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| //===------ PollyIRBuilder.cpp --------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// The Polly IRBuilder file contains Polly specific extensions for the IRBuilder
// that are used e.g. to emit the llvm.loop.parallel metadata.
//
//===----------------------------------------------------------------------===//
#include "polly/CodeGen/IRBuilder.h"
#include "polly/ScopInfo.h"
#include "polly/Support/ScopHelper.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Metadata.h"
using namespace llvm;
using namespace polly;
static const int MaxArraysInAliasScops = 10;
/// Get a self referencing id metadata node.
///
/// The MDNode looks like this (if arg0/arg1 are not null):
///
/// '!n = metadata !{metadata !n, arg0, arg1}'
///
/// @return The self referencing id metadata node.
static MDNode *getID(LLVMContext &Ctx, Metadata *arg0 = nullptr,
Metadata *arg1 = nullptr) {
MDNode *ID;
SmallVector<Metadata *, 3> Args;
// Use a temporary node to safely create a unique pointer for the first arg.
auto TempNode = MDNode::getTemporary(Ctx, None);
// Reserve operand 0 for loop id self reference.
Args.push_back(TempNode.get());
if (arg0)
Args.push_back(arg0);
if (arg1)
Args.push_back(arg1);
ID = MDNode::get(Ctx, Args);
ID->replaceOperandWith(0, ID);
return ID;
}
ScopAnnotator::ScopAnnotator() : SE(nullptr), AliasScopeDomain(nullptr) {}
void ScopAnnotator::buildAliasScopes(Scop &S) {
SE = S.getSE();
LLVMContext &Ctx = SE->getContext();
AliasScopeDomain = getID(Ctx, MDString::get(Ctx, "polly.alias.scope.domain"));
AliasScopeMap.clear();
OtherAliasScopeListMap.clear();
// We are only interested in arrays, but no scalar references. Scalars should
// be handled easily by basicaa.
SmallVector<ScopArrayInfo *, 10> Arrays;
for (ScopArrayInfo *Array : S.arrays())
if (Array->isArrayKind())
Arrays.push_back(Array);
// The construction of alias scopes is quadratic in the number of arrays
// involved. In case of too many arrays, skip the construction of alias
// information to avoid quadratic increases in compile time and code size.
if (Arrays.size() > MaxArraysInAliasScops)
return;
std::string AliasScopeStr = "polly.alias.scope.";
for (const ScopArrayInfo *Array : Arrays) {
assert(Array->getBasePtr() && "Base pointer must be present");
AliasScopeMap[Array->getBasePtr()] =
getID(Ctx, AliasScopeDomain,
MDString::get(Ctx, (AliasScopeStr + Array->getName()).c_str()));
}
for (const ScopArrayInfo *Array : Arrays) {
MDNode *AliasScopeList = MDNode::get(Ctx, {});
for (const auto &AliasScopePair : AliasScopeMap) {
if (Array->getBasePtr() == AliasScopePair.first)
continue;
Metadata *Args = {AliasScopePair.second};
AliasScopeList =
MDNode::concatenate(AliasScopeList, MDNode::get(Ctx, Args));
}
OtherAliasScopeListMap[Array->getBasePtr()] = AliasScopeList;
}
}
void ScopAnnotator::pushLoop(Loop *L, bool IsParallel) {
ActiveLoops.push_back(L);
if (!IsParallel)
return;
BasicBlock *Header = L->getHeader();
MDNode *Id = getID(Header->getContext());
assert(Id->getOperand(0) == Id && "Expected Id to be a self-reference");
assert(Id->getNumOperands() == 1 && "Unexpected extra operands in Id");
MDNode *Ids = ParallelLoops.empty()
? Id
: MDNode::concatenate(ParallelLoops.back(), Id);
ParallelLoops.push_back(Ids);
}
void ScopAnnotator::popLoop(bool IsParallel) {
ActiveLoops.pop_back();
if (!IsParallel)
return;
assert(!ParallelLoops.empty() && "Expected a parallel loop to pop");
ParallelLoops.pop_back();
}
void ScopAnnotator::annotateLoopLatch(BranchInst *B, Loop *L, bool IsParallel,
bool IsLoopVectorizerDisabled) const {
MDNode *MData = nullptr;
if (IsLoopVectorizerDisabled) {
SmallVector<Metadata *, 3> Args;
LLVMContext &Ctx = SE->getContext();
Args.push_back(MDString::get(Ctx, "llvm.loop.vectorize.enable"));
auto *FalseValue = ConstantInt::get(Type::getInt1Ty(Ctx), 0);
Args.push_back(ValueAsMetadata::get(FalseValue));
MData = MDNode::concatenate(MData, getID(Ctx, MDNode::get(Ctx, Args)));
}
if (IsParallel) {
assert(!ParallelLoops.empty() && "Expected a parallel loop to annotate");
MDNode *Ids = ParallelLoops.back();
MDNode *Id = cast<MDNode>(Ids->getOperand(Ids->getNumOperands() - 1));
MData = MDNode::concatenate(MData, Id);
}
B->setMetadata("llvm.loop", MData);
}
/// Get the pointer operand
///
/// @param Inst The instruction to be analyzed.
