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llvm-project/llvm/lib/Target/Hexagon/RDFGraph.cpp

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//===--- RDFGraph.cpp -----------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Target-independent, SSA-based data flow graph for register data flow (RDF).
//
#include "RDFGraph.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominanceFrontier.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
using namespace rdf;
// Printing functions. Have them here first, so that the rest of the code
// can use them.
namespace rdf {
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<RegisterRef> &P) {
auto &TRI = P.G.getTRI();
if (P.Obj.Reg > 0 && P.Obj.Reg < TRI.getNumRegs())
OS << TRI.getName(P.Obj.Reg);
else
OS << '#' << P.Obj.Reg;
if (P.Obj.Sub > 0) {
OS << ':';
if (P.Obj.Sub < TRI.getNumSubRegIndices())
OS << TRI.getSubRegIndexName(P.Obj.Sub);
else
OS << '#' << P.Obj.Sub;
}
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeId> &P) {
auto NA = P.G.addr<NodeBase*>(P.Obj);
uint16_t Attrs = NA.Addr->getAttrs();
uint16_t Kind = NodeAttrs::kind(Attrs);
uint16_t Flags = NodeAttrs::flags(Attrs);
switch (NodeAttrs::type(Attrs)) {
case NodeAttrs::Code:
switch (Kind) {
case NodeAttrs::Func: OS << 'f'; break;
case NodeAttrs::Block: OS << 'b'; break;
case NodeAttrs::Stmt: OS << 's'; break;
case NodeAttrs::Phi: OS << 'p'; break;
default: OS << "c?"; break;
}
break;
case NodeAttrs::Ref:
if (Flags & NodeAttrs::Preserving)
OS << '+';
if (Flags & NodeAttrs::Clobbering)
OS << '~';
switch (Kind) {
case NodeAttrs::Use: OS << 'u'; break;
case NodeAttrs::Def: OS << 'd'; break;
case NodeAttrs::Block: OS << 'b'; break;
default: OS << "r?"; break;
}
break;
default:
OS << '?';
break;
}
OS << P.Obj;
if (Flags & NodeAttrs::Shadow)
OS << '"';
return OS;
}
namespace {
void printRefHeader(raw_ostream &OS, const NodeAddr<RefNode*> RA,
const DataFlowGraph &G) {
OS << Print<NodeId>(RA.Id, G) << '<'
<< Print<RegisterRef>(RA.Addr->getRegRef(), G) << '>';
if (RA.Addr->getFlags() & NodeAttrs::Fixed)
OS << '!';
}
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<DefNode*>> &P) {
printRefHeader(OS, P.Obj, P.G);
OS << '(';
if (NodeId N = P.Obj.Addr->getReachingDef())
OS << Print<NodeId>(N, P.G);
OS << ',';
if (NodeId N = P.Obj.Addr->getReachedDef())
OS << Print<NodeId>(N, P.G);
OS << ',';
if (NodeId N = P.Obj.Addr->getReachedUse())
OS << Print<NodeId>(N, P.G);
OS << "):";
if (NodeId N = P.Obj.Addr->getSibling())
OS << Print<NodeId>(N, P.G);
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<UseNode*>> &P) {
printRefHeader(OS, P.Obj, P.G);
OS << '(';
if (NodeId N = P.Obj.Addr->getReachingDef())
OS << Print<NodeId>(N, P.G);
OS << "):";
if (NodeId N = P.Obj.Addr->getSibling())
OS << Print<NodeId>(N, P.G);
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS,
const Print<NodeAddr<PhiUseNode*>> &P) {
printRefHeader(OS, P.Obj, P.G);
OS << '(';
if (NodeId N = P.Obj.Addr->getReachingDef())
OS << Print<NodeId>(N, P.G);
OS << ',';
if (NodeId N = P.Obj.Addr->getPredecessor())
OS << Print<NodeId>(N, P.G);
OS << "):";
if (NodeId N = P.Obj.Addr->getSibling())
OS << Print<NodeId>(N, P.G);
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<RefNode*>> &P) {
switch (P.Obj.Addr->getKind()) {
case NodeAttrs::Def:
OS << PrintNode<DefNode*>(P.Obj, P.G);
break;
case NodeAttrs::Use:
if (P.Obj.Addr->getFlags() & NodeAttrs::PhiRef)
OS << PrintNode<PhiUseNode*>(P.Obj, P.G);
else
OS << PrintNode<UseNode*>(P.Obj, P.G);
break;
}
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeList> &P) {
unsigned N = P.Obj.size();
for (auto I : P.Obj) {
OS << Print<NodeId>(I.Id, P.G);
if (--N)
OS << ' ';
}
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeSet> &P) {
unsigned N = P.Obj.size();
for (auto I : P.Obj) {
OS << Print<NodeId>(I, P.G);
if (--N)
OS << ' ';
}
return OS;
}
namespace {
template <typename T>
struct PrintListV {
PrintListV(const NodeList &L, const DataFlowGraph &G) : List(L), G(G) {}
typedef T Type;
const NodeList &List;
const DataFlowGraph &G;
};
template <typename T>
raw_ostream &operator<< (raw_ostream &OS, const PrintListV<T> &P) {
unsigned N = P.List.size();
for (NodeAddr<T> A : P.List) {
OS << PrintNode<T>(A, P.G);
if (--N)
OS << ", ";
}
return OS;
}
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<PhiNode*>> &P) {
OS << Print<NodeId>(P.Obj.Id, P.G) << ": phi ["
<< PrintListV<RefNode*>(P.Obj.Addr->members(P.G), P.G) << ']';
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS,
const Print<NodeAddr<StmtNode*>> &P) {
unsigned Opc = P.Obj.Addr->getCode()->getOpcode();
OS << Print<NodeId>(P.Obj.Id, P.G) << ": " << P.G.getTII().getName(Opc)
<< " [" << PrintListV<RefNode*>(P.Obj.Addr->members(P.G), P.G) << ']';
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS,
const Print<NodeAddr<InstrNode*>> &P) {
switch (P.Obj.Addr->getKind()) {
case NodeAttrs::Phi:
OS << PrintNode<PhiNode*>(P.Obj, P.G);
break;
case NodeAttrs::Stmt:
OS << PrintNode<StmtNode*>(P.Obj, P.G);
break;
default:
OS << "instr? " << Print<NodeId>(P.Obj.Id, P.G);
break;
}
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS,
const Print<NodeAddr<BlockNode*>> &P) {
auto *BB = P.Obj.Addr->getCode();
unsigned NP = BB->pred_size();
std::vector<int> Ns;
auto PrintBBs = [&OS,&P] (std::vector<int> Ns) -> void {
unsigned N = Ns.size();
for (auto I : Ns) {
OS << "BB#" << I;
if (--N)
OS << ", ";
}
};
OS << Print<NodeId>(P.Obj.Id, P.G) << ": === BB#" << BB->getNumber()
<< " === preds(" << NP << "): ";
for (auto I : BB->predecessors())
Ns.push_back(I->getNumber());
PrintBBs(Ns);
unsigned NS = BB->succ_size();
OS << " succs(" << NS << "): ";
Ns.clear();
for (auto I : BB->successors())
Ns.push_back(I->getNumber());
PrintBBs(Ns);
OS << '\n';
for (auto I : P.Obj.Addr->members(P.G))
OS << PrintNode<InstrNode*>(I, P.G) << '\n';
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS,
const Print<NodeAddr<FuncNode*>> &P) {
OS << "DFG dump:[\n" << Print<NodeId>(P.Obj.Id, P.G) << ": Function: "
<< P.Obj.Addr->getCode()->getName() << '\n';
for (auto I : P.Obj.Addr->members(P.G))
OS << PrintNode<BlockNode*>(I, P.G) << '\n';
OS << "]\n";
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<RegisterSet> &P) {
OS << '{';
for (auto I : P.Obj)
OS << ' ' << Print<RegisterRef>(I, P.G);
OS << " }";
return OS;
}
template<>
raw_ostream &operator<< (raw_ostream &OS,
const Print<DataFlowGraph::DefStack> &P) {
for (auto I = P.Obj.top(), E = P.Obj.bottom(); I != E; ) {
OS << Print<NodeId>(I->Id, P.G)
<< '<' << Print<RegisterRef>(I->Addr->getRegRef(), P.G) << '>';
I.down();
if (I != E)
OS << ' ';
}
return OS;
}
} // namespace rdf
// Node allocation functions.
