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//===- HexagonLoopIdiomRecognition.cpp ------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "hexagon-lir"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <array>
#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iterator>
#include <map>
#include <set>
#include <utility>
#include <vector>
using namespace llvm;
static cl::opt<bool> DisableMemcpyIdiom("disable-memcpy-idiom",
cl::Hidden, cl::init(false),
cl::desc("Disable generation of memcpy in loop idiom recognition"));
static cl::opt<bool> DisableMemmoveIdiom("disable-memmove-idiom",
cl::Hidden, cl::init(false),
cl::desc("Disable generation of memmove in loop idiom recognition"));
static cl::opt<unsigned> RuntimeMemSizeThreshold("runtime-mem-idiom-threshold",
cl::Hidden, cl::init(0), cl::desc("Threshold (in bytes) for the runtime "
"check guarding the memmove."));
static cl::opt<unsigned> CompileTimeMemSizeThreshold(
"compile-time-mem-idiom-threshold", cl::Hidden, cl::init(64),
cl::desc("Threshold (in bytes) to perform the transformation, if the "
"runtime loop count (mem transfer size) is known at compile-time."));
static cl::opt<bool> OnlyNonNestedMemmove("only-nonnested-memmove-idiom",
cl::Hidden, cl::init(true),
cl::desc("Only enable generating memmove in non-nested loops"));
cl::opt<bool> HexagonVolatileMemcpy("disable-hexagon-volatile-memcpy",
cl::Hidden, cl::init(false),
cl::desc("Enable Hexagon-specific memcpy for volatile destination."));
static cl::opt<unsigned> SimplifyLimit("hlir-simplify-limit", cl::init(10000),
cl::Hidden, cl::desc("Maximum number of simplification steps in HLIR"));
static const char *HexagonVolatileMemcpyName
= "hexagon_memcpy_forward_vp4cp4n2";
namespace llvm {
void initializeHexagonLoopIdiomRecognizePass(PassRegistry&);
Pass *createHexagonLoopIdiomPass();
} // end namespace llvm
namespace {
class HexagonLoopIdiomRecognize : public LoopPass {
public:
static char ID;
explicit HexagonLoopIdiomRecognize() : LoopPass(ID) {
initializeHexagonLoopIdiomRecognizePass(*PassRegistry::getPassRegistry());
}
StringRef getPassName() const override {
return "Recognize Hexagon-specific loop idioms";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<LoopInfoWrapperPass>();
AU.addRequiredID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addRequired<AAResultsWrapperPass>();
AU.addPreserved<AAResultsWrapperPass>();
AU.addRequired<ScalarEvolutionWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addPreserved<TargetLibraryInfoWrapperPass>();
}
bool runOnLoop(Loop *L, LPPassManager &LPM) override;
private:
int getSCEVStride(const SCEVAddRecExpr *StoreEv);
bool isLegalStore(Loop *CurLoop, StoreInst *SI);
void collectStores(Loop *CurLoop, BasicBlock *BB,
SmallVectorImpl<StoreInst*> &Stores);
bool processCopyingStore(Loop *CurLoop, StoreInst *SI, const SCEV *BECount);
bool coverLoop(Loop *L, SmallVectorImpl<Instruction*> &Insts) const;
bool runOnLoopBlock(Loop *CurLoop, BasicBlock *BB, const SCEV *BECount,
SmallVectorImpl<BasicBlock*> &ExitBlocks);
bool runOnCountableLoop(Loop *L);
AliasAnalysis *AA;
const DataLayout *DL;
DominatorTree *DT;
LoopInfo *LF;
const TargetLibraryInfo *TLI;
ScalarEvolution *SE;
bool HasMemcpy, HasMemmove;
};
struct Simplifier {
struct Rule {
using FuncType = std::function<Value* (Instruction*, LLVMContext&)>;
Rule(StringRef N, FuncType F) : Name(N), Fn(F) {}
StringRef Name; // For debugging.
FuncType Fn;
};
void addRule(StringRef N, const Rule::FuncType &F) {
Rules.push_back(Rule(N, F));
}
private:
struct WorkListType {
WorkListType() = default;
void push_back(Value* V) {
// Do not push back duplicates.
if (!S.count(V)) { Q.push_back(V); S.insert(V); }
}
Value *pop_front_val() {
Value *V = Q.front(); Q.pop_front(); S.erase(V);
return V;
}
bool empty() const { return Q.empty(); }
private:
std::deque<Value*> Q;
std::set<Value*> S;
};
using ValueSetType = std::set<Value *>;
std::vector<Rule> Rules;
public:
struct Context {
using ValueMapType = DenseMap<Value *, Value *>;
Value *Root;
ValueSetType Used; // The set of all cloned values used by Root.
ValueSetType Clones; // The set of all cloned values.
LLVMContext &Ctx;
Context(Instruction *Exp)
: Ctx(Exp->getParent()->getParent()->getContext()) {
initialize(Exp);
}
~Context() { cleanup(); }
void print(raw_ostream &OS, const Value *V) const;
Value *materialize(BasicBlock *B, BasicBlock::iterator At);
private:
friend struct Simplifier;
void initialize(Instruction *Exp);
void cleanup();
template <typename FuncT> void traverse(Value *V, FuncT F);
void record(Value *V);
void use(Value *V);
void unuse(Value *V);
bool equal(const Instruction *I, const Instruction *J) const;
Value *find(Value *Tree, Value *Sub) const;
Value *subst(Value *Tree, Value *OldV, Value *NewV);
void replace(Value *OldV, Value *NewV);
void link(Instruction *I, BasicBlock *B, BasicBlock::iterator At);
};
Value *simplify(Context &C);
};
struct PE {
PE(const Simplifier::Context &c, Value *v = nullptr) : C(c), V(v) {}
const Simplifier::Context &C;
const Value *V;
};
raw_ostream &operator<< (raw_ostream &OS, const PE &P) LLVM_ATTRIBUTE_USED;
raw_ostream &operator<< (raw_ostream &OS, const PE &P) {
P.C.print(OS, P.V ? P.V : P.C.Root);
return OS;
}
} // end anonymous namespace
char HexagonLoopIdiomRecognize::ID = 0;
INITIALIZE_PASS_BEGIN(HexagonLoopIdiomRecognize, "hexagon-loop-idiom",
"Recognize Hexagon-specific loop idioms", false, false)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_END(HexagonLoopIdiomRecognize, "hexagon-loop-idiom",
"Recognize Hexagon-specific loop idioms", false, false)
template <typename FuncT>
void Simplifier::Context::traverse(Value *V, FuncT F) {
WorkListType Q;
Q.push_back(V);
while (!Q.empty()) {
Instruction *U = dyn_cast<Instruction>(Q.pop_front_val());
if (!U || U->getParent())
continue;
if (!F(U))
continue;
for (Value *Op : U->operands())
Q.push_back(Op);
}
}
void Simplifier::Context::print(raw_ostream &OS, const Value *V) const {
const auto *U = dyn_cast<const Instruction>(V);
if (!U) {
OS << V << '(' << *V << ')';
return;
}
if (U->getParent()) {
OS << U << '(';
U->printAsOperand(OS, true);
OS << ')';
return;
}
unsigned N = U->getNumOperands();
if (N != 0)
OS << U << '(';
OS << U->getOpcodeName();
for (const Value *Op : U->operands()) {
OS << ' ';
print(OS, Op);
}
if (N != 0)
OS << ')';
}
void Simplifier::Context::initialize(Instruction *Exp) {
// Perform a deep clone of the expression, set Root to the root
// of the clone, and build a map from the cloned values to the
// original ones.
ValueMapType M;
BasicBlock *Block = Exp->getParent();
WorkListType Q;
Q.push_back(Exp);
while (!Q.empty()) {
Value *V = Q.pop_front_val();
if (M.find(V) != M.end())
continue;
if (Instruction *U = dyn_cast<Instruction>(V)) {
if (isa<PHINode>(U) || U->getParent() != Block)
continue;
for (Value *Op : U->operands())
Q.push_back(Op);
M.insert({U, U->clone()});
}
}
for (std::pair<Value*,Value*> P : M) {
Instruction *U = cast<Instruction>(P.second);
for (unsigned i = 0, n = U->getNumOperands(); i != n; ++i) {
auto F = M.find(U->getOperand(i));
if (F != M.end())
U->setOperand(i, F->second);
}
}
auto R = M.find(Exp);
assert(R != M.end());
Root = R->second;
record(Root);
use(Root);
}
void Simplifier::Context::record(Value *V) {
auto Record = [this](Instruction *U) -> bool {
Clones.insert(U);
return true;
};
traverse(V, Record);
}
void Simplifier::Context::use(Value *V) {
auto Use = [this](Instruction *U) -> bool {
Used.insert(U);
return true;
};
traverse(V, Use);
}
void Simplifier::Context::unuse(Value *V) {
if (!isa<Instruction>(V) || cast<Instruction>(V)->getParent() != nullptr)
return;
auto Unuse = [this](Instruction *U) -> bool {
if (!U->use_empty())
return false;
Used.erase(U);
return true;
};
traverse(V, Unuse);
}
Value *Simplifier::Context::subst(Value *Tree, Value *OldV, Value *NewV) {
if (Tree == OldV)
return NewV;
if (OldV == NewV)
return Tree;
WorkListType Q;
Q.push_back(Tree);
while (!Q.empty()) {
Instruction *U = dyn_cast<Instruction>(Q.pop_front_val());
// If U is not an instruction, or it's not a clone, skip it.
if (!U || U->getParent())
continue;
for (unsigned i = 0, n = U->getNumOperands(); i != n; ++i) {
Value *Op = U->getOperand(i);
if (Op == OldV) {
U->setOperand(i, NewV);
unuse(OldV);
} else {
Q.push_back(Op);
}
}
}
return Tree;
}
void Simplifier::Context::replace(Value *OldV, Value *NewV) {
if (Root == OldV) {
Root = NewV;
use(Root);
return;
}
// NewV may be a complex tree that has just been created by one of the
// transformation rules. We need to make sure that it is commoned with
// the existing Root to the maximum extent possible.
// Identify all subtrees of NewV (including NewV itself) that have
// equivalent counterparts in Root, and replace those subtrees with
// these counterparts.
