/
ScopBuilder.cpp
1568 lines (1308 loc) · 53.9 KB
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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/ScopDetection.h"
#include "polly/ScopDetectionDiagnostic.h"
#include "polly/ScopInfo.h"
#include "polly/Support/SCEVValidator.h"
#include "polly/Support/ScopHelper.h"
#include "polly/Support/VirtualInstruction.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
#include "llvm/Analysis/RegionInfo.h"
#include "llvm/Analysis/RegionIterator.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <string>
#include <tuple>
#include <vector>
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.");
bool polly::ModelReadOnlyScalars;
static cl::opt<bool, true> XModelReadOnlyScalars(
"polly-analyze-read-only-scalars",
cl::desc("Model read-only scalar values in the scop description"),
cl::location(ModelReadOnlyScalars), 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));
static cl::opt<bool> DetectReductions("polly-detect-reductions",
cl::desc("Detect and exploit reductions"),
cl::Hidden, cl::ZeroOrMore,
cl::init(true), cl::cat(PollyCategory));
// Multiplicative reductions can be disabled separately as these kind of
// operations can overflow easily. Additive reductions and bit operations
// are in contrast pretty stable.
static cl::opt<bool> DisableMultiplicativeReductions(
"polly-disable-multiplicative-reductions",
cl::desc("Disable multiplicative reductions"), cl::Hidden, cl::ZeroOrMore,
cl::init(false), cl::cat(PollyCategory));
enum class GranularityChoice { BasicBlocks, ScalarIndepependence };
static cl::opt<GranularityChoice> StmtGranularity(
"polly-stmt-granularity",
cl::desc(
"Algorithm to use for splitting basic blocks into multiple statements"),
cl::values(clEnumValN(GranularityChoice::BasicBlocks, "bb",
"One statement per basic block"),
clEnumValN(GranularityChoice::ScalarIndepependence,
"scalar-indep", "Scalar independence heuristic")),
cl::init(GranularityChoice::BasicBlocks), 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.
if (scop->isEscaping(Inst))
ensureValueWrite(Inst);
}
/// 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(), Inst->getParent());
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);
}
// Build write accesses for values that are used after the SCoP.
// The instructions defining them might be synthesizable and therefore not
// contained in any statement, hence we iterate over the original instructions
// to identify all escaping values.
for (BasicBlock *BB : scop->getRegion().blocks()) {
for (Instruction &Inst : *BB)
buildEscapingDependences(&Inst);
}
}
bool ScopBuilder::shouldModelInst(Instruction *Inst, Loop *L) {
return !isa<TerminatorInst>(Inst) && !isIgnoredIntrinsic(Inst) &&
!canSynthesize(Inst, *scop, &SE, L);
}
void ScopBuilder::buildSequentialBlockStmts(BasicBlock *BB) {
Loop *SurroundingLoop = LI.getLoopFor(BB);
int Count = 0;
std::vector<Instruction *> Instructions;
for (Instruction &Inst : *BB) {
if (shouldModelInst(&Inst, SurroundingLoop))
Instructions.push_back(&Inst);
if (Inst.getMetadata("polly_split_after")) {
scop->addScopStmt(BB, SurroundingLoop, Instructions, Count);
Count++;
Instructions.clear();
}
}
scop->addScopStmt(BB, SurroundingLoop, Instructions, Count);
}
/// Is @p Inst an ordered instruction?
///
/// An unordered instruction is an instruction, such that a sequence of
/// unordered instructions can be permuted without changing semantics. Any
/// instruction for which this is not always the case is ordered.
static bool isOrderedInstruction(Instruction *Inst) {
return Inst->mayHaveSideEffects() || Inst->mayReadOrWriteMemory();
}
/// Join instructions to the same statement if one uses the scalar result of the
/// other.
static void joinOperandTree(EquivalenceClasses<Instruction *> &UnionFind,
ArrayRef<Instruction *> ModeledInsts) {
for (Instruction *Inst : ModeledInsts) {
if (isa<PHINode>(Inst))
continue;
for (Use &Op : Inst->operands()) {
Instruction *OpInst = dyn_cast<Instruction>(Op.get());
if (!OpInst)
continue;
// Check if OpInst is in the BB and is a modeled instruction.