/// @return the pointer operand in case @p Inst is a memory access
/// instruction and nullptr otherwise.
static llvm::Value *getMemAccInstPointerOperand(Instruction *Inst) {
auto MemInst = MemAccInst::dyn_cast(Inst);
if (!MemInst)
return nullptr;
return MemInst.getPointerOperand();
}
void ScopAnnotator::annotateSecondLevel(llvm::Instruction *Inst,
llvm::Value *BasePtr) {
Value *Ptr = getMemAccInstPointerOperand(Inst);
if (!Ptr)
return;
auto *PtrSCEV = SE->getSCEV(Ptr);
auto *BasePtrSCEV = SE->getPointerBase(PtrSCEV);
auto SecondLevelAliasScope = SecondLevelAliasScopeMap.lookup(PtrSCEV);
auto SecondLevelOtherAliasScopeList =
SecondLevelOtherAliasScopeListMap.lookup(PtrSCEV);
if (!SecondLevelAliasScope) {
auto AliasScope = AliasScopeMap.lookup(BasePtr);
if (!AliasScope)
return;
LLVMContext &Ctx = SE->getContext();
SecondLevelAliasScope = getID(
Ctx, AliasScope, MDString::get(Ctx, "second level alias metadata"));
SecondLevelAliasScopeMap[PtrSCEV] = SecondLevelAliasScope;
Metadata *Args = {SecondLevelAliasScope};
auto SecondLevelBasePtrAliasScopeList =
SecondLevelAliasScopeMap.lookup(BasePtrSCEV);
SecondLevelAliasScopeMap[BasePtrSCEV] = MDNode::concatenate(
SecondLevelBasePtrAliasScopeList, MDNode::get(Ctx, Args));
auto OtherAliasScopeList = OtherAliasScopeListMap.lookup(BasePtr);
SecondLevelOtherAliasScopeList = MDNode::concatenate(
OtherAliasScopeList, SecondLevelBasePtrAliasScopeList);
SecondLevelOtherAliasScopeListMap[PtrSCEV] = SecondLevelOtherAliasScopeList;
}
Inst->setMetadata("alias.scope", SecondLevelAliasScope);
Inst->setMetadata("noalias", SecondLevelOtherAliasScopeList);
}
void ScopAnnotator::annotate(Instruction *Inst) {
if (!Inst->mayReadOrWriteMemory())
return;
if (!ParallelLoops.empty())
Inst->setMetadata("llvm.mem.parallel_loop_access", ParallelLoops.back());
// TODO: Use the ScopArrayInfo once available here.
if (!AliasScopeDomain)
return;
// Do not apply annotations on memory operations that take more than one
// pointer. It would be ambiguous to which pointer the annotation applies.
// FIXME: How can we specify annotations for all pointer arguments?
if (isa<CallInst>(Inst) && !isa<MemSetInst>(Inst))
return;
auto *Ptr = getMemAccInstPointerOperand(Inst);
if (!Ptr)
return;
auto *PtrSCEV = SE->getSCEV(Ptr);
auto *BaseSCEV = SE->getPointerBase(PtrSCEV);
auto *SU = dyn_cast<SCEVUnknown>(BaseSCEV);
if (!SU)
return;
auto *BasePtr = SU->getValue();
if (!BasePtr)
return;
auto AliasScope = AliasScopeMap.lookup(BasePtr);
if (!AliasScope) {
BasePtr = AlternativeAliasBases.lookup(BasePtr);
if (!BasePtr)
return;
AliasScope = AliasScopeMap.lookup(BasePtr);
if (!AliasScope)
return;
}
assert(OtherAliasScopeListMap.count(BasePtr) &&
"BasePtr either expected in AliasScopeMap and OtherAlias...Map");
auto *OtherAliasScopeList = OtherAliasScopeListMap[BasePtr];
if (InterIterationAliasFreeBasePtrs.count(BasePtr)) {
annotateSecondLevel(Inst, BasePtr);
return;
}
Inst->setMetadata("alias.scope", AliasScope);
Inst->setMetadata("noalias", OtherAliasScopeList);
}
void ScopAnnotator::addInterIterationAliasFreeBasePtr(llvm::Value *BasePtr) {
if (!BasePtr)
return;
InterIterationAliasFreeBasePtrs.insert(BasePtr);
}
|