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llvm-project/polly/lib/CodeGen/BlockGenerators.cpp

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//===--- BlockGenerators.cpp - Generate code for statements -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the BlockGenerator and VectorBlockGenerator classes,
// which generate sequential code and vectorized code for a polyhedral
// statement, respectively.
//
//===----------------------------------------------------------------------===//
#include "polly/CodeGen/BlockGenerators.h"
#include "polly/CodeGen/CodeGeneration.h"
#include "polly/CodeGen/IslExprBuilder.h"
#include "polly/CodeGen/RuntimeDebugBuilder.h"
#include "polly/Options.h"
#include "polly/ScopInfo.h"
#include "polly/Support/GICHelper.h"
#include "polly/Support/SCEVValidator.h"
#include "polly/Support/ScopHelper.h"
#include "polly/Support/VirtualInstruction.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/RegionInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "isl/aff.h"
#include "isl/ast.h"
#include "isl/ast_build.h"
#include "isl/set.h"
#include <deque>
using namespace llvm;
using namespace polly;
static cl::opt<bool> Aligned("enable-polly-aligned",
cl::desc("Assumed aligned memory accesses."),
cl::Hidden, cl::init(false), cl::ZeroOrMore,
cl::cat(PollyCategory));
bool PollyDebugPrinting;
static cl::opt<bool, true> DebugPrintingX(
"polly-codegen-add-debug-printing",
cl::desc("Add printf calls that show the values loaded/stored."),
cl::location(PollyDebugPrinting), cl::Hidden, cl::init(false),
cl::ZeroOrMore, cl::cat(PollyCategory));
BlockGenerator::BlockGenerator(
PollyIRBuilder &B, LoopInfo &LI, ScalarEvolution &SE, DominatorTree &DT,
AllocaMapTy &ScalarMap, EscapeUsersAllocaMapTy &EscapeMap,
ValueMapT &GlobalMap, IslExprBuilder *ExprBuilder, BasicBlock *StartBlock)
: Builder(B), LI(LI), SE(SE), ExprBuilder(ExprBuilder), DT(DT),
EntryBB(nullptr), ScalarMap(ScalarMap), EscapeMap(EscapeMap),
GlobalMap(GlobalMap), StartBlock(StartBlock) {}
Value *BlockGenerator::trySynthesizeNewValue(ScopStmt &Stmt, Value *Old,
ValueMapT &BBMap,
LoopToScevMapT &LTS,
Loop *L) const {
if (!SE.isSCEVable(Old->getType()))
return nullptr;
const SCEV *Scev = SE.getSCEVAtScope(Old, L);
if (!Scev)
return nullptr;
if (isa<SCEVCouldNotCompute>(Scev))
return nullptr;
const SCEV *NewScev = SCEVLoopAddRecRewriter::rewrite(Scev, LTS, SE);
ValueMapT VTV;
VTV.insert(BBMap.begin(), BBMap.end());
VTV.insert(GlobalMap.begin(), GlobalMap.end());
Scop &S = *Stmt.getParent();
const DataLayout &DL = S.getFunction().getParent()->getDataLayout();
auto IP = Builder.GetInsertPoint();
assert(IP != Builder.GetInsertBlock()->end() &&
"Only instructions can be insert points for SCEVExpander");
Value *Expanded =
expandCodeFor(S, SE, DL, "polly", NewScev, Old->getType(), &*IP, &VTV,
StartBlock->getSinglePredecessor());
BBMap[Old] = Expanded;
return Expanded;
}
Value *BlockGenerator::getNewValue(ScopStmt &Stmt, Value *Old, ValueMapT &BBMap,
LoopToScevMapT &LTS, Loop *L) const {
auto lookupGlobally = [this](Value *Old) -> Value * {
Value *New = GlobalMap.lookup(Old);
if (!New)
return nullptr;
// Required by:
// * Isl/CodeGen/OpenMP/invariant_base_pointer_preloaded.ll
// * Isl/CodeGen/OpenMP/invariant_base_pointer_preloaded_different_bb.ll
// * Isl/CodeGen/OpenMP/invariant_base_pointer_preloaded_pass_only_needed.ll
// * Isl/CodeGen/OpenMP/invariant_base_pointers_preloaded.ll
// * Isl/CodeGen/OpenMP/loop-body-references-outer-values-3.ll
// * Isl/CodeGen/OpenMP/single_loop_with_loop_invariant_baseptr.ll
// GlobalMap should be a mapping from (value in original SCoP) to (copied
// value in generated SCoP), without intermediate mappings, which might
// easily require transitiveness as well.
if (Value *NewRemapped = GlobalMap.lookup(New))
New = NewRemapped;
// No test case for this code.
if (Old->getType()->getScalarSizeInBits() <
New->getType()->getScalarSizeInBits())
New = Builder.CreateTruncOrBitCast(New, Old->getType());
return New;
};
Value *New = nullptr;
auto VUse = VirtualUse::create(&Stmt, L, Old, true);
switch (VUse.getKind()) {
case VirtualUse::Block:
// BasicBlock are constants, but the BlockGenerator copies them.
New = BBMap.lookup(Old);
break;
case VirtualUse::Constant:
// Used by:
// * Isl/CodeGen/OpenMP/reference-argument-from-non-affine-region.ll
// Constants should not be redefined. In this case, the GlobalMap just
// contains a mapping to the same constant, which is unnecessary, but
// harmless.
if ((New = lookupGlobally(Old)))
break;
assert(!BBMap.count(Old));
New = Old;
break;
case VirtualUse::ReadOnly:
assert(!GlobalMap.count(Old));
// Required for:
// * Isl/CodeGen/MemAccess/create_arrays.ll
// * Isl/CodeGen/read-only-scalars.ll
// * ScheduleOptimizer/pattern-matching-based-opts_10.ll
// For some reason these reload a read-only value. The reloaded value ends
// up in BBMap, buts its value should be identical.
//
// Required for:
// * Isl/CodeGen/OpenMP/single_loop_with_param.ll
// The parallel subfunctions need to reference the read-only value from the
// parent function, this is done by reloading them locally.
if ((New = BBMap.lookup(Old)))
break;
New = Old;
break;
case VirtualUse::Synthesizable:
// Used by:
// * Isl/CodeGen/OpenMP/loop-body-references-outer-values-3.ll
// * Isl/CodeGen/OpenMP/recomputed-srem.ll
// * Isl/CodeGen/OpenMP/reference-other-bb.ll
// * Isl/CodeGen/OpenMP/two-parallel-loops-reference-outer-indvar.ll
// For some reason synthesizable values end up in GlobalMap. Their values
// are the same as trySynthesizeNewValue would return. The legacy
// implementation prioritized GlobalMap, so this is what we do here as well.
// Ideally, synthesizable values should not end up in GlobalMap.
if ((New = lookupGlobally(Old)))
break;
// Required for:
// * Isl/CodeGen/RuntimeDebugBuilder/combine_different_values.ll
// * Isl/CodeGen/getNumberOfIterations.ll
// * Isl/CodeGen/non_affine_float_compare.ll
// * ScheduleOptimizer/pattern-matching-based-opts_10.ll
// Ideally, synthesizable values are synthesized by trySynthesizeNewValue,
// not precomputed (SCEVExpander has its own caching mechanism).
