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swiftshader / SwiftShader / 23742c0958ddb7216cbb02cde04109df888cd8db / . / third_party / subzero / src / IceCfg.cpp
blob: f75ca292c1bbb05b77bc04583a19874411faca8e [file] [log] [blame]
//===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
//
// The Subzero Code Generator
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief Implements the Cfg class.
///
//===----------------------------------------------------------------------===//
#include "IceCfg.h"
#include "IceAssembler.h"
#include "IceBitVector.h"
#include "IceCfgNode.h"
#include "IceClFlags.h"
#include "IceDefs.h"
#include "IceELFObjectWriter.h"
#include "IceGlobalInits.h"
#include "IceInst.h"
#include "IceInstVarIter.h"
#include "IceInstrumentation.h"
#include "IceLiveness.h"
#include "IceLoopAnalyzer.h"
#include "IceOperand.h"
#include "IceTargetLowering.h"
#include <memory>
#include <utility>
namespace Ice {
Cfg::Cfg(GlobalContext *Ctx, uint32_t SequenceNumber)
: Allocator(createAllocator()), Ctx(Ctx), SequenceNumber(SequenceNumber),
VMask(getFlags().getVerbose()), FunctionName(),
NextInstNumber(Inst::NumberInitial), Live(nullptr) {
NodeStrings.reset(new StringPool);
VarStrings.reset(new StringPool);
CfgLocalAllocatorScope _(this);
Target = TargetLowering::createLowering(getFlags().getTargetArch(), this);
VMetadata.reset(new VariablesMetadata(this));
TargetAssembler = Target->createAssembler();
if (getFlags().getRandomizeAndPoolImmediatesOption() == RPI_Randomize) {
// If -randomize-pool-immediates=randomize, create a random number
// generator to generate a cookie for constant blinding.
RandomNumberGenerator RNG(getFlags().getRandomSeed(), RPE_ConstantBlinding,
this->SequenceNumber);
ConstantBlindingCookie =
(uint32_t)RNG.next((uint64_t)std::numeric_limits<uint32_t>::max() + 1);
}
}
Cfg::~Cfg() {
assert(CfgAllocatorTraits::current() == nullptr);
if (getFlags().getDumpStrings()) {
OstreamLocker _(Ctx);
Ostream &Str = Ctx->getStrDump();
getNodeStrings()->dump(Str);
getVarStrings()->dump(Str);
}
}
// Called in the initalizer list of Cfg's constructor to create the Allocator
// and set it as TLS before any other member fields are constructed, since they
// may depend on it.
ArenaAllocator *Cfg::createAllocator() {
ArenaAllocator *Allocator = new ArenaAllocator();
CfgAllocatorTraits::set_current(Allocator);
return Allocator;
}
/// Create a string like "foo(i=123:b=9)" indicating the function name, number
/// of high-level instructions, and number of basic blocks. This string is only
/// used for dumping and other diagnostics, and the idea is that given a set of
/// functions to debug a problem on, it's easy to find the smallest or simplest
/// function to attack. Note that the counts may change somewhat depending on
/// what point it is called during the translation passes.
std::string Cfg::getFunctionNameAndSize() const {
if (!BuildDefs::dump())
return getFunctionName().toString();
SizeT NodeCount = 0;
SizeT InstCount = 0;
for (CfgNode *Node : getNodes()) {
++NodeCount;
// Note: deleted instructions are *not* ignored.
InstCount += Node->getPhis().size();
for (Inst &I : Node->getInsts()) {
if (!llvm::isa<InstTarget>(&I))
++InstCount;
}
}
return getFunctionName() + "(i=" + std::to_string(InstCount) + ":b=" +
std::to_string(NodeCount) + ")";
}
void Cfg::setError(const std::string &Message) {
HasError = true;
ErrorMessage = Message;
}
CfgNode *Cfg::makeNode() {
SizeT LabelIndex = Nodes.size();
auto *Node = CfgNode::create(this, LabelIndex);
Nodes.push_back(Node);
return Node;
}
void Cfg::swapNodes(NodeList &NewNodes) {
assert(Nodes.size() == NewNodes.size());
Nodes.swap(NewNodes);
for (SizeT I = 0, NumNodes = getNumNodes(); I < NumNodes; ++I)
Nodes[I]->resetIndex(I);
}
template <> Variable *Cfg::makeVariable<Variable>(Type Ty) {
SizeT Index = Variables.size();
Variable *Var;
if (Target->shouldSplitToVariableVecOn32(Ty)) {
Var = VariableVecOn32::create(this, Ty, Index);
} else if (Target->shouldSplitToVariable64On32(Ty)) {
Var = Variable64On32::create(this, Ty, Index);
} else {
Var = Variable::create(this, Ty, Index);
}
Variables.push_back(Var);
return Var;
}
void Cfg::addArg(Variable *Arg) {
Arg->setIsArg();
Args.push_back(Arg);
}
void Cfg::addImplicitArg(Variable *Arg) {
Arg->setIsImplicitArg();
ImplicitArgs.push_back(Arg);
}
// Returns whether the stack frame layout has been computed yet. This is used
// for dumping the stack frame location of Variables.
bool Cfg::hasComputedFrame() const { return getTarget()->hasComputedFrame(); }
namespace {
constexpr char BlockNameGlobalPrefix[] = ".L$profiler$block_name$";
constexpr char BlockStatsGlobalPrefix[] = ".L$profiler$block_info$";
} // end of anonymous namespace
void Cfg::createNodeNameDeclaration(const std::string &NodeAsmName) {
auto *Var = VariableDeclaration::create(GlobalInits.get());
Var->setName(Ctx, BlockNameGlobalPrefix + NodeAsmName);
Var->setIsConstant(true);
Var->addInitializer(VariableDeclaration::DataInitializer::create(
GlobalInits.get(), NodeAsmName.data(), NodeAsmName.size() + 1));
const SizeT Int64ByteSize = typeWidthInBytes(IceType_i64);
Var->setAlignment(Int64ByteSize); // Wasteful, 32-bit could use 4 bytes.
GlobalInits->push_back(Var);
}
void Cfg::createBlockProfilingInfoDeclaration(
const std::string &NodeAsmName, VariableDeclaration *NodeNameDeclaration) {
auto *Var = VariableDeclaration::create(GlobalInits.get());
Var->setName(Ctx, BlockStatsGlobalPrefix + NodeAsmName);
const SizeT Int64ByteSize = typeWidthInBytes(IceType_i64);
Var->addInitializer(VariableDeclaration::ZeroInitializer::create(
GlobalInits.get(), Int64ByteSize));
const RelocOffsetT NodeNameDeclarationOffset = 0;
Var->addInitializer(VariableDeclaration::RelocInitializer::create(
GlobalInits.get(), NodeNameDeclaration,
{RelocOffset::create(Ctx, NodeNameDeclarationOffset)}));
Var->setAlignment(Int64ByteSize);
GlobalInits->push_back(Var);
}
void Cfg::profileBlocks() {
if (GlobalInits == nullptr)
GlobalInits.reset(new VariableDeclarationList());
for (CfgNode *Node : Nodes) {
const std::string NodeAsmName = Node->getAsmName();
createNodeNameDeclaration(NodeAsmName);
createBlockProfilingInfoDeclaration(NodeAsmName, GlobalInits->back());
Node->profileExecutionCount(GlobalInits->back());
}
}
bool Cfg::isProfileGlobal(const VariableDeclaration &Var) {
if (!Var.getName().hasStdString())
return false;
return Var.getName().toString().find(BlockStatsGlobalPrefix) == 0;
}
void Cfg::addCallToProfileSummary() {
// The call(s) to __Sz_profile_summary are added by the profiler in functions
// that cause the program to exit. This function is defined in
// runtime/szrt_profiler.c.
Constant *ProfileSummarySym =
Ctx->getConstantExternSym(Ctx->getGlobalString("__Sz_profile_summary"));
constexpr SizeT NumArgs = 0;
constexpr Variable *Void = nullptr;
constexpr bool HasTailCall = false;
auto *Call =
InstCall::create(this, NumArgs, Void, ProfileSummarySym, HasTailCall);
getEntryNode()->getInsts().push_front(Call);
}
void Cfg::translate() {
if (hasError())
return;
// Cache the possibly-overridden optimization level once translation begins.
// It would be nicer to do this in the constructor, but we need to wait until
// after setFunctionName() has a chance to be called.
