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-rw-r--r--llvm/lib/Target/X86/X86OptimizeLEAs.cpp404
1 files changed, 400 insertions, 4 deletions
diff --git a/llvm/lib/Target/X86/X86OptimizeLEAs.cpp b/llvm/lib/Target/X86/X86OptimizeLEAs.cpp
index 896f6251889..fb0451c5cd8 100644
--- a/llvm/lib/Target/X86/X86OptimizeLEAs.cpp
+++ b/llvm/lib/Target/X86/X86OptimizeLEAs.cpp
@@ -22,6 +22,7 @@
#include "X86Subtarget.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOperand.h"
@@ -44,6 +45,7 @@ static cl::opt<bool>
cl::init(false));
STATISTIC(NumSubstLEAs, "Number of LEA instruction substitutions");
+STATISTIC(NumFactoredLEAs, "Number of LEAs factorized");
STATISTIC(NumRedundantLEAs, "Number of redundant LEA instructions removed");
/// \brief Returns true if two machine operands are identical and they are not
@@ -51,6 +53,10 @@ STATISTIC(NumRedundantLEAs, "Number of redundant LEA instructions removed");
static inline bool isIdenticalOp(const MachineOperand &MO1,
const MachineOperand &MO2);
+/// \brief Returns true if two machine instructions have identical operands.
+static bool isIdenticalMI(MachineRegisterInfo *MRI, const MachineOperand &MO1,
+ const MachineOperand &MO2);
+
/// \brief Returns true if two address displacement operands are of the same
/// type and use the same symbol/index/address regardless of the offset.
static bool isSimilarDispOp(const MachineOperand &MO1,
@@ -59,21 +65,44 @@ static bool isSimilarDispOp(const MachineOperand &MO1,
/// \brief Returns true if the instruction is LEA.
static inline bool isLEA(const MachineInstr &MI);
+/// \brief Returns true if Definition of Operand is a copylike instruction.
+static bool isDefCopyLike(MachineRegisterInfo *MRI, const MachineOperand &Opr);
+
namespace {
/// A key based on instruction's memory operands.
class MemOpKey {
public:
MemOpKey(const MachineOperand *Base, const MachineOperand *Scale,
const MachineOperand *Index, const MachineOperand *Segment,
- const MachineOperand *Disp)
- : Disp(Disp) {
+ const MachineOperand *Disp, bool DispCheck = false)
+ : Disp(Disp), DeepCheck(DispCheck) {
Operands[0] = Base;
Operands[1] = Scale;
Operands[2] = Index;
Operands[3] = Segment;
}
+ /// Checks operands of MemOpKey are identical, if Base or Index
+ /// operand definitions are of kind SUBREG_TO_REG then compare
+ /// operands of defining MI.
+ bool performDeepCheck(const MemOpKey &Other) const {
+ MachineInstr *MI = const_cast<MachineInstr *>(Operands[0]->getParent());
+ MachineRegisterInfo *MRI = MI->getRegInfo();
+
+ for (int i = 0; i < 4; i++) {
+ bool copyLike = isDefCopyLike(MRI, *Operands[i]);
+ if (copyLike && !isIdenticalMI(MRI, *Operands[i], *Other.Operands[i]))
+ return false;
+ else if (!copyLike && !isIdenticalOp(*Operands[i], *Other.Operands[i]))
+ return false;
+ }
+ return isIdenticalOp(*Disp, *Other.Disp);
+ }
+
bool operator==(const MemOpKey &Other) const {
+ if (DeepCheck)
+ return performDeepCheck(Other);
+
// Addresses' bases, scales, indices and segments must be identical.
for (int i = 0; i < 4; ++i)
if (!isIdenticalOp(*Operands[i], *Other.Operands[i]))
@@ -91,6 +120,12 @@ public:
// Address' displacement operand.
const MachineOperand *Disp;
+
+ // If true checks Address' base, index, segment and
+ // displacement are identical, in additions if base/index
+ // are defined by copylike instruction then futher
+ // compare the operands of the defining instruction.
+ bool DeepCheck;
};
} // end anonymous namespace
@@ -114,12 +149,34 @@ template <> struct DenseMapInfo<MemOpKey> {
static unsigned getHashValue(const MemOpKey &Val) {
// Checking any field of MemOpKey is enough to determine if the key is
// empty or tombstone.
