[llvm] r259770 - [X86] Use hash table in LEA optimization pass.
Andrey Turetskiy via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 4 00:57:05 PST 2016
Author: aturetsk
Date: Thu Feb 4 02:57:03 2016
New Revision: 259770
URL: http://llvm.org/viewvc/llvm-project?rev=259770&view=rev
Log:
[X86] Use hash table in LEA optimization pass.
Use hash table (key is a memory operand) to store found LEA instructions to reduce compile time.
Differential Revision: http://reviews.llvm.org/D16404
Modified:
llvm/trunk/lib/Target/X86/X86OptimizeLEAs.cpp
Modified: llvm/trunk/lib/Target/X86/X86OptimizeLEAs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86OptimizeLEAs.cpp?rev=259770&r1=259769&r2=259770&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86OptimizeLEAs.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86OptimizeLEAs.cpp Thu Feb 4 02:57:03 2016
@@ -42,6 +42,133 @@ static cl::opt<bool> EnableX86LEAOpt("en
STATISTIC(NumSubstLEAs, "Number of LEA instruction substitutions");
STATISTIC(NumRedundantLEAs, "Number of redundant LEA instructions removed");
+class MemOpKey;
+
+/// \brief Returns a hash table key based on memory operands of \p MI. The
+/// number of the first memory operand of \p MI is specified through \p N.
+static inline MemOpKey getMemOpKey(const MachineInstr &MI, unsigned N);
+
+/// \brief Returns true if two machine operands are identical and they are not
+/// physical registers.
+static inline bool isIdenticalOp(const MachineOperand &MO1,
+ const MachineOperand &MO2);
+
+/// \brief Returns true if the instruction is LEA.
+static inline bool isLEA(const MachineInstr &MI);
+
+/// 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) {
+ Operands[0] = Base;
+ Operands[1] = Scale;
+ Operands[2] = Index;
+ Operands[3] = Segment;
+ }
+
+ bool operator==(const MemOpKey &Other) const {
+ // Addresses' bases, scales, indices and segments must be identical.
+ for (int i = 0; i < 4; ++i)
+ if (!isIdenticalOp(*Operands[i], *Other.Operands[i]))
+ return false;
+
+ assert((Disp->isImm() || Disp->isGlobal()) &&
+ (Other.Disp->isImm() || Other.Disp->isGlobal()) &&
+ "Address displacement operand is always an immediate or a global");
+
+ // Addresses' displacements must be either immediates or the same global.
+ // Immediates' and offsets' values don't matter for the operator since the
+ // difference will be taken care of during instruction substitution.
+ if ((Disp->isImm() && Other.Disp->isImm()) ||
+ (Disp->isGlobal() && Other.Disp->isGlobal() &&
+ Disp->getGlobal() == Other.Disp->getGlobal()))
+ return true;
+
+ return false;
+ }
+
+ // Address' base, scale, index and segment operands.
+ const MachineOperand *Operands[4];
+
+ // Address' displacement operand.
+ const MachineOperand *Disp;
+};
+
+/// Provide DenseMapInfo for MemOpKey.
+namespace llvm {
+template <> struct DenseMapInfo<MemOpKey> {
+ typedef DenseMapInfo<const MachineOperand *> PtrInfo;
+
+ static inline MemOpKey getEmptyKey() {
+ return MemOpKey(PtrInfo::getEmptyKey(), PtrInfo::getEmptyKey(),
+ PtrInfo::getEmptyKey(), PtrInfo::getEmptyKey(),
+ PtrInfo::getEmptyKey());
+ }
+
+ static inline MemOpKey getTombstoneKey() {
+ return MemOpKey(PtrInfo::getTombstoneKey(), PtrInfo::getTombstoneKey(),
+ PtrInfo::getTombstoneKey(), PtrInfo::getTombstoneKey(),
+ PtrInfo::getTombstoneKey());
+ }
+
+ static unsigned getHashValue(const MemOpKey &Val) {
+ // Checking any field of MemOpKey is enough to determine if the key is
+ // empty or tombstone.
