.";
++ScopFound;
if (scop->getMaxLoopDepth() > 0)
++RichScopFound;
}
emitOptimizationRemarkAnalysis(F->getContext(), DEBUG_TYPE, *F, End, Msg);
}
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