WorkListType Q;
Q.push_back(NewV);
while (!Q.empty()) {
Value *V = Q.pop_front_val();
Instruction *U = dyn_cast<Instruction>(V);
if (!U || U->getParent())
continue;
if (Value *DupV = find(Root, V)) {
if (DupV != V)
NewV = subst(NewV, V, DupV);
} else {
for (Value *Op : U->operands())
Q.push_back(Op);
}
}
// Now, simply replace OldV with NewV in Root.
Root = subst(Root, OldV, NewV);
use(Root);
}
void Simplifier::Context::cleanup() {
for (Value *V : Clones) {
Instruction *U = cast<Instruction>(V);
if (!U->getParent())
U->dropAllReferences();
}
for (Value *V : Clones) {
Instruction *U = cast<Instruction>(V);
if (!U->getParent())
U->deleteValue();
}
}
bool Simplifier::Context::equal(const Instruction *I,
const Instruction *J) const {
if (I == J)
return true;
if (!I->isSameOperationAs(J))
return false;
if (isa<PHINode>(I))
return I->isIdenticalTo(J);
for (unsigned i = 0, n = I->getNumOperands(); i != n; ++i) {
Value *OpI = I->getOperand(i), *OpJ = J->getOperand(i);
if (OpI == OpJ)
continue;
auto *InI = dyn_cast<const Instruction>(OpI);
auto *InJ = dyn_cast<const Instruction>(OpJ);
if (InI && InJ) {
if (!equal(InI, InJ))
return false;
} else if (InI != InJ || !InI)
return false;
}
return true;
}
Value *Simplifier::Context::find(Value *Tree, Value *Sub) const {
Instruction *SubI = dyn_cast<Instruction>(Sub);
WorkListType Q;
Q.push_back(Tree);
while (!Q.empty()) {
Value *V = Q.pop_front_val();
if (V == Sub)
return V;
Instruction *U = dyn_cast<Instruction>(V);
if (!U || U->getParent())
continue;
if (SubI && equal(SubI, U))
return U;
assert(!isa<PHINode>(U));
for (Value *Op : U->operands())
Q.push_back(Op);
}
return nullptr;
}
void Simplifier::Context::link(Instruction *I, BasicBlock *B,
BasicBlock::iterator At) {
if (I->getParent())
return;
for (Value *Op : I->operands()) {
if (Instruction *OpI = dyn_cast<Instruction>(Op))
link(OpI, B, At);
}
B->getInstList().insert(At, I);
}
Value *Simplifier::Context::materialize(BasicBlock *B,
BasicBlock::iterator At) {
if (Instruction *RootI = dyn_cast<Instruction>(Root))
link(RootI, B, At);
return Root;
}
Value *Simplifier::simplify(Context &C) {
WorkListType Q;
Q.push_back(C.Root);
unsigned Count = 0;
const unsigned Limit = SimplifyLimit;
while (!Q.empty()) {
if (Count++ >= Limit)
break;
Instruction *U = dyn_cast<Instruction>(Q.pop_front_val());
if (!U || U->getParent() || !C.Used.count(U))
continue;
bool Changed = false;
for (Rule &R : Rules) {
Value *W = R.Fn(U, C.Ctx);
if (!W)
continue;
Changed = true;
C.record(W);
C.replace(U, W);
Q.push_back(C.Root);
break;
}
if (!Changed) {
for (Value *Op : U->operands())
Q.push_back(Op);
}
}
return Count < Limit ? C.Root : nullptr;
}
//===----------------------------------------------------------------------===//
//
// Implementation of PolynomialMultiplyRecognize
//
//===----------------------------------------------------------------------===//
namespace {
class PolynomialMultiplyRecognize {
public:
explicit PolynomialMultiplyRecognize(Loop *loop, const DataLayout &dl,
const DominatorTree &dt, const TargetLibraryInfo &tli,
ScalarEvolution &se)
: CurLoop(loop), DL(dl), DT(dt), TLI(tli), SE(se) {}
bool recognize();
private:
using ValueSeq = SetVector<Value *>;
IntegerType *getPmpyType() const {
LLVMContext &Ctx = CurLoop->getHeader()->getParent()->getContext();
return IntegerType::get(Ctx, 32);
}
bool isPromotableTo(Value *V, IntegerType *Ty);
void promoteTo(Instruction *In, IntegerType *DestTy, BasicBlock *LoopB);
bool promoteTypes(BasicBlock *LoopB, BasicBlock *ExitB);
Value *getCountIV(BasicBlock *BB);
bool findCycle(Value *Out, Value *In, ValueSeq &Cycle);
void classifyCycle(Instruction *DivI, ValueSeq &Cycle, ValueSeq &Early,
ValueSeq &Late);
bool classifyInst(Instruction *UseI, ValueSeq &Early, ValueSeq &Late);
bool commutesWithShift(Instruction *I);
bool highBitsAreZero(Value *V, unsigned IterCount);
bool keepsHighBitsZero(Value *V, unsigned IterCount);
bool isOperandShifted(Instruction *I, Value *Op);
bool convertShiftsToLeft(BasicBlock *LoopB, BasicBlock *ExitB,
unsigned IterCount);
void cleanupLoopBody(BasicBlock *LoopB);
struct ParsedValues {
ParsedValues() = default;
Value *M = nullptr;
Value *P = nullptr;
Value *Q = nullptr;
Value *R = nullptr;
Value *X = nullptr;
Instruction *Res = nullptr;
unsigned IterCount = 0;
bool Left = false;
bool Inv = false;
};
bool matchLeftShift(SelectInst *SelI, Value *CIV, ParsedValues &PV);
bool matchRightShift(SelectInst *SelI, ParsedValues &PV);
bool scanSelect(SelectInst *SI, BasicBlock *LoopB, BasicBlock *PrehB,
Value *CIV, ParsedValues &PV, bool PreScan);
unsigned getInverseMxN(unsigned QP);
Value *generate(BasicBlock::iterator At, ParsedValues &PV);
void setupSimplifier();
Simplifier Simp;
Loop *CurLoop;
const DataLayout &DL;
const DominatorTree &DT;
const TargetLibraryInfo &TLI;
ScalarEvolution &SE;
};
} // end anonymous namespace
Value *PolynomialMultiplyRecognize::getCountIV(BasicBlock *BB) {
pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
if (std::distance(PI, PE) != 2)
return nullptr;
BasicBlock *PB = (*PI == BB) ? *std::next(PI) : *PI;
for (auto I = BB->begin(), E = BB->end(); I != E && isa<PHINode>(I); ++I) {
auto *PN = cast<PHINode>(I);
Value *InitV = PN->getIncomingValueForBlock(PB);
if (!isa<ConstantInt>(InitV) || !cast<ConstantInt>(InitV)->isZero())
continue;
Value *IterV = PN->getIncomingValueForBlock(BB);
if (!isa<BinaryOperator>(IterV))
continue;
auto *BO = dyn_cast<BinaryOperator>(IterV);
if (BO->getOpcode() != Instruction::Add)
continue;
Value *IncV = nullptr;
if (BO->getOperand(0) == PN)
IncV = BO->getOperand(1);
else if (BO->getOperand(1) == PN)
IncV = BO->getOperand(0);
if (IncV == nullptr)
continue;
if (auto *T = dyn_cast<ConstantInt>(IncV))
if (T->getZExtValue() == 1)
return PN;
}
return nullptr;
}
static void replaceAllUsesOfWithIn(Value *I, Value *J, BasicBlock *BB) {
for (auto UI = I->user_begin(), UE = I->user_end(); UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
if (auto *II = dyn_cast<Instruction>(TheUse.getUser()))
if (BB == II->getParent())
II->replaceUsesOfWith(I, J);
}
}
bool PolynomialMultiplyRecognize::matchLeftShift(SelectInst *SelI,
Value *CIV, ParsedValues &PV) {
// Match the following:
// select (X & (1 << i)) != 0 ? R ^ (Q << i) : R
// select (X & (1 << i)) == 0 ? R : R ^ (Q << i)
// The condition may also check for equality with the masked value, i.e
// select (X & (1 << i)) == (1 << i) ? R ^ (Q << i) : R
// select (X & (1 << i)) != (1 << i) ? R : R ^ (Q << i);
Value *CondV = SelI->getCondition();
Value *TrueV = SelI->getTrueValue();
Value *FalseV = SelI->getFalseValue();
using namespace PatternMatch;
CmpInst::Predicate P;
Value *A = nullptr, *B = nullptr, *C = nullptr;
if (!match(CondV, m_ICmp(P, m_And(m_Value(A), m_Value(B)), m_Value(C))) &&
!match(CondV, m_ICmp(P, m_Value(C), m_And(m_Value(A), m_Value(B)))))
return false;
if (P != CmpInst::ICMP_EQ && P != CmpInst::ICMP_NE)
return false;
// Matched: select (A & B) == C ? ... : ...
// select (A & B) != C ? ... : ...
Value *X = nullptr, *Sh1 = nullptr;
// Check (A & B) for (X & (1 << i)):
if (match(A, m_Shl(m_One(), m_Specific(CIV)))) {
Sh1 = A;
X = B;
} else if (match(B, m_Shl(m_One(), m_Specific(CIV)))) {
Sh1 = B;
X = A;
} else {
// TODO: Could also check for an induction variable containing single
// bit shifted left by 1 in each iteration.
return false;
}
bool TrueIfZero;
// Check C against the possible values for comparison: 0 and (1 << i):
if (match(C, m_Zero()))
TrueIfZero = (P == CmpInst::ICMP_EQ);
else if (C == Sh1)
TrueIfZero = (P == CmpInst::ICMP_NE);
else
return false;
// So far, matched:
// select (X & (1 << i)) ? ... : ...
// including variations of the check against zero/non-zero value.
Value *ShouldSameV = nullptr, *ShouldXoredV = nullptr;
if (TrueIfZero) {
ShouldSameV = TrueV;
ShouldXoredV = FalseV;
} else {
ShouldSameV = FalseV;
ShouldXoredV = TrueV;
}
Value *Q = nullptr, *R = nullptr, *Y = nullptr, *Z = nullptr;
Value *T = nullptr;
if (match(ShouldXoredV, m_Xor(m_Value(Y), m_Value(Z)))) {
// Matched: select +++ ? ... : Y ^ Z
// select +++ ? Y ^ Z : ...