// These tests fail without this, but I think trySynthesizeNewValue would
// just re-synthesize the same instructions.
if ((New = BBMap.lookup(Old)))
break;
New = trySynthesizeNewValue(Stmt, Old, BBMap, LTS, L);
break;
case VirtualUse::Hoisted:
// TODO: Hoisted invariant loads should be found in GlobalMap only, but not
// redefined locally (which will be ignored anyway). That is, the following
// assertion should apply: assert(!BBMap.count(Old))
New = lookupGlobally(Old);
break;
case VirtualUse::Intra:
case VirtualUse::Inter:
assert(!GlobalMap.count(Old) &&
"Intra and inter-stmt values are never global");
New = BBMap.lookup(Old);
break;
}
assert(New && "Unexpected scalar dependence in region!");
return New;
}
void BlockGenerator::copyInstScalar(ScopStmt &Stmt, Instruction *Inst,
ValueMapT &BBMap, LoopToScevMapT &LTS) {
// We do not generate debug intrinsics as we did not investigate how to
// copy them correctly. At the current state, they just crash the code
// generation as the meta-data operands are not correctly copied.
if (isa<DbgInfoIntrinsic>(Inst))
return;
Instruction *NewInst = Inst->clone();
// Replace old operands with the new ones.
for (Value *OldOperand : Inst->operands()) {
Value *NewOperand =
getNewValue(Stmt, OldOperand, BBMap, LTS, getLoopForStmt(Stmt));
if (!NewOperand) {
assert(!isa<StoreInst>(NewInst) &&
"Store instructions are always needed!");
NewInst->deleteValue();
return;
}
NewInst->replaceUsesOfWith(OldOperand, NewOperand);
}
Builder.Insert(NewInst);
BBMap[Inst] = NewInst;
// When copying the instruction onto the Module meant for the GPU,
// debug metadata attached to an instruction causes all related
// metadata to be pulled into the Module. This includes the DICompileUnit,
// which will not be listed in llvm.dbg.cu of the Module since the Module
// doesn't contain one. This fails the verification of the Module and the
// subsequent generation of the ASM string.
if (NewInst->getModule() != Inst->getModule())
NewInst->setDebugLoc(llvm::DebugLoc());
if (!NewInst->getType()->isVoidTy())
NewInst->setName("p_" + Inst->getName());
}
Value *
BlockGenerator::generateLocationAccessed(ScopStmt &Stmt, MemAccInst Inst,
ValueMapT &BBMap, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
const MemoryAccess &MA = Stmt.getArrayAccessFor(Inst);
return generateLocationAccessed(
Stmt, getLoopForStmt(Stmt),
Inst.isNull() ? nullptr : Inst.getPointerOperand(), BBMap, LTS,
NewAccesses, MA.getId().release(), MA.getAccessValue()->getType());
}
Value *BlockGenerator::generateLocationAccessed(
ScopStmt &Stmt, Loop *L, Value *Pointer, ValueMapT &BBMap,
LoopToScevMapT &LTS, isl_id_to_ast_expr *NewAccesses, __isl_take isl_id *Id,
Type *ExpectedType) {
isl_ast_expr *AccessExpr = isl_id_to_ast_expr_get(NewAccesses, Id);
if (AccessExpr) {
AccessExpr = isl_ast_expr_address_of(AccessExpr);
auto Address = ExprBuilder->create(AccessExpr);
// Cast the address of this memory access to a pointer type that has the
// same element type as the original access, but uses the address space of
// the newly generated pointer.
auto OldPtrTy = ExpectedType->getPointerTo();
auto NewPtrTy = Address->getType();
OldPtrTy = PointerType::get(OldPtrTy->getElementType(),
NewPtrTy->getPointerAddressSpace());
if (OldPtrTy != NewPtrTy)
Address = Builder.CreateBitOrPointerCast(Address, OldPtrTy);
return Address;
}
assert(
Pointer &&
"If expression was not generated, must use the original pointer value");
return getNewValue(Stmt, Pointer, BBMap, LTS, L);
}
Value *
BlockGenerator::getImplicitAddress(MemoryAccess &Access, Loop *L,
LoopToScevMapT &LTS, ValueMapT &BBMap,
__isl_keep isl_id_to_ast_expr *NewAccesses) {
if (Access.isLatestArrayKind())
return generateLocationAccessed(*Access.getStatement(), L, nullptr, BBMap,
LTS, NewAccesses, Access.getId().release(),
Access.getAccessValue()->getType());
return getOrCreateAlloca(Access);
}
Loop *BlockGenerator::getLoopForStmt(const ScopStmt &Stmt) const {
auto *StmtBB = Stmt.getEntryBlock();
return LI.getLoopFor(StmtBB);
}
Value *BlockGenerator::generateArrayLoad(ScopStmt &Stmt, LoadInst *Load,
ValueMapT &BBMap, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
if (Value *PreloadLoad = GlobalMap.lookup(Load))
return PreloadLoad;
Value *NewPointer =
generateLocationAccessed(Stmt, Load, BBMap, LTS, NewAccesses);
Value *ScalarLoad = Builder.CreateAlignedLoad(
NewPointer, Load->getAlignment(), Load->getName() + "_p_scalar_");
if (PollyDebugPrinting)
RuntimeDebugBuilder::createCPUPrinter(Builder, "Load from ", NewPointer,
": ", ScalarLoad, "\n");
return ScalarLoad;
}
void BlockGenerator::generateArrayStore(ScopStmt &Stmt, StoreInst *Store,
ValueMapT &BBMap, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
MemoryAccess &MA = Stmt.getArrayAccessFor(Store);
isl::set AccDom = MA.getAccessRelation().domain();
std::string Subject = MA.getId().get_name();
generateConditionalExecution(Stmt, AccDom, Subject.c_str(), [&, this]() {
Value *NewPointer =
generateLocationAccessed(Stmt, Store, BBMap, LTS, NewAccesses);
Value *ValueOperand = getNewValue(Stmt, Store->getValueOperand(), BBMap,
LTS, getLoopForStmt(Stmt));
if (PollyDebugPrinting)
RuntimeDebugBuilder::createCPUPrinter(Builder, "Store to ", NewPointer,
": ", ValueOperand, "\n");
Builder.CreateAlignedStore(ValueOperand, NewPointer, Store->getAlignment());
});
}
bool BlockGenerator::canSyntheziseInStmt(ScopStmt &Stmt, Instruction *Inst) {
Loop *L = getLoopForStmt(Stmt);
return (Stmt.isBlockStmt() || !Stmt.getRegion()->contains(L)) &&
canSynthesize(Inst, *Stmt.getParent(), &SE, L);
}
void BlockGenerator::copyInstruction(ScopStmt &Stmt, Instruction *Inst,
ValueMapT &BBMap, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
// Terminator instructions control the control flow. They are explicitly
// expressed in the clast and do not need to be copied.
if (Inst->isTerminator())
return;
// Synthesizable statements will be generated on-demand.
if (canSyntheziseInStmt(Stmt, Inst))
return;
if (auto *Load = dyn_cast<LoadInst>(Inst)) {
Value *NewLoad = generateArrayLoad(Stmt, Load, BBMap, LTS, NewAccesses);
// Compute NewLoad before its insertion in BBMap to make the insertion
// deterministic.
BBMap[Load] = NewLoad;
return;
}
if (auto *Store = dyn_cast<StoreInst>(Inst)) {
// Identified as redundant by -polly-simplify.
if (!Stmt.getArrayAccessOrNULLFor(Store))
return;
generateArrayStore(Stmt, Store, BBMap, LTS, NewAccesses);
return;
}
if (auto *PHI = dyn_cast<PHINode>(Inst)) {
copyPHIInstruction(Stmt, PHI, BBMap, LTS);
return;
}
// Skip some special intrinsics for which we do not adjust the semantics to
// the new schedule. All others are handled like every other instruction.
if (isIgnoredIntrinsic(Inst))
return;
copyInstScalar(Stmt, Inst, BBMap, LTS);
}
void BlockGenerator::removeDeadInstructions(BasicBlock *BB, ValueMapT &BBMap) {
auto NewBB = Builder.GetInsertBlock();
for (auto I = NewBB->rbegin(); I != NewBB->rend(); I++) {
Instruction *NewInst = &*I;
if (!isInstructionTriviallyDead(NewInst))
continue;
for (auto Pair : BBMap)
if (Pair.second == NewInst) {
BBMap.erase(Pair.first);
}
NewInst->eraseFromParent();
I = NewBB->rbegin();
}
}
void BlockGenerator::copyStmt(ScopStmt &Stmt, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
assert(Stmt.isBlockStmt() &&
"Only block statements can be copied by the block generator");
ValueMapT BBMap;
BasicBlock *BB = Stmt.getBasicBlock();
copyBB(Stmt, BB, BBMap, LTS, NewAccesses);
removeDeadInstructions(BB, BBMap);
}
BasicBlock *BlockGenerator::splitBB(BasicBlock *BB) {
BasicBlock *CopyBB = SplitBlock(Builder.GetInsertBlock(),
&*Builder.GetInsertPoint(), &DT, &LI);
CopyBB->setName("polly.stmt." + BB->getName());
return CopyBB;
}
BasicBlock *BlockGenerator::copyBB(ScopStmt &Stmt, BasicBlock *BB,
ValueMapT &BBMap, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
BasicBlock *CopyBB = splitBB(BB);
Builder.SetInsertPoint(&CopyBB->front());
generateScalarLoads(Stmt, LTS, BBMap, NewAccesses);
copyBB(Stmt, BB, CopyBB, BBMap, LTS, NewAccesses);
// After a basic block was copied store all scalars that escape this block in
// their alloca.
