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

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//===- HexagonCommonGEP.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <map>
#include <set>
#include <utility>
#include <vector>
#define DEBUG_TYPE "commgep"
using namespace llvm;
static cl::opt<bool> OptSpeculate("commgep-speculate", cl::init(true),
cl::Hidden, cl::ZeroOrMore);
static cl::opt<bool> OptEnableInv("commgep-inv", cl::init(true), cl::Hidden,
cl::ZeroOrMore);
static cl::opt<bool> OptEnableConst("commgep-const", cl::init(true),
cl::Hidden, cl::ZeroOrMore);
namespace llvm {
void initializeHexagonCommonGEPPass(PassRegistry&);
} // end namespace llvm
namespace {
struct GepNode;
using NodeSet = std::set<GepNode *>;
using NodeToValueMap = std::map<GepNode *, Value *>;
using NodeVect = std::vector<GepNode *>;
using NodeChildrenMap = std::map<GepNode *, NodeVect>;
using UseSet = SetVector<Use *>;
using NodeToUsesMap = std::map<GepNode *, UseSet>;
// Numbering map for gep nodes. Used to keep track of ordering for
// gep nodes.
struct NodeOrdering {
NodeOrdering() = default;
void insert(const GepNode *N) { Map.insert(std::make_pair(N, ++LastNum)); }
void clear() { Map.clear(); }
bool operator()(const GepNode *N1, const GepNode *N2) const {
auto F1 = Map.find(N1), F2 = Map.find(N2);
assert(F1 != Map.end() && F2 != Map.end());
return F1->second < F2->second;
}
private:
std::map<const GepNode *, unsigned> Map;
unsigned LastNum = 0;
};
class HexagonCommonGEP : public FunctionPass {
public:
static char ID;
HexagonCommonGEP() : FunctionPass(ID) {
initializeHexagonCommonGEPPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
StringRef getPassName() const override { return "Hexagon Common GEP"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<DominatorTreeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<PostDominatorTreeWrapperPass>();
AU.addPreserved<PostDominatorTreeWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
private:
using ValueToNodeMap = std::map<Value *, GepNode *>;
using ValueVect = std::vector<Value *>;
using NodeToValuesMap = std::map<GepNode *, ValueVect>;
void getBlockTraversalOrder(BasicBlock *Root, ValueVect &Order);
bool isHandledGepForm(GetElementPtrInst *GepI);
void processGepInst(GetElementPtrInst *GepI, ValueToNodeMap &NM);
void collect();
void common();
BasicBlock *recalculatePlacement(GepNode *Node, NodeChildrenMap &NCM,
NodeToValueMap &Loc);
BasicBlock *recalculatePlacementRec(GepNode *Node, NodeChildrenMap &NCM,
NodeToValueMap &Loc);
bool isInvariantIn(Value *Val, Loop *L);
bool isInvariantIn(GepNode *Node, Loop *L);
bool isInMainPath(BasicBlock *B, Loop *L);
BasicBlock *adjustForInvariance(GepNode *Node, NodeChildrenMap &NCM,
NodeToValueMap &Loc);
void separateChainForNode(GepNode *Node, Use *U, NodeToValueMap &Loc);
void separateConstantChains(GepNode *Node, NodeChildrenMap &NCM,
NodeToValueMap &Loc);
void computeNodePlacement(NodeToValueMap &Loc);
Value *fabricateGEP(NodeVect &NA, BasicBlock::iterator At,
BasicBlock *LocB);
void getAllUsersForNode(GepNode *Node, ValueVect &Values,
NodeChildrenMap &NCM);
void materialize(NodeToValueMap &Loc);
void removeDeadCode();
NodeVect Nodes;
NodeToUsesMap Uses;
NodeOrdering NodeOrder; // Node ordering, for deterministic behavior.
SpecificBumpPtrAllocator<GepNode> *Mem;
LLVMContext *Ctx;
LoopInfo *LI;
DominatorTree *DT;
PostDominatorTree *PDT;
Function *Fn;
};
} // end anonymous namespace
char HexagonCommonGEP::ID = 0;
INITIALIZE_PASS_BEGIN(HexagonCommonGEP, "hcommgep", "Hexagon Common GEP",
false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(HexagonCommonGEP, "hcommgep", "Hexagon Common GEP",
false, false)
namespace {
struct GepNode {
enum {
None = 0,
Root = 0x01,
Internal = 0x02,
Used = 0x04,
InBounds = 0x08,
Pointer = 0x10, // See note below.
};
// Note: GEP indices generally traverse nested types, and so a GepNode
// (representing a single index) can be associated with some composite
// type. The exception is the GEP input, which is a pointer, and not
// a composite type (at least not in the sense of having sub-types).
// Also, the corresponding index plays a different role as well: it is
// simply added to the input pointer. Since pointer types are becoming
// opaque (i.e. are no longer going to include the pointee type), the
// two pieces of information (1) the fact that it's a pointer, and
// (2) the pointee type, need to be stored separately. The pointee type
// will be stored in the PTy member, while the fact that the node
// operates on a pointer will be reflected by the flag "Pointer".
uint32_t Flags = 0;
union {
GepNode *Parent;
Value *BaseVal;
};
Value *Idx = nullptr;
Type *PTy = nullptr; // Type indexed by this node. For pointer nodes
// this is the "pointee" type, and indexing a
// pointer does not change the type.