//
// Node allocator is like a slab memory allocator: it allocates blocks of
// memory in sizes that are multiples of the size of a node. Each block has
// the same size. Nodes are allocated from the currently active block, and
// when it becomes full, a new one is created.
// There is a mapping scheme between node id and its location in a block,
// and within that block is described in the header file.
//
void NodeAllocator::startNewBlock() {
void *T = MemPool.Allocate(NodesPerBlock*NodeMemSize, NodeMemSize);
char *P = static_cast<char*>(T);
Blocks.push_back(P);
// Check if the block index is still within the allowed range, i.e. less
// than 2^N, where N is the number of bits in NodeId for the block index.
// BitsPerIndex is the number of bits per node index.
assert((Blocks.size() < ((size_t)1 << (8*sizeof(NodeId)-BitsPerIndex))) &&
"Out of bits for block index");
ActiveEnd = P;
}
bool NodeAllocator::needNewBlock() {
if (Blocks.empty())
return true;
char *ActiveBegin = Blocks.back();
uint32_t Index = (ActiveEnd-ActiveBegin)/NodeMemSize;
return Index >= NodesPerBlock;
}
NodeAddr<NodeBase*> NodeAllocator::New() {
if (needNewBlock())
startNewBlock();
uint32_t ActiveB = Blocks.size()-1;
uint32_t Index = (ActiveEnd - Blocks[ActiveB])/NodeMemSize;
NodeAddr<NodeBase*> NA = { reinterpret_cast<NodeBase*>(ActiveEnd),
makeId(ActiveB, Index) };
ActiveEnd += NodeMemSize;
return NA;
}
NodeId NodeAllocator::id(const NodeBase *P) const {
uintptr_t A = reinterpret_cast<uintptr_t>(P);
for (unsigned i = 0, n = Blocks.size(); i != n; ++i) {
uintptr_t B = reinterpret_cast<uintptr_t>(Blocks[i]);
if (A < B || A >= B + NodesPerBlock*NodeMemSize)
continue;
uint32_t Idx = (A-B)/NodeMemSize;
return makeId(i, Idx);
}
llvm_unreachable("Invalid node address");
}
void NodeAllocator::clear() {
MemPool.Reset();
Blocks.clear();
ActiveEnd = nullptr;
}
// Insert node NA after "this" in the circular chain.
void NodeBase::append(NodeAddr<NodeBase*> NA) {
NodeId Nx = Next;
// If NA is already "next", do nothing.
if (Next != NA.Id) {
Next = NA.Id;
NA.Addr->Next = Nx;
}
}
// Fundamental node manipulator functions.
// Obtain the register reference from a reference node.
RegisterRef RefNode::getRegRef() const {
assert(NodeAttrs::type(Attrs) == NodeAttrs::Ref);
if (NodeAttrs::flags(Attrs) & NodeAttrs::PhiRef)
return Ref.RR;
assert(Ref.Op != nullptr);
return { Ref.Op->getReg(), Ref.Op->getSubReg() };
}
// Set the register reference in the reference node directly (for references
// in phi nodes).
void RefNode::setRegRef(RegisterRef RR) {
assert(NodeAttrs::type(Attrs) == NodeAttrs::Ref);
assert(NodeAttrs::flags(Attrs) & NodeAttrs::PhiRef);
Ref.RR = RR;
}
// Set the register reference in the reference node based on a machine
// operand (for references in statement nodes).
void RefNode::setRegRef(MachineOperand *Op) {
assert(NodeAttrs::type(Attrs) == NodeAttrs::Ref);
assert(!(NodeAttrs::flags(Attrs) & NodeAttrs::PhiRef));
Ref.Op = Op;
}
// Get the owner of a given reference node.
NodeAddr<NodeBase*> RefNode::getOwner(const DataFlowGraph &G) {
NodeAddr<NodeBase*> NA = G.addr<NodeBase*>(getNext());
while (NA.Addr != this) {
if (NA.Addr->getType() == NodeAttrs::Code)
return NA;
NA = G.addr<NodeBase*>(NA.Addr->getNext());
}
llvm_unreachable("No owner in circular list");
}
// Connect the def node to the reaching def node.
void DefNode::linkToDef(NodeId Self, NodeAddr<DefNode*> DA) {
Ref.RD = DA.Id;
Ref.Sib = DA.Addr->getReachedDef();
DA.Addr->setReachedDef(Self);
}
// Connect the use node to the reaching def node.
void UseNode::linkToDef(NodeId Self, NodeAddr<DefNode*> DA) {
Ref.RD = DA.Id;
Ref.Sib = DA.Addr->getReachedUse();
DA.Addr->setReachedUse(Self);
}
// Get the first member of the code node.
NodeAddr<NodeBase*> CodeNode::getFirstMember(const DataFlowGraph &G) const {
if (Code.FirstM == 0)
return NodeAddr<NodeBase*>();
return G.addr<NodeBase*>(Code.FirstM);
}
// Get the last member of the code node.
NodeAddr<NodeBase*> CodeNode::getLastMember(const DataFlowGraph &G) const {
if (Code.LastM == 0)
return NodeAddr<NodeBase*>();
return G.addr<NodeBase*>(Code.LastM);
}
// Add node NA at the end of the member list of the given code node.
void CodeNode::addMember(NodeAddr<NodeBase*> NA, const DataFlowGraph &G) {
auto ML = getLastMember(G);
if (ML.Id != 0) {
ML.Addr->append(NA);
} else {
Code.FirstM = NA.Id;
NodeId Self = G.id(this);
NA.Addr->setNext(Self);
}
Code.LastM = NA.Id;
}
// Add node NA after member node MA in the given code node.
void CodeNode::addMemberAfter(NodeAddr<NodeBase*> MA, NodeAddr<NodeBase*> NA,
const DataFlowGraph &G) {
MA.Addr->append(NA);
if (Code.LastM == MA.Id)
Code.LastM = NA.Id;
}
// Remove member node NA from the given code node.
void CodeNode::removeMember(NodeAddr<NodeBase*> NA, const DataFlowGraph &G) {
auto MA = getFirstMember(G);
assert(MA.Id != 0);
// Special handling if the member to remove is the first member.
if (MA.Id == NA.Id) {
if (Code.LastM == MA.Id) {
// If it is the only member, set both first and last to 0.
Code.FirstM = Code.LastM = 0;
} else {
// Otherwise, advance the first member.
Code.FirstM = MA.Addr->getNext();
}
return;
}
while (MA.Addr != this) {
NodeId MX = MA.Addr->getNext();
if (MX == NA.Id) {
MA.Addr->setNext(NA.Addr->getNext());
// If the member to remove happens to be the last one, update the
// LastM indicator.
if (Code.LastM == NA.Id)
Code.LastM = MA.Id;
return;
}
MA = G.addr<NodeBase*>(MX);
}
llvm_unreachable("No such member");
}
// Return the list of all members of the code node.