OptimizationLevel =
getFlags().matchForceO2(getFunctionName(), getSequenceNumber())
? Opt_2
: getFlags().getOptLevel();
if (BuildDefs::timers()) {
if (getFlags().matchTimingFocus(getFunctionName(), getSequenceNumber())) {
setFocusedTiming();
getContext()->resetTimer(GlobalContext::TSK_Default);
}
}
if (BuildDefs::dump()) {
if (isVerbose(IceV_Status) &&
getFlags().matchTestStatus(getFunctionName(), getSequenceNumber())) {
getContext()->getStrDump() << ">>>Translating "
<< getFunctionNameAndSize()
<< " seq=" << getSequenceNumber() << "\n";
}
}
TimerMarker T_func(getContext(), getFunctionName().toStringOrEmpty());
TimerMarker T(TimerStack::TT_translate, this);
dump("Initial CFG");
if (getFlags().getEnableBlockProfile()) {
profileBlocks();
// TODO(jpp): this is fragile, at best. Figure out a better way of
// detecting exit functions.
if (getFunctionName().toStringOrEmpty() == "exit") {
addCallToProfileSummary();
}
dump("Profiled CFG");
}
// Create the Hi and Lo variables where a split was needed
for (Variable *Var : Variables) {
if (auto *Var64On32 = llvm::dyn_cast<Variable64On32>(Var)) {
Var64On32->initHiLo(this);
} else if (auto *VarVecOn32 = llvm::dyn_cast<VariableVecOn32>(Var)) {
VarVecOn32->initVecElement(this);
}
}
// Instrument the Cfg, e.g. with AddressSanitizer
if (!BuildDefs::minimal() && getFlags().getSanitizeAddresses()) {
getContext()->instrumentFunc(this);
dump("Instrumented CFG");
}
// The set of translation passes and their order are determined by the
// target.
getTarget()->translate();
dump("Final output");
if (getFocusedTiming()) {
getContext()->dumpLocalTimers(getFunctionName().toString());
}
}
void Cfg::fixPhiNodes() {
for (auto *Node : Nodes) {
// Fix all the phi edges since WASM can't tell how to make them correctly at
// the beginning.
assert(Node);
const auto &InEdges = Node->getInEdges();
for (auto &Instr : Node->getPhis()) {
auto *Phi = llvm::cast<InstPhi>(&Instr);
assert(Phi);
for (SizeT i = 0; i < InEdges.size(); ++i) {
Phi->setLabel(i, InEdges[i]);
}
}
}
}
void Cfg::computeInOutEdges() {
// Compute the out-edges.
for (CfgNode *Node : Nodes) {
Node->computeSuccessors();
}
// Prune any unreachable nodes before computing in-edges.
SizeT NumNodes = getNumNodes();
BitVector Reachable(NumNodes);
BitVector Pending(NumNodes);
Pending.set(getEntryNode()->getIndex());
while (true) {
int Index = Pending.find_first();
if (Index == -1)
break;
Pending.reset(Index);
Reachable.set(Index);
CfgNode *Node = Nodes[Index];
assert(Node->getIndex() == (SizeT)Index);
for (CfgNode *Succ : Node->getOutEdges()) {
SizeT SuccIndex = Succ->getIndex();
if (!Reachable.test(SuccIndex))
Pending.set(SuccIndex);
}
}
SizeT Dest = 0;
for (SizeT Source = 0; Source < NumNodes; ++Source) {
if (Reachable.test(Source)) {
Nodes[Dest] = Nodes[Source];
Nodes[Dest]->resetIndex(Dest);
// Compute the in-edges.
Nodes[Dest]->computePredecessors();
++Dest;
}
}
Nodes.resize(Dest);
TimerMarker T(TimerStack::TT_phiValidation, this);
for (CfgNode *Node : Nodes)
Node->enforcePhiConsistency();
}
void Cfg::renumberInstructions() {
TimerMarker T(TimerStack::TT_renumberInstructions, this);
NextInstNumber = Inst::NumberInitial;
for (CfgNode *Node : Nodes)
Node->renumberInstructions();
// Make sure the entry node is the first node and therefore got the lowest
// instruction numbers, to facilitate live range computation of function
// arguments. We want to model function arguments as being live on entry to
// the function, otherwise an argument whose only use is in the first
// instruction will be assigned a trivial live range and the register
// allocator will not recognize its live range as overlapping another
// variable's live range.
assert(Nodes.empty() || (*Nodes.begin() == getEntryNode()));
}
// placePhiLoads() must be called before placePhiStores().
void Cfg::placePhiLoads() {
TimerMarker T(TimerStack::TT_placePhiLoads, this);
for (CfgNode *Node : Nodes)
Node->placePhiLoads();
}
// placePhiStores() must be called after placePhiLoads().
void Cfg::placePhiStores() {
TimerMarker T(TimerStack::TT_placePhiStores, this);
for (CfgNode *Node : Nodes)
Node->placePhiStores();
}
void Cfg::deletePhis() {
TimerMarker T(TimerStack::TT_deletePhis, this);
for (CfgNode *Node : Nodes)
Node->deletePhis();
}
void Cfg::advancedPhiLowering() {
TimerMarker T(TimerStack::TT_advancedPhiLowering, this);
// Clear all previously computed live ranges (but not live-in/live-out bit
// vectors or last-use markers), because the follow-on register allocation is
// only concerned with live ranges across the newly created blocks.
for (Variable *Var : Variables) {
Var->getLiveRange().reset();
}
// This splits edges and appends new nodes to the end of the node list. This
// can invalidate iterators, so don't use an iterator.
SizeT NumNodes = getNumNodes();
SizeT NumVars = getNumVariables();
for (SizeT I = 0; I < NumNodes; ++I)
Nodes[I]->advancedPhiLowering();
TimerMarker TT(TimerStack::TT_lowerPhiAssignments, this);
if (true) {
// The following code does an in-place update of liveness and live ranges
// as a result of adding the new phi edge split nodes.
getLiveness()->initPhiEdgeSplits(Nodes.begin() + NumNodes,
Variables.begin() + NumVars);
TimerMarker TTT(TimerStack::TT_liveness, this);
// Iterate over the newly added nodes to add their liveness info.
for (auto I = Nodes.begin() + NumNodes, E = Nodes.end(); I != E; ++I) {
InstNumberT FirstInstNum = getNextInstNumber();
(*I)->renumberInstructions();
InstNumberT LastInstNum = getNextInstNumber() - 1;
(*I)->liveness(getLiveness());
(*I)->livenessAddIntervals(getLiveness(), FirstInstNum, LastInstNum);
}
} else {
// The following code does a brute-force recalculation of live ranges as a
// result of adding the new phi edge split nodes. The liveness calculation
// is particularly expensive because the new nodes are not yet in a proper
// topological order and so convergence is slower.
//
// This code is kept here for reference and can be temporarily enabled in
// case the incremental code is under suspicion.
renumberInstructions();
liveness(Liveness_Intervals);
getVMetadata()->init(VMK_All);
}
Target->regAlloc(RAK_Phi);
}
// Find a reasonable placement for nodes that have not yet been placed, while
// maintaining the same relative ordering among already placed nodes.
void Cfg::reorderNodes() {
// TODO(ascull): it would be nice if the switch tests were always followed by
// the default case to allow for fall through.
using PlacedList = CfgList<CfgNode *>;
PlacedList Placed; // Nodes with relative placement locked down
PlacedList Unreachable; // Unreachable nodes
PlacedList::iterator NoPlace = Placed.end();
// Keep track of where each node has been tentatively placed so that we can
// manage insertions into the middle.
CfgVector<PlacedList::iterator> PlaceIndex(Nodes.size(), NoPlace);
for (CfgNode *Node : Nodes) {
// The "do ... while(0);" construct is to factor out the --PlaceIndex and
// assert() statements before moving to the next node.
do {
if (Node != getEntryNode() && Node->getInEdges().empty()) {
// The node has essentially been deleted since it is not a successor of
// any other node.
Unreachable.push_back(Node);
PlaceIndex[Node->getIndex()] = Unreachable.end();
Node->setNeedsPlacement(false);
continue;
}
if (!Node->needsPlacement()) {
// Add to the end of the Placed list.
Placed.push_back(Node);
PlaceIndex[Node->getIndex()] = Placed.end();
continue;
}
Node->setNeedsPlacement(false);
// Assume for now that the unplaced node is from edge-splitting and
// therefore has 1 in-edge and 1 out-edge (actually, possibly more than 1
// in-edge if the predecessor node was contracted). If this changes in
// the future, rethink the strategy.
assert(Node->getInEdges().size() >= 1);
assert(Node->hasSingleOutEdge());
// If it's a (non-critical) edge where the successor has a single
// in-edge, then place it before the successor.
CfgNode *Succ = Node->getOutEdges().front();
if (Succ->getInEdges().size() == 1 &&
PlaceIndex[Succ->getIndex()] != NoPlace) {
Placed.insert(PlaceIndex[Succ->getIndex()], Node);
PlaceIndex[Node->getIndex()] = PlaceIndex[Succ->getIndex()];
continue;
}
// Otherwise, place it after the (first) predecessor.