// where +++ denotes previously checked matches.
if (ShouldSameV == Y)
T = Z;
else if (ShouldSameV == Z)
T = Y;
else
return false;
R = ShouldSameV;
// Matched: select +++ ? R : R ^ T
// select +++ ? R ^ T : R
// depending on TrueIfZero.
} else if (match(ShouldSameV, m_Zero())) {
// Matched: select +++ ? 0 : ...
// select +++ ? ... : 0
if (!SelI->hasOneUse())
return false;
T = ShouldXoredV;
// Matched: select +++ ? 0 : T
// select +++ ? T : 0
Value *U = *SelI->user_begin();
if (!match(U, m_Xor(m_Specific(SelI), m_Value(R))) &&
!match(U, m_Xor(m_Value(R), m_Specific(SelI))))
return false;
// Matched: xor (select +++ ? 0 : T), R
// xor (select +++ ? T : 0), R
} else
return false;
// The xor input value T is isolated into its own match so that it could
// be checked against an induction variable containing a shifted bit
// (todo).
// For now, check against (Q << i).
if (!match(T, m_Shl(m_Value(Q), m_Specific(CIV))) &&
!match(T, m_Shl(m_ZExt(m_Value(Q)), m_ZExt(m_Specific(CIV)))))
return false;
// Matched: select +++ ? R : R ^ (Q << i)
// select +++ ? R ^ (Q << i) : R
PV.X = X;
PV.Q = Q;
PV.R = R;
PV.Left = true;
return true;
}
bool PolynomialMultiplyRecognize::matchRightShift(SelectInst *SelI,
ParsedValues &PV) {
// Match the following:
// select (X & 1) != 0 ? (R >> 1) ^ Q : (R >> 1)
// select (X & 1) == 0 ? (R >> 1) : (R >> 1) ^ Q
// The condition may also check for equality with the masked value, i.e
// select (X & 1) == 1 ? (R >> 1) ^ Q : (R >> 1)
// select (X & 1) != 1 ? (R >> 1) : (R >> 1) ^ Q
Value *CondV = SelI->getCondition();
Value *TrueV = SelI->getTrueValue();
Value *FalseV = SelI->getFalseValue();
using namespace PatternMatch;
Value *C = nullptr;
CmpInst::Predicate P;
bool TrueIfZero;
if (match(CondV, m_ICmp(P, m_Value(C), m_Zero())) ||
match(CondV, m_ICmp(P, m_Zero(), m_Value(C)))) {
if (P != CmpInst::ICMP_EQ && P != CmpInst::ICMP_NE)
return false;
// Matched: select C == 0 ? ... : ...
// select C != 0 ? ... : ...
TrueIfZero = (P == CmpInst::ICMP_EQ);
} else if (match(CondV, m_ICmp(P, m_Value(C), m_One())) ||
match(CondV, m_ICmp(P, m_One(), m_Value(C)))) {
if (P != CmpInst::ICMP_EQ && P != CmpInst::ICMP_NE)
return false;
// Matched: select C == 1 ? ... : ...
// select C != 1 ? ... : ...
TrueIfZero = (P == CmpInst::ICMP_NE);
} else
return false;
Value *X = nullptr;
if (!match(C, m_And(m_Value(X), m_One())) &&
!match(C, m_And(m_One(), m_Value(X))))
return false;
// Matched: select (X & 1) == +++ ? ... : ...
// select (X & 1) != +++ ? ... : ...
Value *R = nullptr, *Q = nullptr;
if (TrueIfZero) {
// The select's condition is true if the tested bit is 0.
// TrueV must be the shift, FalseV must be the xor.
if (!match(TrueV, m_LShr(m_Value(R), m_One())))
return false;
// Matched: select +++ ? (R >> 1) : ...
if (!match(FalseV, m_Xor(m_Specific(TrueV), m_Value(Q))) &&
!match(FalseV, m_Xor(m_Value(Q), m_Specific(TrueV))))
return false;
// Matched: select +++ ? (R >> 1) : (R >> 1) ^ Q
// with commuting ^.
} else {
// The select's condition is true if the tested bit is 1.
// TrueV must be the xor, FalseV must be the shift.
if (!match(FalseV, m_LShr(m_Value(R), m_One())))
return false;
// Matched: select +++ ? ... : (R >> 1)
if (!match(TrueV, m_Xor(m_Specific(FalseV), m_Value(Q))) &&
!match(TrueV, m_Xor(m_Value(Q), m_Specific(FalseV))))
return false;
// Matched: select +++ ? (R >> 1) ^ Q : (R >> 1)
// with commuting ^.
}
PV.X = X;
PV.Q = Q;
PV.R = R;
PV.Left = false;
return true;
}
bool PolynomialMultiplyRecognize::scanSelect(SelectInst *SelI,
BasicBlock *LoopB, BasicBlock *PrehB, Value *CIV, ParsedValues &PV,
bool PreScan) {
using namespace PatternMatch;
// The basic pattern for R = P.Q is:
// for i = 0..31
// R = phi (0, R')
// if (P & (1 << i)) ; test-bit(P, i)
// R' = R ^ (Q << i)
//
// Similarly, the basic pattern for R = (P/Q).Q - P
// for i = 0..31
// R = phi(P, R')
// if (R & (1 << i))
// R' = R ^ (Q << i)
// There exist idioms, where instead of Q being shifted left, P is shifted
// right. This produces a result that is shifted right by 32 bits (the
// non-shifted result is 64-bit).
//
// For R = P.Q, this would be:
// for i = 0..31
// R = phi (0, R')
// if ((P >> i) & 1)
// R' = (R >> 1) ^ Q ; R is cycled through the loop, so it must
// else ; be shifted by 1, not i.
// R' = R >> 1
//
// And for the inverse:
// for i = 0..31
// R = phi (P, R')
// if (R & 1)
// R' = (R >> 1) ^ Q
// else
// R' = R >> 1
// The left-shifting idioms share the same pattern:
// select (X & (1 << i)) ? R ^ (Q << i) : R
// Similarly for right-shifting idioms:
// select (X & 1) ? (R >> 1) ^ Q
if (matchLeftShift(SelI, CIV, PV)) {
// If this is a pre-scan, getting this far is sufficient.
if (PreScan)
return true;
// Need to make sure that the SelI goes back into R.
auto *RPhi = dyn_cast<PHINode>(PV.R);
if (!RPhi)
return false;
if (SelI != RPhi->getIncomingValueForBlock(LoopB))
return false;
PV.Res = SelI;
// If X is loop invariant, it must be the input polynomial, and the
// idiom is the basic polynomial multiply.
if (CurLoop->isLoopInvariant(PV.X)) {
PV.P = PV.X;
PV.Inv = false;
} else {
// X is not loop invariant. If X == R, this is the inverse pmpy.
// Otherwise, check for an xor with an invariant value. If the
// variable argument to the xor is R, then this is still a valid
// inverse pmpy.
PV.Inv = true;
if (PV.X != PV.R) {
Value *Var = nullptr, *Inv = nullptr, *X1 = nullptr, *X2 = nullptr;
if (!match(PV.X, m_Xor(m_Value(X1), m_Value(X2))))
return false;
auto *I1 = dyn_cast<Instruction>(X1);
auto *I2 = dyn_cast<Instruction>(X2);
if (!I1 || I1->getParent() != LoopB) {
Var = X2;
Inv = X1;
} else if (!I2 || I2->getParent() != LoopB) {
Var = X1;
Inv = X2;
} else
return false;
if (Var != PV.R)
return false;
PV.M = Inv;
}
// The input polynomial P still needs to be determined. It will be
// the entry value of R.
Value *EntryP = RPhi->getIncomingValueForBlock(PrehB);
PV.P = EntryP;
}
return true;
}
if (matchRightShift(SelI, PV)) {
// If this is an inverse pattern, the Q polynomial must be known at
// compile time.
if (PV.Inv && !isa<ConstantInt>(PV.Q))
return false;
if (PreScan)
return true;
// There is no exact matching of right-shift pmpy.
return false;
}
return false;
}
bool PolynomialMultiplyRecognize::isPromotableTo(Value *Val,
IntegerType *DestTy) {
IntegerType *T = dyn_cast<IntegerType>(Val->getType());
if (!T || T->getBitWidth() > DestTy->getBitWidth())
return false;
if (T->getBitWidth() == DestTy->getBitWidth())
return true;
// Non-instructions are promotable. The reason why an instruction may not
// be promotable is that it may produce a different result if its operands
// and the result are promoted, for example, it may produce more non-zero
// bits. While it would still be possible to represent the proper result
// in a wider type, it may require adding additional instructions (which
// we don't want to do).
Instruction *In = dyn_cast<Instruction>(Val);
if (!In)
return true;
// The bitwidth of the source type is smaller than the destination.