generateScalarStores(Stmt, LTS, BBMap, NewAccesses);
return CopyBB;
}
void BlockGenerator::copyBB(ScopStmt &Stmt, BasicBlock *BB, BasicBlock *CopyBB,
ValueMapT &BBMap, LoopToScevMapT &LTS,
isl_id_to_ast_expr *NewAccesses) {
EntryBB = &CopyBB->getParent()->getEntryBlock();
// Block statements and the entry blocks of region statement are code
// generated from instruction lists. This allow us to optimize the
// instructions that belong to a certain scop statement. As the code
// structure of region statements might be arbitrary complex, optimizing the
// instruction list is not yet supported.
if (Stmt.isBlockStmt() || (Stmt.isRegionStmt() && Stmt.getEntryBlock() == BB))
for (Instruction *Inst : Stmt.getInstructions())
copyInstruction(Stmt, Inst, BBMap, LTS, NewAccesses);
else
for (Instruction &Inst : *BB)
copyInstruction(Stmt, &Inst, BBMap, LTS, NewAccesses);
}
Value *BlockGenerator::getOrCreateAlloca(const MemoryAccess &Access) {
assert(!Access.isLatestArrayKind() && "Trying to get alloca for array kind");
return getOrCreateAlloca(Access.getLatestScopArrayInfo());
}
Value *BlockGenerator::getOrCreateAlloca(const ScopArrayInfo *Array) {
assert(!Array->isArrayKind() && "Trying to get alloca for array kind");
auto &Addr = ScalarMap[Array];
if (Addr) {
// Allow allocas to be (temporarily) redirected once by adding a new
// old-alloca-addr to new-addr mapping to GlobalMap. This functionality
// is used for example by the OpenMP code generation where a first use
// of a scalar while still in the host code allocates a normal alloca with
// getOrCreateAlloca. When the values of this scalar are accessed during
// the generation of the parallel subfunction, these values are copied over
// to the parallel subfunction and each request for a scalar alloca slot
// must be forwarded to the temporary in-subfunction slot. This mapping is
// removed when the subfunction has been generated and again normal host
// code is generated. Due to the following reasons it is not possible to
// perform the GlobalMap lookup right after creating the alloca below, but
// instead we need to check GlobalMap at each call to getOrCreateAlloca:
//
// 1) GlobalMap may be changed multiple times (for each parallel loop),
// 2) The temporary mapping is commonly only known after the initial
// alloca has already been generated, and
// 3) The original alloca value must be restored after leaving the
// sub-function.
if (Value *NewAddr = GlobalMap.lookup(&*Addr))
return NewAddr;
return Addr;
}
Type *Ty = Array->getElementType();
Value *ScalarBase = Array->getBasePtr();
std::string NameExt;
if (Array->isPHIKind())
NameExt = ".phiops";
else
NameExt = ".s2a";
const DataLayout &DL = Builder.GetInsertBlock()->getModule()->getDataLayout();
Addr = new AllocaInst(Ty, DL.getAllocaAddrSpace(),
ScalarBase->getName() + NameExt);
EntryBB = &Builder.GetInsertBlock()->getParent()->getEntryBlock();
Addr->insertBefore(&*EntryBB->getFirstInsertionPt());
return Addr;
}
void BlockGenerator::handleOutsideUsers(const Scop &S, ScopArrayInfo *Array) {
Instruction *Inst = cast<Instruction>(Array->getBasePtr());
// If there are escape users we get the alloca for this instruction and put it
// in the EscapeMap for later finalization. Lastly, if the instruction was
// copied multiple times we already did this and can exit.
if (EscapeMap.count(Inst))
return;
EscapeUserVectorTy EscapeUsers;
for (User *U : Inst->users()) {
// Non-instruction user will never escape.
Instruction *UI = dyn_cast<Instruction>(U);
if (!UI)
continue;
if (S.contains(UI))
continue;
EscapeUsers.push_back(UI);
}
// Exit if no escape uses were found.
if (EscapeUsers.empty())
return;
// Get or create an escape alloca for this instruction.
auto *ScalarAddr = getOrCreateAlloca(Array);
// Remember that this instruction has escape uses and the escape alloca.
EscapeMap[Inst] = std::make_pair(ScalarAddr, std::move(EscapeUsers));
}
void BlockGenerator::generateScalarLoads(
ScopStmt &Stmt, LoopToScevMapT &LTS, ValueMapT &BBMap,
__isl_keep isl_id_to_ast_expr *NewAccesses) {
for (MemoryAccess *MA : Stmt) {
if (MA->isOriginalArrayKind() || MA->isWrite())
continue;
#ifndef NDEBUG
auto *StmtDom = Stmt.getDomain().release();
auto *AccDom = isl_map_domain(MA->getAccessRelation().release());
assert(isl_set_is_subset(StmtDom, AccDom) &&
"Scalar must be loaded in all statement instances");
isl_set_free(StmtDom);
isl_set_free(AccDom);
#endif
auto *Address =
getImplicitAddress(*MA, getLoopForStmt(Stmt), LTS, BBMap, NewAccesses);
assert((!isa<Instruction>(Address) ||
DT.dominates(cast<Instruction>(Address)->getParent(),
Builder.GetInsertBlock())) &&
"Domination violation");
BBMap[MA->getAccessValue()] =
Builder.CreateLoad(Address, Address->getName() + ".reload");
}
}
Value *BlockGenerator::buildContainsCondition(ScopStmt &Stmt,
const isl::set &Subdomain) {
isl::ast_build AstBuild = Stmt.getAstBuild();
isl::set Domain = Stmt.getDomain();
isl::union_map USchedule = AstBuild.get_schedule();
USchedule = USchedule.intersect_domain(Domain);
assert(!USchedule.is_empty());
isl::map Schedule = isl::map::from_union_map(USchedule);
isl::set ScheduledDomain = Schedule.range();
isl::set ScheduledSet = Subdomain.apply(Schedule);
isl::ast_build RestrictedBuild = AstBuild.restrict(ScheduledDomain);
isl::ast_expr IsInSet = RestrictedBuild.expr_from(ScheduledSet);
Value *IsInSetExpr = ExprBuilder->create(IsInSet.copy());
IsInSetExpr = Builder.CreateICmpNE(
IsInSetExpr, ConstantInt::get(IsInSetExpr->getType(), 0));
return IsInSetExpr;
}
void BlockGenerator::generateConditionalExecution(
ScopStmt &Stmt, const isl::set &Subdomain, StringRef Subject,
const std::function<void()> &GenThenFunc) {
isl::set StmtDom = Stmt.getDomain();
// If the condition is a tautology, don't generate a condition around the
// code.
bool IsPartialWrite =
!StmtDom.intersect_params(Stmt.getParent()->getContext())
.is_subset(Subdomain);
if (!IsPartialWrite) {
GenThenFunc();
return;
}
// Generate the condition.
Value *Cond = buildContainsCondition(Stmt, Subdomain);
// Don't call GenThenFunc if it is never executed. An ast index expression
// might not be defined in this case.
if (auto *Const = dyn_cast<ConstantInt>(Cond))
if (Const->isZero())
return;
BasicBlock *HeadBlock = Builder.GetInsertBlock();
StringRef BlockName = HeadBlock->getName();
// Generate the conditional block.
SplitBlockAndInsertIfThen(Cond, &*Builder.GetInsertPoint(), false, nullptr,
&DT, &LI);
BranchInst *Branch = cast<BranchInst>(HeadBlock->getTerminator());
BasicBlock *ThenBlock = Branch->getSuccessor(0);
BasicBlock *TailBlock = Branch->getSuccessor(1);
// Assign descriptive names.
if (auto *CondInst = dyn_cast<Instruction>(Cond))
CondInst->setName("polly." + Subject + ".cond");
ThenBlock->setName(BlockName + "." + Subject + ".partial");
TailBlock->setName(BlockName + ".cont");
// Put the client code into the conditional block and continue in the merge
// block afterwards.
