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llvm-project/llvm/lib/Target/AArch64/AArch64CollectLOH.cpp

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//===---------- AArch64CollectLOH.cpp - AArch64 collect LOH pass --*- C++ -*-=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a pass that collect the Linker Optimization Hint (LOH).
// This pass should be run at the very end of the compilation flow, just before
// assembly printer.
// To be useful for the linker, the LOH must be printed into the assembly file.
//
// A LOH describes a sequence of instructions that may be optimized by the
// linker.
// This same sequence cannot be optimized by the compiler because some of
// the information will be known at link time.
// For instance, consider the following sequence:
// L1: adrp xA, sym@PAGE
// L2: add xB, xA, sym@PAGEOFF
// L3: ldr xC, [xB, #imm]
// This sequence can be turned into:
// A literal load if sym@PAGE + sym@PAGEOFF + #imm - address(L3) is < 1MB:
// L3: ldr xC, sym+#imm
// It may also be turned into either the following more efficient
// code sequences:
// - If sym@PAGEOFF + #imm fits the encoding space of L3.
// L1: adrp xA, sym@PAGE
// L3: ldr xC, [xB, sym@PAGEOFF + #imm]
// - If sym@PAGE + sym@PAGEOFF - address(L1) < 1MB:
// L1: adr xA, sym
// L3: ldr xC, [xB, #imm]
//
// To be valid a LOH must meet all the requirements needed by all the related
// possible linker transformations.
// For instance, using the running example, the constraints to emit
// ".loh AdrpAddLdr" are:
// - L1, L2, and L3 instructions are of the expected type, i.e.,
// respectively ADRP, ADD (immediate), and LD.
// - The result of L1 is used only by L2.
// - The register argument (xA) used in the ADD instruction is defined
// only by L1.
// - The result of L2 is used only by L3.
// - The base address (xB) in L3 is defined only L2.
// - The ADRP in L1 and the ADD in L2 must reference the same symbol using
// @PAGE/@PAGEOFF with no additional constants
//
// Currently supported LOHs are:
// * So called non-ADRP-related:
// - .loh AdrpAddLdr L1, L2, L3:
// L1: adrp xA, sym@PAGE
// L2: add xB, xA, sym@PAGEOFF
// L3: ldr xC, [xB, #imm]
// - .loh AdrpLdrGotLdr L1, L2, L3:
// L1: adrp xA, sym@GOTPAGE
// L2: ldr xB, [xA, sym@GOTPAGEOFF]
// L3: ldr xC, [xB, #imm]
// - .loh AdrpLdr L1, L3:
// L1: adrp xA, sym@PAGE
// L3: ldr xC, [xA, sym@PAGEOFF]
// - .loh AdrpAddStr L1, L2, L3:
// L1: adrp xA, sym@PAGE
// L2: add xB, xA, sym@PAGEOFF
// L3: str xC, [xB, #imm]
// - .loh AdrpLdrGotStr L1, L2, L3:
// L1: adrp xA, sym@GOTPAGE
// L2: ldr xB, [xA, sym@GOTPAGEOFF]
// L3: str xC, [xB, #imm]
// - .loh AdrpAdd L1, L2:
// L1: adrp xA, sym@PAGE
// L2: add xB, xA, sym@PAGEOFF
// For all these LOHs, L1, L2, L3 form a simple chain:
// L1 result is used only by L2 and L2 result by L3.
// L3 LOH-related argument is defined only by L2 and L2 LOH-related argument
// by L1.
// All these LOHs aim at using more efficient load/store patterns by folding
// some instructions used to compute the address directly into the load/store.
//
// * So called ADRP-related:
// - .loh AdrpAdrp L2, L1:
// L2: ADRP xA, sym1@PAGE
// L1: ADRP xA, sym2@PAGE
// L2 dominates L1 and xA is not redifined between L2 and L1
// This LOH aims at getting rid of redundant ADRP instructions.
//
// The overall design for emitting the LOHs is:
// 1. AArch64CollectLOH (this pass) records the LOHs in the AArch64FunctionInfo.
// 2. AArch64AsmPrinter reads the LOHs from AArch64FunctionInfo and it:
// 1. Associates them a label.
// 2. Emits them in a MCStreamer (EmitLOHDirective).
// - The MCMachOStreamer records them into the MCAssembler.
// - The MCAsmStreamer prints them.
// - Other MCStreamers ignore them.
// 3. Closes the MCStreamer:
// - The MachObjectWriter gets them from the MCAssembler and writes
// them in the object file.
// - Other ObjectWriters ignore them.