NodeList CodeNode::members(const DataFlowGraph &G) const {
static auto True = [] (NodeAddr<NodeBase*>) -> bool { return true; };
return members_if(True, G);
}
// Return the owner of the given instr node.
NodeAddr<NodeBase*> InstrNode::getOwner(const DataFlowGraph &G) {
NodeAddr<NodeBase*> NA = G.addr<NodeBase*>(getNext());
while (NA.Addr != this) {
assert(NA.Addr->getType() == NodeAttrs::Code);
if (NA.Addr->getKind() == NodeAttrs::Block)
return NA;
NA = G.addr<NodeBase*>(NA.Addr->getNext());
}
llvm_unreachable("No owner in circular list");
}
// Add the phi node PA to the given block node.
void BlockNode::addPhi(NodeAddr<PhiNode*> PA, const DataFlowGraph &G) {
auto M = getFirstMember(G);
if (M.Id == 0) {
addMember(PA, G);
return;
}
assert(M.Addr->getType() == NodeAttrs::Code);
if (M.Addr->getKind() == NodeAttrs::Stmt) {
// If the first member of the block is a statement, insert the phi as
// the first member.
Code.FirstM = PA.Id;
PA.Addr->setNext(M.Id);
} else {
// If the first member is a phi, find the last phi, and append PA to it.
assert(M.Addr->getKind() == NodeAttrs::Phi);
NodeAddr<NodeBase*> MN = M;
do {
M = MN;
MN = G.addr<NodeBase*>(M.Addr->getNext());
assert(MN.Addr->getType() == NodeAttrs::Code);
} while (MN.Addr->getKind() == NodeAttrs::Phi);
// M is the last phi.
addMemberAfter(M, PA, G);
}
}
// Find the block node corresponding to the machine basic block BB in the
// given func node.
NodeAddr<BlockNode*> FuncNode::findBlock(const MachineBasicBlock *BB,
const DataFlowGraph &G) const {
auto EqBB = [BB] (NodeAddr<NodeBase*> NA) -> bool {
return NodeAddr<BlockNode*>(NA).Addr->getCode() == BB;
};
NodeList Ms = members_if(EqBB, G);
if (!Ms.empty())
return Ms[0];
return NodeAddr<BlockNode*>();
}
// Get the block node for the entry block in the given function.
NodeAddr<BlockNode*> FuncNode::getEntryBlock(const DataFlowGraph &G) {
MachineBasicBlock *EntryB = &getCode()->front();
return findBlock(EntryB, G);
}
// Register aliasing information.
//
// In theory, the lane information could be used to determine register
// covering (and aliasing), but depending on the sub-register structure,
// the lane mask information may be missing. The covering information
// must be available for this framework to work, so relying solely on
// the lane data is not sufficient.
// Determine whether RA covers RB.
bool RegisterAliasInfo::covers(RegisterRef RA, RegisterRef RB) const {
if (RA == RB)
return true;
if (TargetRegisterInfo::isVirtualRegister(RA.Reg)) {
assert(TargetRegisterInfo::isVirtualRegister(RB.Reg));
if (RA.Reg != RB.Reg)
return false;
if (RA.Sub == 0)
return true;
return TRI.composeSubRegIndices(RA.Sub, RB.Sub) == RA.Sub;
}
assert(TargetRegisterInfo::isPhysicalRegister(RA.Reg) &&
TargetRegisterInfo::isPhysicalRegister(RB.Reg));
unsigned A = RA.Sub != 0 ? TRI.getSubReg(RA.Reg, RA.Sub) : RA.Reg;
unsigned B = RB.Sub != 0 ? TRI.getSubReg(RB.Reg, RB.Sub) : RB.Reg;
return TRI.isSubRegister(A, B);
}
// Determine whether RR is covered by the set of references RRs.
bool RegisterAliasInfo::covers(const RegisterSet &RRs, RegisterRef RR) const {
if (RRs.count(RR))
return true;
// For virtual registers, we cannot accurately determine covering based
// on subregisters. If RR itself is not present in RRs, but it has a sub-
// register reference, check for the super-register alone. Otherwise,
// assume non-covering.
if (TargetRegisterInfo::isVirtualRegister(RR.Reg)) {
if (RR.Sub != 0)
return RRs.count({RR.Reg, 0});
return false;
}
// If any super-register of RR is present, then RR is covered.
unsigned Reg = RR.Sub == 0 ? RR.Reg : TRI.getSubReg(RR.Reg, RR.Sub);
for (MCSuperRegIterator SR(Reg, &TRI); SR.isValid(); ++SR)
if (RRs.count({*SR, 0}))
return true;
return false;
}
// Get the list of references aliased to RR.
std::vector<RegisterRef> RegisterAliasInfo::getAliasSet(RegisterRef RR) const {
// Do not include RR in the alias set. For virtual registers return an
// empty set.
std::vector<RegisterRef> AS;
if (TargetRegisterInfo::isVirtualRegister(RR.Reg))
return AS;
assert(TargetRegisterInfo::isPhysicalRegister(RR.Reg));
unsigned R = RR.Reg;
if (RR.Sub)
R = TRI.getSubReg(RR.Reg, RR.Sub);
for (MCRegAliasIterator AI(R, &TRI, false); AI.isValid(); ++AI)
AS.push_back(RegisterRef({*AI, 0}));
return AS;
}
// Check whether RA and RB are aliased.
bool RegisterAliasInfo::alias(RegisterRef RA, RegisterRef RB) const {
bool VirtA = TargetRegisterInfo::isVirtualRegister(RA.Reg);
bool VirtB = TargetRegisterInfo::isVirtualRegister(RB.Reg);
bool PhysA = TargetRegisterInfo::isPhysicalRegister(RA.Reg);
bool PhysB = TargetRegisterInfo::isPhysicalRegister(RB.Reg);
if (VirtA != VirtB)
return false;
if (VirtA) {
if (RA.Reg != RB.Reg)
return false;
// RA and RB refer to the same register. If any of them refer to the
// whole register, they must be aliased.
if (RA.Sub == 0 || RB.Sub == 0)
return true;
unsigned SA = TRI.getSubRegIdxSize(RA.Sub);
unsigned OA = TRI.getSubRegIdxOffset(RA.Sub);
unsigned SB = TRI.getSubRegIdxSize(RB.Sub);
unsigned OB = TRI.getSubRegIdxOffset(RB.Sub);
if (OA <= OB && OA+SA > OB)
return true;
if (OB <= OA && OB+SB > OA)
return true;
return false;
}
assert(PhysA && PhysB);
(void)PhysA, (void)PhysB;
unsigned A = RA.Sub ? TRI.getSubReg(RA.Reg, RA.Sub) : RA.Reg;
unsigned B = RB.Sub ? TRI.getSubReg(RB.Reg, RB.Sub) : RB.Reg;
for (MCRegAliasIterator I(A, &TRI, true); I.isValid(); ++I)
if (B == *I)
return true;
return false;
}
// Target operand information.
//
// For a given instruction, check if there are any bits of RR that can remain
// unchanged across this def.
bool TargetOperandInfo::isPreserving(const MachineInstr &In, unsigned OpNum)
const {
return TII.isPredicated(In);
}
// Check if the definition of RR produces an unspecified value.
bool TargetOperandInfo::isClobbering(const MachineInstr &In, unsigned OpNum)
const {
if (In.isCall())
if (In.getOperand(OpNum).isImplicit())
return true;
return false;
}
// Check if the given instruction specifically requires
bool TargetOperandInfo::isFixedReg(const MachineInstr &In, unsigned OpNum)
const {
if (In.isCall() || In.isReturn())
return true;
const MCInstrDesc &D = In.getDesc();
if (!D.getImplicitDefs() && !D.getImplicitUses())
return false;
const MachineOperand &Op = In.getOperand(OpNum);
// If there is a sub-register, treat the operand as non-fixed. Currently,
// fixed registers are those that are listed in the descriptor as implicit
// uses or defs, and those lists do not allow sub-registers.
if (Op.getSubReg() != 0)
return false;
unsigned Reg = Op.getReg();
const MCPhysReg *ImpR = Op.isDef() ? D.getImplicitDefs()
: D.getImplicitUses();
if (!ImpR)
return false;
while (*ImpR)
if (*ImpR++ == Reg)
return true;
return false;
}
//
// The data flow graph construction.