GepNode() : Parent(nullptr) {}
GepNode(const GepNode *N) : Flags(N->Flags), Idx(N->Idx), PTy(N->PTy) {
if (Flags & Root)
BaseVal = N->BaseVal;
else
Parent = N->Parent;
}
friend raw_ostream &operator<< (raw_ostream &OS, const GepNode &GN);
};
raw_ostream &operator<< (raw_ostream &OS, const GepNode &GN) {
OS << "{ {";
bool Comma = false;
if (GN.Flags & GepNode::Root) {
OS << "root";
Comma = true;
}
if (GN.Flags & GepNode::Internal) {
if (Comma)
OS << ',';
OS << "internal";
Comma = true;
}
if (GN.Flags & GepNode::Used) {
if (Comma)
OS << ',';
OS << "used";
}
if (GN.Flags & GepNode::InBounds) {
if (Comma)
OS << ',';
OS << "inbounds";
}
if (GN.Flags & GepNode::Pointer) {
if (Comma)
OS << ',';
OS << "pointer";
}
OS << "} ";
if (GN.Flags & GepNode::Root)
OS << "BaseVal:" << GN.BaseVal->getName() << '(' << GN.BaseVal << ')';
else
OS << "Parent:" << GN.Parent;
OS << " Idx:";
if (ConstantInt *CI = dyn_cast<ConstantInt>(GN.Idx))
OS << CI->getValue().getSExtValue();
else if (GN.Idx->hasName())
OS << GN.Idx->getName();
else
OS << "<anon> =" << *GN.Idx;
OS << " PTy:";
if (GN.PTy->isStructTy()) {
StructType *STy = cast<StructType>(GN.PTy);
if (!STy->isLiteral())
OS << GN.PTy->getStructName();
else
OS << "<anon-struct>:" << *STy;
}
else
OS << *GN.PTy;
OS << " }";
return OS;
}
template <typename NodeContainer>
void dump_node_container(raw_ostream &OS, const NodeContainer &S) {
using const_iterator = typename NodeContainer::const_iterator;
for (const_iterator I = S.begin(), E = S.end(); I != E; ++I)
OS << *I << ' ' << **I << '\n';
}
raw_ostream &operator<< (raw_ostream &OS,
const NodeVect &S) LLVM_ATTRIBUTE_UNUSED;
raw_ostream &operator<< (raw_ostream &OS, const NodeVect &S) {
dump_node_container(OS, S);
return OS;
}
raw_ostream &operator<< (raw_ostream &OS,
const NodeToUsesMap &M) LLVM_ATTRIBUTE_UNUSED;
raw_ostream &operator<< (raw_ostream &OS, const NodeToUsesMap &M){
for (const auto &I : M) {
const UseSet &Us = I.second;
OS << I.first << " -> #" << Us.size() << '{';
for (const Use *U : Us) {
User *R = U->getUser();
if (R->hasName())
OS << ' ' << R->getName();
else
OS << " <?>(" << *R << ')';
}
OS << " }\n";
}
return OS;
}
struct in_set {
in_set(const NodeSet &S) : NS(S) {}
bool operator() (GepNode *N) const {
return NS.find(N) != NS.end();
}
private:
const NodeSet &NS;
};
} // end anonymous namespace
inline void *operator new(size_t, SpecificBumpPtrAllocator<GepNode> &A) {
return A.Allocate();
}
void HexagonCommonGEP::getBlockTraversalOrder(BasicBlock *Root,
ValueVect &Order) {
// Compute block ordering for a typical DT-based traversal of the flow
// graph: "before visiting a block, all of its dominators must have been
// visited".
Order.push_back(Root);
for (auto *DTN : children<DomTreeNode*>(DT->getNode(Root)))
getBlockTraversalOrder(DTN->getBlock(), Order);
}
bool HexagonCommonGEP::isHandledGepForm(GetElementPtrInst *GepI) {
// No vector GEPs.
if (!GepI->getType()->isPointerTy())
return false;
// No GEPs without any indices. (Is this possible?)
if (GepI->idx_begin() == GepI->idx_end())
return false;
return true;
}
void HexagonCommonGEP::processGepInst(GetElementPtrInst *GepI,
ValueToNodeMap &NM) {
LLVM_DEBUG(dbgs() << "Visiting GEP: " << *GepI << '\n');
GepNode *N = new (*Mem) GepNode;
Value *PtrOp = GepI->getPointerOperand();
uint32_t InBounds = GepI->isInBounds() ? GepNode::InBounds : 0;
ValueToNodeMap::iterator F = NM.find(PtrOp);
if (F == NM.end()) {
N->BaseVal = PtrOp;
N->Flags |= GepNode::Root | InBounds;
} else {
// If PtrOp was a GEP instruction, it must have already been processed.
// The ValueToNodeMap entry for it is the last gep node in the generated
// chain. Link to it here.
N->Parent = F->second;
}
N->PTy = GepI->getSourceElementType();
N->Flags |= GepNode::Pointer;
N->Idx = *GepI->idx_begin();
// Collect the list of users of this GEP instruction. Will add it to the
// last node created for it.