//===----------------------------------------------------------------------===//
#include "AArch64.h"
#include "AArch64InstrInfo.h"
#include "AArch64MachineFunctionInfo.h"
#include "AArch64Subtarget.h"
#include "MCTargetDesc/AArch64AddressingModes.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
#define DEBUG_TYPE "aarch64-collect-loh"
static cl::opt<bool>
PreCollectRegister("aarch64-collect-loh-pre-collect-register", cl::Hidden,
cl::desc("Restrict analysis to registers invovled"
" in LOHs"),
cl::init(true));
static cl::opt<bool>
BasicBlockScopeOnly("aarch64-collect-loh-bb-only", cl::Hidden,
cl::desc("Restrict analysis at basic block scope"),
cl::init(true));
STATISTIC(NumADRPSimpleCandidate,
"Number of simplifiable ADRP dominate by another");
STATISTIC(NumADRPComplexCandidate2,
"Number of simplifiable ADRP reachable by 2 defs");
STATISTIC(NumADRPComplexCandidate3,
"Number of simplifiable ADRP reachable by 3 defs");
STATISTIC(NumADRPComplexCandidateOther,
"Number of simplifiable ADRP reachable by 4 or more defs");
STATISTIC(NumADDToSTRWithImm,
"Number of simplifiable STR with imm reachable by ADD");
STATISTIC(NumLDRToSTRWithImm,
"Number of simplifiable STR with imm reachable by LDR");
STATISTIC(NumADDToSTR, "Number of simplifiable STR reachable by ADD");
STATISTIC(NumLDRToSTR, "Number of simplifiable STR reachable by LDR");
STATISTIC(NumADDToLDRWithImm,
"Number of simplifiable LDR with imm reachable by ADD");
STATISTIC(NumLDRToLDRWithImm,
"Number of simplifiable LDR with imm reachable by LDR");
STATISTIC(NumADDToLDR, "Number of simplifiable LDR reachable by ADD");
STATISTIC(NumLDRToLDR, "Number of simplifiable LDR reachable by LDR");
STATISTIC(NumADRPToLDR, "Number of simplifiable LDR reachable by ADRP");
STATISTIC(NumCplxLvl1, "Number of complex case of level 1");
STATISTIC(NumTooCplxLvl1, "Number of too complex case of level 1");
STATISTIC(NumCplxLvl2, "Number of complex case of level 2");
STATISTIC(NumTooCplxLvl2, "Number of too complex case of level 2");
STATISTIC(NumADRSimpleCandidate, "Number of simplifiable ADRP + ADD");
STATISTIC(NumADRComplexCandidate, "Number of too complex ADRP + ADD");
namespace llvm {
void initializeAArch64CollectLOHPass(PassRegistry &);
}
namespace {
struct AArch64CollectLOH : public MachineFunctionPass {
static char ID;
AArch64CollectLOH() : MachineFunctionPass(ID) {
initializeAArch64CollectLOHPass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
const char *getPassName() const override {
return "AArch64 Collect Linker Optimization Hint (LOH)";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
AU.addRequired<MachineDominatorTree>();
}
private:
};
/// A set of MachineInstruction.
typedef SetVector<const MachineInstr *> SetOfMachineInstr;
/// Map a basic block to a set of instructions per register.
/// This is used to represent the exposed uses of a basic block
/// per register.
typedef MapVector<const MachineBasicBlock *,
std::unique_ptr<SetOfMachineInstr[]>>
BlockToSetOfInstrsPerColor;
/// Map a basic block to an instruction per register.
/// This is used to represent the live-out definitions of a basic block
/// per register.
typedef MapVector<const MachineBasicBlock *,
std::unique_ptr<const MachineInstr *[]>>
BlockToInstrPerColor;
/// Map an instruction to a set of instructions. Used to represent the
/// mapping def to reachable uses or use to definitions.
typedef MapVector<const MachineInstr *, SetOfMachineInstr> InstrToInstrs;
/// Map a basic block to a BitVector.
/// This is used to record the kill registers per basic block.
typedef MapVector<const MachineBasicBlock *, BitVector> BlockToRegSet;
/// Map a register to a dense id.
typedef DenseMap<unsigned, unsigned> MapRegToId;
/// Map a dense id to a register. Used for debug purposes.
typedef SmallVector<unsigned, 32> MapIdToReg;
} // end anonymous namespace.
char AArch64CollectLOH::ID = 0;
INITIALIZE_PASS_BEGIN(AArch64CollectLOH, "aarch64-collect-loh",
"AArch64 Collect Linker Optimization Hint (LOH)", false,
false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_END(AArch64CollectLOH, "aarch64-collect-loh",
"AArch64 Collect Linker Optimization Hint (LOH)", false,
false)
/// Given a couple (MBB, reg) get the corresponding set of instruction from
/// the given "sets".
/// If this couple does not reference any set, an empty set is added to "sets"
/// for this couple and returned.