CfgNode *Pred = Node->getInEdges().front();
auto PredPosition = PlaceIndex[Pred->getIndex()];
// It shouldn't be the case that PredPosition==NoPlace, but if that
// somehow turns out to be true, we just insert Node before
// PredPosition=NoPlace=Placed.end() .
if (PredPosition != NoPlace)
++PredPosition;
Placed.insert(PredPosition, Node);
PlaceIndex[Node->getIndex()] = PredPosition;
} while (0);
--PlaceIndex[Node->getIndex()];
assert(*PlaceIndex[Node->getIndex()] == Node);
}
// Reorder Nodes according to the built-up lists.
NodeList Reordered;
Reordered.reserve(Placed.size() + Unreachable.size());
for (CfgNode *Node : Placed)
Reordered.push_back(Node);
for (CfgNode *Node : Unreachable)
Reordered.push_back(Node);
assert(getNumNodes() == Reordered.size());
swapNodes(Reordered);
}
namespace {
void getRandomPostOrder(CfgNode *Node, BitVector &ToVisit,
Ice::NodeList &PostOrder,
Ice::RandomNumberGenerator *RNG) {
assert(ToVisit[Node->getIndex()]);
ToVisit[Node->getIndex()] = false;
NodeList Outs = Node->getOutEdges();
Ice::RandomShuffle(Outs.begin(), Outs.end(),
[RNG](int N) { return RNG->next(N); });
for (CfgNode *Next : Outs) {
if (ToVisit[Next->getIndex()])
getRandomPostOrder(Next, ToVisit, PostOrder, RNG);
}
PostOrder.push_back(Node);
}
} // end of anonymous namespace
void Cfg::shuffleNodes() {
if (!getFlags().getReorderBasicBlocks())
return;
NodeList ReversedReachable;
NodeList Unreachable;
BitVector ToVisit(Nodes.size(), true);
// Create Random number generator for function reordering
RandomNumberGenerator RNG(getFlags().getRandomSeed(),
RPE_BasicBlockReordering, SequenceNumber);
// Traverse from entry node.
getRandomPostOrder(getEntryNode(), ToVisit, ReversedReachable, &RNG);
// Collect the unreachable nodes.
for (CfgNode *Node : Nodes)
if (ToVisit[Node->getIndex()])
Unreachable.push_back(Node);
// Copy the layout list to the Nodes.
NodeList Shuffled;
Shuffled.reserve(ReversedReachable.size() + Unreachable.size());
for (CfgNode *Node : reverse_range(ReversedReachable))
Shuffled.push_back(Node);
for (CfgNode *Node : Unreachable)
Shuffled.push_back(Node);
assert(Nodes.size() == Shuffled.size());
swapNodes(Shuffled);
dump("After basic block shuffling");
}
void Cfg::localCSE(bool AssumeSSA) {
// Performs basic-block local common-subexpression elimination
// If we have
// t1 = op b c
// t2 = op b c
// This pass will replace future references to t2 in a basic block by t1
// Points to note:
// 1. Assumes SSA by default. To change this, use -lcse=no-ssa
// This is needed if this pass is moved to a point later in the pipeline.
// If variables have a single definition (in the node), CSE can work just
// on the basis of an equality compare on instructions (sans Dest). When
// variables can be updated (hence, non-SSA) the result of a previous
// instruction which used that variable as an operand can not be reused.
// 2. Leaves removal of instructions to DCE.
// 3. Only enabled on arithmetic instructions. pnacl-clang (-O2) is expected
// to take care of cases not arising from GEP simplification.
// 4. By default, a single pass is made over each basic block. Control this
// with -lcse-max-iters=N
TimerMarker T(TimerStack::TT_localCse, this);
struct VariableHash {
size_t operator()(const Variable *Var) const { return Var->hashValue(); }
};
struct InstHash {
size_t operator()(const Inst *Instr) const {
auto Kind = Instr->getKind();
auto Result =
std::hash<typename std::underlying_type<Inst::InstKind>::type>()(
Kind);
for (SizeT i = 0; i < Instr->getSrcSize(); ++i) {
Result ^= Instr->getSrc(i)->hashValue();
}
return Result;
}
};
struct InstEq {
bool srcEq(const Operand *A, const Operand *B) const {
if (llvm::isa<Variable>(A) || llvm::isa<Constant>(A))
return (A == B);
return false;
}
bool operator()(const Inst *InstrA, const Inst *InstrB) const {
if ((InstrA->getKind() != InstrB->getKind()) ||
(InstrA->getSrcSize() != InstrB->getSrcSize()))
return false;
if (auto *A = llvm::dyn_cast<InstArithmetic>(InstrA)) {
auto *B = llvm::cast<InstArithmetic>(InstrB);
// A, B are guaranteed to be of the same 'kind' at this point
// So, dyn_cast is not needed
if (A->getOp() != B->getOp())
return false;
}
// Does not enter loop if different kind or number of operands
for (SizeT i = 0; i < InstrA->getSrcSize(); ++i) {
if (!srcEq(InstrA->getSrc(i), InstrB->getSrc(i)))
return false;
}
return true;
}
};
for (CfgNode *Node : getNodes()) {
CfgUnorderedSet<Inst *, InstHash, InstEq> Seen;
// Stores currently available instructions.
CfgUnorderedMap<Variable *, Variable *, VariableHash> Replacements;
// Combining the above two into a single data structure might consume less
// memory but will be slower i.e map of Instruction -> Set of Variables
CfgUnorderedMap<Variable *, std::vector<Inst *>, VariableHash> Dependency;
// Maps a variable to the Instructions that depend on it.
// a = op1 b c
// x = op2 c d
// Will result in the map : b -> {a}, c -> {a, x}, d -> {x}
// Not necessary for SSA as dependencies will never be invalidated, and the
// container will use minimal memory when left unused.
auto IterCount = getFlags().getLocalCseMaxIterations();
for (uint32_t i = 0; i < IterCount; ++i) {
// TODO(manasijm): Stats on IterCount -> performance
for (Inst &Instr : Node->getInsts()) {
if (Instr.isDeleted() || !llvm::isa<InstArithmetic>(&Instr))
continue;
if (!AssumeSSA) {
// Invalidate replacements
auto Iter = Replacements.find(Instr.getDest());
if (Iter != Replacements.end()) {
Replacements.erase(Iter);
}
// Invalidate 'seen' instructions whose operands were just updated.
auto DepIter = Dependency.find(Instr.getDest());
if (DepIter != Dependency.end()) {
for (auto *DepInst : DepIter->second) {
Seen.erase(DepInst);
}
}
}
// Replace - doing this before checking for repetitions might enable
// more optimizations
for (SizeT i = 0; i < Instr.getSrcSize(); ++i) {
auto *Opnd = Instr.getSrc(i);
if (auto *Var = llvm::dyn_cast<Variable>(Opnd)) {
if (Replacements.find(Var) != Replacements.end()) {
Instr.replaceSource(i, Replacements[Var]);
}
}
}
// Check for repetitions
auto SeenIter = Seen.find(&Instr);
if (SeenIter != Seen.end()) { // seen before
const Inst *Found = *SeenIter;
Replacements[Instr.getDest()] = Found->getDest();
} else { // new
Seen.insert(&Instr);
if (!AssumeSSA) {
// Update dependencies
for (SizeT i = 0; i < Instr.getSrcSize(); ++i) {
auto *Opnd = Instr.getSrc(i);
if (auto *Var = llvm::dyn_cast<Variable>(Opnd)) {
Dependency[Var].push_back(&Instr);
}
}
}
}
}
}
}
}
void Cfg::loopInvariantCodeMotion() {
TimerMarker T(TimerStack::TT_loopInvariantCodeMotion, this);
// Does not introduce new nodes as of now.