Builder.SetInsertPoint(ThenBlock, ThenBlock->getFirstInsertionPt());
GenThenFunc();
Builder.SetInsertPoint(TailBlock, TailBlock->getFirstInsertionPt());
}
void BlockGenerator::generateScalarStores(
ScopStmt &Stmt, LoopToScevMapT &LTS, ValueMapT &BBMap,
__isl_keep isl_id_to_ast_expr *NewAccesses) {
Loop *L = LI.getLoopFor(Stmt.getBasicBlock());
assert(Stmt.isBlockStmt() &&
"Region statements need to use the generateScalarStores() function in "
"the RegionGenerator");
for (MemoryAccess *MA : Stmt) {
if (MA->isOriginalArrayKind() || MA->isRead())
continue;
isl::set AccDom = MA->getAccessRelation().domain();
std::string Subject = MA->getId().get_name();
generateConditionalExecution(
Stmt, AccDom, Subject.c_str(), [&, this, MA]() {
Value *Val = MA->getAccessValue();
if (MA->isAnyPHIKind()) {
assert(MA->getIncoming().size() >= 1 &&
"Block statements have exactly one exiting block, or "
"multiple but "
"with same incoming block and value");
assert(std::all_of(MA->getIncoming().begin(),
MA->getIncoming().end(),
[&](std::pair<BasicBlock *, Value *> p) -> bool {
return p.first == Stmt.getBasicBlock();
}) &&
"Incoming block must be statement's block");
Val = MA->getIncoming()[0].second;
}
auto Address = getImplicitAddress(*MA, getLoopForStmt(Stmt), LTS,
BBMap, NewAccesses);
Val = getNewValue(Stmt, Val, BBMap, LTS, L);
assert((!isa<Instruction>(Val) ||
DT.dominates(cast<Instruction>(Val)->getParent(),
Builder.GetInsertBlock())) &&
"Domination violation");
assert((!isa<Instruction>(Address) ||
DT.dominates(cast<Instruction>(Address)->getParent(),
Builder.GetInsertBlock())) &&
"Domination violation");
// The new Val might have a different type than the old Val due to
// ScalarEvolution looking through bitcasts.
if (Val->getType() != Address->getType()->getPointerElementType())
Address = Builder.CreateBitOrPointerCast(
Address, Val->getType()->getPointerTo());
Builder.CreateStore(Val, Address);
});
}
}
void BlockGenerator::createScalarInitialization(Scop &S) {
BasicBlock *ExitBB = S.getExit();
BasicBlock *PreEntryBB = S.getEnteringBlock();
Builder.SetInsertPoint(&*StartBlock->begin());
for (auto &Array : S.arrays()) {
if (Array->getNumberOfDimensions() != 0)
continue;
if (Array->isPHIKind()) {
// For PHI nodes, the only values we need to store are the ones that
// reach the PHI node from outside the region. In general there should
// only be one such incoming edge and this edge should enter through
// 'PreEntryBB'.
auto PHI = cast<PHINode>(Array->getBasePtr());
for (auto BI = PHI->block_begin(), BE = PHI->block_end(); BI != BE; BI++)
if (!S.contains(*BI) && *BI != PreEntryBB)
llvm_unreachable("Incoming edges from outside the scop should always "
"come from PreEntryBB");
int Idx = PHI->getBasicBlockIndex(PreEntryBB);
if (Idx < 0)
continue;
Value *ScalarValue = PHI->getIncomingValue(Idx);
Builder.CreateStore(ScalarValue, getOrCreateAlloca(Array));
continue;
}
auto *Inst = dyn_cast<Instruction>(Array->getBasePtr());
if (Inst && S.contains(Inst))
continue;
// PHI nodes that are not marked as such in their SAI object are either exit
// PHI nodes we model as common scalars but without initialization, or
// incoming phi nodes that need to be initialized. Check if the first is the
// case for Inst and do not create and initialize memory if so.
if (auto *PHI = dyn_cast_or_null<PHINode>(Inst))
if (!S.hasSingleExitEdge() && PHI->getBasicBlockIndex(ExitBB) >= 0)
continue;
Builder.CreateStore(Array->getBasePtr(), getOrCreateAlloca(Array));
}
}
void BlockGenerator::createScalarFinalization(Scop &S) {
// The exit block of the __unoptimized__ region.
BasicBlock *ExitBB = S.getExitingBlock();
// The merge block __just after__ the region and the optimized region.
BasicBlock *MergeBB = S.getExit();
// The exit block of the __optimized__ region.
BasicBlock *OptExitBB = *(pred_begin(MergeBB));
if (OptExitBB == ExitBB)
OptExitBB = *(++pred_begin(MergeBB));
Builder.SetInsertPoint(OptExitBB->getTerminator());
for (const auto &EscapeMapping : EscapeMap) {
// Extract the escaping instruction and the escaping users as well as the
// alloca the instruction was demoted to.
Instruction *EscapeInst = EscapeMapping.first;
const auto &EscapeMappingValue = EscapeMapping.second;
const EscapeUserVectorTy &EscapeUsers = EscapeMappingValue.second;
Value *ScalarAddr = EscapeMappingValue.first;
// Reload the demoted instruction in the optimized version of the SCoP.
Value *EscapeInstReload =
Builder.CreateLoad(ScalarAddr, EscapeInst->getName() + ".final_reload");
EscapeInstReload =
Builder.CreateBitOrPointerCast(EscapeInstReload, EscapeInst->getType());
// Create the merge PHI that merges the optimized and unoptimized version.
PHINode *MergePHI = PHINode::Create(EscapeInst->getType(), 2,
EscapeInst->getName() + ".merge");
MergePHI->insertBefore(&*MergeBB->getFirstInsertionPt());
// Add the respective values to the merge PHI.
MergePHI->addIncoming(EscapeInstReload, OptExitBB);
MergePHI->addIncoming(EscapeInst, ExitBB);
// The information of scalar evolution about the escaping instruction needs
// to be revoked so the new merged instruction will be used.
if (SE.isSCEVable(EscapeInst->getType()))
SE.forgetValue(EscapeInst);
// Replace all uses of the demoted instruction with the merge PHI.
for (Instruction *EUser : EscapeUsers)
EUser->replaceUsesOfWith(EscapeInst, MergePHI);
}
}
void BlockGenerator::findOutsideUsers(Scop &S) {
for (auto &Array : S.arrays()) {
if (Array->getNumberOfDimensions() != 0)
continue;
if (Array->isPHIKind())
continue;
auto *Inst = dyn_cast<Instruction>(Array->getBasePtr());
if (!Inst)
continue;
// Scop invariant hoisting moves some of the base pointers out of the scop.
// We can ignore these, as the invariant load hoisting already registers the
// relevant outside users.
if (!S.contains(Inst))
continue;
handleOutsideUsers(S, Array);
}
}
void BlockGenerator::createExitPHINodeMerges(Scop &S) {
if (S.hasSingleExitEdge())
return;
auto *ExitBB = S.getExitingBlock();
auto *MergeBB = S.getExit();
auto *AfterMergeBB = MergeBB->getSingleSuccessor();
BasicBlock *OptExitBB = *(pred_begin(MergeBB));
if (OptExitBB == ExitBB)
OptExitBB = *(++pred_begin(MergeBB));
Builder.SetInsertPoint(OptExitBB->getTerminator());
for (auto &SAI : S.arrays()) {
auto *Val = SAI->getBasePtr();
// Only Value-like scalars need a merge PHI. Exit block PHIs receive either
// the original PHI's value or the reloaded incoming values from the
// generated code. An llvm::Value is merged between the original code's
// value or the generated one.