//
DataFlowGraph::DataFlowGraph(MachineFunction &mf, const TargetInstrInfo &tii,
const TargetRegisterInfo &tri, const MachineDominatorTree &mdt,
const MachineDominanceFrontier &mdf, const RegisterAliasInfo &rai,
const TargetOperandInfo &toi)
: TimeG("rdf"), MF(mf), TII(tii), TRI(tri), MDT(mdt), MDF(mdf), RAI(rai),
TOI(toi) {
}
// The implementation of the definition stack.
// Each register reference has its own definition stack. In particular,
// for a register references "Reg" and "Reg:subreg" will each have their
// own definition stacks.
// Construct a stack iterator.
DataFlowGraph::DefStack::Iterator::Iterator(const DataFlowGraph::DefStack &S,
bool Top) : DS(S) {
if (!Top) {
// Initialize to bottom.
Pos = 0;
return;
}
// Initialize to the top, i.e. top-most non-delimiter (or 0, if empty).
Pos = DS.Stack.size();
while (Pos > 0 && DS.isDelimiter(DS.Stack[Pos-1]))
Pos--;
}
// Return the size of the stack, including block delimiters.
unsigned DataFlowGraph::DefStack::size() const {
unsigned S = 0;
for (auto I = top(), E = bottom(); I != E; I.down())
S++;
return S;
}
// Remove the top entry from the stack. Remove all intervening delimiters
// so that after this, the stack is either empty, or the top of the stack
// is a non-delimiter.
void DataFlowGraph::DefStack::pop() {
assert(!empty());
unsigned P = nextDown(Stack.size());
Stack.resize(P);
}
// Push a delimiter for block node N on the stack.
void DataFlowGraph::DefStack::start_block(NodeId N) {
assert(N != 0);
Stack.push_back(NodeAddr<DefNode*>(nullptr, N));
}
// Remove all nodes from the top of the stack, until the delimited for
// block node N is encountered. Remove the delimiter as well. In effect,
// this will remove from the stack all definitions from block N.
void DataFlowGraph::DefStack::clear_block(NodeId N) {
assert(N != 0);
unsigned P = Stack.size();
while (P > 0) {
bool Found = isDelimiter(Stack[P-1], N);
P--;
if (Found)
break;
}
// This will also remove the delimiter, if found.
Stack.resize(P);
}
// Move the stack iterator up by one.
unsigned DataFlowGraph::DefStack::nextUp(unsigned P) const {
// Get the next valid position after P (skipping all delimiters).
// The input position P does not have to point to a non-delimiter.
unsigned SS = Stack.size();
bool IsDelim;
assert(P < SS);
do {
P++;
IsDelim = isDelimiter(Stack[P-1]);
} while (P < SS && IsDelim);
assert(!IsDelim);
return P;
}
// Move the stack iterator down by one.
unsigned DataFlowGraph::DefStack::nextDown(unsigned P) const {
// Get the preceding valid position before P (skipping all delimiters).
// The input position P does not have to point to a non-delimiter.
assert(P > 0 && P <= Stack.size());
bool IsDelim = isDelimiter(Stack[P-1]);
do {
if (--P == 0)
break;
IsDelim = isDelimiter(Stack[P-1]);
} while (P > 0 && IsDelim);
assert(!IsDelim);
return P;
}
// Node management functions.
// Get the pointer to the node with the id N.
NodeBase *DataFlowGraph::ptr(NodeId N) const {
if (N == 0)
return nullptr;
return Memory.ptr(N);
}
// Get the id of the node at the address P.
NodeId DataFlowGraph::id(const NodeBase *P) const {
if (P == nullptr)
return 0;
return Memory.id(P);
}
// Allocate a new node and set the attributes to Attrs.
NodeAddr<NodeBase*> DataFlowGraph::newNode(uint16_t Attrs) {
NodeAddr<NodeBase*> P = Memory.New();
P.Addr->init();
P.Addr->setAttrs(Attrs);
return P;
}
// Make a copy of the given node B, except for the data-flow links, which
// are set to 0.
NodeAddr<NodeBase*> DataFlowGraph::cloneNode(const NodeAddr<NodeBase*> B) {
NodeAddr<NodeBase*> NA = newNode(0);
memcpy(NA.Addr, B.Addr, sizeof(NodeBase));
// Ref nodes need to have the data-flow links reset.
if (NA.Addr->getType() == NodeAttrs::Ref) {
NodeAddr<RefNode*> RA = NA;
RA.Addr->setReachingDef(0);
RA.Addr->setSibling(0);
if (NA.Addr->getKind() == NodeAttrs::Def) {
NodeAddr<DefNode*> DA = NA;
DA.Addr->setReachedDef(0);
DA.Addr->setReachedUse(0);
}
}
return NA;
}
// Allocation routines for specific node types/kinds.
NodeAddr<UseNode*> DataFlowGraph::newUse(NodeAddr<InstrNode*> Owner,
MachineOperand &Op, uint16_t Flags) {
NodeAddr<UseNode*> UA = newNode(NodeAttrs::Ref | NodeAttrs::Use | Flags);
UA.Addr->setRegRef(&Op);
return UA;
}
NodeAddr<PhiUseNode*> DataFlowGraph::newPhiUse(NodeAddr<PhiNode*> Owner,
RegisterRef RR, NodeAddr<BlockNode*> PredB, uint16_t Flags) {
NodeAddr<PhiUseNode*> PUA = newNode(NodeAttrs::Ref | NodeAttrs::Use | Flags);
assert(Flags & NodeAttrs::PhiRef);
PUA.Addr->setRegRef(RR);
PUA.Addr->setPredecessor(PredB.Id);
return PUA;
}
NodeAddr<DefNode*> DataFlowGraph::newDef(NodeAddr<InstrNode*> Owner,
MachineOperand &Op, uint16_t Flags) {
NodeAddr<DefNode*> DA = newNode(NodeAttrs::Ref | NodeAttrs::Def | Flags);
DA.Addr->setRegRef(&Op);
return DA;
}
NodeAddr<DefNode*> DataFlowGraph::newDef(NodeAddr<InstrNode*> Owner,
RegisterRef RR, uint16_t Flags) {
NodeAddr<DefNode*> DA = newNode(NodeAttrs::Ref | NodeAttrs::Def | Flags);
assert(Flags & NodeAttrs::PhiRef);
DA.Addr->setRegRef(RR);
return DA;
}
NodeAddr<PhiNode*> DataFlowGraph::newPhi(NodeAddr<BlockNode*> Owner) {
NodeAddr<PhiNode*> PA = newNode(NodeAttrs::Code | NodeAttrs::Phi);
Owner.Addr->addPhi(PA, *this);
return PA;
}
NodeAddr<StmtNode*> DataFlowGraph::newStmt(NodeAddr<BlockNode*> Owner,
MachineInstr *MI) {
NodeAddr<StmtNode*> SA = newNode(NodeAttrs::Code | NodeAttrs::Stmt);
SA.Addr->setCode(MI);
Owner.Addr->addMember(SA, *this);
return SA;
}
NodeAddr<BlockNode*> DataFlowGraph::newBlock(NodeAddr<FuncNode*> Owner,
MachineBasicBlock *BB) {
NodeAddr<BlockNode*> BA = newNode(NodeAttrs::Code | NodeAttrs::Block);
BA.Addr->setCode(BB);
Owner.Addr->addMember(BA, *this);
return BA;
}
NodeAddr<FuncNode*> DataFlowGraph::newFunc(MachineFunction *MF) {
NodeAddr<FuncNode*> FA = newNode(NodeAttrs::Code | NodeAttrs::Func);
FA.Addr->setCode(MF);
return FA;
}
// Build the data flow graph.
void DataFlowGraph::build() {
reset();
Func = newFunc(&MF);
if (MF.empty())
return;
for (auto &B : MF) {
auto BA = newBlock(Func, &B);
for (auto &I : B) {
if (I.isDebugValue())
continue;
buildStmt(BA, I);
}
}
// Collect information about block references.