// Check if the individual operation can be promoted.
switch (In->getOpcode()) {
case Instruction::PHI:
case Instruction::ZExt:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::LShr: // Shift right is ok.
case Instruction::Select:
return true;
case Instruction::ICmp:
if (CmpInst *CI = cast<CmpInst>(In))
return CI->isEquality() || CI->isUnsigned();
llvm_unreachable("Cast failed unexpectedly");
case Instruction::Add:
return In->hasNoSignedWrap() && In->hasNoUnsignedWrap();
}
return false;
}
void PolynomialMultiplyRecognize::promoteTo(Instruction *In,
IntegerType *DestTy, BasicBlock *LoopB) {
// Leave boolean values alone.
if (!In->getType()->isIntegerTy(1))
In->mutateType(DestTy);
unsigned DestBW = DestTy->getBitWidth();
// Handle PHIs.
if (PHINode *P = dyn_cast<PHINode>(In)) {
unsigned N = P->getNumIncomingValues();
for (unsigned i = 0; i != N; ++i) {
BasicBlock *InB = P->getIncomingBlock(i);
if (InB == LoopB)
continue;
Value *InV = P->getIncomingValue(i);
IntegerType *Ty = cast<IntegerType>(InV->getType());
// Do not promote values in PHI nodes of type i1.
if (Ty != P->getType()) {
// If the value type does not match the PHI type, the PHI type
// must have been promoted.
assert(Ty->getBitWidth() < DestBW);
InV = IRBuilder<>(InB->getTerminator()).CreateZExt(InV, DestTy);
P->setIncomingValue(i, InV);
}
}
} else if (ZExtInst *Z = dyn_cast<ZExtInst>(In)) {
Value *Op = Z->getOperand(0);
if (Op->getType() == Z->getType())
Z->replaceAllUsesWith(Op);
Z->eraseFromParent();
return;
}
// Promote immediates.
for (unsigned i = 0, n = In->getNumOperands(); i != n; ++i) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(In->getOperand(i)))
if (CI->getType()->getBitWidth() < DestBW)
In->setOperand(i, ConstantInt::get(DestTy, CI->getZExtValue()));
}
}
bool PolynomialMultiplyRecognize::promoteTypes(BasicBlock *LoopB,
BasicBlock *ExitB) {
assert(LoopB);
// Skip loops where the exit block has more than one predecessor. The values
// coming from the loop block will be promoted to another type, and so the
// values coming into the exit block from other predecessors would also have
// to be promoted.
if (!ExitB || (ExitB->getSinglePredecessor() != LoopB))
return false;
IntegerType *DestTy = getPmpyType();
// Check if the exit values have types that are no wider than the type
// that we want to promote to.
unsigned DestBW = DestTy->getBitWidth();
for (PHINode &P : ExitB->phis()) {
if (P.getNumIncomingValues() != 1)
return false;
assert(P.getIncomingBlock(0) == LoopB);
IntegerType *T = dyn_cast<IntegerType>(P.getType());
if (!T || T->getBitWidth() > DestBW)
return false;
}
// Check all instructions in the loop.
for (Instruction &In : *LoopB)
if (!In.isTerminator() && !isPromotableTo(&In, DestTy))
return false;
// Perform the promotion.
std::vector<Instruction*> LoopIns;
std::transform(LoopB->begin(), LoopB->end(), std::back_inserter(LoopIns),
[](Instruction &In) { return &In; });
for (Instruction *In : LoopIns)
promoteTo(In, DestTy, LoopB);
// Fix up the PHI nodes in the exit block.
Instruction *EndI = ExitB->getFirstNonPHI();
BasicBlock::iterator End = EndI ? EndI->getIterator() : ExitB->end();
for (auto I = ExitB->begin(); I != End; ++I) {
PHINode *P = dyn_cast<PHINode>(I);
if (!P)
break;
Type *Ty0 = P->getIncomingValue(0)->getType();
Type *PTy = P->getType();
if (PTy != Ty0) {
assert(Ty0 == DestTy);
// In order to create the trunc, P must have the promoted type.
P->mutateType(Ty0);
Value *T = IRBuilder<>(ExitB, End).CreateTrunc(P, PTy);
// In order for the RAUW to work, the types of P and T must match.
P->mutateType(PTy);
P->replaceAllUsesWith(T);
// Final update of the P's type.
P->mutateType(Ty0);
cast<Instruction>(T)->setOperand(0, P);
}
}
return true;
}
bool PolynomialMultiplyRecognize::findCycle(Value *Out, Value *In,
ValueSeq &Cycle) {
// Out = ..., In, ...
if (Out == In)
return true;
auto *BB = cast<Instruction>(Out)->getParent();
bool HadPhi = false;
for (auto U : Out->users()) {
auto *I = dyn_cast<Instruction>(&*U);
if (I == nullptr || I->getParent() != BB)
continue;
// Make sure that there are no multi-iteration cycles, e.g.
// p1 = phi(p2)
// p2 = phi(p1)
// The cycle p1->p2->p1 would span two loop iterations.
// Check that there is only one phi in the cycle.
bool IsPhi = isa<PHINode>(I);
if (IsPhi && HadPhi)
return false;
HadPhi |= IsPhi;
if (Cycle.count(I))
return false;
Cycle.insert(I);
if (findCycle(I, In, Cycle))
break;
Cycle.remove(I);
}
return !Cycle.empty();
}
void PolynomialMultiplyRecognize::classifyCycle(Instruction *DivI,
ValueSeq &Cycle, ValueSeq &Early, ValueSeq &Late) {
// All the values in the cycle that are between the phi node and the
// divider instruction will be classified as "early", all other values
// will be "late".
bool IsE = true;
unsigned I, N = Cycle.size();
for (I = 0; I < N; ++I) {
Value *V = Cycle[I];
if (DivI == V)
IsE = false;
else if (!isa<PHINode>(V))
continue;
// Stop if found either.
break;
}
// "I" is the index of either DivI or the phi node, whichever was first.
// "E" is "false" or "true" respectively.
ValueSeq &First = !IsE ? Early : Late;
for (unsigned J = 0; J < I; ++J)
First.insert(Cycle[J]);
ValueSeq &Second = IsE ? Early : Late;
Second.insert(Cycle[I]);
for (++I; I < N; ++I) {
Value *V = Cycle[I];
if (DivI == V || isa<PHINode>(V))
break;
Second.insert(V);
}
for (; I < N; ++I)
First.insert(Cycle[I]);
}
bool PolynomialMultiplyRecognize::classifyInst(Instruction *UseI,
ValueSeq &Early, ValueSeq &Late) {
// Select is an exception, since the condition value does not have to be
// classified in the same way as the true/false values. The true/false
// values do have to be both early or both late.
if (UseI->getOpcode() == Instruction::Select) {
Value *TV = UseI->getOperand(1), *FV = UseI->getOperand(2);
if (Early.count(TV) || Early.count(FV)) {
if (Late.count(TV) || Late.count(FV))
return false;
Early.insert(UseI);
} else if (Late.count(TV) || Late.count(FV)) {
if (Early.count(TV) || Early.count(FV))
return false;
Late.insert(UseI);
}
return true;
}
// Not sure what would be the example of this, but the code below relies
// on having at least one operand.
if (UseI->getNumOperands() == 0)
return true;
bool AE = true, AL = true;
for (auto &I : UseI->operands()) {
if (Early.count(&*I))
AL = false;
else if (Late.count(&*I))
AE = false;
}
// If the operands appear "all early" and "all late" at the same time,
// then it means that none of them are actually classified as either.
// This is harmless.
if (AE && AL)
return true;
// Conversely, if they are neither "all early" nor "all late", then
// we have a mixture of early and late operands that is not a known
// exception.
if (!AE && !AL)
return false;
// Check that we have covered the two special cases.
assert(AE != AL);
if (AE)
Early.insert(UseI);
else
Late.insert(UseI);
return true;
}
bool PolynomialMultiplyRecognize::commutesWithShift(Instruction *I) {
switch (I->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::LShr:
case Instruction::Shl:
case Instruction::Select:
case Instruction::ICmp:
case Instruction::PHI:
break;
default:
return false;
}
return true;
}
bool PolynomialMultiplyRecognize::highBitsAreZero(Value *V,
unsigned IterCount) {
auto *T = dyn_cast<IntegerType>(V->getType());
if (!T)
return false;
KnownBits Known(T->getBitWidth());
computeKnownBits(V, Known, DL);
return Known.countMinLeadingZeros() >= IterCount;
}
bool PolynomialMultiplyRecognize::keepsHighBitsZero(Value *V,
unsigned IterCount) {
// Assume that all inputs to the value have the high bits zero.
// Check if the value itself preserves the zeros in the high bits.
if (auto *C = dyn_cast<ConstantInt>(V))
return C->getValue().countLeadingZeros() >= IterCount;
if (auto *I = dyn_cast<Instruction>(V)) {
switch (I->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::LShr:
case Instruction::Select:
case Instruction::ICmp:
case Instruction::PHI:
case Instruction::ZExt:
return true;
}
}
return false;
}
bool PolynomialMultiplyRecognize::isOperandShifted(Instruction *I, Value *Op) {
unsigned Opc = I->getOpcode();
if (Opc == Instruction::Shl || Opc == Instruction::LShr)
return Op != I->getOperand(1);
return true;
}
bool PolynomialMultiplyRecognize::convertShiftsToLeft(BasicBlock *LoopB,
BasicBlock *ExitB, unsigned IterCount) {
Value *CIV = getCountIV(LoopB);
if (CIV == nullptr)
return false;
auto *CIVTy = dyn_cast<IntegerType>(CIV->getType());
if (CIVTy == nullptr)
return false;
ValueSeq RShifts;
ValueSeq Early, Late, Cycled;
// Find all value cycles that contain logical right shifts by 1.
for (Instruction &I : *LoopB) {
using namespace PatternMatch;
Value *V = nullptr;
if (!match(&I, m_LShr(m_Value(V), m_One())))
continue;
ValueSeq C;
if (!findCycle(&I, V, C))
continue;
// Found a cycle.
C.insert(&I);
classifyCycle(&I, C, Early, Late);
Cycled.insert(C.begin(), C.end());
RShifts.insert(&I);
}
// Find the set of all values affected by the shift cycles, i.e. all
// cycled values, and (recursively) all their users.
ValueSeq Users(Cycled.begin(), Cycled.end());
for (unsigned i = 0; i < Users.size(); ++i) {
Value *V = Users[i];
if (!isa<IntegerType>(V->getType()))
return false;
auto *R = cast<Instruction>(V);
// If the instruction does not commute with shifts, the loop cannot
// be unshifted.
if (!commutesWithShift(R))
return false;
for (auto I = R->user_begin(), E = R->user_end(); I != E; ++I) {
auto *T = cast<Instruction>(*I);
// Skip users from outside of the loop. They will be handled later.
// Also, skip the right-shifts and phi nodes, since they mix early
// and late values.
if (T->getParent() != LoopB || RShifts.count(T) || isa<PHINode>(T))
continue;
Users.insert(T);
if (!classifyInst(T, Early, Late))
return false;
}
}
if (Users.empty())
return false;
// Verify that high bits remain zero.