auto OpVal = UnionFind.findValue(OpInst);
if (OpVal == UnionFind.end())
continue;
UnionFind.unionSets(Inst, OpInst);
}
}
}
/// Join instructions that are used as incoming value in successor PHIs into the
/// epilogue.
static void
joinIncomingPHIValuesIntoEpilogue(EquivalenceClasses<Instruction *> &UnionFind,
ArrayRef<Instruction *> ModeledInsts,
BasicBlock *BB) {
for (BasicBlock *Succ : successors(BB)) {
for (Instruction &SuccInst : *Succ) {
PHINode *SuccPHI = dyn_cast<PHINode>(&SuccInst);
if (!SuccPHI)
break;
Value *IncomingVal = SuccPHI->getIncomingValueForBlock(BB);
Instruction *IncomingInst = dyn_cast<Instruction>(IncomingVal);
if (!IncomingInst)
continue;
if (IncomingInst->getParent() != BB)
continue;
if (UnionFind.findValue(IncomingInst) == UnionFind.end())
continue;
UnionFind.unionSets(nullptr, IncomingInst);
}
}
}
/// Ensure that the order of ordered instructions does not change.
///
/// If we encounter an ordered instruction enclosed in instructions belonging to
/// a different statement (which might as well contain ordered instructions, but
/// this is not tested here), join them.
static void
joinOrderedInstructions(EquivalenceClasses<Instruction *> &UnionFind,
ArrayRef<Instruction *> ModeledInsts) {
SetVector<Instruction *> SeenLeaders;
for (Instruction *Inst : ModeledInsts) {
if (!isOrderedInstruction(Inst))
continue;
Instruction *Leader = UnionFind.getLeaderValue(Inst);
bool Inserted = SeenLeaders.insert(Leader);
if (Inserted)
continue;
// Merge statements to close holes. Say, we have already seen statements A
// and B, in this order. Then we see an instruction of A again and we would
// see the pattern "A B A". This function joins all statements until the
// only seen occurrence of A.
for (Instruction *Prev : reverse(SeenLeaders)) {
// Items added to 'SeenLeaders' are leaders, but may have lost their
// leadership status when merged into another statement.
Instruction *PrevLeader = UnionFind.getLeaderValue(SeenLeaders.back());
if (PrevLeader == Leader)
break;
UnionFind.unionSets(Prev, Leader);
}
}
}
/// Also ensure that the epilogue is the last statement relative to all ordered
/// instructions.
///
/// This is basically joinOrderedInstructions() but using the epilogue as
/// 'ordered instruction'.
static void joinAllAfterEpilogue(EquivalenceClasses<Instruction *> &UnionFind,
ArrayRef<Instruction *> ModeledInsts) {
bool EpilogueSeen = false;
for (Instruction *Inst : ModeledInsts) {
auto PHIWritesLeader = UnionFind.findLeader(nullptr);
auto InstLeader = UnionFind.findLeader(Inst);
if (PHIWritesLeader == InstLeader)
EpilogueSeen = true;
if (!isOrderedInstruction(Inst))
continue;
if (EpilogueSeen)
UnionFind.unionSets(PHIWritesLeader, InstLeader);
}
}
void ScopBuilder::buildEqivClassBlockStmts(BasicBlock *BB) {
Loop *L = LI.getLoopFor(BB);
// Extracting out modeled instructions saves us from checking
// shouldModelInst() repeatedly.
SmallVector<Instruction *, 32> ModeledInsts;
EquivalenceClasses<Instruction *> UnionFind;
for (Instruction &Inst : *BB) {
if (!shouldModelInst(&Inst, L))
continue;
ModeledInsts.push_back(&Inst);
UnionFind.insert(&Inst);
}
// 'nullptr' represents the last statement for a basic block. It contains no
// instructions, but holds the PHI write accesses for successor basic blocks.
// If a PHI has an incoming value defined in this BB, it can also be merged
// with other statements.