+ 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]);
+
+ // If the address displacement is an immediate, it should not affect the
+ // hash so that memory operands which differ only be immediate displacement
+ // would have the same hash. If the address displacement is a global, we
+ // should reflect this global in the hash.
+ if (Val.Disp->isGlobal())
+ Hash = hash_combine(Hash, Val.Disp->getGlobal());
+
+ return (unsigned)Hash;
+ }
+
+ static bool isEqual(const MemOpKey &LHS, const MemOpKey &RHS) {
+ // Checking any field of MemOpKey is enough to determine if the key is
+ // empty or tombstone.
+ if (RHS.Disp == PtrInfo::getEmptyKey())
+ return LHS.Disp == PtrInfo::getEmptyKey();
+ if (RHS.Disp == PtrInfo::getTombstoneKey())
+ return LHS.Disp == PtrInfo::getTombstoneKey();
+ return LHS == RHS;
+ }
+};
+}
+
+static inline MemOpKey getMemOpKey(const MachineInstr &MI, unsigned N) {
+ assert((isLEA(MI) || MI.mayLoadOrStore()) &&
+ "The instruction must be a LEA, a load or a store");
+ return MemOpKey(&MI.getOperand(N + X86::AddrBaseReg),
+ &MI.getOperand(N + X86::AddrScaleAmt),
+ &MI.getOperand(N + X86::AddrIndexReg),
+ &MI.getOperand(N + X86::AddrSegmentReg),
+ &MI.getOperand(N + X86::AddrDisp));
+}
+
+static inline bool isIdenticalOp(const MachineOperand &MO1,
+ const MachineOperand &MO2) {
+ return MO1.isIdenticalTo(MO2) &&
+ (!MO1.isReg() ||
+ !TargetRegisterInfo::isPhysicalRegister(MO1.getReg()));
+}
+
+static inline bool isLEA(const MachineInstr &MI) {
+ unsigned Opcode = MI.getOpcode();
+ return Opcode == X86::LEA16r || Opcode == X86::LEA32r ||
+ Opcode == X86::LEA64r || Opcode == X86::LEA64_32r;
+}
+
namespace {
class OptimizeLEAPass : public MachineFunctionPass {
public:
@@ -55,51 +182,43 @@ public:
bool runOnMachineFunction(MachineFunction &MF) override;
private:
+ typedef DenseMap<MemOpKey, SmallVector<MachineInstr *, 16>> MemOpMap;
+
/// \brief Returns a distance between two instructions inside one basic block.
/// Negative result means, that instructions occur in reverse order.
int calcInstrDist(const MachineInstr &First, const MachineInstr &Last);
/// \brief Choose the best \p LEA instruction from the \p List to replace
/// address calculation in \p MI instruction. Return the address displacement
- /// and the distance between \p MI and the choosen \p LEA in \p AddrDispShift
- /// and \p Dist.
+ /// and the distance between \p MI and the choosen \p BestLEA in
+ /// \p AddrDispShift and \p Dist.
bool chooseBestLEA(const SmallVectorImpl<MachineInstr *> &List,
- const MachineInstr &MI, MachineInstr *&LEA,
+ const MachineInstr &MI, MachineInstr *&BestLEA,
int64_t &AddrDispShift, int &Dist);
- /// \brief Returns true if two machine operand are identical and they are not
- /// physical registers.
- bool isIdenticalOp(const MachineOperand &MO1, const MachineOperand &MO2);
-
- /// \brief Returns true if the instruction is LEA.
- bool isLEA(const MachineInstr &MI);
+ /// \brief Returns the difference between addresses' displacements of \p MI1
+ /// and \p MI2. The numbers of the first memory operands for the instructions
+ /// are specified through \p N1 and \p N2.