if (!SAI->isExitPHIKind())
continue;
PHINode *PHI = dyn_cast<PHINode>(Val);
if (!PHI)
continue;
if (PHI->getParent() != AfterMergeBB)
continue;
std::string Name = PHI->getName();
Value *ScalarAddr = getOrCreateAlloca(SAI);
Value *Reload = Builder.CreateLoad(ScalarAddr, Name + ".ph.final_reload");
Reload = Builder.CreateBitOrPointerCast(Reload, PHI->getType());
Value *OriginalValue = PHI->getIncomingValueForBlock(MergeBB);
assert((!isa<Instruction>(OriginalValue) ||
cast<Instruction>(OriginalValue)->getParent() != MergeBB) &&
"Original value must no be one we just generated.");
auto *MergePHI = PHINode::Create(PHI->getType(), 2, Name + ".ph.merge");
MergePHI->insertBefore(&*MergeBB->getFirstInsertionPt());
MergePHI->addIncoming(Reload, OptExitBB);
MergePHI->addIncoming(OriginalValue, ExitBB);
int Idx = PHI->getBasicBlockIndex(MergeBB);
PHI->setIncomingValue(Idx, MergePHI);
}
}
void BlockGenerator::invalidateScalarEvolution(Scop &S) {
for (auto &Stmt : S)
if (Stmt.isCopyStmt())
continue;
else if (Stmt.isBlockStmt())
for (auto &Inst : *Stmt.getBasicBlock())
SE.forgetValue(&Inst);
else if (Stmt.isRegionStmt())
for (auto *BB : Stmt.getRegion()->blocks())
for (auto &Inst : *BB)
SE.forgetValue(&Inst);
else
llvm_unreachable("Unexpected statement type found");
// Invalidate SCEV of loops surrounding the EscapeUsers.
for (const auto &EscapeMapping : EscapeMap) {
const EscapeUserVectorTy &EscapeUsers = EscapeMapping.second.second;
for (Instruction *EUser : EscapeUsers) {
if (Loop *L = LI.getLoopFor(EUser->getParent()))
while (L) {
SE.forgetLoop(L);
L = L->getParentLoop();
}
}
}
}
void BlockGenerator::finalizeSCoP(Scop &S) {
findOutsideUsers(S);
createScalarInitialization(S);
createExitPHINodeMerges(S);
createScalarFinalization(S);
invalidateScalarEvolution(S);
}
VectorBlockGenerator::VectorBlockGenerator(BlockGenerator &BlockGen,
std::vector<LoopToScevMapT> &VLTS,
isl_map *Schedule)
: BlockGenerator(BlockGen), VLTS(VLTS), Schedule(Schedule) {
assert(Schedule && "No statement domain provided");
}
Value *VectorBlockGenerator::getVectorValue(ScopStmt &Stmt, Value *Old,
ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps,
Loop *L) {
if (Value *NewValue = VectorMap.lookup(Old))
return NewValue;
int Width = getVectorWidth();
Value *Vector = UndefValue::get(VectorType::get(Old->getType(), Width));
for (int Lane = 0; Lane < Width; Lane++)
Vector = Builder.CreateInsertElement(
Vector, getNewValue(Stmt, Old, ScalarMaps[Lane], VLTS[Lane], L),
Builder.getInt32(Lane));
VectorMap[Old] = Vector;
return Vector;
}
Type *VectorBlockGenerator::getVectorPtrTy(const Value *Val, int Width) {
PointerType *PointerTy = dyn_cast<PointerType>(Val->getType());
assert(PointerTy && "PointerType expected");
Type *ScalarType = PointerTy->getElementType();
VectorType *VectorType = VectorType::get(ScalarType, Width);
return PointerType::getUnqual(VectorType);
}
Value *VectorBlockGenerator::generateStrideOneLoad(
ScopStmt &Stmt, LoadInst *Load, VectorValueMapT &ScalarMaps,
__isl_keep isl_id_to_ast_expr *NewAccesses, bool NegativeStride = false) {
unsigned VectorWidth = getVectorWidth();
auto *Pointer = Load->getPointerOperand();
Type *VectorPtrType = getVectorPtrTy(Pointer, VectorWidth);
unsigned Offset = NegativeStride ? VectorWidth - 1 : 0;
Value *NewPointer = generateLocationAccessed(Stmt, Load, ScalarMaps[Offset],
VLTS[Offset], NewAccesses);
Value *VectorPtr =
Builder.CreateBitCast(NewPointer, VectorPtrType, "vector_ptr");
LoadInst *VecLoad =
Builder.CreateLoad(VectorPtr, Load->getName() + "_p_vec_full");
if (!Aligned)
VecLoad->setAlignment(8);
if (NegativeStride) {
SmallVector<Constant *, 16> Indices;
for (int i = VectorWidth - 1; i >= 0; i--)
Indices.push_back(ConstantInt::get(Builder.getInt32Ty(), i));
Constant *SV = llvm::ConstantVector::get(Indices);
Value *RevVecLoad = Builder.CreateShuffleVector(
VecLoad, VecLoad, SV, Load->getName() + "_reverse");
return RevVecLoad;
}
return VecLoad;
}
Value *VectorBlockGenerator::generateStrideZeroLoad(
ScopStmt &Stmt, LoadInst *Load, ValueMapT &BBMap,
__isl_keep isl_id_to_ast_expr *NewAccesses) {
auto *Pointer = Load->getPointerOperand();
Type *VectorPtrType = getVectorPtrTy(Pointer, 1);
Value *NewPointer =
generateLocationAccessed(Stmt, Load, BBMap, VLTS[0], NewAccesses);
Value *VectorPtr = Builder.CreateBitCast(NewPointer, VectorPtrType,
Load->getName() + "_p_vec_p");
LoadInst *ScalarLoad =
Builder.CreateLoad(VectorPtr, Load->getName() + "_p_splat_one");
if (!Aligned)
ScalarLoad->setAlignment(8);
Constant *SplatVector = Constant::getNullValue(
VectorType::get(Builder.getInt32Ty(), getVectorWidth()));
Value *VectorLoad = Builder.CreateShuffleVector(
ScalarLoad, ScalarLoad, SplatVector, Load->getName() + "_p_splat");
return VectorLoad;
}
Value *VectorBlockGenerator::generateUnknownStrideLoad(
ScopStmt &Stmt, LoadInst *Load, VectorValueMapT &ScalarMaps,
__isl_keep isl_id_to_ast_expr *NewAccesses) {
int VectorWidth = getVectorWidth();
auto *Pointer = Load->getPointerOperand();
VectorType *VectorType = VectorType::get(
dyn_cast<PointerType>(Pointer->getType())->getElementType(), VectorWidth);
Value *Vector = UndefValue::get(VectorType);
for (int i = 0; i < VectorWidth; i++) {
Value *NewPointer = generateLocationAccessed(Stmt, Load, ScalarMaps[i],
VLTS[i], NewAccesses);
Value *ScalarLoad =
Builder.CreateLoad(NewPointer, Load->getName() + "_p_scalar_");
Vector = Builder.CreateInsertElement(
Vector, ScalarLoad, Builder.getInt32(i), Load->getName() + "_p_vec_");
}
return Vector;
}
void VectorBlockGenerator::generateLoad(
ScopStmt &Stmt, LoadInst *Load, ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps, __isl_keep isl_id_to_ast_expr *NewAccesses) {
if (Value *PreloadLoad = GlobalMap.lookup(Load)) {
VectorMap[Load] = Builder.CreateVectorSplat(getVectorWidth(), PreloadLoad,
Load->getName() + "_p");
return;
}
if (!VectorType::isValidElementType(Load->getType())) {
for (int i = 0; i < getVectorWidth(); i++)
ScalarMaps[i][Load] =
generateArrayLoad(Stmt, Load, ScalarMaps[i], VLTS[i], NewAccesses);
return;
}
const MemoryAccess &Access = Stmt.getArrayAccessFor(Load);
// Make sure we have scalar values available to access the pointer to
// the data location.