// TODO: We wouldn't need this if we would add PHIWrites into the statement
// that defines the incoming value (if in the BB) instead of always the last,
// so we could unconditionally always add a last statement.
UnionFind.insert(nullptr);
joinOperandTree(UnionFind, ModeledInsts);
joinIncomingPHIValuesIntoEpilogue(UnionFind, ModeledInsts, BB);
joinOrderedInstructions(UnionFind, ModeledInsts);
joinAllAfterEpilogue(UnionFind, ModeledInsts);
// The list of instructions for statement (statement represented by the leader
// instruction). The order of statements instructions is reversed such that
// the epilogue is first. This makes it easier to ensure that the epilogue is
// the last statement.
MapVector<Instruction *, std::vector<Instruction *>> LeaderToInstList;
// Ensure that the epilogue is last.
LeaderToInstList[nullptr];
// Collect the instructions of all leaders. UnionFind's member iterator
// unfortunately are not in any specific order.
for (Instruction &Inst : reverse(*BB)) {
auto LeaderIt = UnionFind.findLeader(&Inst);
if (LeaderIt == UnionFind.member_end())
continue;
std::vector<Instruction *> &InstList = LeaderToInstList[*LeaderIt];
InstList.push_back(&Inst);
}
// Finally build the statements.
int Count = 0;
for (auto &Instructions : reverse(LeaderToInstList)) {
std::vector<Instruction *> &InstList = Instructions.second;
std::reverse(InstList.begin(), InstList.end());
scop->addScopStmt(BB, L, std::move(InstList), Count);
Count += 1;
}
}
void ScopBuilder::buildStmts(Region &SR) {
if (scop->isNonAffineSubRegion(&SR)) {
std::vector<Instruction *> Instructions;
Loop *SurroundingLoop =
getFirstNonBoxedLoopFor(SR.getEntry(), LI, scop->getBoxedLoops());
for (Instruction &Inst : *SR.getEntry())
if (shouldModelInst(&Inst, SurroundingLoop))
Instructions.push_back(&Inst);
scop->addScopStmt(&SR, SurroundingLoop, Instructions);
return;
}
for (auto I = SR.element_begin(), E = SR.element_end(); I != E; ++I)
if (I->isSubRegion())
buildStmts(*I->getNodeAs<Region>());
else {
BasicBlock *BB = I->getNodeAs<BasicBlock>();
switch (StmtGranularity) {
case GranularityChoice::BasicBlocks:
buildSequentialBlockStmts(BB);
break;
case GranularityChoice::ScalarIndepependence:
buildEqivClassBlockStmts(BB);
break;
}
}
}
void ScopBuilder::buildAccessFunctions(ScopStmt *Stmt, BasicBlock &BB,
Region *NonAffineSubRegion) {
assert(
Stmt &&
"The exit BB is the only one that cannot be represented by a statement");
assert(Stmt->represents(&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))
return;
auto BuildAccessesForInst = [this, Stmt,
NonAffineSubRegion](Instruction *Inst) {
PHINode *PHI = dyn_cast<PHINode>(Inst);
if (PHI)
buildPHIAccesses(Stmt, PHI, NonAffineSubRegion, false);
if (auto MemInst = MemAccInst::dyn_cast(*Inst)) {
assert(Stmt && "Cannot build access function in non-existing statement");
buildMemoryAccess(MemInst, Stmt);
}
// 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)
buildScalarDependences(Stmt, Inst);
};
const InvariantLoadsSetTy &RIL = scop->getRequiredInvariantLoads();
bool IsEntryBlock = (Stmt->getEntryBlock() == &BB);
if (IsEntryBlock) {
for (Instruction *Inst : Stmt->getInstructions())
BuildAccessesForInst(Inst);
if (Stmt->isRegionStmt())
BuildAccessesForInst(BB.getTerminator());
} else {
for (Instruction &Inst : BB) {
if (isIgnoredIntrinsic(&Inst))
continue;
// Invariant loads already have been processed.
if (isa<LoadInst>(Inst) && RIL.count(cast<LoadInst>(&Inst)))
continue;
BuildAccessesForInst(&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,