UseSet Us;
for (Value::user_iterator UI = GepI->user_begin(), UE = GepI->user_end();
UI != UE; ++UI) {
// Check if this gep is used by anything other than other geps that
// we will process.
if (isa<GetElementPtrInst>(*UI)) {
GetElementPtrInst *UserG = cast<GetElementPtrInst>(*UI);
if (isHandledGepForm(UserG))
continue;
}
Us.insert(&UI.getUse());
}
Nodes.push_back(N);
NodeOrder.insert(N);
// Skip the first index operand, since it was already handled above. This
// dereferences the pointer operand.
GepNode *PN = N;
Type *PtrTy = GepI->getSourceElementType();
for (Use &U : llvm::drop_begin(GepI->indices())) {
Value *Op = U;
GepNode *Nx = new (*Mem) GepNode;
Nx->Parent = PN; // Link Nx to the previous node.
Nx->Flags |= GepNode::Internal | InBounds;
Nx->PTy = PtrTy;
Nx->Idx = Op;
Nodes.push_back(Nx);
NodeOrder.insert(Nx);
PN = Nx;
PtrTy = GetElementPtrInst::getTypeAtIndex(PtrTy, Op);
}
// After last node has been created, update the use information.
if (!Us.empty()) {
PN->Flags |= GepNode::Used;
Uses[PN].insert(Us.begin(), Us.end());
}
// Link the last node with the originating GEP instruction. This is to
// help with linking chained GEP instructions.
NM.insert(std::make_pair(GepI, PN));
}
void HexagonCommonGEP::collect() {
// Establish depth-first traversal order of the dominator tree.
ValueVect BO;
getBlockTraversalOrder(&Fn->front(), BO);
// The creation of gep nodes requires DT-traversal. When processing a GEP
// instruction that uses another GEP instruction as the base pointer, the
// gep node for the base pointer should already exist.
ValueToNodeMap NM;
for (Value *I : BO) {
BasicBlock *B = cast<BasicBlock>(I);
for (Instruction &J : *B)
if (auto *GepI = dyn_cast<GetElementPtrInst>(&J))
if (isHandledGepForm(GepI))
processGepInst(GepI, NM);
}
LLVM_DEBUG(dbgs() << "Gep nodes after initial collection:\n" << Nodes);
}
static void invert_find_roots(const NodeVect &Nodes, NodeChildrenMap &NCM,
NodeVect &Roots) {
for (GepNode *N : Nodes) {
if (N->Flags & GepNode::Root) {
Roots.push_back(N);
continue;
}
GepNode *PN = N->Parent;
NCM[PN].push_back(N);
}
}
static void nodes_for_root(GepNode *Root, NodeChildrenMap &NCM,
NodeSet &Nodes) {
NodeVect Work;
Work.push_back(Root);
Nodes.insert(Root);
while (!Work.empty()) {
NodeVect::iterator First = Work.begin();
GepNode *N = *First;
Work.erase(First);
NodeChildrenMap::iterator CF = NCM.find(N);
if (CF != NCM.end()) {
llvm::append_range(Work, CF->second);
Nodes.insert(CF->second.begin(), CF->second.end());
}
}
}
namespace {
using NodeSymRel = std::set<NodeSet>;
using NodePair = std::pair<GepNode *, GepNode *>;
using NodePairSet = std::set<NodePair>;
} // end anonymous namespace
static const NodeSet *node_class(GepNode *N, NodeSymRel &Rel) {
for (const NodeSet &S : Rel)
if (S.count(N))
return &S;
return nullptr;
}
// Create an ordered pair of GepNode pointers. The pair will be used in
// determining equality. The only purpose of the ordering is to eliminate
// duplication due to the commutativity of equality/non-equality.
static NodePair node_pair(GepNode *N1, GepNode *N2) {
uintptr_t P1 = reinterpret_cast<uintptr_t>(N1);
uintptr_t P2 = reinterpret_cast<uintptr_t>(N2);
if (P1 <= P2)
return std::make_pair(N1, N2);
return std::make_pair(N2, N1);
}
static unsigned node_hash(GepNode *N) {
// Include everything except flags and parent.
FoldingSetNodeID ID;
ID.AddPointer(N->Idx);
ID.AddPointer(N->PTy);
return ID.ComputeHash();
}
static bool node_eq(GepNode *N1, GepNode *N2, NodePairSet &Eq,
NodePairSet &Ne) {
// Don't cache the result for nodes with different hashes. The hash
// comparison is fast enough.
if (node_hash(N1) != node_hash(N2))
return false;
NodePair NP = node_pair(N1, N2);
NodePairSet::iterator FEq = Eq.find(NP);
if (FEq != Eq.end())
return true;
NodePairSet::iterator FNe = Ne.find(NP);
if (FNe != Ne.end())
return false;
// Not previously compared.
bool Root1 = N1->Flags & GepNode::Root;
uint32_t CmpFlags = GepNode::Root | GepNode::Pointer;
bool Different = (N1->Flags & CmpFlags) != (N2->Flags & CmpFlags);
NodePair P = node_pair(N1, N2);
// If the root/pointer flags have different values, the nodes are
// different.
// If both nodes are root nodes, but their base pointers differ,
// they are different.
if (Different || (Root1 && N1->BaseVal != N2->BaseVal)) {
Ne.insert(P);
return false;
}
// Here the root/pointer flags are identical, and for root nodes the
// base pointers are equal, so the root nodes are equal.