NodeAddr<BlockNode*> EA = Func.Addr->getEntryBlock(*this);
BlockRefsMap RefM;
buildBlockRefs(EA, RefM);
// Add function-entry phi nodes.
MachineRegisterInfo &MRI = MF.getRegInfo();
for (auto I = MRI.livein_begin(), E = MRI.livein_end(); I != E; ++I) {
NodeAddr<PhiNode*> PA = newPhi(EA);
RegisterRef RR = { I->first, 0 };
uint16_t PhiFlags = NodeAttrs::PhiRef | NodeAttrs::Preserving;
NodeAddr<DefNode*> DA = newDef(PA, RR, PhiFlags);
PA.Addr->addMember(DA, *this);
}
// Build a map "PhiM" which will contain, for each block, the set
// of references that will require phi definitions in that block.
BlockRefsMap PhiM;
auto Blocks = Func.Addr->members(*this);
for (NodeAddr<BlockNode*> BA : Blocks)
recordDefsForDF(PhiM, RefM, BA);
for (NodeAddr<BlockNode*> BA : Blocks)
buildPhis(PhiM, RefM, BA);
// Link all the refs. This will recursively traverse the dominator tree.
DefStackMap DM;
linkBlockRefs(DM, EA);
// Finally, remove all unused phi nodes.
removeUnusedPhis();
}
// For each stack in the map DefM, push the delimiter for block B on it.
void DataFlowGraph::markBlock(NodeId B, DefStackMap &DefM) {
// Push block delimiters.
for (auto I = DefM.begin(), E = DefM.end(); I != E; ++I)
I->second.start_block(B);
}
// Remove all definitions coming from block B from each stack in DefM.
void DataFlowGraph::releaseBlock(NodeId B, DefStackMap &DefM) {
// Pop all defs from this block from the definition stack. Defs that were
// added to the map during the traversal of instructions will not have a
// delimiter, but for those, the whole stack will be emptied.
for (auto I = DefM.begin(), E = DefM.end(); I != E; ++I)
I->second.clear_block(B);
// Finally, remove empty stacks from the map.
for (auto I = DefM.begin(), E = DefM.end(), NextI = I; I != E; I = NextI) {
NextI = std::next(I);
// This preserves the validity of iterators other than I.
if (I->second.empty())
DefM.erase(I);
}
}
// Push all definitions from the instruction node IA to an appropriate
// stack in DefM.
void DataFlowGraph::pushDefs(NodeAddr<InstrNode*> IA, DefStackMap &DefM) {
NodeList Defs = IA.Addr->members_if(IsDef, *this);
NodeSet Visited;
#ifndef NDEBUG
RegisterSet Defined;
#endif
// The important objectives of this function are:
// - to be able to handle instructions both while the graph is being
// constructed, and after the graph has been constructed, and
// - maintain proper ordering of definitions on the stack for each
// register reference:
// - if there are two or more related defs in IA (i.e. coming from
// the same machine operand), then only push one def on the stack,
// - if there are multiple unrelated defs of non-overlapping
// subregisters of S, then the stack for S will have both (in an
// unspecified order), but the order does not matter from the data-
// -flow perspective.
for (NodeAddr<DefNode*> DA : Defs) {
if (Visited.count(DA.Id))
continue;
NodeList Rel = getRelatedRefs(IA, DA);
NodeAddr<DefNode*> PDA = Rel.front();
// Push the definition on the stack for the register and all aliases.
RegisterRef RR = PDA.Addr->getRegRef();
#ifndef NDEBUG
// Assert if the register is defined in two or more unrelated defs.
// This could happen if there are two or more def operands defining it.
if (!Defined.insert(RR).second) {
auto *MI = NodeAddr<StmtNode*>(IA).Addr->getCode();
dbgs() << "Multiple definitions of register: "
<< Print<RegisterRef>(RR, *this) << " in\n " << *MI
<< "in BB#" << MI->getParent()->getNumber() << '\n';
llvm_unreachable(nullptr);
}
#endif
DefM[RR].push(DA);
for (auto A : RAI.getAliasSet(RR)) {
assert(A != RR);
DefM[A].push(DA);
}
// Mark all the related defs as visited.
for (auto T : Rel)
Visited.insert(T.Id);
}
}
// Return the list of all reference nodes related to RA, including RA itself.
// See "getNextRelated" for the meaning of a "related reference".
NodeList DataFlowGraph::getRelatedRefs(NodeAddr<InstrNode*> IA,
NodeAddr<RefNode*> RA) const {
assert(IA.Id != 0 && RA.Id != 0);
NodeList Refs;
NodeId Start = RA.Id;
do {
Refs.push_back(RA);
RA = getNextRelated(IA, RA);
} while (RA.Id != 0 && RA.Id != Start);
return Refs;
}
// Clear all information in the graph.
void DataFlowGraph::reset() {
Memory.clear();
Func = NodeAddr<FuncNode*>();
}
// Return the next reference node in the instruction node IA that is related
// to RA. Conceptually, two reference nodes are related if they refer to the
// same instance of a register access, but differ in flags or other minor
// characteristics. Specific examples of related nodes are shadow reference
// nodes.
// Return the equivalent of nullptr if there are no more related references.
NodeAddr<RefNode*> DataFlowGraph::getNextRelated(NodeAddr<InstrNode*> IA,
NodeAddr<RefNode*> RA) const {
assert(IA.Id != 0 && RA.Id != 0);
auto Related = [RA](NodeAddr<RefNode*> TA) -> bool {
if (TA.Addr->getKind() != RA.Addr->getKind())
return false;
if (TA.Addr->getRegRef() != RA.Addr->getRegRef())
return false;
return true;
};
auto RelatedStmt = [&Related,RA](NodeAddr<RefNode*> TA) -> bool {
return Related(TA) &&
&RA.Addr->getOp() == &TA.Addr->getOp();
};
auto RelatedPhi = [&Related,RA](NodeAddr<RefNode*> TA) -> bool {
if (!Related(TA))
return false;
if (TA.Addr->getKind() != NodeAttrs::Use)
return true;
// For phi uses, compare predecessor blocks.
const NodeAddr<const PhiUseNode*> TUA = TA;
const NodeAddr<const PhiUseNode*> RUA = RA;
return TUA.Addr->getPredecessor() == RUA.Addr->getPredecessor();
};
RegisterRef RR = RA.Addr->getRegRef();
if (IA.Addr->getKind() == NodeAttrs::Stmt)
return RA.Addr->getNextRef(RR, RelatedStmt, true, *this);
return RA.Addr->getNextRef(RR, RelatedPhi, true, *this);
}
// Find the next node related to RA in IA that satisfies condition P.