+ int64_t getAddrDispShift(const MachineInstr &MI1, unsigned N1,
+ const MachineInstr &MI2, unsigned N2) const;
/// \brief Returns true if the \p Last LEA instruction can be replaced by the
/// \p First. The difference between displacements of the addresses calculated
/// by these LEAs is returned in \p AddrDispShift. It'll be used for proper
/// replacement of the \p Last LEA's uses with the \p First's def register.
bool isReplaceable(const MachineInstr &First, const MachineInstr &Last,
- int64_t &AddrDispShift);
-
- /// \brief Returns true if two instructions have memory operands that only
- /// differ by displacement. The numbers of the first memory operands for both
- /// instructions are specified through \p N1 and \p N2. The address
- /// displacement is returned through AddrDispShift.
- bool isSimilarMemOp(const MachineInstr &MI1, unsigned N1,
- const MachineInstr &MI2, unsigned N2,
- int64_t &AddrDispShift);
+ int64_t &AddrDispShift) const;
/// \brief Find all LEA instructions in the basic block. Also, assign position
/// numbers to all instructions in the basic block to speed up calculation of
/// distance between them.
- void findLEAs(const MachineBasicBlock &MBB,
- SmallVectorImpl<MachineInstr *> &List);
+ void findLEAs(const MachineBasicBlock &MBB, MemOpMap &LEAs);
/// \brief Removes redundant address calculations.
- bool removeRedundantAddrCalc(const SmallVectorImpl<MachineInstr *> &List);
+ bool removeRedundantAddrCalc(MemOpMap &LEAs);
/// \brief Removes LEAs which calculate similar addresses.
- bool removeRedundantLEAs(SmallVectorImpl<MachineInstr *> &List);
+ bool removeRedundantLEAs(MemOpMap &LEAs);
DenseMap<const MachineInstr *, unsigned> InstrPos;
@@ -137,22 +256,20 @@ int OptimizeLEAPass::calcInstrDist(const
// 4) The LEA should be as close to MI as possible, and prior to it if
// possible.
bool OptimizeLEAPass::chooseBestLEA(const SmallVectorImpl<MachineInstr *> &List,
- const MachineInstr &MI, MachineInstr *&LEA,
+ const MachineInstr &MI,
+ MachineInstr *&BestLEA,
int64_t &AddrDispShift, int &Dist) {
const MachineFunction *MF = MI.getParent()->getParent();
const MCInstrDesc &Desc = MI.getDesc();
int MemOpNo = X86II::getMemoryOperandNo(Desc.TSFlags, MI.getOpcode()) +
X86II::getOperandBias(Desc);
- LEA = nullptr;
+ BestLEA = nullptr;
// Loop over all LEA instructions.
for (auto DefMI : List) {
- int64_t AddrDispShiftTemp = 0;
-
- // Compare instructions memory operands.
- if (!isSimilarMemOp(MI, MemOpNo, *DefMI, 1, AddrDispShiftTemp))
- continue;
+ // Get new address displacement.
+ int64_t AddrDispShiftTemp = getAddrDispShift(MI, MemOpNo, *DefMI, 1);
// Make sure address displacement fits 4 bytes.
if (!isInt<32>(AddrDispShiftTemp))
@@ -174,14 +291,14 @@ bool OptimizeLEAPass::chooseBestLEA(cons
int DistTemp = calcInstrDist(*DefMI, MI);
assert(DistTemp != 0 &&
"The distance between two different instructions cannot be zero");
- if (DistTemp > 0 || LEA == nullptr) {
+ if (DistTemp > 0 || BestLEA == nullptr) {
// Do not update return LEA, if the current one provides a displacement
// which fits in 1 byte, while the new candidate does not.