ValueSeq Internal(Users.begin(), Users.end());
ValueSeq Inputs;
for (unsigned i = 0; i < Internal.size(); ++i) {
auto *R = dyn_cast<Instruction>(Internal[i]);
if (!R)
continue;
for (Value *Op : R->operands()) {
auto *T = dyn_cast<Instruction>(Op);
if (T && T->getParent() != LoopB)
Inputs.insert(Op);
else
Internal.insert(Op);
}
}
for (Value *V : Inputs)
if (!highBitsAreZero(V, IterCount))
return false;
for (Value *V : Internal)
if (!keepsHighBitsZero(V, IterCount))
return false;
// Finally, the work can be done. Unshift each user.
IRBuilder<> IRB(LoopB);
std::map<Value*,Value*> ShiftMap;
using CastMapType = std::map<std::pair<Value *, Type *>, Value *>;
CastMapType CastMap;
auto upcast = [] (CastMapType &CM, IRBuilder<> &IRB, Value *V,
IntegerType *Ty) -> Value* {
auto H = CM.find(std::make_pair(V, Ty));
if (H != CM.end())
return H->second;
Value *CV = IRB.CreateIntCast(V, Ty, false);
CM.insert(std::make_pair(std::make_pair(V, Ty), CV));
return CV;
};
for (auto I = LoopB->begin(), E = LoopB->end(); I != E; ++I) {
using namespace PatternMatch;
if (isa<PHINode>(I) || !Users.count(&*I))
continue;
// Match lshr x, 1.
Value *V = nullptr;
if (match(&*I, m_LShr(m_Value(V), m_One()))) {
replaceAllUsesOfWithIn(&*I, V, LoopB);
continue;
}
// For each non-cycled operand, replace it with the corresponding
// value shifted left.
for (auto &J : I->operands()) {
Value *Op = J.get();
if (!isOperandShifted(&*I, Op))
continue;
if (Users.count(Op))
continue;
// Skip shifting zeros.
if (isa<ConstantInt>(Op) && cast<ConstantInt>(Op)->isZero())
continue;
// Check if we have already generated a shift for this value.
auto F = ShiftMap.find(Op);
Value *W = (F != ShiftMap.end()) ? F->second : nullptr;
if (W == nullptr) {
IRB.SetInsertPoint(&*I);
// First, the shift amount will be CIV or CIV+1, depending on
// whether the value is early or late. Instead of creating CIV+1,
// do a single shift of the value.
Value *ShAmt = CIV, *ShVal = Op;
auto *VTy = cast<IntegerType>(ShVal->getType());
auto *ATy = cast<IntegerType>(ShAmt->getType());
if (Late.count(&*I))
ShVal = IRB.CreateShl(Op, ConstantInt::get(VTy, 1));
// Second, the types of the shifted value and the shift amount
// must match.
if (VTy != ATy) {
if (VTy->getBitWidth() < ATy->getBitWidth())
ShVal = upcast(CastMap, IRB, ShVal, ATy);
else
ShAmt = upcast(CastMap, IRB, ShAmt, VTy);
}
// Ready to generate the shift and memoize it.
W = IRB.CreateShl(ShVal, ShAmt);
ShiftMap.insert(std::make_pair(Op, W));
}
I->replaceUsesOfWith(Op, W);
}
}
// Update the users outside of the loop to account for having left
// shifts. They would normally be shifted right in the loop, so shift
// them right after the loop exit.
// Take advantage of the loop-closed SSA form, which has all the post-
// loop values in phi nodes.
IRB.SetInsertPoint(ExitB, ExitB->getFirstInsertionPt());
for (auto P = ExitB->begin(), Q = ExitB->end(); P != Q; ++P) {
if (!isa<PHINode>(P))
break;
auto *PN = cast<PHINode>(P);
Value *U = PN->getIncomingValueForBlock(LoopB);
if (!Users.count(U))
continue;
Value *S = IRB.CreateLShr(PN, ConstantInt::get(PN->getType(), IterCount));
PN->replaceAllUsesWith(S);
// The above RAUW will create
// S = lshr S, IterCount
// so we need to fix it back into
// S = lshr PN, IterCount
cast<User>(S)->replaceUsesOfWith(S, PN);
}
return true;
}
void PolynomialMultiplyRecognize::cleanupLoopBody(BasicBlock *LoopB) {
for (auto &I : *LoopB)
if (Value *SV = SimplifyInstruction(&I, {DL, &TLI, &DT}))
I.replaceAllUsesWith(SV);
for (auto I = LoopB->begin(), N = I; I != LoopB->end(); I = N) {
N = std::next(I);
RecursivelyDeleteTriviallyDeadInstructions(&*I, &TLI);
}
}
unsigned PolynomialMultiplyRecognize::getInverseMxN(unsigned QP) {
// Arrays of coefficients of Q and the inverse, C.
// Q[i] = coefficient at x^i.
std::array<char,32> Q, C;
for (unsigned i = 0; i < 32; ++i) {
Q[i] = QP & 1;
QP >>= 1;
}
assert(Q[0] == 1);
// Find C, such that
// (Q[n]*x^n + ... + Q[1]*x + Q[0]) * (C[n]*x^n + ... + C[1]*x + C[0]) = 1
//
// For it to have a solution, Q[0] must be 1. Since this is Z2[x], the
// operations * and + are & and ^ respectively.
//
// Find C[i] recursively, by comparing i-th coefficient in the product
// with 0 (or 1 for i=0).
//
// C[0] = 1, since C[0] = Q[0], and Q[0] = 1.
C[0] = 1;
for (unsigned i = 1; i < 32; ++i) {
// Solve for C[i] in:
// C[0]Q[i] ^ C[1]Q[i-1] ^ ... ^ C[i-1]Q[1] ^ C[i]Q[0] = 0
// This is equivalent to
// C[0]Q[i] ^ C[1]Q[i-1] ^ ... ^ C[i-1]Q[1] ^ C[i] = 0
// which is
// C[0]Q[i] ^ C[1]Q[i-1] ^ ... ^ C[i-1]Q[1] = C[i]
unsigned T = 0;
for (unsigned j = 0; j < i; ++j)
T = T ^ (C[j] & Q[i-j]);
C[i] = T;
}
unsigned QV = 0;
for (unsigned i = 0; i < 32; ++i)
if (C[i])
QV |= (1 << i);
return QV;
}
Value *PolynomialMultiplyRecognize::generate(BasicBlock::iterator At,
ParsedValues &PV) {
IRBuilder<> B(&*At);
Module *M = At->getParent()->getParent()->getParent();
Value *PMF = Intrinsic::getDeclaration(M, Intrinsic::hexagon_M4_pmpyw);
Value *P = PV.P, *Q = PV.Q, *P0 = P;
unsigned IC = PV.IterCount;
if (PV.M != nullptr)
P0 = P = B.CreateXor(P, PV.M);
// Create a bit mask to clear the high bits beyond IterCount.
auto *BMI = ConstantInt::get(P->getType(), APInt::getLowBitsSet(32, IC));
if (PV.IterCount != 32)
P = B.CreateAnd(P, BMI);
if (PV.Inv) {
auto *QI = dyn_cast<ConstantInt>(PV.Q);
assert(QI && QI->getBitWidth() <= 32);
// Again, clearing bits beyond IterCount.
unsigned M = (1 << PV.IterCount) - 1;
unsigned Tmp = (QI->getZExtValue() | 1) & M;
unsigned QV = getInverseMxN(Tmp) & M;
auto *QVI = ConstantInt::get(QI->getType(), QV);
P = B.CreateCall(PMF, {P, QVI});
P = B.CreateTrunc(P, QI->getType());
if (IC != 32)
P = B.CreateAnd(P, BMI);
}
Value *R = B.CreateCall(PMF, {P, Q});
if (PV.M != nullptr)
R = B.CreateXor(R, B.CreateIntCast(P0, R->getType(), false));
return R;
}
static bool hasZeroSignBit(const Value *V) {
if (const auto *CI = dyn_cast<const ConstantInt>(V))
return (CI->getType()->getSignBit() & CI->getSExtValue()) == 0;
const Instruction *I = dyn_cast<const Instruction>(V);
if (!I)
return false;
switch (I->getOpcode()) {
case Instruction::LShr:
if (const auto SI = dyn_cast<const ConstantInt>(I->getOperand(1)))
return SI->getZExtValue() > 0;
return false;
case Instruction::Or:
case Instruction::Xor:
return hasZeroSignBit(I->getOperand(0)) &&
hasZeroSignBit(I->getOperand(1));
case Instruction::And:
return hasZeroSignBit(I->getOperand(0)) ||
hasZeroSignBit(I->getOperand(1));
}
return false;
}
void PolynomialMultiplyRecognize::setupSimplifier() {
Simp.addRule("sink-zext",
// Sink zext past bitwise operations.