// If such a node was found, return a pair where the second element is the
// located node. If such a node does not exist, return a pair where the
// first element is the element after which such a node should be inserted,
// and the second element is a null-address.
template <typename Predicate>
std::pair<NodeAddr<RefNode*>,NodeAddr<RefNode*>>
DataFlowGraph::locateNextRef(NodeAddr<InstrNode*> IA, NodeAddr<RefNode*> RA,
Predicate P) const {
assert(IA.Id != 0 && RA.Id != 0);
NodeAddr<RefNode*> NA;
NodeId Start = RA.Id;
while (true) {
NA = getNextRelated(IA, RA);
if (NA.Id == 0 || NA.Id == Start)
break;
if (P(NA))
break;
RA = NA;
}
if (NA.Id != 0 && NA.Id != Start)
return std::make_pair(RA, NA);
return std::make_pair(RA, NodeAddr<RefNode*>());
}
// Get the next shadow node in IA corresponding to RA, and optionally create
// such a node if it does not exist.
NodeAddr<RefNode*> DataFlowGraph::getNextShadow(NodeAddr<InstrNode*> IA,
NodeAddr<RefNode*> RA, bool Create) {
assert(IA.Id != 0 && RA.Id != 0);
uint16_t Flags = RA.Addr->getFlags() | NodeAttrs::Shadow;
auto IsShadow = [Flags] (NodeAddr<RefNode*> TA) -> bool {
return TA.Addr->getFlags() == Flags;
};
auto Loc = locateNextRef(IA, RA, IsShadow);
if (Loc.second.Id != 0 || !Create)
return Loc.second;
// Create a copy of RA and mark is as shadow.
NodeAddr<RefNode*> NA = cloneNode(RA);
NA.Addr->setFlags(Flags | NodeAttrs::Shadow);
IA.Addr->addMemberAfter(Loc.first, NA, *this);
return NA;
}
// Get the next shadow node in IA corresponding to RA. Return null-address
// if such a node does not exist.
NodeAddr<RefNode*> DataFlowGraph::getNextShadow(NodeAddr<InstrNode*> IA,
NodeAddr<RefNode*> RA) const {
assert(IA.Id != 0 && RA.Id != 0);
uint16_t Flags = RA.Addr->getFlags() | NodeAttrs::Shadow;
auto IsShadow = [Flags] (NodeAddr<RefNode*> TA) -> bool {
return TA.Addr->getFlags() == Flags;
};
return locateNextRef(IA, RA, IsShadow).second;
}
// Create a new statement node in the block node BA that corresponds to
// the machine instruction MI.
void DataFlowGraph::buildStmt(NodeAddr<BlockNode*> BA, MachineInstr &In) {
auto SA = newStmt(BA, &In);
// Collect a set of registers that this instruction implicitly uses
// or defines. Implicit operands from an instruction will be ignored
// unless they are listed here.
RegisterSet ImpUses, ImpDefs;
if (const uint16_t *ImpD = In.getDesc().getImplicitDefs())
while (uint16_t R = *ImpD++)
ImpDefs.insert({R, 0});
if (const uint16_t *ImpU = In.getDesc().getImplicitUses())
while (uint16_t R = *ImpU++)
ImpUses.insert({R, 0});
bool IsCall = In.isCall(), IsReturn = In.isReturn();
bool IsPredicated = TII.isPredicated(In);
unsigned NumOps = In.getNumOperands();
// Avoid duplicate implicit defs. This will not detect cases of implicit
// defs that define registers that overlap, but it is not clear how to
// interpret that in the absence of explicit defs. Overlapping explicit
// defs are likely illegal already.
RegisterSet DoneDefs;
// Process explicit defs first.
for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
MachineOperand &Op = In.getOperand(OpN);
if (!Op.isReg() || !Op.isDef() || Op.isImplicit())
continue;
RegisterRef RR = { Op.getReg(), Op.getSubReg() };
uint16_t Flags = NodeAttrs::None;
if (TOI.isPreserving(In, OpN))
Flags |= NodeAttrs::Preserving;
if (TOI.isClobbering(In, OpN))
Flags |= NodeAttrs::Clobbering;
if (TOI.isFixedReg(In, OpN))
Flags |= NodeAttrs::Fixed;
NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
SA.Addr->addMember(DA, *this);
DoneDefs.insert(RR);
}
// Process implicit defs, skipping those that have already been added
// as explicit.
for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
MachineOperand &Op = In.getOperand(OpN);
if (!Op.isReg() || !Op.isDef() || !Op.isImplicit())
continue;
RegisterRef RR = { Op.getReg(), Op.getSubReg() };
if (!IsCall && !ImpDefs.count(RR))
continue;
if (DoneDefs.count(RR))
continue;
uint16_t Flags = NodeAttrs::None;
if (TOI.isPreserving(In, OpN))
Flags |= NodeAttrs::Preserving;
if (TOI.isClobbering(In, OpN))
Flags |= NodeAttrs::Clobbering;
if (TOI.isFixedReg(In, OpN))
Flags |= NodeAttrs::Fixed;
NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
SA.Addr->addMember(DA, *this);
DoneDefs.insert(RR);
}
for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
MachineOperand &Op = In.getOperand(OpN);
if (!Op.isReg() || !Op.isUse())
continue;
RegisterRef RR = { Op.getReg(), Op.getSubReg() };
// Add implicit uses on return and call instructions, and on predicated
// instructions regardless of whether or not they appear in the instruction
// descriptor's list.
bool Implicit = Op.isImplicit();
bool TakeImplicit = IsReturn || IsCall || IsPredicated;
if (Implicit && !TakeImplicit && !ImpUses.count(RR))
continue;
uint16_t Flags = NodeAttrs::None;
if (TOI.isFixedReg(In, OpN))
Flags |= NodeAttrs::Fixed;
NodeAddr<UseNode*> UA = newUse(SA, Op, Flags);
SA.Addr->addMember(UA, *this);
}
}
// Build a map that for each block will have the set of all references from
// that block, and from all blocks dominated by it.
void DataFlowGraph::buildBlockRefs(NodeAddr<BlockNode*> BA,
BlockRefsMap &RefM) {
auto &Refs = RefM[BA.Id];
MachineDomTreeNode *N = MDT.getNode(BA.Addr->getCode());
assert(N);
for (auto I : *N) {
MachineBasicBlock *SB = I->getBlock();
auto SBA = Func.Addr->findBlock(SB, *this);
buildBlockRefs(SBA, RefM);
const auto &SRs = RefM[SBA.Id];
Refs.insert(SRs.begin(), SRs.end());
}
for (NodeAddr<InstrNode*> IA : BA.Addr->members(*this))
for (NodeAddr<RefNode*> RA : IA.Addr->members(*this))
Refs.insert(RA.Addr->getRegRef());
}
// Scan all defs in the block node BA and record in PhiM the locations of
// phi nodes corresponding to these defs.
void DataFlowGraph::recordDefsForDF(BlockRefsMap &PhiM, BlockRefsMap &RefM,
NodeAddr<BlockNode*> BA) {
// Check all defs from block BA and record them in each block in BA's
// iterated dominance frontier. This information will later be used to
// create phi nodes.
MachineBasicBlock *BB = BA.Addr->getCode();
assert(BB);
auto DFLoc = MDF.find(BB);
if (DFLoc == MDF.end() || DFLoc->second.empty())
return;
// Traverse all instructions in the block and collect the set of all
// defined references. For each reference there will be a phi created
// in the block's iterated dominance frontier.
// This is done to make sure that each defined reference gets only one
// phi node, even if it is defined multiple times.