- if (LEA != nullptr && !isInt<8>(AddrDispShiftTemp) &&
+ if (BestLEA != nullptr && !isInt<8>(AddrDispShiftTemp) &&
isInt<8>(AddrDispShift))
continue;
- LEA = DefMI;
+ BestLEA = DefMI;
AddrDispShift = AddrDispShiftTemp;
Dist = DistTemp;
}
@@ -191,20 +308,25 @@ bool OptimizeLEAPass::chooseBestLEA(cons
break;
}
- return LEA != nullptr;
-}
-
-bool OptimizeLEAPass::isIdenticalOp(const MachineOperand &MO1,
- const MachineOperand &MO2) {
- return MO1.isIdenticalTo(MO2) &&
- (!MO1.isReg() ||
- !TargetRegisterInfo::isPhysicalRegister(MO1.getReg()));
+ return BestLEA != nullptr;
}
-bool OptimizeLEAPass::isLEA(const MachineInstr &MI) {
- unsigned Opcode = MI.getOpcode();
- return Opcode == X86::LEA16r || Opcode == X86::LEA32r ||
- Opcode == X86::LEA64r || Opcode == X86::LEA64_32r;
+// Get the difference between the addresses' displacements of the two
+// instructions \p MI1 and \p MI2. The numbers of the first memory operands are
+// passed through \p N1 and \p N2.
+int64_t OptimizeLEAPass::getAddrDispShift(const MachineInstr &MI1, unsigned N1,
+ const MachineInstr &MI2,
+ unsigned N2) const {
+ // Address displacement operands may differ by a constant.
+ const MachineOperand &Op1 = MI1.getOperand(N1 + X86::AddrDisp);
+ const MachineOperand &Op2 = MI2.getOperand(N2 + X86::AddrDisp);
+ if (Op1.isImm() && Op2.isImm())
+ return Op1.getImm() - Op2.getImm();
+ else if (Op1.isGlobal() && Op2.isGlobal() &&
+ Op1.getGlobal() == Op2.getGlobal())
+ return Op1.getOffset() - Op2.getOffset();
+ else
+ llvm_unreachable("Invalid address displacement operand");
}
// Check that the Last LEA can be replaced by the First LEA. To be so,
@@ -215,13 +337,12 @@ bool OptimizeLEAPass::isLEA(const Machin
// register is used only as address base.
bool OptimizeLEAPass::isReplaceable(const MachineInstr &First,
const MachineInstr &Last,
- int64_t &AddrDispShift) {
+ int64_t &AddrDispShift) const {
assert(isLEA(First) && isLEA(Last) &&
"The function works only with LEA instructions");
- // Compare instructions' memory operands.
- if (!isSimilarMemOp(Last, 1, First, 1, AddrDispShift))
- return false;
+ // Get new address displacement.
+ AddrDispShift = getAddrDispShift(Last, 1, First, 1);
// Make sure that LEA def registers belong to the same class. There may be
// instructions (like MOV8mr_NOREX) which allow a limited set of registers to
@@ -270,36 +391,7 @@ bool OptimizeLEAPass::isReplaceable(cons
return true;
}
-// Check if MI1 and MI2 have memory operands which represent addresses that
-// differ only by displacement.
-bool OptimizeLEAPass::isSimilarMemOp(const MachineInstr &MI1, unsigned N1,
- const MachineInstr &MI2, unsigned N2,
- int64_t &AddrDispShift) {
- // Address base, scale, index and segment operands must be identical.
- static const int IdenticalOpNums[] = {X86::AddrBaseReg, X86::AddrScaleAmt,
- X86::AddrIndexReg, X86::AddrSegmentReg};
- for (auto &N : IdenticalOpNums)
- if (!isIdenticalOp(MI1.getOperand(N1 + N), MI2.getOperand(N2 + N)))
- return false;
-
- // Address displacement operands may differ by a constant.