[](Instruction *I, LLVMContext &Ctx) -> Value* {
if (I->getOpcode() != Instruction::ZExt)
return nullptr;
Instruction *T = dyn_cast<Instruction>(I->getOperand(0));
if (!T)
return nullptr;
switch (T->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
break;
default:
return nullptr;
}
IRBuilder<> B(Ctx);
return B.CreateBinOp(cast<BinaryOperator>(T)->getOpcode(),
B.CreateZExt(T->getOperand(0), I->getType()),
B.CreateZExt(T->getOperand(1), I->getType()));
});
Simp.addRule("xor/and -> and/xor",
// (xor (and x a) (and y a)) -> (and (xor x y) a)
[](Instruction *I, LLVMContext &Ctx) -> Value* {
if (I->getOpcode() != Instruction::Xor)
return nullptr;
Instruction *And0 = dyn_cast<Instruction>(I->getOperand(0));
Instruction *And1 = dyn_cast<Instruction>(I->getOperand(1));
if (!And0 || !And1)
return nullptr;
if (And0->getOpcode() != Instruction::And ||
And1->getOpcode() != Instruction::And)
return nullptr;
if (And0->getOperand(1) != And1->getOperand(1))
return nullptr;
IRBuilder<> B(Ctx);
return B.CreateAnd(B.CreateXor(And0->getOperand(0), And1->getOperand(0)),
And0->getOperand(1));
});
Simp.addRule("sink binop into select",
// (Op (select c x y) z) -> (select c (Op x z) (Op y z))
// (Op x (select c y z)) -> (select c (Op x y) (Op x z))
[](Instruction *I, LLVMContext &Ctx) -> Value* {
BinaryOperator *BO = dyn_cast<BinaryOperator>(I);
if (!BO)
return nullptr;
Instruction::BinaryOps Op = BO->getOpcode();
if (SelectInst *Sel = dyn_cast<SelectInst>(BO->getOperand(0))) {
IRBuilder<> B(Ctx);
Value *X = Sel->getTrueValue(), *Y = Sel->getFalseValue();
Value *Z = BO->getOperand(1);
return B.CreateSelect(Sel->getCondition(),
B.CreateBinOp(Op, X, Z),
B.CreateBinOp(Op, Y, Z));
}
if (SelectInst *Sel = dyn_cast<SelectInst>(BO->getOperand(1))) {
IRBuilder<> B(Ctx);
Value *X = BO->getOperand(0);
Value *Y = Sel->getTrueValue(), *Z = Sel->getFalseValue();
return B.CreateSelect(Sel->getCondition(),
B.CreateBinOp(Op, X, Y),
B.CreateBinOp(Op, X, Z));
}
return nullptr;
});
Simp.addRule("fold select-select",
// (select c (select c x y) z) -> (select c x z)
// (select c x (select c y z)) -> (select c x z)
[](Instruction *I, LLVMContext &Ctx) -> Value* {
SelectInst *Sel = dyn_cast<SelectInst>(I);
if (!Sel)
return nullptr;
IRBuilder<> B(Ctx);
Value *C = Sel->getCondition();
if (SelectInst *Sel0 = dyn_cast<SelectInst>(Sel->getTrueValue())) {
if (Sel0->getCondition() == C)
return B.CreateSelect(C, Sel0->getTrueValue(), Sel->getFalseValue());
}
if (SelectInst *Sel1 = dyn_cast<SelectInst>(Sel->getFalseValue())) {
if (Sel1->getCondition() == C)
return B.CreateSelect(C, Sel->getTrueValue(), Sel1->getFalseValue());
}
return nullptr;
});
Simp.addRule("or-signbit -> xor-signbit",
// (or (lshr x 1) 0x800.0) -> (xor (lshr x 1) 0x800.0)
[](Instruction *I, LLVMContext &Ctx) -> Value* {
if (I->getOpcode() != Instruction::Or)
return nullptr;
ConstantInt *Msb = dyn_cast<ConstantInt>(I->getOperand(1));
if (!Msb || Msb->getZExtValue() != Msb->getType()->getSignBit())
return nullptr;
if (!hasZeroSignBit(I->getOperand(0)))
return nullptr;
return IRBuilder<>(Ctx).CreateXor(I->getOperand(0), Msb);
});
Simp.addRule("sink lshr into binop",
// (lshr (BitOp x y) c) -> (BitOp (lshr x c) (lshr y c))
[](Instruction *I, LLVMContext &Ctx) -> Value* {
if (I->getOpcode() != Instruction::LShr)
return nullptr;
BinaryOperator *BitOp = dyn_cast<BinaryOperator>(I->getOperand(0));
if (!BitOp)
return nullptr;
switch (BitOp->getOpcode()) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
break;
default:
return nullptr;
}
IRBuilder<> B(Ctx);
Value *S = I->getOperand(1);
return B.CreateBinOp(BitOp->getOpcode(),
B.CreateLShr(BitOp->getOperand(0), S),
B.CreateLShr(BitOp->getOperand(1), S));
});
Simp.addRule("expose bitop-const",
// (BitOp1 (BitOp2 x a) b) -> (BitOp2 x (BitOp1 a b))
[](Instruction *I, LLVMContext &Ctx) -> Value* {
auto IsBitOp = [](unsigned Op) -> bool {
switch (Op) {
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
return true;
}
return false;
};
BinaryOperator *BitOp1 = dyn_cast<BinaryOperator>(I);
if (!BitOp1 || !IsBitOp(BitOp1->getOpcode()))
return nullptr;
BinaryOperator *BitOp2 = dyn_cast<BinaryOperator>(BitOp1->getOperand(0));
if (!BitOp2 || !IsBitOp(BitOp2->getOpcode()))
return nullptr;
ConstantInt *CA = dyn_cast<ConstantInt>(BitOp2->getOperand(1));
ConstantInt *CB = dyn_cast<ConstantInt>(BitOp1->getOperand(1));
if (!CA || !CB)
return nullptr;
IRBuilder<> B(Ctx);
Value *X = BitOp2->getOperand(0);
return B.CreateBinOp(BitOp2->getOpcode(), X,
B.CreateBinOp(BitOp1->getOpcode(), CA, CB));
});
}
bool PolynomialMultiplyRecognize::recognize() {
DEBUG(dbgs() << "Starting PolynomialMultiplyRecognize on loop\n"
<< *CurLoop << '\n');
// Restrictions:
// - The loop must consist of a single block.
// - The iteration count must be known at compile-time.
// - The loop must have an induction variable starting from 0, and
// incremented in each iteration of the loop.
BasicBlock *LoopB = CurLoop->getHeader();
DEBUG(dbgs() << "Loop header:\n" << *LoopB);
if (LoopB != CurLoop->getLoopLatch())
return false;
BasicBlock *ExitB = CurLoop->getExitBlock();
if (ExitB == nullptr)
return false;
BasicBlock *EntryB = CurLoop->getLoopPreheader();
if (EntryB == nullptr)
return false;
unsigned IterCount = 0;
const SCEV *CT = SE.getBackedgeTakenCount(CurLoop);
if (isa<SCEVCouldNotCompute>(CT))
return false;
if (auto *CV = dyn_cast<SCEVConstant>(CT))
IterCount = CV->getValue()->getZExtValue() + 1;
Value *CIV = getCountIV(LoopB);
ParsedValues PV;
PV.IterCount = IterCount;
DEBUG(dbgs() << "Loop IV: " << *CIV << "\nIterCount: " << IterCount << '\n');
setupSimplifier();
// Perform a preliminary scan of select instructions to see if any of them
// looks like a generator of the polynomial multiply steps. Assume that a
// loop can only contain a single transformable operation, so stop the
// traversal after the first reasonable candidate was found.
// XXX: Currently this approach can modify the loop before being 100% sure
// that the transformation can be carried out.
bool FoundPreScan = false;
auto FeedsPHI = [LoopB](const Value *V) -> bool {
for (const Value *U : V->users()) {
if (const auto *P = dyn_cast<const PHINode>(U))
if (P->getParent() == LoopB)
return true;
}
return false;
};
for (Instruction &In : *LoopB) {
SelectInst *SI = dyn_cast<SelectInst>(&In);
if (!SI || !FeedsPHI(SI))
continue;
Simplifier::Context C(SI);
Value *T = Simp.simplify(C);
SelectInst *SelI = (T && isa<SelectInst>(T)) ? cast<SelectInst>(T) : SI;
DEBUG(dbgs() << "scanSelect(pre-scan): " << PE(C, SelI) << '\n');
if (scanSelect(SelI, LoopB, EntryB, CIV, PV, true)) {
FoundPreScan = true;
if (SelI != SI) {
Value *NewSel = C.materialize(LoopB, SI->getIterator());
SI->replaceAllUsesWith(NewSel);
RecursivelyDeleteTriviallyDeadInstructions(SI, &TLI);
}
break;
}
}
if (!FoundPreScan) {
DEBUG(dbgs() << "Have not found candidates for pmpy\n");
return false;
}
if (!PV.Left) {
// The right shift version actually only returns the higher bits of
// the result (each iteration discards the LSB). If we want to convert it
// to a left-shifting loop, the working data type must be at least as
// wide as the target's pmpy instruction.
if (!promoteTypes(LoopB, ExitB))
return false;
if (!convertShiftsToLeft(LoopB, ExitB, IterCount))
return false;
cleanupLoopBody(LoopB);
}
// Scan the loop again, find the generating select instruction.
bool FoundScan = false;
for (Instruction &In : *LoopB) {
SelectInst *SelI = dyn_cast<SelectInst>(&In);
if (!SelI)
continue;
DEBUG(dbgs() << "scanSelect: " << *SelI << '\n');
FoundScan = scanSelect(SelI, LoopB, EntryB, CIV, PV, false);
if (FoundScan)
break;
}
assert(FoundScan);
DEBUG({
StringRef PP = (PV.M ? "(P+M)" : "P");
if (!PV.Inv)
dbgs() << "Found pmpy idiom: R = " << PP << ".Q\n";
else
dbgs() << "Found inverse pmpy idiom: R = (" << PP << "/Q).Q) + "
<< PP << "\n";
dbgs() << " Res:" << *PV.Res << "\n P:" << *PV.P << "\n";
if (PV.M)
dbgs() << " M:" << *PV.M << "\n";
dbgs() << " Q:" << *PV.Q << "\n";
dbgs() << " Iteration count:" << PV.IterCount << "\n";
});
BasicBlock::iterator At(EntryB->getTerminator());
Value *PM = generate(At, PV);
if (PM == nullptr)
return false;
if (PM->getType() != PV.Res->getType())
PM = IRBuilder<>(&*At).CreateIntCast(PM, PV.Res->getType(), false);
PV.Res->replaceAllUsesWith(PM);
PV.Res->eraseFromParent();
return true;
}
int HexagonLoopIdiomRecognize::getSCEVStride(const SCEVAddRecExpr *S) {
if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(1)))
return SC->getAPInt().getSExtValue();
return 0;
}
bool HexagonLoopIdiomRecognize::isLegalStore(Loop *CurLoop, StoreInst *SI) {
// Allow volatile stores if HexagonVolatileMemcpy is enabled.
if (!(SI->isVolatile() && HexagonVolatileMemcpy) && !SI->isSimple())
return false;
Value *StoredVal = SI->getValueOperand();
Value *StorePtr = SI->getPointerOperand();
// Reject stores that are so large that they overflow an unsigned.
uint64_t SizeInBits = DL->getTypeSizeInBits(StoredVal->getType());
if ((SizeInBits & 7) || (SizeInBits >> 32) != 0)
return false;
// See if the pointer expression is an AddRec like {base,+,1} on the current
// loop, which indicates a strided store. If we have something else, it's a
// random store we can't handle.
auto *StoreEv = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
if (!StoreEv || StoreEv->getLoop() != CurLoop || !StoreEv->isAffine())
return false;
// Check to see if the stride matches the size of the store. If so, then we
// know that every byte is touched in the loop.
int Stride = getSCEVStride(StoreEv);
if (Stride == 0)
return false;
unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());
if (StoreSize != unsigned(std::abs(Stride)))
return false;
// The store must be feeding a non-volatile load.