+ hash_code Hash(0);
assert(Val.Disp != PtrInfo::getEmptyKey() && "Cannot hash the empty key");
assert(Val.Disp != PtrInfo::getTombstoneKey() &&
"Cannot hash the tombstone key");
- hash_code Hash = hash_combine(*Val.Operands[0], *Val.Operands[1],
- *Val.Operands[2], *Val.Operands[3]);
+ auto getMIHash = [](MachineInstr *MI) -> hash_code {
+ hash_code h(0);
+ for (unsigned i = 1, e = MI->getNumOperands(); i < e; i++)
+ h = hash_combine(h, MI->getOperand(i));
+ return h;
+ };
+
+ const MachineOperand &Base = *Val.Operands[0];
+ const MachineOperand &Index = *Val.Operands[2];
+ MachineInstr *MI = const_cast<MachineInstr *>(Base.getParent());
+ MachineRegisterInfo *MRI = MI->getRegInfo();
+
+ if (isDefCopyLike(MRI, Base))
+ Hash = getMIHash(MRI->getVRegDef(Base.getReg()));
+ else
+ Hash = hash_combine(Hash, Base);
+
+ if (isDefCopyLike(MRI, Index))
+ Hash = getMIHash(MRI->getVRegDef(Index.getReg()));
+ else
+ Hash = hash_combine(Hash, Index);
+
+ Hash = hash_combine(Hash, *Val.Operands[1], *Val.Operands[3]);
// If the address displacement is an immediate, it should not affect the
// hash so that memory operands which differ only be immediate displacement
@@ -178,6 +235,16 @@ static inline MemOpKey getMemOpKey(const MachineInstr &MI, unsigned N) {
&MI.getOperand(N + X86::AddrDisp));
}
+static inline MemOpKey getMemOpCSEKey(const MachineInstr &MI, unsigned N) {
+ static MachineOperand DummyScale = MachineOperand::CreateImm(1);
+ assert((isLEA(MI) || MI.mayLoadOrStore()) &&
+ "The instruction must be a LEA, a load or a store");
+ return MemOpKey(&MI.getOperand(N + X86::AddrBaseReg), &DummyScale,
+ &MI.getOperand(N + X86::AddrIndexReg),
+ &MI.getOperand(N + X86::AddrSegmentReg),
+ &MI.getOperand(N + X86::AddrDisp), true);
+}
+
static inline bool isIdenticalOp(const MachineOperand &MO1,
const MachineOperand &MO2) {
return MO1.isIdenticalTo(MO2) &&
@@ -185,6 +252,27 @@ static inline bool isIdenticalOp(const MachineOperand &MO1,
!TargetRegisterInfo::isPhysicalRegister(MO1.getReg()));
}
+static bool isIdenticalMI(MachineRegisterInfo *MRI, const MachineOperand &MO1,
+ const MachineOperand &MO2) {
+ MachineInstr *MI1 = nullptr;
+ MachineInstr *MI2 = nullptr;
+ if (!MO1.isReg() || !MO2.isReg())
+ return false;
+
+ MI1 = MRI->getVRegDef(MO1.getReg());
+ MI2 = MRI->getVRegDef(MO2.getReg());
+ if (!MI1 || !MI2)
+ return false;
+ if (MI1->getOpcode() != MI2->getOpcode())
+ return false;
+ if (MI1->getNumOperands() != MI2->getNumOperands())
+ return false;
+ for (unsigned i = 1, e = MI1->getNumOperands(); i < e; ++i)
+ if (!isIdenticalOp(MI1->getOperand(i), MI2->getOperand(i)))
+ return false;
+ return true;
+}
+
#ifndef NDEBUG
static bool isValidDispOp(const MachineOperand &MO) {
return MO.isImm() || MO.isCPI() || MO.isJTI() || MO.isSymbol() ||
@@ -216,7 +304,140 @@ static inline bool isLEA(const MachineInstr &MI) {
Opcode == X86::LEA64r || Opcode == X86::LEA64_32r;
}
+static bool isDefCopyLike(MachineRegisterInfo *MRI, const MachineOperand &Opr) {
+ if (!Opr.isReg() || TargetRegisterInfo::isPhysicalRegister(Opr.getReg()))
+ return false;
+ MachineInstr *MI = MRI->getVRegDef(Opr.getReg());
+ return MI && MI->isCopyLike();
+}
+
namespace {
+
+/// This class captures the functions and attributes
+/// needed to factorize LEA within and across basic
+/// blocks.LEA instruction with same BASE,OFFSET and
+/// INDEX are the candidates for factorization.