- const MachineOperand *Op1 = &MI1.getOperand(N1 + X86::AddrDisp);
- const MachineOperand *Op2 = &MI2.getOperand(N2 + X86::AddrDisp);
- if (!isIdenticalOp(*Op1, *Op2)) {
- if (Op1->isImm() && Op2->isImm())
- AddrDispShift = Op1->getImm() - Op2->getImm();
- else if (Op1->isGlobal() && Op2->isGlobal() &&
- Op1->getGlobal() == Op2->getGlobal())
- AddrDispShift = Op1->getOffset() - Op2->getOffset();
- else
- return false;
- }
-
- return true;
-}
-
-void OptimizeLEAPass::findLEAs(const MachineBasicBlock &MBB,
- SmallVectorImpl<MachineInstr *> &List) {
+void OptimizeLEAPass::findLEAs(const MachineBasicBlock &MBB, MemOpMap &LEAs) {
unsigned Pos = 0;
for (auto &MI : MBB) {
// Assign the position number to the instruction. Note that we are going to
@@ -310,19 +402,18 @@ void OptimizeLEAPass::findLEAs(const Mac
InstrPos[&MI] = Pos += 2;
if (isLEA(MI))
- List.push_back(const_cast<MachineInstr *>(&MI));
+ LEAs[getMemOpKey(MI, 1)].push_back(const_cast<MachineInstr *>(&MI));
}
}
// Try to find load and store instructions which recalculate addresses already
// calculated by some LEA and replace their memory operands with its def
// register.
-bool OptimizeLEAPass::removeRedundantAddrCalc(
- const SmallVectorImpl<MachineInstr *> &List) {
+bool OptimizeLEAPass::removeRedundantAddrCalc(MemOpMap &LEAs) {
bool Changed = false;
- assert(List.size() > 0);
- MachineBasicBlock *MBB = List[0]->getParent();
+ assert(!LEAs.empty());
+ MachineBasicBlock *MBB = (*LEAs.begin()->second.begin())->getParent();
// Process all instructions in basic block.
for (auto I = MBB->begin(), E = MBB->end(); I != E;) {
@@ -347,7 +438,8 @@ bool OptimizeLEAPass::removeRedundantAdd
MachineInstr *DefMI;
int64_t AddrDispShift;
int Dist;
- if (!chooseBestLEA(List, MI, DefMI, AddrDispShift, Dist))
+ if (!chooseBestLEA(LEAs[getMemOpKey(MI, MemOpNo)], MI, DefMI, AddrDispShift,
+ Dist))
continue;
// If LEA occurs before current instruction, we can freely replace
@@ -393,75 +485,80 @@ bool OptimizeLEAPass::removeRedundantAdd
}
// Try to find similar LEAs in the list and replace one with another.
-bool
-OptimizeLEAPass::removeRedundantLEAs(SmallVectorImpl<MachineInstr *> &List) {
+bool OptimizeLEAPass::removeRedundantLEAs(MemOpMap &LEAs) {
bool Changed = false;
- // Loop over all LEA pairs.
- auto I1 = List.begin();
- while (I1 != List.end()) {
- MachineInstr &First = **I1;
- auto I2 = std::next(I1);
- while (I2 != List.end()) {
- MachineInstr &Last = **I2;
- int64_t AddrDispShift;
-
- // LEAs should be in occurence order in the list, so we can freely
- // replace later LEAs with earlier ones.
- assert(calcInstrDist(First, Last) > 0 &&
- "LEAs must be in occurence order in the list");
-
- // Check that the Last LEA instruction can be replaced by the First.
- if (!isReplaceable(First, Last, AddrDispShift)) {
- ++I2;
- continue;
- }
-
- // Loop over all uses of the Last LEA and update their operands. Note that
- // the correctness of this has already been checked in the isReplaceable
- // function.
- for (auto UI = MRI->use_begin(Last.getOperand(0).getReg()),
- UE = MRI->use_end();
- UI != UE;) {
- MachineOperand &MO = *UI++;
- MachineInstr &MI = *MO.getParent();
-
- // Get the number of the first memory operand.
- const MCInstrDesc &Desc = MI.getDesc();
- int MemOpNo = X86II::getMemoryOperandNo(Desc.TSFlags, MI.getOpcode()) +
- X86II::getOperandBias(Desc);
-
- // Update address base.
- MO.setReg(First.getOperand(0).getReg());
-
- // Update address disp.