for (auto &Loop : LoopInfo) {
CfgNode *Header = Loop.Header;
assert(Header);
if (Header->getLoopNestDepth() < 1)
return;
CfgNode *PreHeader = Loop.PreHeader;
if (PreHeader == nullptr || PreHeader->getInsts().size() == 0) {
return; // try next loop
}
auto &Insts = PreHeader->getInsts();
auto &LastInst = Insts.back();
Insts.pop_back();
for (auto *Inst : findLoopInvariantInstructions(Loop.Body)) {
PreHeader->appendInst(Inst);
}
PreHeader->appendInst(&LastInst);
}
}
CfgVector<Inst *>
Cfg::findLoopInvariantInstructions(const CfgUnorderedSet<SizeT> &Body) {
CfgUnorderedSet<Inst *> InvariantInsts;
CfgUnorderedSet<Variable *> InvariantVars;
for (auto *Var : getArgs()) {
InvariantVars.insert(Var);
}
bool Changed = false;
do {
Changed = false;
for (auto NodeIndex : Body) {
auto *Node = Nodes[NodeIndex];
CfgVector<std::reference_wrapper<Inst>> Insts(Node->getInsts().begin(),
Node->getInsts().end());
for (auto &InstRef : Insts) {
auto &Inst = InstRef.get();
if (Inst.isDeleted() ||
InvariantInsts.find(&Inst) != InvariantInsts.end())
continue;
switch (Inst.getKind()) {
case Inst::InstKind::Alloca:
case Inst::InstKind::Br:
case Inst::InstKind::Ret:
case Inst::InstKind::Phi:
case Inst::InstKind::Call:
case Inst::InstKind::IntrinsicCall:
case Inst::InstKind::Load:
case Inst::InstKind::Store:
case Inst::InstKind::Switch:
continue;
default:
break;
}
bool IsInvariant = true;
for (SizeT i = 0; i < Inst.getSrcSize(); ++i) {
if (auto *Var = llvm::dyn_cast<Variable>(Inst.getSrc(i))) {
if (InvariantVars.find(Var) == InvariantVars.end()) {
IsInvariant = false;
}
}
}
if (IsInvariant) {
Changed = true;
InvariantInsts.insert(&Inst);
Node->getInsts().remove(Inst);
if (Inst.getDest() != nullptr) {
InvariantVars.insert(Inst.getDest());
}
}
}
}
} while (Changed);
CfgVector<Inst *> InstVector(InvariantInsts.begin(), InvariantInsts.end());
std::sort(InstVector.begin(), InstVector.end(),
[](Inst *A, Inst *B) { return A->getNumber() < B->getNumber(); });
return InstVector;
}
void Cfg::shortCircuitJumps() {
// Split Nodes whenever an early jump is possible.
// __N :
// a = <something>
// Instruction 1 without side effect
// ... b = <something> ...
// Instruction N without side effect
// t1 = or a b
// br t1 __X __Y
//
// is transformed into:
// __N :
// a = <something>
// br a __X __N_ext
//
// __N_ext :
// Instruction 1 without side effect
// ... b = <something> ...
// Instruction N without side effect
// br b __X __Y
// (Similar logic for AND, jump to false instead of true target.)
TimerMarker T(TimerStack::TT_shortCircuit, this);
getVMetadata()->init(VMK_Uses);
auto NodeStack = this->getNodes();
CfgUnorderedMap<SizeT, CfgVector<CfgNode *>> Splits;
while (!NodeStack.empty()) {
auto *Node = NodeStack.back();
NodeStack.pop_back();
auto NewNode = Node->shortCircuit();
if (NewNode) {
NodeStack.push_back(NewNode);
NodeStack.push_back(Node);
Splits[Node->getIndex()].push_back(NewNode);
}
}
// Insert nodes in the right place
NodeList NewList;
NewList.reserve(Nodes.size());
CfgUnorderedSet<SizeT> Inserted;
for (auto *Node : Nodes) {
if (Inserted.find(Node->getIndex()) != Inserted.end())
continue; // already inserted
NodeList Stack{Node};
while (!Stack.empty()) {
auto *Current = Stack.back();
Stack.pop_back();
Inserted.insert(Current->getIndex());
NewList.push_back(Current);
for (auto *Next : Splits[Current->getIndex()]) {
Stack.push_back(Next);
}
}
}
SizeT NodeIndex = 0;
for (auto *Node : NewList) {
Node->resetIndex(NodeIndex++);
}
Nodes = NewList;
}
void Cfg::floatConstantCSE() {
// Load multiple uses of a floating point constant (between two call
// instructions or block start/end) into a variable before its first use.
// t1 = b + 1.0
// t2 = c + 1.0
// Gets transformed to:
// t0 = 1.0
// t0_1 = t0
// t1 = b + t0_1
// t2 = c + t0_1
// Call instructions reset the procedure, but use the same variable, just in
// case it got a register. We are assuming floating point registers are not
// callee saved in general. Example, continuing from before:
// result = call <some function>
// t3 = d + 1.0
// Gets transformed to:
// result = call <some function>
// t0_2 = t0
// t3 = d + t0_2
// TODO(manasijm, stichnot): Figure out how to 'link' t0 to the stack slot of
// 1.0. When t0 does not get a register, introducing an extra assignment
// statement does not make sense. The relevant portion is marked below.
TimerMarker _(TimerStack::TT_floatConstantCse, this);
for (CfgNode *Node : getNodes()) {
CfgUnorderedMap<Constant *, Variable *> ConstCache;
auto Current = Node->getInsts().begin();
auto End = Node->getInsts().end();
while (Current != End) {
CfgUnorderedMap<Constant *, CfgVector<InstList::iterator>> FloatUses;
if (llvm::isa<InstCall>(iteratorToInst(Current))) {
++Current;
assert(Current != End);
// Block should not end with a call
}
while (Current != End && !llvm::isa<InstCall>(iteratorToInst(Current))) {
if (!Current->isDeleted()) {
for (SizeT i = 0; i < Current->getSrcSize(); ++i) {
if (auto *Const = llvm::dyn_cast<Constant>(Current->getSrc(i))) {
if (Const->getType() == IceType_f32 ||
Const->getType() == IceType_f64) {
FloatUses[Const].push_back(Current);
}
}
}
}
++Current;
}
for (auto &Pair : FloatUses) {
static constexpr SizeT MinUseThreshold = 3;
if (Pair.second.size() < MinUseThreshold)
continue;
// Only consider constants with at least `MinUseThreshold` uses
auto &Insts = Node->getInsts();
if (ConstCache.find(Pair.first) == ConstCache.end()) {
// Saw a constant (which is used at least twice) for the first time
auto *NewVar = makeVariable(Pair.first->getType());
// NewVar->setLinkedTo(Pair.first);
// TODO(manasijm): Plumbing for linking to an Operand.
auto *Assign = InstAssign::create(Node->getCfg(), NewVar, Pair.first);
Insts.insert(Pair.second[0], Assign);
ConstCache[Pair.first] = NewVar;
}
auto *NewVar = makeVariable(Pair.first->getType());
NewVar->setLinkedTo(ConstCache[Pair.first]);
auto *Assign =
InstAssign::create(Node->getCfg(), NewVar, ConstCache[Pair.first]);
Insts.insert(Pair.second[0], Assign);
for (auto InstUse : Pair.second) {
for (SizeT i = 0; i < InstUse->getSrcSize(); ++i) {
if (auto *Const = llvm::dyn_cast<Constant>(InstUse->getSrc(i))) {
if (Const == Pair.first) {
InstUse->replaceSource(i, NewVar);
}
}
}
}
}
}
}
}
void Cfg::doArgLowering() {
TimerMarker T(TimerStack::TT_doArgLowering, this);
getTarget()->lowerArguments();
}
void Cfg::sortAndCombineAllocas(CfgVector<InstAlloca *> &Allocas,
uint32_t CombinedAlignment, InstList &Insts,
AllocaBaseVariableType BaseVariableType) {
if (Allocas.empty())
return;
// Sort by decreasing alignment.
std::sort(Allocas.begin(), Allocas.end(), [](InstAlloca *A1, InstAlloca *A2) {
uint32_t Align1 = A1->getAlignInBytes();
uint32_t Align2 = A2->getAlignInBytes();
if (Align1 == Align2)
return A1->getNumber() < A2->getNumber();
else
return Align1 > Align2;
});
// Process the allocas in order of decreasing stack alignment. This allows
// us to pack less-aligned pieces after more-aligned ones, resulting in less
// stack growth. It also allows there to be at most one stack alignment "and"
// instruction for a whole list of allocas.
uint32_t CurrentOffset = 0;
CfgVector<int32_t> Offsets;
for (Inst *Instr : Allocas) {
auto *Alloca = llvm::cast<InstAlloca>(Instr);
// Adjust the size of the allocation up to the next multiple of the
// object's alignment.
uint32_t Alignment = std::max(Alloca->getAlignInBytes(), 1u);
auto *ConstSize =
llvm::dyn_cast<ConstantInteger32>(Alloca->getSizeInBytes());
uint32_t Size = Utils::applyAlignment(ConstSize->getValue(), Alignment);
if (BaseVariableType == BVT_FramePointer) {
// Addressing is relative to the frame pointer. Subtract the offset after
// adding the size of the alloca, because it grows downwards from the
// frame pointer.
Offsets.push_back(Target->getFramePointerOffset(CurrentOffset, Size));
} else {
// Addressing is relative to the stack pointer or to a user pointer. Add
// the offset before adding the size of the object, because it grows
// upwards from the stack pointer. In addition, if the addressing is
// relative to the stack pointer, we need to add the pre-computed max out
// args size bytes.
const uint32_t OutArgsOffsetOrZero =
(BaseVariableType == BVT_StackPointer)
? getTarget()->maxOutArgsSizeBytes()
: 0;
Offsets.push_back(CurrentOffset + OutArgsOffsetOrZero);
}
// Update the running offset of the fused alloca region.