extractScalarValues(Load, VectorMap, ScalarMaps);
Value *NewLoad;
if (Access.isStrideZero(isl::manage_copy(Schedule)))
NewLoad = generateStrideZeroLoad(Stmt, Load, ScalarMaps[0], NewAccesses);
else if (Access.isStrideOne(isl::manage_copy(Schedule)))
NewLoad = generateStrideOneLoad(Stmt, Load, ScalarMaps, NewAccesses);
else if (Access.isStrideX(isl::manage_copy(Schedule), -1))
NewLoad = generateStrideOneLoad(Stmt, Load, ScalarMaps, NewAccesses, true);
else
NewLoad = generateUnknownStrideLoad(Stmt, Load, ScalarMaps, NewAccesses);
VectorMap[Load] = NewLoad;
}
void VectorBlockGenerator::copyUnaryInst(ScopStmt &Stmt, UnaryInstruction *Inst,
ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps) {
int VectorWidth = getVectorWidth();
Value *NewOperand = getVectorValue(Stmt, Inst->getOperand(0), VectorMap,
ScalarMaps, getLoopForStmt(Stmt));
assert(isa<CastInst>(Inst) && "Can not generate vector code for instruction");
const CastInst *Cast = dyn_cast<CastInst>(Inst);
VectorType *DestType = VectorType::get(Inst->getType(), VectorWidth);
VectorMap[Inst] = Builder.CreateCast(Cast->getOpcode(), NewOperand, DestType);
}
void VectorBlockGenerator::copyBinaryInst(ScopStmt &Stmt, BinaryOperator *Inst,
ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps) {
Loop *L = getLoopForStmt(Stmt);
Value *OpZero = Inst->getOperand(0);
Value *OpOne = Inst->getOperand(1);
Value *NewOpZero, *NewOpOne;
NewOpZero = getVectorValue(Stmt, OpZero, VectorMap, ScalarMaps, L);
NewOpOne = getVectorValue(Stmt, OpOne, VectorMap, ScalarMaps, L);
Value *NewInst = Builder.CreateBinOp(Inst->getOpcode(), NewOpZero, NewOpOne,
Inst->getName() + "p_vec");
VectorMap[Inst] = NewInst;
}
void VectorBlockGenerator::copyStore(
ScopStmt &Stmt, StoreInst *Store, ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps, __isl_keep isl_id_to_ast_expr *NewAccesses) {
const MemoryAccess &Access = Stmt.getArrayAccessFor(Store);
auto *Pointer = Store->getPointerOperand();
Value *Vector = getVectorValue(Stmt, Store->getValueOperand(), VectorMap,
ScalarMaps, getLoopForStmt(Stmt));
// Make sure we have scalar values available to access the pointer to
// the data location.
extractScalarValues(Store, VectorMap, ScalarMaps);
if (Access.isStrideOne(isl::manage_copy(Schedule))) {
Type *VectorPtrType = getVectorPtrTy(Pointer, getVectorWidth());
Value *NewPointer = generateLocationAccessed(Stmt, Store, ScalarMaps[0],
VLTS[0], NewAccesses);
Value *VectorPtr =
Builder.CreateBitCast(NewPointer, VectorPtrType, "vector_ptr");
StoreInst *Store = Builder.CreateStore(Vector, VectorPtr);
if (!Aligned)
Store->setAlignment(8);
} else {
for (unsigned i = 0; i < ScalarMaps.size(); i++) {
Value *Scalar = Builder.CreateExtractElement(Vector, Builder.getInt32(i));
Value *NewPointer = generateLocationAccessed(Stmt, Store, ScalarMaps[i],
VLTS[i], NewAccesses);
Builder.CreateStore(Scalar, NewPointer);
}
}
}
bool VectorBlockGenerator::hasVectorOperands(const Instruction *Inst,
ValueMapT &VectorMap) {
for (Value *Operand : Inst->operands())
if (VectorMap.count(Operand))
return true;
return false;
}
bool VectorBlockGenerator::extractScalarValues(const Instruction *Inst,
ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps) {
bool HasVectorOperand = false;
int VectorWidth = getVectorWidth();
for (Value *Operand : Inst->operands()) {
ValueMapT::iterator VecOp = VectorMap.find(Operand);
if (VecOp == VectorMap.end())
continue;
HasVectorOperand = true;
Value *NewVector = VecOp->second;
for (int i = 0; i < VectorWidth; ++i) {
ValueMapT &SM = ScalarMaps[i];
// If there is one scalar extracted, all scalar elements should have
// already been extracted by the code here. So no need to check for the
// existence of all of them.
if (SM.count(Operand))
break;
SM[Operand] =
Builder.CreateExtractElement(NewVector, Builder.getInt32(i));
}
}
return HasVectorOperand;
}
void VectorBlockGenerator::copyInstScalarized(
ScopStmt &Stmt, Instruction *Inst, ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps, __isl_keep isl_id_to_ast_expr *NewAccesses) {
bool HasVectorOperand;
int VectorWidth = getVectorWidth();
HasVectorOperand = extractScalarValues(Inst, VectorMap, ScalarMaps);
for (int VectorLane = 0; VectorLane < getVectorWidth(); VectorLane++)
BlockGenerator::copyInstruction(Stmt, Inst, ScalarMaps[VectorLane],
VLTS[VectorLane], NewAccesses);
if (!VectorType::isValidElementType(Inst->getType()) || !HasVectorOperand)
return;
// Make the result available as vector value.
VectorType *VectorType = VectorType::get(Inst->getType(), VectorWidth);
Value *Vector = UndefValue::get(VectorType);
for (int i = 0; i < VectorWidth; i++)
Vector = Builder.CreateInsertElement(Vector, ScalarMaps[i][Inst],
Builder.getInt32(i));
VectorMap[Inst] = Vector;
}
int VectorBlockGenerator::getVectorWidth() { return VLTS.size(); }
void VectorBlockGenerator::copyInstruction(
ScopStmt &Stmt, Instruction *Inst, ValueMapT &VectorMap,
VectorValueMapT &ScalarMaps, __isl_keep isl_id_to_ast_expr *NewAccesses) {
// Terminator instructions control the control flow. They are explicitly
// expressed in the clast and do not need to be copied.
if (Inst->isTerminator())
return;
if (canSyntheziseInStmt(Stmt, Inst))
return;
if (auto *Load = dyn_cast<LoadInst>(Inst)) {
generateLoad(Stmt, Load, VectorMap, ScalarMaps, NewAccesses);
return;
}
if (hasVectorOperands(Inst, VectorMap)) {
if (auto *Store = dyn_cast<StoreInst>(Inst)) {
// Identified as redundant by -polly-simplify.
if (!Stmt.getArrayAccessOrNULLFor(Store))
return;
copyStore(Stmt, Store, VectorMap, ScalarMaps, NewAccesses);
return;
}
if (auto *Unary = dyn_cast<UnaryInstruction>(Inst)) {
copyUnaryInst(Stmt, Unary, VectorMap, ScalarMaps);
return;
}
if (auto *Binary = dyn_cast<BinaryOperator>(Inst)) {
copyBinaryInst(Stmt, Binary, VectorMap, ScalarMaps);
return;
}
// Fallthrough: We generate scalar instructions, if we don't know how to
// generate vector code.
}
copyInstScalarized(Stmt, Inst, VectorMap, ScalarMaps, NewAccesses);
}
void VectorBlockGenerator::generateScalarVectorLoads(
ScopStmt &Stmt, ValueMapT &VectorBlockMap) {
for (MemoryAccess *MA : Stmt) {
if (MA->isArrayKind() || MA->isWrite())
continue;
auto *Address = getOrCreateAlloca(*MA);
Type *VectorPtrType = getVectorPtrTy(Address, 1);
Value *VectorPtr = Builder.CreateBitCast(Address, VectorPtrType,
Address->getName() + "_p_vec_p");
auto *Val = Builder.CreateLoad(VectorPtr, Address->getName() + ".reload");
Constant *SplatVector = Constant::getNullValue(
VectorType::get(Builder.getInt32Ty(), getVectorWidth()));
Value *VectorVal = Builder.CreateShuffleVector(
Val, Val, SplatVector, Address->getName() + "_p_splat");
VectorBlockMap[MA->getAccessValue()] = VectorVal;
}
}
void VectorBlockGenerator::verifyNoScalarStores(ScopStmt &Stmt) {
for (MemoryAccess *MA : Stmt) {
if (MA->isArrayKind() || MA->isRead())
continue;
llvm_unreachable("Scalar stores not expected in vector loop");
}
}
void VectorBlockGenerator::copyStmt(
ScopStmt &Stmt, __isl_keep isl_id_to_ast_expr *NewAccesses) {
assert(Stmt.isBlockStmt() &&
"TODO: Only block statements can be copied by the vector block "
"generator");
BasicBlock *BB = Stmt.getBasicBlock();
BasicBlock *CopyBB = SplitBlock(Builder.GetInsertBlock(),
&*Builder.GetInsertPoint(), &DT, &LI);
CopyBB->setName("polly.stmt." + BB->getName());
Builder.SetInsertPoint(&CopyBB->front());
// Create two maps that store the mapping from the original instructions of
// the old basic block to their copies in the new basic block. Those maps
// are basic block local.
//
// As vector code generation is supported there is one map for scalar values
// and one for vector values.
//
// In case we just do scalar code generation, the vectorMap is not used and
// the scalarMap has just one dimension, which contains the mapping.