// For non-root nodes, compare their parent nodes.
if (Root1 || node_eq(N1->Parent, N2->Parent, Eq, Ne)) {
Eq.insert(P);
return true;
}
return false;
}
void HexagonCommonGEP::common() {
// The essence of this commoning is finding gep nodes that are equal.
// To do this we need to compare all pairs of nodes. To save time,
// first, partition the set of all nodes into sets of potentially equal
// nodes, and then compare pairs from within each partition.
using NodeSetMap = std::map<unsigned, NodeSet>;
NodeSetMap MaybeEq;
for (GepNode *N : Nodes) {
unsigned H = node_hash(N);
MaybeEq[H].insert(N);
}
// Compute the equivalence relation for the gep nodes. Use two caches,
// one for equality and the other for non-equality.
NodeSymRel EqRel; // Equality relation (as set of equivalence classes).
NodePairSet Eq, Ne; // Caches.
for (auto &I : MaybeEq) {
NodeSet &S = I.second;
for (NodeSet::iterator NI = S.begin(), NE = S.end(); NI != NE; ++NI) {
GepNode *N = *NI;
// If node already has a class, then the class must have been created
// in a prior iteration of this loop. Since equality is transitive,
// nothing more will be added to that class, so skip it.
if (node_class(N, EqRel))
continue;
// Create a new class candidate now.
NodeSet C;
for (NodeSet::iterator NJ = std::next(NI); NJ != NE; ++NJ)
if (node_eq(N, *NJ, Eq, Ne))
C.insert(*NJ);
// If Tmp is empty, N would be the only element in it. Don't bother
// creating a class for it then.
if (!C.empty()) {
C.insert(N); // Finalize the set before adding it to the relation.
std::pair<NodeSymRel::iterator, bool> Ins = EqRel.insert(C);
(void)Ins;
assert(Ins.second && "Cannot add a class");
}
}
}
LLVM_DEBUG({
dbgs() << "Gep node equality:\n";
for (NodePairSet::iterator I = Eq.begin(), E = Eq.end(); I != E; ++I)
dbgs() << "{ " << I->first << ", " << I->second << " }\n";
dbgs() << "Gep equivalence classes:\n";
for (const NodeSet &S : EqRel) {
dbgs() << '{';
for (NodeSet::const_iterator J = S.begin(), F = S.end(); J != F; ++J) {
if (J != S.begin())
dbgs() << ',';
dbgs() << ' ' << *J;
}
dbgs() << " }\n";
}
});
// Create a projection from a NodeSet to the minimal element in it.
using ProjMap = std::map<const NodeSet *, GepNode *>;
ProjMap PM;
for (const NodeSet &S : EqRel) {
GepNode *Min = *std::min_element(S.begin(), S.end(), NodeOrder);
std::pair<ProjMap::iterator,bool> Ins = PM.insert(std::make_pair(&S, Min));
(void)Ins;
assert(Ins.second && "Cannot add minimal element");
// Update the min element's flags, and user list.
uint32_t Flags = 0;
UseSet &MinUs = Uses[Min];
for (GepNode *N : S) {
uint32_t NF = N->Flags;
// If N is used, append all original values of N to the list of
// original values of Min.
if (NF & GepNode::Used)
MinUs.insert(Uses[N].begin(), Uses[N].end());
Flags |= NF;
}
if (MinUs.empty())
Uses.erase(Min);
// The collected flags should include all the flags from the min element.
assert((Min->Flags & Flags) == Min->Flags);
Min->Flags = Flags;
}
// Commoning: for each non-root gep node, replace "Parent" with the
// selected (minimum) node from the corresponding equivalence class.
// If a given parent does not have an equivalence class, leave it
// unchanged (it means that it's the only element in its class).
for (GepNode *N : Nodes) {
if (N->Flags & GepNode::Root)
continue;
const NodeSet *PC = node_class(N->Parent, EqRel);
if (!PC)
continue;
ProjMap::iterator F = PM.find(PC);
if (F == PM.end())
continue;
// Found a replacement, use it.
GepNode *Rep = F->second;
N->Parent = Rep;
}
LLVM_DEBUG(dbgs() << "Gep nodes after commoning:\n" << Nodes);
// Finally, erase the nodes that are no longer used.
NodeSet Erase;
for (GepNode *N : Nodes) {
const NodeSet *PC = node_class(N, EqRel);
if (!PC)
continue;
ProjMap::iterator F = PM.find(PC);
if (F == PM.end())
continue;
if (N == F->second)
continue;
// Node for removal.
Erase.insert(N);
}
erase_if(Nodes, in_set(Erase));
LLVM_DEBUG(dbgs() << "Gep nodes after post-commoning cleanup:\n" << Nodes);
}
template <typename T>
static BasicBlock *nearest_common_dominator(DominatorTree *DT, T &Blocks) {
LLVM_DEBUG({
dbgs() << "NCD of {";
for (typename T::iterator I = Blocks.begin(), E = Blocks.end(); I != E;
++I) {
if (!*I)
continue;
BasicBlock *B = cast<BasicBlock>(*I);
dbgs() << ' ' << B->getName();
}
dbgs() << " }\n";
});
// Allow null basic blocks in Blocks. In such cases, return nullptr.