CurrentOffset += Size;
}
// Round the offset up to the alignment granularity to use as the size.
uint32_t TotalSize = Utils::applyAlignment(CurrentOffset, CombinedAlignment);
// Ensure every alloca was assigned an offset.
assert(Allocas.size() == Offsets.size());
switch (BaseVariableType) {
case BVT_UserPointer: {
Variable *BaseVariable = makeVariable(IceType_i32);
for (SizeT i = 0; i < Allocas.size(); ++i) {
auto *Alloca = llvm::cast<InstAlloca>(Allocas[i]);
// Emit a new addition operation to replace the alloca.
Operand *AllocaOffset = Ctx->getConstantInt32(Offsets[i]);
InstArithmetic *Add =
InstArithmetic::create(this, InstArithmetic::Add, Alloca->getDest(),
BaseVariable, AllocaOffset);
Insts.push_front(Add);
Alloca->setDeleted();
}
Operand *AllocaSize = Ctx->getConstantInt32(TotalSize);
InstAlloca *CombinedAlloca =
InstAlloca::create(this, BaseVariable, AllocaSize, CombinedAlignment);
CombinedAlloca->setKnownFrameOffset();
Insts.push_front(CombinedAlloca);
} break;
case BVT_StackPointer:
case BVT_FramePointer: {
for (SizeT i = 0; i < Allocas.size(); ++i) {
auto *Alloca = llvm::cast<InstAlloca>(Allocas[i]);
// Emit a fake definition of the rematerializable variable.
Variable *Dest = Alloca->getDest();
auto *Def = InstFakeDef::create(this, Dest);
if (BaseVariableType == BVT_StackPointer)
Dest->setRematerializable(getTarget()->getStackReg(), Offsets[i]);
else
Dest->setRematerializable(getTarget()->getFrameReg(), Offsets[i]);
Insts.push_front(Def);
Alloca->setDeleted();
}
// Allocate the fixed area in the function prolog.
getTarget()->reserveFixedAllocaArea(TotalSize, CombinedAlignment);
} break;
}
}
void Cfg::processAllocas(bool SortAndCombine) {
TimerMarker _(TimerStack::TT_alloca, this);
const uint32_t StackAlignment = getTarget()->getStackAlignment();
CfgNode *EntryNode = getEntryNode();
assert(EntryNode);
// LLVM enforces power of 2 alignment.
assert(llvm::isPowerOf2_32(StackAlignment));
// If the ABI's stack alignment is smaller than the vector size (16 bytes),
// conservatively use a frame pointer to allow for explicit alignment of the
// stack pointer. This needs to happen before register allocation so the frame
// pointer can be reserved.
if (getTarget()->needsStackPointerAlignment()) {
getTarget()->setHasFramePointer();
}
// Determine if there are large alignment allocations in the entry block or
// dynamic allocations (variable size in the entry block).
bool HasLargeAlignment = false;
bool HasDynamicAllocation = false;
for (Inst &Instr : EntryNode->getInsts()) {
if (Instr.isDeleted())
continue;
if (auto *Alloca = llvm::dyn_cast<InstAlloca>(&Instr)) {
uint32_t AlignmentParam = Alloca->getAlignInBytes();
if (AlignmentParam > StackAlignment)
HasLargeAlignment = true;
if (llvm::isa<Constant>(Alloca->getSizeInBytes()))
Alloca->setKnownFrameOffset();
else {
HasDynamicAllocation = true;
// If Allocas are not sorted, the first dynamic allocation causes
// later Allocas to be at unknown offsets relative to the stack/frame.
if (!SortAndCombine)
break;
}
}
}
// Don't do the heavyweight sorting and layout for low optimization levels.
if (!SortAndCombine)
return;
// Any alloca outside the entry block is a dynamic allocation.
for (CfgNode *Node : Nodes) {
if (Node == EntryNode)
continue;
for (Inst &Instr : Node->getInsts()) {
if (Instr.isDeleted())
continue;
if (llvm::isa<InstAlloca>(&Instr)) {
// Allocations outside the entry block require a frame pointer.
HasDynamicAllocation = true;
break;
}
}
if (HasDynamicAllocation)
break;
}
// Mark the target as requiring a frame pointer.
if (HasLargeAlignment || HasDynamicAllocation)
getTarget()->setHasFramePointer();
// Collect the Allocas into the two vectors.
// Allocas in the entry block that have constant size and alignment less
// than or equal to the function's stack alignment.
CfgVector<InstAlloca *> FixedAllocas;
// Allocas in the entry block that have constant size and alignment greater
// than the function's stack alignment.
CfgVector<InstAlloca *> AlignedAllocas;
// Maximum alignment used by any alloca.
uint32_t MaxAlignment = StackAlignment;
for (Inst &Instr : EntryNode->getInsts()) {
if (Instr.isDeleted())
continue;
if (auto *Alloca = llvm::dyn_cast<InstAlloca>(&Instr)) {
if (!llvm::isa<Constant>(Alloca->getSizeInBytes()))
continue;
uint32_t AlignmentParam = Alloca->getAlignInBytes();
// For default align=0, set it to the real value 1, to avoid any
// bit-manipulation problems below.
AlignmentParam = std::max(AlignmentParam, 1u);
assert(llvm::isPowerOf2_32(AlignmentParam));
if (HasDynamicAllocation && AlignmentParam > StackAlignment) {
// If we have both dynamic allocations and large stack alignments,
// high-alignment allocations are pulled out with their own base.
AlignedAllocas.push_back(Alloca);
} else {
FixedAllocas.push_back(Alloca);
}
MaxAlignment = std::max(AlignmentParam, MaxAlignment);
}
}
// Add instructions to the head of the entry block in reverse order.
InstList &Insts = getEntryNode()->getInsts();
if (HasDynamicAllocation && HasLargeAlignment) {
// We are using a frame pointer, but fixed large-alignment alloca addresses
// do not have a known offset from either the stack or frame pointer.
// They grow up from a user pointer from an alloca.
sortAndCombineAllocas(AlignedAllocas, MaxAlignment, Insts, BVT_UserPointer);
// Fixed size allocas are addressed relative to the frame pointer.
sortAndCombineAllocas(FixedAllocas, StackAlignment, Insts,
BVT_FramePointer);
} else {
// Otherwise, fixed size allocas are addressed relative to the stack unless
// there are dynamic allocas.
const AllocaBaseVariableType BasePointerType =
(HasDynamicAllocation ? BVT_FramePointer : BVT_StackPointer);
sortAndCombineAllocas(FixedAllocas, MaxAlignment, Insts, BasePointerType);
}
if (!FixedAllocas.empty() || !AlignedAllocas.empty())
// No use calling findRematerializable() unless there is some
// rematerializable alloca instruction to seed it.
findRematerializable();
}
namespace {
// Helpers for findRematerializable(). For each of them, if a suitable
// rematerialization is found, the instruction's Dest variable is set to be
// rematerializable and it returns true, otherwise it returns false.
bool rematerializeArithmetic(const Inst *Instr) {
// Check that it's an Arithmetic instruction with an Add operation.
auto *Arith = llvm::dyn_cast<InstArithmetic>(Instr);
if (Arith == nullptr || Arith->getOp() != InstArithmetic::Add)
return false;
// Check that Src(0) is rematerializable.
auto *Src0Var = llvm::dyn_cast<Variable>(Arith->getSrc(0));
if (Src0Var == nullptr || !Src0Var->isRematerializable())
return false;
// Check that Src(1) is an immediate.
auto *Src1Imm = llvm::dyn_cast<ConstantInteger32>(Arith->getSrc(1));
if (Src1Imm == nullptr)
return false;
Arith->getDest()->setRematerializable(
Src0Var->getRegNum(), Src0Var->getStackOffset() + Src1Imm->getValue());
return true;
}
bool rematerializeAssign(const Inst *Instr) {
// An InstAssign only originates from an inttoptr or ptrtoint instruction,
// which never occurs in a MINIMAL build.
if (BuildDefs::minimal())
return false;
// Check that it's an Assign instruction.
if (!llvm::isa<InstAssign>(Instr))
return false;
// Check that Src(0) is rematerializable.
auto *Src0Var = llvm::dyn_cast<Variable>(Instr->getSrc(0));
if (Src0Var == nullptr || !Src0Var->isRematerializable())
return false;
Instr->getDest()->setRematerializable(Src0Var->getRegNum(),
Src0Var->getStackOffset());
return true;
}
bool rematerializeCast(const Inst *Instr) {
// An pointer-type bitcast never occurs in a MINIMAL build.
if (BuildDefs::minimal())
return false;
// Check that it's a Cast instruction with a Bitcast operation.
auto *Cast = llvm::dyn_cast<InstCast>(Instr);
if (Cast == nullptr || Cast->getCastKind() != InstCast::Bitcast)
return false;
// Check that Src(0) is rematerializable.
auto *Src0Var = llvm::dyn_cast<Variable>(Cast->getSrc(0));
if (Src0Var == nullptr || !Src0Var->isRematerializable())
return false;
// Check that Dest and Src(0) have the same type.