//
// In case vector code generation is done, an instruction may either appear
// in the vector map once (as it is calculating >vectorwidth< values at a
// time. Or (if the values are calculated using scalar operations), it
// appears once in every dimension of the scalarMap.
VectorValueMapT ScalarBlockMap(getVectorWidth());
ValueMapT VectorBlockMap;
generateScalarVectorLoads(Stmt, VectorBlockMap);
for (Instruction &Inst : *BB)
copyInstruction(Stmt, &Inst, VectorBlockMap, ScalarBlockMap, NewAccesses);
verifyNoScalarStores(Stmt);
}
BasicBlock *RegionGenerator::repairDominance(BasicBlock *BB,
BasicBlock *BBCopy) {
BasicBlock *BBIDom = DT.getNode(BB)->getIDom()->getBlock();
BasicBlock *BBCopyIDom = EndBlockMap.lookup(BBIDom);
if (BBCopyIDom)
DT.changeImmediateDominator(BBCopy, BBCopyIDom);
return StartBlockMap.lookup(BBIDom);
}
// This is to determine whether an llvm::Value (defined in @p BB) is usable when
// leaving a subregion. The straight-forward DT.dominates(BB, R->getExitBlock())
// does not work in cases where the exit block has edges from outside the
// region. In that case the llvm::Value would never be usable in in the exit
// block. The RegionGenerator however creates an new exit block ('ExitBBCopy')
// for the subregion's exiting edges only. We need to determine whether an
// llvm::Value is usable in there. We do this by checking whether it dominates
// all exiting blocks individually.
static bool isDominatingSubregionExit(const DominatorTree &DT, Region *R,
BasicBlock *BB) {
for (auto ExitingBB : predecessors(R->getExit())) {
// Check for non-subregion incoming edges.
if (!R->contains(ExitingBB))
continue;
if (!DT.dominates(BB, ExitingBB))
return false;
}
return true;
}
// Find the direct dominator of the subregion's exit block if the subregion was
// simplified.
static BasicBlock *findExitDominator(DominatorTree &DT, Region *R) {
BasicBlock *Common = nullptr;
for (auto ExitingBB : predecessors(R->getExit())) {
// Check for non-subregion incoming edges.
if (!R->contains(ExitingBB))
continue;
// First exiting edge.
if (!Common) {
Common = ExitingBB;
continue;
}
Common = DT.findNearestCommonDominator(Common, ExitingBB);
}
assert(Common && R->contains(Common));
return Common;
}
void RegionGenerator::copyStmt(ScopStmt &Stmt, LoopToScevMapT &LTS,
isl_id_to_ast_expr *IdToAstExp) {
assert(Stmt.isRegionStmt() &&
"Only region statements can be copied by the region generator");
// Forget all old mappings.
StartBlockMap.clear();
EndBlockMap.clear();
RegionMaps.clear();
IncompletePHINodeMap.clear();
// Collection of all values related to this subregion.
ValueMapT ValueMap;
// The region represented by the statement.
Region *R = Stmt.getRegion();
// Create a dedicated entry for the region where we can reload all demoted
// inputs.
BasicBlock *EntryBB = R->getEntry();
BasicBlock *EntryBBCopy = SplitBlock(Builder.GetInsertBlock(),
&*Builder.GetInsertPoint(), &DT, &LI);
EntryBBCopy->setName("polly.stmt." + EntryBB->getName() + ".entry");
Builder.SetInsertPoint(&EntryBBCopy->front());
ValueMapT &EntryBBMap = RegionMaps[EntryBBCopy];
generateScalarLoads(Stmt, LTS, EntryBBMap, IdToAstExp);
for (auto PI = pred_begin(EntryBB), PE = pred_end(EntryBB); PI != PE; ++PI)
if (!R->contains(*PI)) {
StartBlockMap[*PI] = EntryBBCopy;
EndBlockMap[*PI] = EntryBBCopy;
}
// Iterate over all blocks in the region in a breadth-first search.
std::deque<BasicBlock *> Blocks;
SmallSetVector<BasicBlock *, 8> SeenBlocks;
Blocks.push_back(EntryBB);
SeenBlocks.insert(EntryBB);
while (!Blocks.empty()) {
BasicBlock *BB = Blocks.front();
Blocks.pop_front();
// First split the block and update dominance information.
BasicBlock *BBCopy = splitBB(BB);
BasicBlock *BBCopyIDom = repairDominance(BB, BBCopy);
// Get the mapping for this block and initialize it with either the scalar
// loads from the generated entering block (which dominates all blocks of
// this subregion) or the maps of the immediate dominator, if part of the
// subregion. The latter necessarily includes the former.
ValueMapT *InitBBMap;
if (BBCopyIDom) {
assert(RegionMaps.count(BBCopyIDom));
InitBBMap = &RegionMaps[BBCopyIDom];
} else
InitBBMap = &EntryBBMap;
auto Inserted = RegionMaps.insert(std::make_pair(BBCopy, *InitBBMap));
ValueMapT &RegionMap = Inserted.first->second;
// Copy the block with the BlockGenerator.
Builder.SetInsertPoint(&BBCopy->front());
copyBB(Stmt, BB, BBCopy, RegionMap, LTS, IdToAstExp);
// In order to remap PHI nodes we store also basic block mappings.
StartBlockMap[BB] = BBCopy;
EndBlockMap[BB] = Builder.GetInsertBlock();
// Add values to incomplete PHI nodes waiting for this block to be copied.
for (const PHINodePairTy &PHINodePair : IncompletePHINodeMap[BB])
addOperandToPHI(Stmt, PHINodePair.first, PHINodePair.second, BB, LTS);
IncompletePHINodeMap[BB].clear();
// And continue with new successors inside the region.
for (auto SI = succ_begin(BB), SE = succ_end(BB); SI != SE; SI++)
if (R->contains(*SI) && SeenBlocks.insert(*SI))
Blocks.push_back(*SI);
// Remember value in case it is visible after this subregion.
if (isDominatingSubregionExit(DT, R, BB))
ValueMap.insert(RegionMap.begin(), RegionMap.end());
}
// Now create a new dedicated region exit block and add it to the region map.
BasicBlock *ExitBBCopy = SplitBlock(Builder.GetInsertBlock(),
&*Builder.GetInsertPoint(), &DT, &LI);
ExitBBCopy->setName("polly.stmt." + R->getExit()->getName() + ".exit");
StartBlockMap[R->getExit()] = ExitBBCopy;
EndBlockMap[R->getExit()] = ExitBBCopy;
BasicBlock *ExitDomBBCopy = EndBlockMap.lookup(findExitDominator(DT, R));
assert(ExitDomBBCopy &&
"Common exit dominator must be within region; at least the entry node "
"must match");
DT.changeImmediateDominator(ExitBBCopy, ExitDomBBCopy);
// As the block generator doesn't handle control flow we need to add the
// region control flow by hand after all blocks have been copied.
for (BasicBlock *BB : SeenBlocks) {
BasicBlock *BBCopyStart = StartBlockMap[BB];
BasicBlock *BBCopyEnd = EndBlockMap[BB];
TerminatorInst *TI = BB->getTerminator();
if (isa<UnreachableInst>(TI)) {
while (!BBCopyEnd->empty())
BBCopyEnd->begin()->eraseFromParent();
new UnreachableInst(BBCopyEnd->getContext(), BBCopyEnd);
continue;
}
Instruction *BICopy = BBCopyEnd->getTerminator();
ValueMapT &RegionMap = RegionMaps[BBCopyStart];
RegionMap.insert(StartBlockMap.begin(), StartBlockMap.end());
Builder.SetInsertPoint(BICopy);
copyInstScalar(Stmt, TI, RegionMap, LTS);
BICopy->eraseFromParent();
}
// Add counting PHI nodes to all loops in the region that can be used as
// replacement for SCEVs referring to the old loop.
for (BasicBlock *BB : SeenBlocks) {
Loop *L = LI.getLoopFor(BB);
if (L == nullptr || L->getHeader() != BB || !R->contains(L))
continue;
BasicBlock *BBCopy = StartBlockMap[BB];
Value *NullVal = Builder.getInt32(0);
PHINode *LoopPHI =
PHINode::Create(Builder.getInt32Ty(), 2, "polly.subregion.iv");
Instruction *LoopPHIInc = BinaryOperator::CreateAdd(
LoopPHI, Builder.getInt32(1), "polly.subregion.iv.inc");
LoopPHI->insertBefore(&BBCopy->front());
LoopPHIInc->insertBefore(BBCopy->getTerminator());
for (auto *PredBB : make_range(pred_begin(BB), pred_end(BB))) {
if (!R->contains(PredBB))
continue;
if (L->contains(PredBB))
LoopPHI->addIncoming(LoopPHIInc, EndBlockMap[PredBB]);
else
LoopPHI->addIncoming(NullVal, EndBlockMap[PredBB]);
}
for (auto *PredBBCopy : make_range(pred_begin(BBCopy), pred_end(BBCopy)))
if (LoopPHI->getBasicBlockIndex(PredBBCopy) < 0)
LoopPHI->addIncoming(NullVal, PredBBCopy);
LTS[L] = SE.getUnknown(LoopPHI);
}
// Continue generating code in the exit block.