typename T::iterator I = Blocks.begin(), E = Blocks.end();
if (I == E || !*I)
return nullptr;
BasicBlock *Dom = cast<BasicBlock>(*I);
while (++I != E) {
BasicBlock *B = cast_or_null<BasicBlock>(*I);
Dom = B ? DT->findNearestCommonDominator(Dom, B) : nullptr;
if (!Dom)
return nullptr;
}
LLVM_DEBUG(dbgs() << "computed:" << Dom->getName() << '\n');
return Dom;
}
template <typename T>
static BasicBlock *nearest_common_dominatee(DominatorTree *DT, T &Blocks) {
// If two blocks, A and B, dominate a block C, then A dominates B,
// or B dominates A.
typename T::iterator I = Blocks.begin(), E = Blocks.end();
// Find the first non-null block.
while (I != E && !*I)
++I;
if (I == E)
return DT->getRoot();
BasicBlock *DomB = cast<BasicBlock>(*I);
while (++I != E) {
if (!*I)
continue;
BasicBlock *B = cast<BasicBlock>(*I);
if (DT->dominates(B, DomB))
continue;
if (!DT->dominates(DomB, B))
return nullptr;
DomB = B;
}
return DomB;
}
// Find the first use in B of any value from Values. If no such use,
// return B->end().
template <typename T>
static BasicBlock::iterator first_use_of_in_block(T &Values, BasicBlock *B) {
BasicBlock::iterator FirstUse = B->end(), BEnd = B->end();
using iterator = typename T::iterator;
for (iterator I = Values.begin(), E = Values.end(); I != E; ++I) {
Value *V = *I;
// If V is used in a PHI node, the use belongs to the incoming block,
// not the block with the PHI node. In the incoming block, the use
// would be considered as being at the end of it, so it cannot
// influence the position of the first use (which is assumed to be
// at the end to start with).
if (isa<PHINode>(V))
continue;
if (!isa<Instruction>(V))
continue;
Instruction *In = cast<Instruction>(V);
if (In->getParent() != B)
continue;
BasicBlock::iterator It = In->getIterator();
if (std::distance(FirstUse, BEnd) < std::distance(It, BEnd))
FirstUse = It;
}
return FirstUse;
}
static bool is_empty(const BasicBlock *B) {
return B->empty() || (&*B->begin() == B->getTerminator());
}
BasicBlock *HexagonCommonGEP::recalculatePlacement(GepNode *Node,
NodeChildrenMap &NCM, NodeToValueMap &Loc) {
LLVM_DEBUG(dbgs() << "Loc for node:" << Node << '\n');
// Recalculate the placement for Node, assuming that the locations of
// its children in Loc are valid.
// Return nullptr if there is no valid placement for Node (for example, it
// uses an index value that is not available at the location required
// to dominate all children, etc.).
// Find the nearest common dominator for:
// - all users, if the node is used, and
// - all children.
ValueVect Bs;
if (Node->Flags & GepNode::Used) {
// Append all blocks with uses of the original values to the
// block vector Bs.
NodeToUsesMap::iterator UF = Uses.find(Node);
assert(UF != Uses.end() && "Used node with no use information");
UseSet &Us = UF->second;
for (Use *U : Us) {
User *R = U->getUser();
if (!isa<Instruction>(R))
continue;
BasicBlock *PB = isa<PHINode>(R)
? cast<PHINode>(R)->getIncomingBlock(*U)
: cast<Instruction>(R)->getParent();
Bs.push_back(PB);
}
}
// Append the location of each child.
NodeChildrenMap::iterator CF = NCM.find(Node);
if (CF != NCM.end()) {
NodeVect &Cs = CF->second;
for (GepNode *CN : Cs) {
NodeToValueMap::iterator LF = Loc.find(CN);
// If the child is only used in GEP instructions (i.e. is not used in
// non-GEP instructions), the nearest dominator computed for it may
// have been null. In such case it won't have a location available.
if (LF == Loc.end())
continue;
Bs.push_back(LF->second);
}
}
BasicBlock *DomB = nearest_common_dominator(DT, Bs);
if (!DomB)
return nullptr;
// Check if the index used by Node dominates the computed dominator.
Instruction *IdxI = dyn_cast<Instruction>(Node->Idx);
if (IdxI && !DT->dominates(IdxI->getParent(), DomB))
return nullptr;
// Avoid putting nodes into empty blocks.
while (is_empty(DomB)) {
DomTreeNode *N = (*DT)[DomB]->getIDom();
if (!N)
break;
DomB = N->getBlock();
}
// Otherwise, DomB is fine. Update the location map.
Loc[Node] = DomB;
return DomB;
}
BasicBlock *HexagonCommonGEP::recalculatePlacementRec(GepNode *Node,
NodeChildrenMap &NCM, NodeToValueMap &Loc) {
LLVM_DEBUG(dbgs() << "LocRec begin for node:" << Node << '\n');
// Recalculate the placement of Node, after recursively recalculating the
// placements of all its children.