- MachineOperand *Op = &MI.getOperand(MemOpNo + X86::AddrDisp);
- if (Op->isImm())
- Op->setImm(Op->getImm() + AddrDispShift);
- else if (Op->isGlobal())
- Op->setOffset(Op->getOffset() + AddrDispShift);
- else
- llvm_unreachable("Invalid address displacement operand");
- }
+ // Loop over all entries in the table.
+ for (auto &E : LEAs) {
+ auto &List = E.second;
+
+ // Loop over all LEA pairs.
+ auto I1 = List.begin();
+ while (I1 != List.end()) {
+ MachineInstr &First = **I1;
+ auto I2 = std::next(I1);
+ while (I2 != List.end()) {
+ MachineInstr &Last = **I2;
+ int64_t AddrDispShift;
+
+ // LEAs should be in occurence order in the list, so we can freely
+ // replace later LEAs with earlier ones.
+ assert(calcInstrDist(First, Last) > 0 &&
+ "LEAs must be in occurence order in the list");
+
+ // Check that the Last LEA instruction can be replaced by the First.
+ if (!isReplaceable(First, Last, AddrDispShift)) {
+ ++I2;
+ continue;
+ }
+
+ // Loop over all uses of the Last LEA and update their operands. Note
+ // that the correctness of this has already been checked in the
+ // isReplaceable function.
+ for (auto UI = MRI->use_begin(Last.getOperand(0).getReg()),
+ UE = MRI->use_end();
+ UI != UE;) {
+ MachineOperand &MO = *UI++;
+ MachineInstr &MI = *MO.getParent();
+
+ // Get the number of the first memory operand.
+ const MCInstrDesc &Desc = MI.getDesc();
+ int MemOpNo =
+ X86II::getMemoryOperandNo(Desc.TSFlags, MI.getOpcode()) +
+ X86II::getOperandBias(Desc);
+
+ // Update address base.
+ MO.setReg(First.getOperand(0).getReg());
+
+ // Update address disp.
+ MachineOperand *Op = &MI.getOperand(MemOpNo + X86::AddrDisp);
+ if (Op->isImm())
+ Op->setImm(Op->getImm() + AddrDispShift);
+ else if (Op->isGlobal())
+ Op->setOffset(Op->getOffset() + AddrDispShift);
+ else
+ llvm_unreachable("Invalid address displacement operand");
+ }
+
+ // Since we can possibly extend register lifetime, clear kill flags.
+ MRI->clearKillFlags(First.getOperand(0).getReg());
+
+ ++NumRedundantLEAs;
+ DEBUG(dbgs() << "OptimizeLEAs: Remove redundant LEA: "; Last.dump(););
+
+ // By this moment, all of the Last LEA's uses must be replaced. So we
+ // can freely remove it.
+ assert(MRI->use_empty(Last.getOperand(0).getReg()) &&
+ "The LEA's def register must have no uses");
+ Last.eraseFromParent();
- // Since we can possibly extend register lifetime, clear kill flags.
- MRI->clearKillFlags(First.getOperand(0).getReg());
+ // Erase removed LEA from the list.
+ I2 = List.erase(I2);
- ++NumRedundantLEAs;
- DEBUG(dbgs() << "OptimizeLEAs: Remove redundant LEA: "; Last.dump(););
-
- // By this moment, all of the Last LEA's uses must be replaced. So we can
- // freely remove it.
- assert(MRI->use_empty(Last.getOperand(0).getReg()) &&
- "The LEA's def register must have no uses");
- Last.eraseFromParent();
-
- // Erase removed LEA from the list.
- I2 = List.erase(I2);
-
- Changed = true;
+ Changed = true;
+ }
+ ++I1;
}
- ++I1;
}
return Changed;
@@ -480,7 +577,7 @@ bool OptimizeLEAPass::runOnMachineFuncti
// Process all basic blocks.
for (auto &MBB : MF) {
- SmallVector<MachineInstr *, 16> LEAs;
+ MemOpMap LEAs;
InstrPos.clear();
// Find all LEA instructions in basic block.
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