RegisterSet Defs;
for (auto I : BA.Addr->members(*this)) {
assert(I.Addr->getType() == NodeAttrs::Code);
assert(I.Addr->getKind() == NodeAttrs::Phi ||
I.Addr->getKind() == NodeAttrs::Stmt);
NodeAddr<InstrNode*> IA = I;
for (NodeAddr<RefNode*> RA : IA.Addr->members_if(IsDef, *this))
Defs.insert(RA.Addr->getRegRef());
}
// Finally, add the set of defs to each block in the iterated dominance
// frontier.
const MachineDominanceFrontier::DomSetType &DF = DFLoc->second;
SetVector<MachineBasicBlock*> IDF(DF.begin(), DF.end());
for (unsigned i = 0; i < IDF.size(); ++i) {
auto F = MDF.find(IDF[i]);
if (F != MDF.end())
IDF.insert(F->second.begin(), F->second.end());
}
// Get the register references that are reachable from this block.
RegisterSet &Refs = RefM[BA.Id];
for (auto DB : IDF) {
auto DBA = Func.Addr->findBlock(DB, *this);
const auto &Rs = RefM[DBA.Id];
Refs.insert(Rs.begin(), Rs.end());
}
for (auto DB : IDF) {
auto DBA = Func.Addr->findBlock(DB, *this);
PhiM[DBA.Id].insert(Defs.begin(), Defs.end());
}
}
// Given the locations of phi nodes in the map PhiM, create the phi nodes
// that are located in the block node BA.
void DataFlowGraph::buildPhis(BlockRefsMap &PhiM, BlockRefsMap &RefM,
NodeAddr<BlockNode*> BA) {
// Check if this blocks has any DF defs, i.e. if there are any defs
// that this block is in the iterated dominance frontier of.
auto HasDF = PhiM.find(BA.Id);
if (HasDF == PhiM.end() || HasDF->second.empty())
return;
// First, remove all R in Refs in such that there exists T in Refs
// such that T covers R. In other words, only leave those refs that
// are not covered by another ref (i.e. maximal with respect to covering).
auto MaxCoverIn = [this] (RegisterRef RR, RegisterSet &RRs) -> RegisterRef {
for (auto I : RRs)
if (I != RR && RAI.covers(I, RR))
RR = I;
return RR;
};
RegisterSet MaxDF;
for (auto I : HasDF->second)
MaxDF.insert(MaxCoverIn(I, HasDF->second));
std::vector<RegisterRef> MaxRefs;
auto &RefB = RefM[BA.Id];
for (auto I : MaxDF)
MaxRefs.push_back(MaxCoverIn(I, RefB));
// Now, for each R in MaxRefs, get the alias closure of R. If the closure
// only has R in it, create a phi a def for R. Otherwise, create a phi,
// and add a def for each S in the closure.
// Sort the refs so that the phis will be created in a deterministic order.
std::sort(MaxRefs.begin(), MaxRefs.end());
// Remove duplicates.
auto NewEnd = std::unique(MaxRefs.begin(), MaxRefs.end());
MaxRefs.erase(NewEnd, MaxRefs.end());
auto Aliased = [this,&MaxRefs](RegisterRef RR,
std::vector<unsigned> &Closure) -> bool {
for (auto I : Closure)
if (RAI.alias(RR, MaxRefs[I]))
return true;
return false;
};
// Prepare a list of NodeIds of the block's predecessors.
std::vector<NodeId> PredList;
const MachineBasicBlock *MBB = BA.Addr->getCode();
for (auto PB : MBB->predecessors()) {
auto B = Func.Addr->findBlock(PB, *this);
PredList.push_back(B.Id);
}
while (!MaxRefs.empty()) {
// Put the first element in the closure, and then add all subsequent
// elements from MaxRefs to it, if they alias at least one element
// already in the closure.
// ClosureIdx: vector of indices in MaxRefs of members of the closure.
std::vector<unsigned> ClosureIdx = { 0 };
for (unsigned i = 1; i != MaxRefs.size(); ++i)
if (Aliased(MaxRefs[i], ClosureIdx))
ClosureIdx.push_back(i);
// Build a phi for the closure.
unsigned CS = ClosureIdx.size();
NodeAddr<PhiNode*> PA = newPhi(BA);
// Add defs.
for (unsigned X = 0; X != CS; ++X) {
RegisterRef RR = MaxRefs[ClosureIdx[X]];
uint16_t PhiFlags = NodeAttrs::PhiRef | NodeAttrs::Preserving;
NodeAddr<DefNode*> DA = newDef(PA, RR, PhiFlags);
PA.Addr->addMember(DA, *this);
}
// Add phi uses.
for (auto P : PredList) {
auto PBA = addr<BlockNode*>(P);
for (unsigned X = 0; X != CS; ++X) {
RegisterRef RR = MaxRefs[ClosureIdx[X]];
NodeAddr<PhiUseNode*> PUA = newPhiUse(PA, RR, PBA);
PA.Addr->addMember(PUA, *this);
}
}
// Erase from MaxRefs all elements in the closure.
auto Begin = MaxRefs.begin();
for (unsigned i = ClosureIdx.size(); i != 0; --i)
MaxRefs.erase(Begin + ClosureIdx[i-1]);
}
}
// Remove any unneeded phi nodes that were created during the build process.
void DataFlowGraph::removeUnusedPhis() {
// This will remove unused phis, i.e. phis where each def does not reach
// any uses or other defs. This will not detect or remove circular phi
// chains that are otherwise dead. Unused/dead phis are created during
// the build process and this function is intended to remove these cases
// that are easily determinable to be unnecessary.
SetVector<NodeId> PhiQ;
for (NodeAddr<BlockNode*> BA : Func.Addr->members(*this)) {
for (auto P : BA.Addr->members_if(IsPhi, *this))
PhiQ.insert(P.Id);
}
static auto HasUsedDef = [](NodeList &Ms) -> bool {
for (auto M : Ms) {
if (M.Addr->getKind() != NodeAttrs::Def)
continue;
NodeAddr<DefNode*> DA = M;
if (DA.Addr->getReachedDef() != 0 || DA.Addr->getReachedUse() != 0)
return true;
}
return false;
};
// Any phi, if it is removed, may affect other phis (make them dead).
// For each removed phi, collect the potentially affected phis and add
// them back to the queue.
while (!PhiQ.empty()) {
auto PA = addr<PhiNode*>(PhiQ[0]);
PhiQ.remove(PA.Id);
NodeList Refs = PA.Addr->members(*this);
if (HasUsedDef(Refs))
continue;
for (NodeAddr<RefNode*> RA : Refs) {
if (NodeId RD = RA.Addr->getReachingDef()) {
auto RDA = addr<DefNode*>(RD);
NodeAddr<InstrNode*> OA = RDA.Addr->getOwner(*this);
if (IsPhi(OA))
PhiQ.insert(OA.Id);
}
if (RA.Addr->isDef())
unlinkDef(RA, true);
else
unlinkUse(RA, true);
}
NodeAddr<BlockNode*> BA = PA.Addr->getOwner(*this);
BA.Addr->removeMember(PA, *this);
}
}
// For a given reference node TA in an instruction node IA, connect the
// reaching def of TA to the appropriate def node. Create any shadow nodes
// as appropriate.
template <typename T>
void DataFlowGraph::linkRefUp(NodeAddr<InstrNode*> IA, NodeAddr<T> TA,
DefStack &DS) {
if (DS.empty())
return;
RegisterRef RR = TA.Addr->getRegRef();
NodeAddr<T> TAP;
// References from the def stack that have been examined so far.
RegisterSet Defs;
for (auto I = DS.top(), E = DS.bottom(); I != E; I.down()) {
RegisterRef QR = I->Addr->getRegRef();
auto AliasQR = [QR,this] (RegisterRef RR) -> bool {
return RAI.alias(QR, RR);
};
bool PrecUp = RAI.covers(QR, RR);
// Skip all defs that are aliased to any of the defs that we have already
// seen. If we encounter a covering def, stop the stack traversal early.
if (std::any_of(Defs.begin(), Defs.end(), AliasQR)) {
if (PrecUp)
break;
continue;
}
// The reaching def.