NodeChildrenMap::iterator CF = NCM.find(Node);
if (CF != NCM.end()) {
NodeVect &Cs = CF->second;
for (GepNode *C : Cs)
recalculatePlacementRec(C, NCM, Loc);
}
BasicBlock *LB = recalculatePlacement(Node, NCM, Loc);
LLVM_DEBUG(dbgs() << "LocRec end for node:" << Node << '\n');
return LB;
}
bool HexagonCommonGEP::isInvariantIn(Value *Val, Loop *L) {
if (isa<Constant>(Val) || isa<Argument>(Val))
return true;
Instruction *In = dyn_cast<Instruction>(Val);
if (!In)
return false;
BasicBlock *HdrB = L->getHeader(), *DefB = In->getParent();
return DT->properlyDominates(DefB, HdrB);
}
bool HexagonCommonGEP::isInvariantIn(GepNode *Node, Loop *L) {
if (Node->Flags & GepNode::Root)
if (!isInvariantIn(Node->BaseVal, L))
return false;
return isInvariantIn(Node->Idx, L);
}
bool HexagonCommonGEP::isInMainPath(BasicBlock *B, Loop *L) {
BasicBlock *HB = L->getHeader();
BasicBlock *LB = L->getLoopLatch();
// B must post-dominate the loop header or dominate the loop latch.
if (PDT->dominates(B, HB))
return true;
if (LB && DT->dominates(B, LB))
return true;
return false;
}
static BasicBlock *preheader(DominatorTree *DT, Loop *L) {
if (BasicBlock *PH = L->getLoopPreheader())
return PH;
if (!OptSpeculate)
return nullptr;
DomTreeNode *DN = DT->getNode(L->getHeader());
if (!DN)
return nullptr;
return DN->getIDom()->getBlock();
}
BasicBlock *HexagonCommonGEP::adjustForInvariance(GepNode *Node,
NodeChildrenMap &NCM, NodeToValueMap &Loc) {
// Find the "topmost" location for Node: it must be dominated by both,
// its parent (or the BaseVal, if it's a root node), and by the index
// value.
ValueVect Bs;
if (Node->Flags & GepNode::Root) {
if (Instruction *PIn = dyn_cast<Instruction>(Node->BaseVal))
Bs.push_back(PIn->getParent());
} else {
Bs.push_back(Loc[Node->Parent]);
}
if (Instruction *IIn = dyn_cast<Instruction>(Node->Idx))
Bs.push_back(IIn->getParent());
BasicBlock *TopB = nearest_common_dominatee(DT, Bs);
// Traverse the loop nest upwards until we find a loop in which Node
// is no longer invariant, or until we get to the upper limit of Node's
// placement. The traversal will also stop when a suitable "preheader"
// cannot be found for a given loop. The "preheader" may actually be
// a regular block outside of the loop (i.e. not guarded), in which case
// the Node will be speculated.
// For nodes that are not in the main path of the containing loop (i.e.
// are not executed in each iteration), do not move them out of the loop.
BasicBlock *LocB = cast_or_null<BasicBlock>(Loc[Node]);
if (LocB) {
Loop *Lp = LI->getLoopFor(LocB);
while (Lp) {
if (!isInvariantIn(Node, Lp) || !isInMainPath(LocB, Lp))
break;
BasicBlock *NewLoc = preheader(DT, Lp);
if (!NewLoc || !DT->dominates(TopB, NewLoc))
break;
Lp = Lp->getParentLoop();
LocB = NewLoc;
}
}
Loc[Node] = LocB;
// Recursively compute the locations of all children nodes.
NodeChildrenMap::iterator CF = NCM.find(Node);
if (CF != NCM.end()) {
NodeVect &Cs = CF->second;
for (GepNode *C : Cs)
adjustForInvariance(C, NCM, Loc);
}
return LocB;
}
namespace {
struct LocationAsBlock {
LocationAsBlock(const NodeToValueMap &L) : Map(L) {}
const NodeToValueMap &Map;
};
raw_ostream &operator<< (raw_ostream &OS,
const LocationAsBlock &Loc) LLVM_ATTRIBUTE_UNUSED ;
raw_ostream &operator<< (raw_ostream &OS, const LocationAsBlock &Loc) {
for (const auto &I : Loc.Map) {
OS << I.first << " -> ";
if (BasicBlock *B = cast_or_null<BasicBlock>(I.second))
OS << B->getName() << '(' << B << ')';
else
OS << "<null-block>";
OS << '\n';
}
return OS;
}
inline bool is_constant(GepNode *N) {
return isa<ConstantInt>(N->Idx);
}
} // end anonymous namespace
void HexagonCommonGEP::separateChainForNode(GepNode *Node, Use *U,
NodeToValueMap &Loc) {
User *R = U->getUser();
LLVM_DEBUG(dbgs() << "Separating chain for node (" << Node << ") user: " << *R
<< '\n');
BasicBlock *PB = cast<Instruction>(R)->getParent();
GepNode *N = Node;
GepNode *C = nullptr, *NewNode = nullptr;
while (is_constant(N) && !(N->Flags & GepNode::Root)) {
// XXX if (single-use) dont-replicate;
GepNode *NewN = new (*Mem) GepNode(N);
Nodes.push_back(NewN);
Loc[NewN] = PB;
if (N == Node)
NewNode = NewN;
NewN->Flags &= ~GepNode::Used;
if (C)
C->Parent = NewN;
C = NewN;
N = N->Parent;
}
if (!NewNode)
return;
// Move over all uses that share the same user as U from Node to NewNode.
NodeToUsesMap::iterator UF = Uses.find(Node);
assert(UF != Uses.end());
UseSet &Us = UF->second;
UseSet NewUs;
for (Use *U : Us) {
if (U->getUser() == R)
NewUs.insert(U);
}
for (Use *U : NewUs)
Us.remove(U); // erase takes an iterator.
if (Us.empty()) {
Node->Flags &= ~GepNode::Used;
Uses.erase(UF);
}
// Should at least have U in NewUs.