Builder.SetInsertPoint(&*ExitBBCopy->getFirstInsertionPt());
// Write values visible to other statements.
generateScalarStores(Stmt, LTS, ValueMap, IdToAstExp);
StartBlockMap.clear();
EndBlockMap.clear();
RegionMaps.clear();
IncompletePHINodeMap.clear();
}
PHINode *RegionGenerator::buildExitPHI(MemoryAccess *MA, LoopToScevMapT &LTS,
ValueMapT &BBMap, Loop *L) {
ScopStmt *Stmt = MA->getStatement();
Region *SubR = Stmt->getRegion();
auto Incoming = MA->getIncoming();
PollyIRBuilder::InsertPointGuard IPGuard(Builder);
PHINode *OrigPHI = cast<PHINode>(MA->getAccessInstruction());
BasicBlock *NewSubregionExit = Builder.GetInsertBlock();
// This can happen if the subregion is simplified after the ScopStmts
// have been created; simplification happens as part of CodeGeneration.
if (OrigPHI->getParent() != SubR->getExit()) {
BasicBlock *FormerExit = SubR->getExitingBlock();
if (FormerExit)
NewSubregionExit = StartBlockMap.lookup(FormerExit);
}
PHINode *NewPHI = PHINode::Create(OrigPHI->getType(), Incoming.size(),
"polly." + OrigPHI->getName(),
NewSubregionExit->getFirstNonPHI());
// Add the incoming values to the PHI.
for (auto &Pair : Incoming) {
BasicBlock *OrigIncomingBlock = Pair.first;
BasicBlock *NewIncomingBlockStart = StartBlockMap.lookup(OrigIncomingBlock);
BasicBlock *NewIncomingBlockEnd = EndBlockMap.lookup(OrigIncomingBlock);
Builder.SetInsertPoint(NewIncomingBlockEnd->getTerminator());
assert(RegionMaps.count(NewIncomingBlockStart));
assert(RegionMaps.count(NewIncomingBlockEnd));
ValueMapT *LocalBBMap = &RegionMaps[NewIncomingBlockStart];
Value *OrigIncomingValue = Pair.second;
Value *NewIncomingValue =
getNewValue(*Stmt, OrigIncomingValue, *LocalBBMap, LTS, L);
NewPHI->addIncoming(NewIncomingValue, NewIncomingBlockEnd);
}
return NewPHI;
}
Value *RegionGenerator::getExitScalar(MemoryAccess *MA, LoopToScevMapT &LTS,
ValueMapT &BBMap) {
ScopStmt *Stmt = MA->getStatement();
// TODO: Add some test cases that ensure this is really the right choice.
Loop *L = LI.getLoopFor(Stmt->getRegion()->getExit());
if (MA->isAnyPHIKind()) {
auto Incoming = MA->getIncoming();
assert(!Incoming.empty() &&
"PHI WRITEs must have originate from at least one incoming block");
// If there is only one incoming value, we do not need to create a PHI.
if (Incoming.size() == 1) {
Value *OldVal = Incoming[0].second;
return getNewValue(*Stmt, OldVal, BBMap, LTS, L);
}
return buildExitPHI(MA, LTS, BBMap, L);
}
// MemoryKind::Value accesses leaving the subregion must dominate the exit
// block; just pass the copied value.
Value *OldVal = MA->getAccessValue();
return getNewValue(*Stmt, OldVal, BBMap, LTS, L);
}
void RegionGenerator::generateScalarStores(
ScopStmt &Stmt, LoopToScevMapT &LTS, ValueMapT &BBMap,
__isl_keep isl_id_to_ast_expr *NewAccesses) {
assert(Stmt.getRegion() &&
"Block statements need to use the generateScalarStores() "
"function in the BlockGenerator");
for (MemoryAccess *MA : Stmt) {
if (MA->isOriginalArrayKind() || MA->isRead())
continue;
isl::set AccDom = MA->getAccessRelation().domain();
std::string Subject = MA->getId().get_name();
generateConditionalExecution(
Stmt, AccDom, Subject.c_str(), [&, this, MA]() {
Value *NewVal = getExitScalar(MA, LTS, BBMap);
Value *Address = getImplicitAddress(*MA, getLoopForStmt(Stmt), LTS,
BBMap, NewAccesses);
assert((!isa<Instruction>(NewVal) ||
DT.dominates(cast<Instruction>(NewVal)->getParent(),
Builder.GetInsertBlock())) &&
"Domination violation");
assert((!isa<Instruction>(Address) ||
DT.dominates(cast<Instruction>(Address)->getParent(),
Builder.GetInsertBlock())) &&
"Domination violation");
Builder.CreateStore(NewVal, Address);
});
}
}
void RegionGenerator::addOperandToPHI(ScopStmt &Stmt, PHINode *PHI,
PHINode *PHICopy, BasicBlock *IncomingBB,
LoopToScevMapT &LTS) {
// If the incoming block was not yet copied mark this PHI as incomplete.
// Once the block will be copied the incoming value will be added.
BasicBlock *BBCopyStart = StartBlockMap[IncomingBB];
BasicBlock *BBCopyEnd = EndBlockMap[IncomingBB];
if (!BBCopyStart) {
assert(!BBCopyEnd);
assert(Stmt.represents(IncomingBB) &&
"Bad incoming block for PHI in non-affine region");
IncompletePHINodeMap[IncomingBB].push_back(std::make_pair(PHI, PHICopy));
return;
}
assert(RegionMaps.count(BBCopyStart) &&
"Incoming PHI block did not have a BBMap");
ValueMapT &BBCopyMap = RegionMaps[BBCopyStart];
Value *OpCopy = nullptr;
if (Stmt.represents(IncomingBB)) {
Value *Op = PHI->getIncomingValueForBlock(IncomingBB);
// If the current insert block is different from the PHIs incoming block
// change it, otherwise do not.
auto IP = Builder.GetInsertPoint();
if (IP->getParent() != BBCopyEnd)
Builder.SetInsertPoint(BBCopyEnd->getTerminator());
OpCopy = getNewValue(Stmt, Op, BBCopyMap, LTS, getLoopForStmt(Stmt));
if (IP->getParent() != BBCopyEnd)
Builder.SetInsertPoint(&*IP);
} else {
// All edges from outside the non-affine region become a single edge
// in the new copy of the non-affine region. Make sure to only add the
// corresponding edge the first time we encounter a basic block from
// outside the non-affine region.
if (PHICopy->getBasicBlockIndex(BBCopyEnd) >= 0)
return;
// Get the reloaded value.
OpCopy = getNewValue(Stmt, PHI, BBCopyMap, LTS, getLoopForStmt(Stmt));
}
assert(OpCopy && "Incoming PHI value was not copied properly");
PHICopy->addIncoming(OpCopy, BBCopyEnd);
}
void RegionGenerator::copyPHIInstruction(ScopStmt &Stmt, PHINode *PHI,
ValueMapT &BBMap,
LoopToScevMapT &LTS) {
unsigned NumIncoming = PHI->getNumIncomingValues();
PHINode *PHICopy =
Builder.CreatePHI(PHI->getType(), NumIncoming, "polly." + PHI->getName());
PHICopy->moveBefore(PHICopy->getParent()->getFirstNonPHI());
BBMap[PHI] = PHICopy;
for (BasicBlock *IncomingBB : PHI->blocks())
addOperandToPHI(Stmt, PHI, PHICopy, IncomingBB, LTS);
}
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