Variable *Dest = Cast->getDest();
if (Dest->getType() != Src0Var->getType())
return false;
Dest->setRematerializable(Src0Var->getRegNum(), Src0Var->getStackOffset());
return true;
}
} // end of anonymous namespace
/// Scan the function to find additional rematerializable variables. This is
/// possible when the source operand of an InstAssignment is a rematerializable
/// variable, or the same for a pointer-type InstCast::Bitcast, or when an
/// InstArithmetic is an add of a rematerializable variable and an immediate.
/// Note that InstAssignment instructions and pointer-type InstCast::Bitcast
/// instructions generally only come about from the IceConverter's treatment of
/// inttoptr, ptrtoint, and bitcast instructions. TODO(stichnot): Consider
/// other possibilities, however unlikely, such as InstArithmetic::Sub, or
/// commutativity.
void Cfg::findRematerializable() {
// Scan the instructions in order, and repeat until no new opportunities are
// found. It may take more than one iteration because a variable's defining
// block may happen to come after a block where it is used, depending on the
// CfgNode linearization order.
bool FoundNewAssignment;
do {
FoundNewAssignment = false;
for (CfgNode *Node : getNodes()) {
// No need to process Phi instructions.
for (Inst &Instr : Node->getInsts()) {
if (Instr.isDeleted())
continue;
Variable *Dest = Instr.getDest();
if (Dest == nullptr || Dest->isRematerializable())
continue;
if (rematerializeArithmetic(&Instr) || rematerializeAssign(&Instr) ||
rematerializeCast(&Instr)) {
FoundNewAssignment = true;
}
}
}
} while (FoundNewAssignment);
}
void Cfg::doAddressOpt() {
TimerMarker T(TimerStack::TT_doAddressOpt, this);
for (CfgNode *Node : Nodes)
Node->doAddressOpt();
}
namespace {
// ShuffleVectorUtils implements helper functions for rematerializing
// shufflevector instructions from a sequence of extractelement/insertelement
// instructions. It looks for the following pattern:
//
// %t0 = extractelement A, %n0
// %t1 = extractelement B, %n1
// %t2 = extractelement C, %n2
// ...
// %tN = extractelement N, %nN
// %d0 = insertelement undef, %t0, 0
// %d1 = insertelement %d0, %t1, 1
// %d2 = insertelement %d1, %t2, 2
// ...
// %dest = insertelement %d_N-1, %tN, N
//
// where N is num_element(typeof(%dest)), and A, B, C, ... N are at most two
// distinct variables.
namespace ShuffleVectorUtils {
// findAllInserts is used when searching for all the insertelements that are
// used in a shufflevector operation. This function works recursively, when
// invoked with I = i, the function assumes Insts[i] is the last found
// insertelement in the chain. The next insertelement insertruction is saved in
// Insts[i+1].
bool findAllInserts(Cfg *Func, GlobalContext *Ctx, VariablesMetadata *VM,
CfgVector<const Inst *> *Insts, SizeT I = 0) {
const bool Verbose = BuildDefs::dump() && Func->isVerbose(IceV_ShufMat);
if (I > Insts->size()) {
if (Verbose) {
Ctx->getStrDump() << "\tToo many inserts.\n";
}
return false;
}
const auto *LastInsert = Insts->at(I);
assert(llvm::isa<InstInsertElement>(LastInsert));
if (I == Insts->size() - 1) {
// Matching against undef is not really needed because the value in Src(0)
// will be totally overwritten. We still enforce it anyways because the
// PNaCl toolchain generates the bitcode with it.
if (!llvm::isa<ConstantUndef>(LastInsert->getSrc(0))) {
if (Verbose) {
Ctx->getStrDump() << "\tSrc0 is not undef: " << I << " "
<< Insts->size();
LastInsert->dump(Func);
Ctx->getStrDump() << "\n";
}
return false;
}
// The following loop ensures that the insertelements are sorted. In theory,
// we could relax this restriction and allow any order. As long as each
// index appears exactly once, this chain is still a candidate for becoming
// a shufflevector. The Insts vector is traversed backwards because the
// instructions are "enqueued" in reverse order.
int32_t ExpectedElement = 0;
for (const auto *I : reverse_range(*Insts)) {
if (llvm::cast<ConstantInteger32>(I->getSrc(2))->getValue() !=
ExpectedElement) {
return false;
}
++ExpectedElement;
}
return true;
}
const auto *Src0V = llvm::cast<Variable>(LastInsert->getSrc(0));
const auto *Def = VM->getSingleDefinition(Src0V);
// Only optimize if the first operand in
//
// Dest = insertelement A, B, 10
//
// is singly-def'ed.
if (Def == nullptr) {
if (Verbose) {
Ctx->getStrDump() << "\tmulti-def: ";
(*Insts)[I]->dump(Func);
Ctx->getStrDump() << "\n";
}
return false;
}
// We also require the (single) definition to come from an insertelement
// instruction.
if (!llvm::isa<InstInsertElement>(Def)) {
if (Verbose) {
Ctx->getStrDump() << "\tnot insert element: ";
Def->dump(Func);
Ctx->getStrDump() << "\n";
}
return false;
}
// Everything seems fine, so we save Def in Insts, and delegate the decision
// to findAllInserts.
(*Insts)[I + 1] = Def;
return findAllInserts(Func, Ctx, VM, Insts, I + 1);
}
// insertsLastElement returns true if Insert is inserting an element in the last
// position of a vector.
bool insertsLastElement(const Inst &Insert) {
const Type DestTy = Insert.getDest()->getType();
assert(isVectorType(DestTy));
const SizeT Elem =
llvm::cast<ConstantInteger32>(Insert.getSrc(2))->getValue();
return Elem == typeNumElements(DestTy) - 1;
}
// findAllExtracts goes over all the insertelement instructions that are
// candidates to be replaced by a shufflevector, and searches for all the
// definitions of the elements being inserted. If all of the elements are the
// result of an extractelement instruction, and all of the extractelements
// operate on at most two different sources, than the instructions can be
// replaced by a shufflevector.
bool findAllExtracts(Cfg *Func, GlobalContext *Ctx, VariablesMetadata *VM,
const CfgVector<const Inst *> &Insts, Variable **Src0,
Variable **Src1, CfgVector<const Inst *> *Extracts) {
const bool Verbose = BuildDefs::dump() && Func->isVerbose(IceV_ShufMat);
*Src0 = nullptr;
*Src1 = nullptr;
assert(Insts.size() > 0);
for (SizeT I = 0; I < Insts.size(); ++I) {
const auto *Insert = Insts.at(I);
const auto *Src1V = llvm::dyn_cast<Variable>(Insert->getSrc(1));
if (Src1V == nullptr) {
if (Verbose) {
Ctx->getStrDump() << "src(1) is not a variable: ";
Insert->dump(Func);
Ctx->getStrDump() << "\n";
}
return false;
}
const auto *Def = VM->getSingleDefinition(Src1V);
if (Def == nullptr) {
if (Verbose) {
Ctx->getStrDump() << "multi-def src(1): ";
Insert->dump(Func);
Ctx->getStrDump() << "\n";
}
return false;
}
if (!llvm::isa<InstExtractElement>(Def)) {
if (Verbose) {
Ctx->getStrDump() << "not extractelement: ";
Def->dump(Func);
Ctx->getStrDump() << "\n";
}
return false;
}
auto *Src = llvm::cast<Variable>(Def->getSrc(0));
if (*Src0 == nullptr) {
// No sources yet. Save Src to Src0.