NewNode->Flags |= GepNode::Used;
LLVM_DEBUG(dbgs() << "new node: " << NewNode << " " << *NewNode << '\n');
assert(!NewUs.empty());
Uses[NewNode] = NewUs;
}
void HexagonCommonGEP::separateConstantChains(GepNode *Node,
NodeChildrenMap &NCM, NodeToValueMap &Loc) {
// First approximation: extract all chains.
NodeSet Ns;
nodes_for_root(Node, NCM, Ns);
LLVM_DEBUG(dbgs() << "Separating constant chains for node: " << Node << '\n');
// Collect all used nodes together with the uses from loads and stores,
// where the GEP node could be folded into the load/store instruction.
NodeToUsesMap FNs; // Foldable nodes.
for (GepNode *N : Ns) {
if (!(N->Flags & GepNode::Used))
continue;
NodeToUsesMap::iterator UF = Uses.find(N);
assert(UF != Uses.end());
UseSet &Us = UF->second;
// Loads/stores that use the node N.
UseSet LSs;
for (Use *U : Us) {
User *R = U->getUser();
// We're interested in uses that provide the address. It can happen
// that the value may also be provided via GEP, but we won't handle
// those cases here for now.
if (LoadInst *Ld = dyn_cast<LoadInst>(R)) {
unsigned PtrX = LoadInst::getPointerOperandIndex();
if (&Ld->getOperandUse(PtrX) == U)
LSs.insert(U);
} else if (StoreInst *St = dyn_cast<StoreInst>(R)) {
unsigned PtrX = StoreInst::getPointerOperandIndex();
if (&St->getOperandUse(PtrX) == U)
LSs.insert(U);
}
}
// Even if the total use count is 1, separating the chain may still be
// beneficial, since the constant chain may be longer than the GEP alone
// would be (e.g. if the parent node has a constant index and also has
// other children).
if (!LSs.empty())
FNs.insert(std::make_pair(N, LSs));
}
LLVM_DEBUG(dbgs() << "Nodes with foldable users:\n" << FNs);
for (auto &FN : FNs) {
GepNode *N = FN.first;
UseSet &Us = FN.second;
for (Use *U : Us)
separateChainForNode(N, U, Loc);
}
}
void HexagonCommonGEP::computeNodePlacement(NodeToValueMap &Loc) {
// Compute the inverse of the Node.Parent links. Also, collect the set
// of root nodes.
NodeChildrenMap NCM;
NodeVect Roots;
invert_find_roots(Nodes, NCM, Roots);
// Compute the initial placement determined by the users' locations, and
// the locations of the child nodes.
for (GepNode *Root : Roots)
recalculatePlacementRec(Root, NCM, Loc);
LLVM_DEBUG(dbgs() << "Initial node placement:\n" << LocationAsBlock(Loc));
if (OptEnableInv) {
for (GepNode *Root : Roots)
adjustForInvariance(Root, NCM, Loc);
LLVM_DEBUG(dbgs() << "Node placement after adjustment for invariance:\n"
<< LocationAsBlock(Loc));
}
if (OptEnableConst) {
for (GepNode *Root : Roots)
separateConstantChains(Root, NCM, Loc);
}
LLVM_DEBUG(dbgs() << "Node use information:\n" << Uses);
// At the moment, there is no further refinement of the initial placement.
// Such a refinement could include splitting the nodes if they are placed
// too far from some of its users.
LLVM_DEBUG(dbgs() << "Final node placement:\n" << LocationAsBlock(Loc));
}
Value *HexagonCommonGEP::fabricateGEP(NodeVect &NA, BasicBlock::iterator At,
BasicBlock *LocB) {
LLVM_DEBUG(dbgs() << "Fabricating GEP in " << LocB->getName()
<< " for nodes:\n"
<< NA);
unsigned Num = NA.size();
GepNode *RN = NA[0];
assert((RN->Flags & GepNode::Root) && "Creating GEP for non-root");
GetElementPtrInst *NewInst = nullptr;
Value *Input = RN->BaseVal;
Type *InpTy = RN->PTy;
unsigned Idx = 0;
do {
SmallVector<Value*, 4> IdxList;
// If the type of the input of the first node is not a pointer,
// we need to add an artificial i32 0 to the indices (because the
// actual input in the IR will be a pointer).
if (!(NA[Idx]->Flags & GepNode::Pointer)) {
Type *Int32Ty = Type::getInt32Ty(*Ctx);
IdxList.push_back(ConstantInt::get(Int32Ty, 0));
}
// Keep adding indices from NA until we have to stop and generate
// an "intermediate" GEP.
while (++Idx <= Num) {
GepNode *N = NA[Idx-1];
IdxList.push_back(N->Idx);
if (Idx < Num) {
// We have to stop if we reach a pointer.