+class FactorizeLEAOpt {
+public:
+ using LEAListT = std::list<MachineInstr *>;
+ using LEAMapT = DenseMap<MemOpKey, LEAListT>;
+ using ValueT = DenseMap<MemOpKey, unsigned>;
+ using ScopeEntryT = std::pair<MachineBasicBlock *, ValueT>;
+ using ScopeStackT = std::vector<ScopeEntryT>;
+
+ FactorizeLEAOpt() = default;
+ FactorizeLEAOpt(const FactorizeLEAOpt &) = delete;
+ FactorizeLEAOpt &operator=(const FactorizeLEAOpt &) = delete;
+
+ void performCleanup() {
+ for (auto LEA : removedLEAs)
+ LEA->eraseFromParent();
+ LEAs.clear();
+ Stack.clear();
+ removedLEAs.clear();
+ }
+
+ LEAMapT &getLEAMap() { return LEAs; }
+ ScopeEntryT *getTopScope() { return &Stack.back(); }
+
+ void addForLazyRemoval(MachineInstr *Instr) { removedLEAs.insert(Instr); }
+
+ bool checkIfScheduledForRemoval(MachineInstr *Instr) {
+ return removedLEAs.find(Instr) != removedLEAs.end();
+ }
+
+ /// Push the ScopeEntry for the BasicBlock over Stack.
+ /// Also traverses over list of instruction and update
+ /// LEAs Map and ScopeEntry for each LEA instruction
+ /// found using insertLEA().
+ void pushScope(MachineBasicBlock *MBB);
+
+ /// Stores the size of MachineInstr list corrosponding
+ /// to key K from LEAs MAP into the ScopeEntry of
+ /// the basic block, then insert the LEA at the beginning
+ /// of the list.
+ void insertLEA(MachineInstr *MI);
+
+ /// Pops out ScopeEntry of top most BasicBlock from the stack
+ /// and remove the LEA instructions contained in the scope
+ /// from the LEAs Map.
+ void popScope();
+
+ /// If LEA contains Physical Registers then its not a candidate
+ /// for factorizations since physical registers may violate SSA
+ /// semantics of MI.
+ bool containsPhyReg(MachineInstr *MI, unsigned RecLevel);
+
+private:
+ ScopeStackT Stack;
+ LEAMapT LEAs;
+ std::set<MachineInstr *> removedLEAs;
+};
+
+void FactorizeLEAOpt::pushScope(MachineBasicBlock *MBB) {
+ ValueT EmptyMap;
+ ScopeEntryT SE = std::make_pair(MBB, EmptyMap);
+ Stack.push_back(SE);
+ for (auto &MI : *MBB) {
+ if (isLEA(MI))
+ insertLEA(&MI);
+ }
+}
+
+void FactorizeLEAOpt::popScope() {
+ ScopeEntryT &SE = Stack.back();
+ for (auto MapEntry : SE.second) {
+ LEAMapT::iterator Itr = LEAs.find(MapEntry.first);
+ assert((Itr != LEAs.end()) &&
+ "LEAs map must have a node corresponding to ScopeEntry's Key.");
+
+ while (((*Itr).second.size() > MapEntry.second))
+ (*Itr).second.pop_front();
+ // If list goes empty remove entry from LEAs Map.
+ if ((*Itr).second.empty())
+ LEAs.erase(Itr);
+ }
+ Stack.pop_back();
+}
+
+bool FactorizeLEAOpt::containsPhyReg(MachineInstr *MI, unsigned RecLevel) {
+ if (!MI || !RecLevel)
+ return false;
+
+ MachineRegisterInfo *MRI = MI->getRegInfo();
+ for (auto Operand : MI->operands()) {
+ if (!Operand.isReg())
+ continue;
+ if (TargetRegisterInfo::isPhysicalRegister(Operand.getReg()))
+ return true;
+ MachineInstr *OperDefMI = MRI->getVRegDef(Operand.getReg());
+ if (OperDefMI && (MI != OperDefMI) && OperDefMI->isCopyLike() &&
+ containsPhyReg(OperDefMI, RecLevel - 1))
+ return true;
+ }
+ return false;
+}
+
+void FactorizeLEAOpt::insertLEA(MachineInstr *MI) {
+ unsigned lsize;
+ if (containsPhyReg(MI, 2))
+ return;
+
+ MemOpKey Key = getMemOpCSEKey(*MI, 1);
+ ScopeEntryT *TopScope = getTopScope();
+
+ LEAMapT::iterator Itr = LEAs.find(Key);
+ if (Itr == LEAs.end()) {
+ lsize = 0;
+ LEAs[Key].push_front(MI);
+ } else {
+ lsize = (*Itr).second.size();
+ (*Itr).second.push_front(MI);
+ }
+ if (TopScope->second.find(Key) == TopScope->second.end())
+ TopScope->second[Key] = lsize;
+}
+
class OptimizeLEAPass : public MachineFunctionPass {
public:
OptimizeLEAPass() : MachineFunctionPass(ID) {}
@@ -228,6 +449,12 @@ public:
/// been calculated by LEA. Also, remove redundant LEAs.