LoadInst *LI = dyn_cast<LoadInst>(SI->getValueOperand());
if (!LI || !LI->isSimple())
return false;
// See if the pointer expression is an AddRec like {base,+,1} on the current
// loop, which indicates a strided load. If we have something else, it's a
// random load we can't handle.
Value *LoadPtr = LI->getPointerOperand();
auto *LoadEv = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(LoadPtr));
if (!LoadEv || LoadEv->getLoop() != CurLoop || !LoadEv->isAffine())
return false;
// The store and load must share the same stride.
if (StoreEv->getOperand(1) != LoadEv->getOperand(1))
return false;
// Success. This store can be converted into a memcpy.
return true;
}
/// mayLoopAccessLocation - Return true if the specified loop might access the
/// specified pointer location, which is a loop-strided access. The 'Access'
/// argument specifies what the verboten forms of access are (read or write).
static bool
mayLoopAccessLocation(Value *Ptr, ModRefInfo Access, Loop *L,
const SCEV *BECount, unsigned StoreSize,
AliasAnalysis &AA,
SmallPtrSetImpl<Instruction *> &Ignored) {
// Get the location that may be stored across the loop. Since the access
// is strided positively through memory, we say that the modified location
// starts at the pointer and has infinite size.
uint64_t AccessSize = MemoryLocation::UnknownSize;
// If the loop iterates a fixed number of times, we can refine the access
// size to be exactly the size of the memset, which is (BECount+1)*StoreSize
if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
AccessSize = (BECst->getValue()->getZExtValue() + 1) * StoreSize;
// TODO: For this to be really effective, we have to dive into the pointer
// operand in the store. Store to &A[i] of 100 will always return may alias
// with store of &A[100], we need to StoreLoc to be "A" with size of 100,
// which will then no-alias a store to &A[100].
MemoryLocation StoreLoc(Ptr, AccessSize);
for (auto *B : L->blocks())
for (auto &I : *B)
if (Ignored.count(&I) == 0 &&
isModOrRefSet(
intersectModRef(AA.getModRefInfo(&I, StoreLoc), Access)))
return true;
return false;
}
void HexagonLoopIdiomRecognize::collectStores(Loop *CurLoop, BasicBlock *BB,
SmallVectorImpl<StoreInst*> &Stores) {
Stores.clear();
for (Instruction &I : *BB)
if (StoreInst *SI = dyn_cast<StoreInst>(&I))
if (isLegalStore(CurLoop, SI))
Stores.push_back(SI);
}
bool HexagonLoopIdiomRecognize::processCopyingStore(Loop *CurLoop,
StoreInst *SI, const SCEV *BECount) {
assert((SI->isSimple() || (SI->isVolatile() && HexagonVolatileMemcpy)) &&
"Expected only non-volatile stores, or Hexagon-specific memcpy"
"to volatile destination.");
Value *StorePtr = SI->getPointerOperand();
auto *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
unsigned Stride = getSCEVStride(StoreEv);
unsigned StoreSize = DL->getTypeStoreSize(SI->getValueOperand()->getType());
if (Stride != StoreSize)
return false;
// See if the pointer expression is an AddRec like {base,+,1} on the current
// loop, which indicates a strided load. If we have something else, it's a
// random load we can't handle.
LoadInst *LI = dyn_cast<LoadInst>(SI->getValueOperand());
auto *LoadEv = cast<SCEVAddRecExpr>(SE->getSCEV(LI->getPointerOperand()));
// The trip count of the loop and the base pointer of the addrec SCEV is
// guaranteed to be loop invariant, which means that it should dominate the
// header. This allows us to insert code for it in the preheader.
BasicBlock *Preheader = CurLoop->getLoopPreheader();
Instruction *ExpPt = Preheader->getTerminator();
IRBuilder<> Builder(ExpPt);
SCEVExpander Expander(*SE, *DL, "hexagon-loop-idiom");
Type *IntPtrTy = Builder.getIntPtrTy(*DL, SI->getPointerAddressSpace());
// Okay, we have a strided store "p[i]" of a loaded value. We can turn
// this into a memcpy/memmove in the loop preheader now if we want. However,
// this would be unsafe to do if there is anything else in the loop that may
// read or write the memory region we're storing to. For memcpy, this
// includes the load that feeds the stores. Check for an alias by generating
// the base address and checking everything.
Value *StoreBasePtr = Expander.expandCodeFor(StoreEv->getStart(),
Builder.getInt8PtrTy(SI->getPointerAddressSpace()), ExpPt);
Value *LoadBasePtr = nullptr;
bool Overlap = false;
bool DestVolatile = SI->isVolatile();
Type *BECountTy = BECount->getType();
if (DestVolatile) {
// The trip count must fit in i32, since it is the type of the "num_words"
// argument to hexagon_memcpy_forward_vp4cp4n2.
if (StoreSize != 4 || DL->getTypeSizeInBits(BECountTy) > 32) {
CleanupAndExit:
// If we generated new code for the base pointer, clean up.
Expander.clear();
if (StoreBasePtr && (LoadBasePtr != StoreBasePtr)) {
RecursivelyDeleteTriviallyDeadInstructions(StoreBasePtr, TLI);
StoreBasePtr = nullptr;
}
if (LoadBasePtr) {
RecursivelyDeleteTriviallyDeadInstructions(LoadBasePtr, TLI);
LoadBasePtr = nullptr;
}
return false;
}
}
SmallPtrSet<Instruction*, 2> Ignore1;
Ignore1.insert(SI);
if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop, BECount,
StoreSize, *AA, Ignore1)) {
// Check if the load is the offending instruction.
Ignore1.insert(LI);
if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop,
BECount, StoreSize, *AA, Ignore1)) {
// Still bad. Nothing we can do.
goto CleanupAndExit;
}
// It worked with the load ignored.
Overlap = true;
}
if (!Overlap) {
if (DisableMemcpyIdiom || !HasMemcpy)
goto CleanupAndExit;
} else {
// Don't generate memmove if this function will be inlined. This is
// because the caller will undergo this transformation after inlining.
Function *Func = CurLoop->getHeader()->getParent();
if (Func->hasFnAttribute(Attribute::AlwaysInline))
goto CleanupAndExit;
// In case of a memmove, the call to memmove will be executed instead
// of the loop, so we need to make sure that there is nothing else in
// the loop than the load, store and instructions that these two depend
// on.
SmallVector<Instruction*,2> Insts;
Insts.push_back(SI);
Insts.push_back(LI);
if (!coverLoop(CurLoop, Insts))
goto CleanupAndExit;
if (DisableMemmoveIdiom || !HasMemmove)
goto CleanupAndExit;
bool IsNested = CurLoop->getParentLoop() != nullptr;
if (IsNested && OnlyNonNestedMemmove)
goto CleanupAndExit;
}
// For a memcpy, we have to make sure that the input array is not being
// mutated by the loop.
LoadBasePtr = Expander.expandCodeFor(LoadEv->getStart(),
Builder.getInt8PtrTy(LI->getPointerAddressSpace()), ExpPt);
SmallPtrSet<Instruction*, 2> Ignore2;
Ignore2.insert(SI);
if (mayLoopAccessLocation(LoadBasePtr, ModRefInfo::Mod, CurLoop, BECount,
StoreSize, *AA, Ignore2))
goto CleanupAndExit;
// Check the stride.
bool StridePos = getSCEVStride(LoadEv) >= 0;
// Currently, the volatile memcpy only emulates traversing memory forward.
if (!StridePos && DestVolatile)
goto CleanupAndExit;
bool RuntimeCheck = (Overlap || DestVolatile);
BasicBlock *ExitB;
if (RuntimeCheck) {
// The runtime check needs a single exit block.
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
if (ExitBlocks.size() != 1)
goto CleanupAndExit;
ExitB = ExitBlocks[0];
}
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
LLVMContext &Ctx = SI->getContext();
BECount = SE->getTruncateOrZeroExtend(BECount, IntPtrTy);
unsigned Alignment = std::min(SI->getAlignment(), LI->getAlignment());
DebugLoc DLoc = SI->getDebugLoc();
const SCEV *NumBytesS =
SE->getAddExpr(BECount, SE->getOne(IntPtrTy), SCEV::FlagNUW);
if (StoreSize != 1)
NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtrTy, StoreSize),
SCEV::FlagNUW);
Value *NumBytes = Expander.expandCodeFor(NumBytesS, IntPtrTy, ExpPt);
if (Instruction *In = dyn_cast<Instruction>(NumBytes))
if (Value *Simp = SimplifyInstruction(In, {*DL, TLI, DT}))
NumBytes = Simp;
CallInst *NewCall;
if (RuntimeCheck) {
unsigned Threshold = RuntimeMemSizeThreshold;
if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes)) {
uint64_t C = CI->getZExtValue();
if (Threshold != 0 && C < Threshold)
goto CleanupAndExit;
if (C < CompileTimeMemSizeThreshold)
goto CleanupAndExit;
}
BasicBlock *Header = CurLoop->getHeader();
Function *Func = Header->getParent();
Loop *ParentL = LF->getLoopFor(Preheader);
StringRef HeaderName = Header->getName();
// Create a new (empty) preheader, and update the PHI nodes in the
// header to use the new preheader.
BasicBlock *NewPreheader = BasicBlock::Create(Ctx, HeaderName+".rtli.ph",
Func, Header);
if (ParentL)
ParentL->addBasicBlockToLoop(NewPreheader, *LF);
IRBuilder<>(NewPreheader).CreateBr(Header);
for (auto &In : *Header) {
PHINode *PN = dyn_cast<PHINode>(&In);
if (!PN)
break;
int bx = PN->getBasicBlockIndex(Preheader);
if (bx >= 0)
PN->setIncomingBlock(bx, NewPreheader);
}
DT->addNewBlock(NewPreheader, Preheader);
DT->changeImmediateDominator(Header, NewPreheader);
// Check for safe conditions to execute memmove.