*Src0 = Src;
} else if (*Src1 == nullptr) {
// We already have a source, so we might save Src in Src1 -- but only if
// Src0 is not Src.
if (*Src0 != Src) {
*Src1 = Src;
}
} else if (Src != *Src0 && Src != *Src1) {
// More than two sources, so we can't rematerialize the shufflevector
// instruction.
if (Verbose) {
Ctx->getStrDump() << "Can't shuffle more than two sources.\n";
}
return false;
}
(*Extracts)[I] = Def;
}
// We should have seen at least one source operand.
assert(*Src0 != nullptr);
// If a second source was not seen, then we just make Src1 = Src0 to simplify
// things down stream. This should not matter, as all of the indexes in the
// shufflevector instruction will point to Src0.
if (*Src1 == nullptr) {
*Src1 = *Src0;
}
return true;
}
} // end of namespace ShuffleVectorUtils
} // end of anonymous namespace
void Cfg::materializeVectorShuffles() {
const bool Verbose = BuildDefs::dump() && isVerbose(IceV_ShufMat);
std::unique_ptr<OstreamLocker> L;
if (Verbose) {
L.reset(new OstreamLocker(getContext()));
getContext()->getStrDump() << "\nShuffle materialization:\n";
}
// MaxVectorElements is the maximum number of elements in the vector types
// handled by Subzero. We use it to create the Inserts and Extracts vectors
// with the appropriate size, thus avoiding resize() calls.
const SizeT MaxVectorElements = typeNumElements(IceType_v16i8);
CfgVector<const Inst *> Inserts(MaxVectorElements);
CfgVector<const Inst *> Extracts(MaxVectorElements);
TimerMarker T(TimerStack::TT_materializeVectorShuffles, this);
for (CfgNode *Node : Nodes) {
for (auto &Instr : Node->getInsts()) {
if (!llvm::isa<InstInsertElement>(Instr)) {
continue;
}
if (!ShuffleVectorUtils::insertsLastElement(Instr)) {
// To avoid wasting time, we only start the pattern match at the last
// insertelement instruction -- and go backwards from there.
continue;
}
if (Verbose) {
getContext()->getStrDump() << "\tCandidate: ";
Instr.dump(this);
getContext()->getStrDump() << "\n";
}
Inserts.resize(typeNumElements(Instr.getDest()->getType()));
Inserts[0] = &Instr;
if (!ShuffleVectorUtils::findAllInserts(this, getContext(),
VMetadata.get(), &Inserts)) {
// If we fail to find a sequence of insertelements, we stop the
// optimization.
if (Verbose) {
getContext()->getStrDump() << "\tFalse alarm.\n";
}
continue;
}
if (Verbose) {
getContext()->getStrDump() << "\tFound the following insertelement: \n";
for (auto *I : reverse_range(Inserts)) {
getContext()->getStrDump() << "\t\t";
I->dump(this);
getContext()->getStrDump() << "\n";
}
}
Extracts.resize(Inserts.size());
Variable *Src0;
Variable *Src1;
if (!ShuffleVectorUtils::findAllExtracts(this, getContext(),
VMetadata.get(), Inserts, &Src0,
&Src1, &Extracts)) {
// If we fail to match the definitions of the insertelements' sources
// with extractelement instructions -- or if those instructions operate
// on more than two different variables -- we stop the optimization.
if (Verbose) {
getContext()->getStrDump() << "\tFailed to match extractelements.\n";
}
continue;
}
if (Verbose) {
getContext()->getStrDump()
<< "\tFound the following insert/extract element pairs: \n";
for (SizeT I = 0; I < Inserts.size(); ++I) {
const SizeT Pos = Inserts.size() - I - 1;
getContext()->getStrDump() << "\t\tInsert : ";
Inserts[Pos]->dump(this);
getContext()->getStrDump() << "\n\t\tExtract: ";
Extracts[Pos]->dump(this);
getContext()->getStrDump() << "\n";
}
}
assert(Src0 != nullptr);
assert(Src1 != nullptr);
auto *ShuffleVector =
InstShuffleVector::create(this, Instr.getDest(), Src0, Src1);
assert(ShuffleVector->getSrc(0) == Src0);
assert(ShuffleVector->getSrc(1) == Src1);
for (SizeT I = 0; I < Extracts.size(); ++I) {
const SizeT Pos = Extracts.size() - I - 1;
auto *Index = llvm::cast<ConstantInteger32>(Extracts[Pos]->getSrc(1));
if (Src0 == Extracts[Pos]->getSrc(0)) {
ShuffleVector->addIndex(Index);
} else {
ShuffleVector->addIndex(llvm::cast<ConstantInteger32>(
Ctx->getConstantInt32(Index->getValue() + Extracts.size())));
}
}
if (Verbose) {
getContext()->getStrDump() << "Created: ";
ShuffleVector->dump(this);
getContext()->getStrDump() << "\n";
}
Instr.setDeleted();
auto &LoweringContext = getTarget()->getContext();
LoweringContext.setInsertPoint(instToIterator(&Instr));
LoweringContext.insert(ShuffleVector);
}
}
}
void Cfg::doNopInsertion() {
if (!getFlags().getShouldDoNopInsertion())
return;
TimerMarker T(TimerStack::TT_doNopInsertion, this);
RandomNumberGenerator RNG(getFlags().getRandomSeed(), RPE_NopInsertion,
SequenceNumber);
for (CfgNode *Node : Nodes)
Node->doNopInsertion(RNG);
}
void Cfg::genCode() {
TimerMarker T(TimerStack::TT_genCode, this);
for (CfgNode *Node : Nodes)
Node->genCode();
}
// Compute the stack frame layout.
void Cfg::genFrame() {
TimerMarker T(TimerStack::TT_genFrame, this);
getTarget()->addProlog(Entry);
for (CfgNode *Node : Nodes)
if (Node->getHasReturn())
getTarget()->addEpilog(Node);
}
void Cfg::generateLoopInfo() {
TimerMarker T(TimerStack::TT_computeLoopNestDepth, this);
LoopInfo = ComputeLoopInfo(this);
}
// This is a lightweight version of live-range-end calculation. Marks the last
// use of only those variables whose definition and uses are completely with a
// single block. It is a quick single pass and doesn't need to iterate until
// convergence.
void Cfg::livenessLightweight() {
TimerMarker T(TimerStack::TT_livenessLightweight, this);
getVMetadata()->init(VMK_Uses);
for (CfgNode *Node : Nodes)
Node->livenessLightweight();
}
void Cfg::liveness(LivenessMode Mode) {
TimerMarker T(TimerStack::TT_liveness, this);
// Destroying the previous (if any) Liveness information clears the Liveness
// allocator TLS pointer.
Live = nullptr;
Live = Liveness::create(this, Mode);
getVMetadata()->init(VMK_Uses);
Live->init();
// Initialize with all nodes needing to be processed.
BitVector NeedToProcess(Nodes.size(), true);
while (NeedToProcess.any()) {
// Iterate in reverse topological order to speed up convergence.
for (CfgNode *Node : reverse_range(Nodes)) {
if (NeedToProcess[Node->getIndex()]) {
NeedToProcess[Node->getIndex()] = false;
bool Changed = Node->liveness(getLiveness());
if (Changed) {
// If the beginning-of-block liveness changed since the last
// iteration, mark all in-edges as needing to be processed.
for (CfgNode *Pred : Node->getInEdges())
NeedToProcess[Pred->getIndex()] = true;
}
}
}
}
if (Mode == Liveness_Intervals) {
// Reset each variable's live range.
for (Variable *Var : Variables)
Var->resetLiveRange();
}
// Make a final pass over each node to delete dead instructions, collect the
// first and last instruction numbers, and add live range segments for that
// node.
for (CfgNode *Node : Nodes) {
InstNumberT FirstInstNum = Inst::NumberSentinel;
InstNumberT LastInstNum = Inst::NumberSentinel;
for (Inst &I : Node->getPhis()) {
I.deleteIfDead();
if (Mode == Liveness_Intervals && !I.isDeleted()) {
if (FirstInstNum == Inst::NumberSentinel)
FirstInstNum = I.getNumber();
assert(I.getNumber() > LastInstNum);
LastInstNum = I.getNumber();
}
}
for (Inst &I : Node->getInsts()) {
I.deleteIfDead();
if (Mode == Liveness_Intervals && !I.isDeleted()) {
if (FirstInstNum == Inst::NumberSentinel)
FirstInstNum = I.getNumber();
assert(I.getNumber() > LastInstNum);
LastInstNum = I.getNumber();
}
}
if (Mode == Liveness_Intervals) {
// Special treatment for live in-args. Their liveness needs to extend
// beyond the beginning of the function, otherwise an arg whose only use
// is in the first instruction will end up having the trivial live range
// [2,2) and will *not* interfere with other arguments. So if the first
// instruction of the method is "r=arg1+arg2", both args may be assigned
// the same register. This is accomplished by extending the entry block's
// instruction range from [2,n) to [1,n) which will transform the
// problematic [2,2) live ranges into [1,2). This extension works because
// the entry node is guaranteed to have the lowest instruction numbers.
if (Node == getEntryNode()) {
FirstInstNum = Inst::NumberExtended;
// Just in case the entry node somehow contains no instructions...
if (LastInstNum == Inst::NumberSentinel)
LastInstNum = FirstInstNum;
}
// If this node somehow contains no instructions, don't bother trying to
// add liveness intervals for it, because variables that are live-in and
// live-out will have a bogus interval added.
if (FirstInstNum != Inst::NumberSentinel)
Node->livenessAddIntervals(getLiveness(), FirstInstNum, LastInstNum);
}
}
}
// Traverse every Variable of every Inst and verify that it appears within the
// Variable's computed live range.