bool runOnMachineFunction(MachineFunction &MF) override;
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.setPreservesCFG();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ AU.addRequired<MachineDominatorTree>();
+ }
+
private:
typedef DenseMap<MemOpKey, SmallVector<MachineInstr *, 16>> MemOpMap;
@@ -273,8 +500,24 @@ private:
/// \brief Removes LEAs which calculate similar addresses.
bool removeRedundantLEAs(MemOpMap &LEAs);
+ /// \brief Visit over basic blocks, collect LEAs in a scoped
+ /// hash map (FactorizeLEAOpt::LEAs) and try to factor them out.
+ bool FactorizeLEAsAllBasicBlocks(MachineFunction &MF);
+
+ bool FactorizeLEAsBasicBlock(MachineDomTreeNode *DN);
+
+ /// \brief Factor out LEAs which share Base,Index,Offset and Segment.
+ bool processBasicBlock(const MachineBasicBlock &MBB);
+
+ /// \brief Try to replace LEA with a lower strength instruction
+ /// to improves latency and throughput.
+ bool strengthReduceLEAs(MemOpMap &LEAs, const MachineBasicBlock &MBB);
+
DenseMap<const MachineInstr *, unsigned> InstrPos;
+ FactorizeLEAOpt FactorOpt;
+
+ MachineDominatorTree *DT;
MachineRegisterInfo *MRI;
const X86InstrInfo *TII;
const X86RegisterInfo *TRI;
@@ -647,6 +890,152 @@ bool OptimizeLEAPass::removeRedundantLEAs(MemOpMap &LEAs) {
return Changed;
}
+static inline int getADDrrFromLEA(int LEAOpcode) {
+ switch (LEAOpcode) {
+ default:
+ llvm_unreachable("Unexpected LEA instruction");
+ case X86::LEA16r:
+ return X86::ADD16rr;
+ case X86::LEA32r:
+ return X86::ADD32rr;
+ case X86::LEA64_32r:
+ case X86::LEA64r:
+ return X86::ADD64rr;
+ }
+}
+
+bool OptimizeLEAPass::strengthReduceLEAs(MemOpMap &LEAs,
+ const MachineBasicBlock &BB) {
+ bool Changed = false;
+
+ // Loop over all entries in the table.
+ for (auto &E : LEAs) {
+ auto &List = E.second;
+
+ // Loop over all LEA pairs.
+ for (auto I1 = List.begin(); I1 != List.end(); I1++) {
+ MachineInstrBuilder NewMI;
+ MachineInstr &First = **I1;
+ MachineOperand &Res = First.getOperand(0);
+ MachineOperand &Base = First.getOperand(1);
+ MachineOperand &Scale = First.getOperand(2);
+ MachineOperand &Index = First.getOperand(3);
+ MachineOperand &Offset = First.getOperand(4);
+
+ const MCInstrDesc &ADDrr = TII->get(getADDrrFromLEA(First.getOpcode()));
+ const DebugLoc DL = First.getDebugLoc();
+
+ if (!Base.isReg() || !Index.isReg())
+ continue;
+ if (TargetRegisterInfo::isPhysicalRegister(Res.getReg()) ||
+ TargetRegisterInfo::isPhysicalRegister(Base.getReg()) ||
+ TargetRegisterInfo::isPhysicalRegister(Index.getReg()))
+ continue;
+
+ MachineBasicBlock &MBB = *(const_cast<MachineBasicBlock *>(&BB));
+ if (Scale.isImm() && Scale.getImm() == 1) {
+ // R = B + I
+ if (Offset.isImm() && !Offset.getImm()) {
+ NewMI = BuildMI(MBB, &First, DL, ADDrr)
+ .addDef(Res.getReg())
+ .addUse(Base.getReg())
+ .addUse(Index.getReg());
+ Changed = NewMI.getInstr() != nullptr;
+ First.eraseFromParent();
+ }
+ }
+ }
+ }
+ return Changed;
+}
+
+bool OptimizeLEAPass::processBasicBlock(const MachineBasicBlock &MBB) {
+ bool cseDone = false;
+
+ // Legal scale value (1,2,4 & 8) vector.
+ int LegalScale[9] = {0, 1, 1, 0, 1, 0, 0, 0, 1};
+
+ auto CompareFn = [](const MachineInstr *Arg1,
+ const MachineInstr *Arg2) -> bool {
+ if (Arg1->getOperand(2).getImm() < Arg2->getOperand(2).getImm())
+ return false;
+ return true;
+ };
+
+ // Loop over all entries in the table.