if (NA[Idx]->Flags & GepNode::Pointer)
break;
}
}
NewInst = GetElementPtrInst::Create(InpTy, Input, IdxList, "cgep", &*At);
NewInst->setIsInBounds(RN->Flags & GepNode::InBounds);
LLVM_DEBUG(dbgs() << "new GEP: " << *NewInst << '\n');
if (Idx < Num) {
Input = NewInst;
InpTy = NA[Idx]->PTy;
}
} while (Idx <= Num);
return NewInst;
}
void HexagonCommonGEP::getAllUsersForNode(GepNode *Node, ValueVect &Values,
NodeChildrenMap &NCM) {
NodeVect Work;
Work.push_back(Node);
while (!Work.empty()) {
NodeVect::iterator First = Work.begin();
GepNode *N = *First;
Work.erase(First);
if (N->Flags & GepNode::Used) {
NodeToUsesMap::iterator UF = Uses.find(N);
assert(UF != Uses.end() && "No use information for used node");
UseSet &Us = UF->second;
for (const auto &U : Us)
Values.push_back(U->getUser());
}
NodeChildrenMap::iterator CF = NCM.find(N);
if (CF != NCM.end()) {
NodeVect &Cs = CF->second;
llvm::append_range(Work, Cs);
}
}
}
void HexagonCommonGEP::materialize(NodeToValueMap &Loc) {
LLVM_DEBUG(dbgs() << "Nodes before materialization:\n" << Nodes << '\n');
NodeChildrenMap NCM;
NodeVect Roots;
// Compute the inversion again, since computing placement could alter
// "parent" relation between nodes.
invert_find_roots(Nodes, NCM, Roots);
while (!Roots.empty()) {
NodeVect::iterator First = Roots.begin();
GepNode *Root = *First, *Last = *First;
Roots.erase(First);
NodeVect NA; // Nodes to assemble.
// Append to NA all child nodes up to (and including) the first child
// that:
// (1) has more than 1 child, or
// (2) is used, or
// (3) has a child located in a different block.
bool LastUsed = false;
unsigned LastCN = 0;
// The location may be null if the computation failed (it can legitimately
// happen for nodes created from dead GEPs).
Value *LocV = Loc[Last];
if (!LocV)
continue;
BasicBlock *LastB = cast<BasicBlock>(LocV);
do {
NA.push_back(Last);
LastUsed = (Last->Flags & GepNode::Used);
if (LastUsed)
break;
NodeChildrenMap::iterator CF = NCM.find(Last);
LastCN = (CF != NCM.end()) ? CF->second.size() : 0;
if (LastCN != 1)
break;
GepNode *Child = CF->second.front();
BasicBlock *ChildB = cast_or_null<BasicBlock>(Loc[Child]);
if (ChildB != nullptr && LastB != ChildB)
break;
Last = Child;
} while (true);
BasicBlock::iterator InsertAt = LastB->getTerminator()->getIterator();
if (LastUsed || LastCN > 0) {
ValueVect Urs;
getAllUsersForNode(Root, Urs, NCM);
BasicBlock::iterator FirstUse = first_use_of_in_block(Urs, LastB);
if (FirstUse != LastB->end())
InsertAt = FirstUse;
}
// Generate a new instruction for NA.
Value *NewInst = fabricateGEP(NA, InsertAt, LastB);
// Convert all the children of Last node into roots, and append them
// to the Roots list.
if (LastCN > 0) {
NodeVect &Cs = NCM[Last];
for (GepNode *CN : Cs) {
CN->Flags &= ~GepNode::Internal;
CN->Flags |= GepNode::Root;
CN->BaseVal = NewInst;
Roots.push_back(CN);
}
}
// Lastly, if the Last node was used, replace all uses with the new GEP.
// The uses reference the original GEP values.
if (LastUsed) {
NodeToUsesMap::iterator UF = Uses.find(Last);
assert(UF != Uses.end() && "No use information found");
UseSet &Us = UF->second;
for (Use *U : Us)
U->set(NewInst);
}
}
}
void HexagonCommonGEP::removeDeadCode() {
ValueVect BO;
BO.push_back(&Fn->front());
for (unsigned i = 0; i < BO.size(); ++i) {
BasicBlock *B = cast<BasicBlock>(BO[i]);
for (auto DTN : children<DomTreeNode*>(DT->getNode(B)))
BO.push_back(DTN->getBlock());
}
for (Value *V : llvm::reverse(BO)) {
BasicBlock *B = cast<BasicBlock>(V);
ValueVect Ins;
for (Instruction &I : llvm::reverse(*B))
Ins.push_back(&I);
for (Value *I : Ins) {
Instruction *In = cast<Instruction>(I);
if (isInstructionTriviallyDead(In))
In->eraseFromParent();
}
}
}
bool HexagonCommonGEP::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
// For now bail out on C++ exception handling.
for (const BasicBlock &BB : F)
for (const Instruction &I : BB)
if (isa<InvokeInst>(I) || isa<LandingPadInst>(I))
return false;
Fn = &F;
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
PDT = &getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
Ctx = &F.getContext();
Nodes.clear();
Uses.clear();
NodeOrder.clear();
SpecificBumpPtrAllocator<GepNode> Allocator;
Mem = &Allocator;
collect();
common();
NodeToValueMap Loc;
computeNodePlacement(Loc);
materialize(Loc);
removeDeadCode();
#ifdef EXPENSIVE_CHECKS
// Run this only when expensive checks are enabled.
if (verifyFunction(F, &dbgs()))
report_fatal_error("Broken function");
#endif
return true;
}
namespace llvm {
FunctionPass *createHexagonCommonGEP() {
return new HexagonCommonGEP();
}
} // end namespace llvm
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