bool Cfg::validateLiveness() const {
TimerMarker T(TimerStack::TT_validateLiveness, this);
bool Valid = true;
OstreamLocker L(Ctx);
Ostream &Str = Ctx->getStrDump();
for (CfgNode *Node : Nodes) {
Inst *FirstInst = nullptr;
for (Inst &Instr : Node->getInsts()) {
if (Instr.isDeleted())
continue;
if (FirstInst == nullptr)
FirstInst = &Instr;
InstNumberT InstNumber = Instr.getNumber();
if (Variable *Dest = Instr.getDest()) {
if (!Dest->getIgnoreLiveness()) {
bool Invalid = false;
constexpr bool IsDest = true;
if (!Dest->getLiveRange().containsValue(InstNumber, IsDest))
Invalid = true;
// Check that this instruction actually *begins* Dest's live range,
// by checking that Dest is not live in the previous instruction. As
// a special exception, we don't check this for the first instruction
// of the block, because a Phi temporary may be live at the end of
// the previous block, and if it is also assigned in the first
// instruction of this block, the adjacent live ranges get merged.
if (&Instr != FirstInst && !Instr.isDestRedefined() &&
Dest->getLiveRange().containsValue(InstNumber - 1, IsDest))
Invalid = true;
if (Invalid) {
Valid = false;
Str << "Liveness error: inst " << Instr.getNumber() << " dest ";
Dest->dump(this);
Str << " live range " << Dest->getLiveRange() << "\n";
}
}
}
FOREACH_VAR_IN_INST(Var, Instr) {
static constexpr bool IsDest = false;
if (!Var->getIgnoreLiveness() &&
!Var->getLiveRange().containsValue(InstNumber, IsDest)) {
Valid = false;
Str << "Liveness error: inst " << Instr.getNumber() << " var ";
Var->dump(this);
Str << " live range " << Var->getLiveRange() << "\n";
}
}
}
}
return Valid;
}
void Cfg::contractEmptyNodes() {
// If we're decorating the asm output with register liveness info, this
// information may become corrupted or incorrect after contracting nodes that
// contain only redundant assignments. As such, we disable this pass when
// DecorateAsm is specified. This may make the resulting code look more
// branchy, but it should have no effect on the register assignments.
if (getFlags().getDecorateAsm())
return;
for (CfgNode *Node : Nodes) {
Node->contractIfEmpty();
}
}
void Cfg::doBranchOpt() {
TimerMarker T(TimerStack::TT_doBranchOpt, this);
for (auto I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
auto NextNode = I + 1;
(*I)->doBranchOpt(NextNode == E ? nullptr : *NextNode);
}
}
void Cfg::markNodesForSandboxing() {
for (const InstJumpTable *JT : JumpTables)
for (SizeT I = 0; I < JT->getNumTargets(); ++I)
JT->getTarget(I)->setNeedsAlignment();
}
// ======================== Dump routines ======================== //
// emitTextHeader() is not target-specific (apart from what is abstracted by
// the Assembler), so it is defined here rather than in the target lowering
// class.
void Cfg::emitTextHeader(GlobalString Name, GlobalContext *Ctx,
const Assembler *Asm) {
if (!BuildDefs::dump())
return;
Ostream &Str = Ctx->getStrEmit();
Str << "\t.text\n";
if (getFlags().getFunctionSections())
Str << "\t.section\t.text." << Name << ",\"ax\",%progbits\n";
if (!Asm->getInternal() || getFlags().getDisableInternal()) {
Str << "\t.globl\t" << Name << "\n";
Str << "\t.type\t" << Name << ",%function\n";
}
Str << "\t" << Asm->getAlignDirective() << " "
<< Asm->getBundleAlignLog2Bytes() << ",0x";
for (uint8_t I : Asm->getNonExecBundlePadding())
Str.write_hex(I);
Str << "\n";
Str << Name << ":\n";
}
void Cfg::emitJumpTables() {
switch (getFlags().getOutFileType()) {
case FT_Elf:
case FT_Iasm: {
// The emission needs to be delayed until the after the text section so
// save the offsets in the global context.
for (const InstJumpTable *JumpTable : JumpTables) {
Ctx->addJumpTableData(JumpTable->toJumpTableData(getAssembler()));
}
} break;
case FT_Asm: {
// Emit the assembly directly so we don't need to hang on to all the names
for (const InstJumpTable *JumpTable : JumpTables)
getTarget()->emitJumpTable(this, JumpTable);
} break;
}
}
void Cfg::emit() {
if (!BuildDefs::dump())
return;
TimerMarker T(TimerStack::TT_emitAsm, this);
if (getFlags().getDecorateAsm()) {
renumberInstructions();
getVMetadata()->init(VMK_Uses);
liveness(Liveness_Basic);
dump("After recomputing liveness for -decorate-asm");
}
OstreamLocker L(Ctx);
Ostream &Str = Ctx->getStrEmit();
const Assembler *Asm = getAssembler<>();
const bool NeedSandboxing = getFlags().getUseSandboxing();
emitTextHeader(FunctionName, Ctx, Asm);
if (getFlags().getDecorateAsm()) {
for (Variable *Var : getVariables()) {
if (Var->hasKnownStackOffset() && !Var->isRematerializable()) {
Str << "\t" << Var->getSymbolicStackOffset() << " = "
<< Var->getStackOffset() << "\n";
}
}
}
for (CfgNode *Node : Nodes) {
if (NeedSandboxing && Node->needsAlignment()) {
Str << "\t" << Asm->getAlignDirective() << " "
<< Asm->getBundleAlignLog2Bytes() << "\n";
}
Node->emit(this);
}
emitJumpTables();
Str << "\n";
}
void Cfg::emitIAS() {
TimerMarker T(TimerStack::TT_emitAsm, this);
// The emitIAS() routines emit into the internal assembler buffer, so there's
// no need to lock the streams.
const bool NeedSandboxing = getFlags().getUseSandboxing();
for (CfgNode *Node : Nodes) {
if (NeedSandboxing && Node->needsAlignment())
getAssembler()->alignCfgNode();
Node->emitIAS(this);
}
emitJumpTables();
}
size_t Cfg::getTotalMemoryMB() const {
constexpr size_t _1MB = 1024 * 1024;
assert(Allocator != nullptr);
assert(CfgAllocatorTraits::current() == Allocator.get());
return Allocator->getTotalMemory() / _1MB;
}
size_t Cfg::getLivenessMemoryMB() const {
constexpr size_t _1MB = 1024 * 1024;
if (Live == nullptr) {
return 0;
}
return Live->getAllocator()->getTotalMemory() / _1MB;
}
// Dumps the IR with an optional introductory message.
void Cfg::dump(const char *Message) {
if (!BuildDefs::dump())
return;
if (!isVerbose())
return;
OstreamLocker L(Ctx);
Ostream &Str = Ctx->getStrDump();
if (Message[0])
Str << "================ " << Message << " ================\n";
if (isVerbose(IceV_Mem)) {
Str << "Memory size = " << getTotalMemoryMB() << " MB\n";
}
setCurrentNode(getEntryNode());
// Print function name+args
if (isVerbose(IceV_Instructions)) {
Str << "define ";
if (getInternal() && !getFlags().getDisableInternal())
Str << "internal ";
Str << ReturnType << " @" << getFunctionName() << "(";
for (SizeT i = 0; i < Args.size(); ++i) {
if (i > 0)
Str << ", ";
Str << Args[i]->getType() << " ";
Args[i]->dump(this);
}
// Append an extra copy of the function name here, in order to print its
// size stats but not mess up lit tests.
Str << ") { # " << getFunctionNameAndSize() << "\n";
}
resetCurrentNode();
if (isVerbose(IceV_Liveness)) {
// Print summary info about variables
for (Variable *Var : Variables) {
Str << "// multiblock=";
if (getVMetadata()->isTracked(Var))
Str << getVMetadata()->isMultiBlock(Var);
else
Str << "?";
Str << " defs=";
bool FirstPrint = true;
if (VMetadata->getKind() != VMK_Uses) {
if (const Inst *FirstDef = VMetadata->getFirstDefinition(Var)) {
Str << FirstDef->getNumber();
FirstPrint = false;
}
}
if (VMetadata->getKind() == VMK_All) {
for (const Inst *Instr : VMetadata->getLatterDefinitions(Var)) {
if (!FirstPrint)
Str << ",";
Str << Instr->getNumber();
FirstPrint = false;
}
}
Str << " weight=" << Var->getWeight(this) << " ";
Var->dump(this);
Str << " LIVE=" << Var->getLiveRange() << "\n";
}
}
// Print each basic block
for (CfgNode *Node : Nodes)
Node->dump(this);
if (isVerbose(IceV_Instructions))
Str << "}\n";
}
} // end of namespace Ice