// If stride is positive, copying things from higher to lower addresses
// is equivalent to memmove. For negative stride, it's the other way
// around. Copying forward in memory with positive stride may not be
// same as memmove since we may be copying values that we just stored
// in some previous iteration.
Value *LA = Builder.CreatePtrToInt(LoadBasePtr, IntPtrTy);
Value *SA = Builder.CreatePtrToInt(StoreBasePtr, IntPtrTy);
Value *LowA = StridePos ? SA : LA;
Value *HighA = StridePos ? LA : SA;
Value *CmpA = Builder.CreateICmpULT(LowA, HighA);
Value *Cond = CmpA;
// Check for distance between pointers. Since the case LowA < HighA
// is checked for above, assume LowA >= HighA.
Value *Dist = Builder.CreateSub(LowA, HighA);
Value *CmpD = Builder.CreateICmpSLE(NumBytes, Dist);
Value *CmpEither = Builder.CreateOr(Cond, CmpD);
Cond = CmpEither;
if (Threshold != 0) {
Type *Ty = NumBytes->getType();
Value *Thr = ConstantInt::get(Ty, Threshold);
Value *CmpB = Builder.CreateICmpULT(Thr, NumBytes);
Value *CmpBoth = Builder.CreateAnd(Cond, CmpB);
Cond = CmpBoth;
}
BasicBlock *MemmoveB = BasicBlock::Create(Ctx, Header->getName()+".rtli",
Func, NewPreheader);
if (ParentL)
ParentL->addBasicBlockToLoop(MemmoveB, *LF);
Instruction *OldT = Preheader->getTerminator();
Builder.CreateCondBr(Cond, MemmoveB, NewPreheader);
OldT->eraseFromParent();
Preheader->setName(Preheader->getName()+".old");
DT->addNewBlock(MemmoveB, Preheader);
// Find the new immediate dominator of the exit block.
BasicBlock *ExitD = Preheader;
for (auto PI = pred_begin(ExitB), PE = pred_end(ExitB); PI != PE; ++PI) {
BasicBlock *PB = *PI;
ExitD = DT->findNearestCommonDominator(ExitD, PB);
if (!ExitD)
break;
}
// If the prior immediate dominator of ExitB was dominated by the
// old preheader, then the old preheader becomes the new immediate
// dominator. Otherwise don't change anything (because the newly
// added blocks are dominated by the old preheader).
if (ExitD && DT->dominates(Preheader, ExitD)) {
DomTreeNode *BN = DT->getNode(ExitB);
DomTreeNode *DN = DT->getNode(ExitD);
BN->setIDom(DN);
}
// Add a call to memmove to the conditional block.
IRBuilder<> CondBuilder(MemmoveB);
CondBuilder.CreateBr(ExitB);
CondBuilder.SetInsertPoint(MemmoveB->getTerminator());
if (DestVolatile) {
Type *Int32Ty = Type::getInt32Ty(Ctx);
Type *Int32PtrTy = Type::getInt32PtrTy(Ctx);
Type *VoidTy = Type::getVoidTy(Ctx);
Module *M = Func->getParent();
Constant *CF = M->getOrInsertFunction(HexagonVolatileMemcpyName, VoidTy,
Int32PtrTy, Int32PtrTy, Int32Ty);
Function *Fn = cast<Function>(CF);
Fn->setLinkage(Function::ExternalLinkage);
const SCEV *OneS = SE->getConstant(Int32Ty, 1);
const SCEV *BECount32 = SE->getTruncateOrZeroExtend(BECount, Int32Ty);
const SCEV *NumWordsS = SE->getAddExpr(BECount32, OneS, SCEV::FlagNUW);
Value *NumWords = Expander.expandCodeFor(NumWordsS, Int32Ty,
MemmoveB->getTerminator());
if (Instruction *In = dyn_cast<Instruction>(NumWords))
if (Value *Simp = SimplifyInstruction(In, {*DL, TLI, DT}))
NumWords = Simp;
Value *Op0 = (StoreBasePtr->getType() == Int32PtrTy)
? StoreBasePtr
: CondBuilder.CreateBitCast(StoreBasePtr, Int32PtrTy);
Value *Op1 = (LoadBasePtr->getType() == Int32PtrTy)
? LoadBasePtr
: CondBuilder.CreateBitCast(LoadBasePtr, Int32PtrTy);
NewCall = CondBuilder.CreateCall(Fn, {Op0, Op1, NumWords});
} else {
NewCall = CondBuilder.CreateMemMove(StoreBasePtr, LoadBasePtr,
NumBytes, Alignment);
}
} else {
NewCall = Builder.CreateMemCpy(StoreBasePtr, LoadBasePtr,
NumBytes, Alignment);
// Okay, the memcpy has been formed. Zap the original store and
// anything that feeds into it.
RecursivelyDeleteTriviallyDeadInstructions(SI, TLI);
}
NewCall->setDebugLoc(DLoc);
DEBUG(dbgs() << " Formed " << (Overlap ? "memmove: " : "memcpy: ")
<< *NewCall << "\n"
<< " from load ptr=" << *LoadEv << " at: " << *LI << "\n"
<< " from store ptr=" << *StoreEv << " at: " << *SI << "\n");
return true;
}
// \brief Check if the instructions in Insts, together with their dependencies
// cover the loop in the sense that the loop could be safely eliminated once
// the instructions in Insts are removed.
bool HexagonLoopIdiomRecognize::coverLoop(Loop *L,
SmallVectorImpl<Instruction*> &Insts) const {
SmallSet<BasicBlock*,8> LoopBlocks;
for (auto *B : L->blocks())
LoopBlocks.insert(B);
SetVector<Instruction*> Worklist(Insts.begin(), Insts.end());
// Collect all instructions from the loop that the instructions in Insts
// depend on (plus their dependencies, etc.). These instructions will
// constitute the expression trees that feed those in Insts, but the trees
// will be limited only to instructions contained in the loop.
for (unsigned i = 0; i < Worklist.size(); ++i) {
Instruction *In = Worklist[i];
for (auto I = In->op_begin(), E = In->op_end(); I != E; ++I) {
Instruction *OpI = dyn_cast<Instruction>(I);
if (!OpI)
continue;
BasicBlock *PB = OpI->getParent();
if (!LoopBlocks.count(PB))
continue;
Worklist.insert(OpI);
}
}
// Scan all instructions in the loop, if any of them have a user outside
// of the loop, or outside of the expressions collected above, then either
// the loop has a side-effect visible outside of it, or there are
// instructions in it that are not involved in the original set Insts.
for (auto *B : L->blocks()) {
for (auto &In : *B) {
if (isa<BranchInst>(In) || isa<DbgInfoIntrinsic>(In))
continue;
if (!Worklist.count(&In) && In.mayHaveSideEffects())
return false;
for (const auto &K : In.users()) {
Instruction *UseI = dyn_cast<Instruction>(K);
if (!UseI)
continue;
BasicBlock *UseB = UseI->getParent();
if (LF->getLoopFor(UseB) != L)
return false;
}
}
}
return true;
}
/// runOnLoopBlock - Process the specified block, which lives in a counted loop
/// with the specified backedge count. This block is known to be in the current
/// loop and not in any subloops.
bool HexagonLoopIdiomRecognize::runOnLoopBlock(Loop *CurLoop, BasicBlock *BB,
const SCEV *BECount, SmallVectorImpl<BasicBlock*> &ExitBlocks) {
// We can only promote stores in this block if they are unconditionally
// executed in the loop. For a block to be unconditionally executed, it has
// to dominate all the exit blocks of the loop. Verify this now.
auto DominatedByBB = [this,BB] (BasicBlock *EB) -> bool {
return DT->dominates(BB, EB);
};
if (!std::all_of(ExitBlocks.begin(), ExitBlocks.end(), DominatedByBB))
return false;
bool MadeChange = false;
// Look for store instructions, which may be optimized to memset/memcpy.
SmallVector<StoreInst*,8> Stores;
collectStores(CurLoop, BB, Stores);
// Optimize the store into a memcpy, if it feeds an similarly strided load.
for (auto &SI : Stores)
MadeChange |= processCopyingStore(CurLoop, SI, BECount);
return MadeChange;
}
bool HexagonLoopIdiomRecognize::runOnCountableLoop(Loop *L) {
PolynomialMultiplyRecognize PMR(L, *DL, *DT, *TLI, *SE);
if (PMR.recognize())
return true;
if (!HasMemcpy && !HasMemmove)
return false;
const SCEV *BECount = SE->getBackedgeTakenCount(L);
assert(!isa<SCEVCouldNotCompute>(BECount) &&
"runOnCountableLoop() called on a loop without a predictable"
"backedge-taken count");
SmallVector<BasicBlock *, 8> ExitBlocks;
L->getUniqueExitBlocks(ExitBlocks);
bool Changed = false;
// Scan all the blocks in the loop that are not in subloops.
for (auto *BB : L->getBlocks()) {
// Ignore blocks in subloops.
if (LF->getLoopFor(BB) != L)
continue;
Changed |= runOnLoopBlock(L, BB, BECount, ExitBlocks);
}
return Changed;
}
bool HexagonLoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
const Module &M = *L->getHeader()->getParent()->getParent();
if (Triple(M.getTargetTriple()).getArch() != Triple::hexagon)
return false;
if (skipLoop(L))
return false;
// If the loop could not be converted to canonical form, it must have an
// indirectbr in it, just give up.
if (!L->getLoopPreheader())
return false;
// Disable loop idiom recognition if the function's name is a common idiom.
StringRef Name = L->getHeader()->getParent()->getName();
if (Name == "memset" || Name == "memcpy" || Name == "memmove")
return false;
AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
DL = &L->getHeader()->getModule()->getDataLayout();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
LF = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
HasMemcpy = TLI->has(LibFunc_memcpy);
HasMemmove = TLI->has(LibFunc_memmove);
if (SE->hasLoopInvariantBackedgeTakenCount(L))
return runOnCountableLoop(L);
return false;
}
Pass *llvm::createHexagonLoopIdiomPass() {
return new HexagonLoopIdiomRecognize();
}
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