NodeAddr<DefNode*> RDA = *I;
// Pick the reached node.
if (TAP.Id == 0) {
TAP = TA;
} else {
// Mark the existing ref as "shadow" and create a new shadow.
TAP.Addr->setFlags(TAP.Addr->getFlags() | NodeAttrs::Shadow);
TAP = getNextShadow(IA, TAP, true);
}
// Create the link.
TAP.Addr->linkToDef(TAP.Id, RDA);
if (PrecUp)
break;
Defs.insert(QR);
}
}
// Create data-flow links for all reference nodes in the statement node SA.
void DataFlowGraph::linkStmtRefs(DefStackMap &DefM, NodeAddr<StmtNode*> SA) {
RegisterSet Defs;
// Link all nodes (upwards in the data-flow) with their reaching defs.
for (NodeAddr<RefNode*> RA : SA.Addr->members(*this)) {
uint16_t Kind = RA.Addr->getKind();
assert(Kind == NodeAttrs::Def || Kind == NodeAttrs::Use);
RegisterRef RR = RA.Addr->getRegRef();
// Do not process multiple defs of the same reference.
if (Kind == NodeAttrs::Def && Defs.count(RR))
continue;
Defs.insert(RR);
auto F = DefM.find(RR);
if (F == DefM.end())
continue;
DefStack &DS = F->second;
if (Kind == NodeAttrs::Use)
linkRefUp<UseNode*>(SA, RA, DS);
else if (Kind == NodeAttrs::Def)
linkRefUp<DefNode*>(SA, RA, DS);
else
llvm_unreachable("Unexpected node in instruction");
}
}
// Create data-flow links for all instructions in the block node BA. This
// will include updating any phi nodes in BA.
void DataFlowGraph::linkBlockRefs(DefStackMap &DefM, NodeAddr<BlockNode*> BA) {
// Push block delimiters.
markBlock(BA.Id, DefM);
// For each non-phi instruction in the block, link all the defs and uses
// to their reaching defs. For any member of the block (including phis),
// push the defs on the corresponding stacks.
for (NodeAddr<InstrNode*> IA : BA.Addr->members(*this)) {
// Ignore phi nodes here. They will be linked part by part from the
// predecessors.
if (IA.Addr->getKind() == NodeAttrs::Stmt)
linkStmtRefs(DefM, IA);
// Push the definitions on the stack.
pushDefs(IA, DefM);
}
// Recursively process all children in the dominator tree.
MachineDomTreeNode *N = MDT.getNode(BA.Addr->getCode());
for (auto I : *N) {
MachineBasicBlock *SB = I->getBlock();
auto SBA = Func.Addr->findBlock(SB, *this);
linkBlockRefs(DefM, SBA);
}
// Link the phi uses from the successor blocks.
auto IsUseForBA = [BA](NodeAddr<NodeBase*> NA) -> bool {
if (NA.Addr->getKind() != NodeAttrs::Use)
return false;
assert(NA.Addr->getFlags() & NodeAttrs::PhiRef);
NodeAddr<PhiUseNode*> PUA = NA;
return PUA.Addr->getPredecessor() == BA.Id;
};
MachineBasicBlock *MBB = BA.Addr->getCode();
for (auto SB : MBB->successors()) {
auto SBA = Func.Addr->findBlock(SB, *this);
for (NodeAddr<InstrNode*> IA : SBA.Addr->members_if(IsPhi, *this)) {
// Go over each phi use associated with MBB, and link it.
for (auto U : IA.Addr->members_if(IsUseForBA, *this)) {
NodeAddr<PhiUseNode*> PUA = U;
RegisterRef RR = PUA.Addr->getRegRef();
linkRefUp<UseNode*>(IA, PUA, DefM[RR]);
}
}
}
// Pop all defs from this block from the definition stacks.
releaseBlock(BA.Id, DefM);
}
// Remove the use node UA from any data-flow and structural links.
void DataFlowGraph::unlinkUseDF(NodeAddr<UseNode*> UA) {
NodeId RD = UA.Addr->getReachingDef();
NodeId Sib = UA.Addr->getSibling();
if (RD == 0) {
assert(Sib == 0);
return;
}
auto RDA = addr<DefNode*>(RD);
auto TA = addr<UseNode*>(RDA.Addr->getReachedUse());
if (TA.Id == UA.Id) {
RDA.Addr->setReachedUse(Sib);
return;
}
while (TA.Id != 0) {
NodeId S = TA.Addr->getSibling();
if (S == UA.Id) {
TA.Addr->setSibling(UA.Addr->getSibling());
return;
}
TA = addr<UseNode*>(S);
}
}
// Remove the def node DA from any data-flow and structural links.
void DataFlowGraph::unlinkDefDF(NodeAddr<DefNode*> DA) {
//
// RD
// | reached
// | def
// :
// .
// +----+
// ... -- | DA | -- ... -- 0 : sibling chain of DA
// +----+
// | | reached
// | : def
// | .
// | ... : Siblings (defs)
// |
// : reached
// . use
// ... : sibling chain of reached uses
NodeId RD = DA.Addr->getReachingDef();
// Visit all siblings of the reached def and reset their reaching defs.
// Also, defs reached by DA are now "promoted" to being reached by RD,
// so all of them will need to be spliced into the sibling chain where
// DA belongs.
auto getAllNodes = [this] (NodeId N) -> NodeList {
NodeList Res;
while (N) {
auto RA = addr<RefNode*>(N);
// Keep the nodes in the exact sibling order.
Res.push_back(RA);
N = RA.Addr->getSibling();
}
return Res;
};
NodeList ReachedDefs = getAllNodes(DA.Addr->getReachedDef());
NodeList ReachedUses = getAllNodes(DA.Addr->getReachedUse());
if (RD == 0) {
for (NodeAddr<RefNode*> I : ReachedDefs)
I.Addr->setSibling(0);
for (NodeAddr<RefNode*> I : ReachedUses)
I.Addr->setSibling(0);
}
for (NodeAddr<DefNode*> I : ReachedDefs)
I.Addr->setReachingDef(RD);
for (NodeAddr<UseNode*> I : ReachedUses)
I.Addr->setReachingDef(RD);
NodeId Sib = DA.Addr->getSibling();
if (RD == 0) {
assert(Sib == 0);
return;
}
// Update the reaching def node and remove DA from the sibling list.
auto RDA = addr<DefNode*>(RD);
auto TA = addr<DefNode*>(RDA.Addr->getReachedDef());
if (TA.Id == DA.Id) {
// If DA is the first reached def, just update the RD's reached def
// to the DA's sibling.
RDA.Addr->setReachedDef(Sib);
} else {
// Otherwise, traverse the sibling list of the reached defs and remove
// DA from it.
while (TA.Id != 0) {
NodeId S = TA.Addr->getSibling();
if (S == DA.Id) {
TA.Addr->setSibling(Sib);
break;
}
TA = addr<DefNode*>(S);
}
}
// Splice the DA's reached defs into the RDA's reached def chain.
if (!ReachedDefs.empty()) {
auto Last = NodeAddr<DefNode*>(ReachedDefs.back());
Last.Addr->setSibling(RDA.Addr->getReachedDef());
RDA.Addr->setReachedDef(ReachedDefs.front().Id);
}
// Splice the DA's reached uses into the RDA's reached use chain.
if (!ReachedUses.empty()) {
auto Last = NodeAddr<UseNode*>(ReachedUses.back());
Last.Addr->setSibling(RDA.Addr->getReachedUse());
RDA.Addr->setReachedUse(ReachedUses.front().Id);
}
}
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