+ for (auto &E : FactorOpt.getLEAMap()) {
+ auto &List = E.second;
+ if (List.size() > 1)
+ List.sort(CompareFn);
+
+ // Loop over all LEA pairs.
+ for (auto Iter1 = List.begin(); Iter1 != List.end(); Iter1++) {
+ for (auto Iter2 = std::next(Iter1); Iter2 != List.end(); Iter2++) {
+ MachineInstr &LI1 = **Iter1;
+ MachineInstr &LI2 = **Iter2;
+
+ if (!DT->dominates(&LI2, &LI1))
+ continue;
+
+ int Scale1 = LI1.getOperand(2).getImm();
+ int Scale2 = LI2.getOperand(2).getImm();
+ assert(LI2.getOperand(0).isReg() && "Result is a VirtualReg");
+ DebugLoc DL = LI1.getDebugLoc();
+
+ if (FactorOpt.checkIfScheduledForRemoval(&LI1))
+ continue;
+
+ int Factor = Scale1 - Scale2;
+ if (Factor > 0 && LegalScale[Factor]) {
+ DEBUG(dbgs() << "CSE LEAs: Candidate to replace: "; LI1.dump(););
+ MachineInstrBuilder NewMI =
+ BuildMI(*(const_cast<MachineBasicBlock *>(&MBB)), &LI1, DL,
+ TII->get(LI1.getOpcode()))
+ .addDef(LI1.getOperand(0).getReg()) // Dst = Dst of LI1.
+ .addUse(LI2.getOperand(0).getReg()) // Base = Dst of LI2.
+ .addImm(Factor) // Scale = Diff b/w scales.
+ .addUse(LI1.getOperand(3).getReg()) // Index = Index of LI1.
+ .addImm(0) // Disp = 0
+ .addUse(
+ LI1.getOperand(5).getReg()); // Segment = Segmant of LI1.
+
+ cseDone = NewMI.getInstr() != nullptr;
+
+ /// Lazy removal shall ensure that replaced LEA remains
+ /// till we finish processing all the basic block. This shall
+ /// provide opportunity for further factorization based on
+ /// the replaced LEA which will be legal since it has same
+ /// destination as newly formed LEA.
+ FactorOpt.addForLazyRemoval(&LI1);
+
+ NumFactoredLEAs++;
+ DEBUG(dbgs() << "CSE LEAs: Replaced by: "; NewMI->dump(););
+ }
+ }
+ }
+ }
+ return cseDone;
+}
+
+bool OptimizeLEAPass::FactorizeLEAsBasicBlock(MachineDomTreeNode *DN) {
+ bool Changed = false;
+ MachineBasicBlock *MBB = DN->getBlock();
+ FactorOpt.pushScope(MBB);
+
+ Changed |= processBasicBlock(*MBB);
+ for (auto Child : DN->getChildren())
+ FactorizeLEAsBasicBlock(Child);
+
+ FactorOpt.popScope();
+ return Changed;
+}
+
+bool OptimizeLEAPass::FactorizeLEAsAllBasicBlocks(MachineFunction &MF) {
+ bool Changed = FactorizeLEAsBasicBlock(DT->getRootNode());
+ FactorOpt.performCleanup();
+ return Changed;
+}
+
bool OptimizeLEAPass::runOnMachineFunction(MachineFunction &MF) {
bool Changed = false;
@@ -656,6 +1045,10 @@ bool OptimizeLEAPass::runOnMachineFunction(MachineFunction &MF) {
MRI = &MF.getRegInfo();
TII = MF.getSubtarget<X86Subtarget>().getInstrInfo();
TRI = MF.getSubtarget<X86Subtarget>().getRegisterInfo();
+ DT = &getAnalysis<MachineDominatorTree>();
+
+ // Attempt factorizing LEAs.
+ Changed |= FactorizeLEAsAllBasicBlocks(MF);
// Process all basic blocks.
for (auto &MBB : MF) {
@@ -672,6 +1065,9 @@ bool OptimizeLEAPass::runOnMachineFunction(MachineFunction &MF) {
// Remove redundant LEA instructions.
Changed |= removeRedundantLEAs(LEAs);
+ // Strength reduce LEA instructions.
+ Changed |= strengthReduceLEAs(LEAs, MBB);
+
// Remove redundant address calculations. Do it only for -Os/-Oz since only
// a code size gain is expected from this part of the pass.
if (MF.getFunction()->optForSize())
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