/// \param nbRegs is used internally allocate some memory. It must be consistent
/// with the way sets is used.
static SetOfMachineInstr &getSet(BlockToSetOfInstrsPerColor &sets,
const MachineBasicBlock &MBB, unsigned reg,
unsigned nbRegs) {
SetOfMachineInstr *result;
BlockToSetOfInstrsPerColor::iterator it = sets.find(&MBB);
if (it != sets.end())
result = it->second.get();
else
result = (sets[&MBB] = make_unique<SetOfMachineInstr[]>(nbRegs)).get();
return result[reg];
}
/// Given a couple (reg, MI) get the corresponding set of instructions from the
/// the given "sets".
/// This is used to get the uses record in sets of a definition identified by
/// MI and reg, i.e., MI defines reg.
/// If the couple does not reference anything, an empty set is added to
/// "sets[reg]".
/// \pre set[reg] is valid.
static SetOfMachineInstr &getUses(InstrToInstrs *sets, unsigned reg,
const MachineInstr &MI) {
return sets[reg][&MI];
}
/// Same as getUses but does not modify the input map: sets.
/// \return NULL if the couple (reg, MI) is not in sets.
static const SetOfMachineInstr *getUses(const InstrToInstrs *sets, unsigned reg,
const MachineInstr &MI) {
InstrToInstrs::const_iterator Res = sets[reg].find(&MI);
if (Res != sets[reg].end())
return &(Res->second);
return nullptr;
}
/// Initialize the reaching definition algorithm:
/// For each basic block BB in MF, record:
/// - its kill set.
/// - its reachable uses (uses that are exposed to BB's predecessors).
/// - its the generated definitions.
/// \param DummyOp if not NULL, specifies a Dummy Operation to be added to
/// the list of uses of exposed defintions.
/// \param ADRPMode specifies to only consider ADRP instructions for generated
/// definition. It also consider definitions of ADRP instructions as uses and
/// ignore other uses. The ADRPMode is used to collect the information for LHO
/// that involve ADRP operation only.
static void initReachingDef(MachineFunction &MF,
InstrToInstrs *ColorOpToReachedUses,
BlockToInstrPerColor &Gen, BlockToRegSet &Kill,
BlockToSetOfInstrsPerColor &ReachableUses,
const MapRegToId &RegToId,
const MachineInstr *DummyOp, bool ADRPMode) {
const TargetMachine &TM = MF.getTarget();
const TargetRegisterInfo *TRI = TM.getSubtargetImpl()->getRegisterInfo();
unsigned NbReg = RegToId.size();
for (MachineBasicBlock &MBB : MF) {
auto &BBGen = Gen[&MBB];
BBGen = make_unique<const MachineInstr *[]>(NbReg);
std::fill(BBGen.get(), BBGen.get() + NbReg, nullptr);
BitVector &BBKillSet = Kill[&MBB];
BBKillSet.resize(NbReg);
for (const MachineInstr &MI : MBB) {
bool IsADRP = MI.getOpcode() == AArch64::ADRP;
// Process uses first.
if (IsADRP || !ADRPMode)
for (const MachineOperand &MO : MI.operands()) {
// Treat ADRP def as use, as the goal of the analysis is to find
// ADRP defs reached by other ADRP defs.
if (!MO.isReg() || (!ADRPMode && !MO.isUse()) ||
(ADRPMode && (!IsADRP || !MO.isDef())))
continue;
unsigned CurReg = MO.getReg();
MapRegToId::const_iterator ItCurRegId = RegToId.find(CurReg);
if (ItCurRegId == RegToId.end())
continue;
CurReg = ItCurRegId->second;
// if CurReg has not been defined, this use is reachable.
if (!BBGen[CurReg] && !BBKillSet.test(CurReg))
getSet(ReachableUses, MBB, CurReg, NbReg).insert(&MI);
// current basic block definition for this color, if any, is in Gen.
if (BBGen[CurReg])
getUses(ColorOpToReachedUses, CurReg, *BBGen[CurReg]).insert(&MI);
}
// Process clobbers.
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isRegMask())
continue;
// Clobbers kill the related colors.
const uint32_t *PreservedRegs = MO.getRegMask();
// Set generated regs.
for (const auto Entry : RegToId) {
unsigned Reg = Entry.second;
// Use the global register ID when querying APIs external to this
// pass.
if (MachineOperand::clobbersPhysReg(PreservedRegs, Entry.first)) {
// Do not register clobbered definition for no ADRP.
// This definition is not used anyway (otherwise register
// allocation is wrong).
BBGen[Reg] = ADRPMode ? &MI : nullptr;
BBKillSet.set(Reg);
}
}
}
// Process register defs.
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg() || !MO.isDef())
continue;
unsigned CurReg = MO.getReg();
MapRegToId::const_iterator ItCurRegId = RegToId.find(CurReg);
if (ItCurRegId == RegToId.end())
continue;
for (MCRegAliasIterator AI(CurReg, TRI, true); AI.isValid(); ++AI) {
MapRegToId::const_iterator ItRegId = RegToId.find(*AI);
assert(ItRegId != RegToId.end() &&
"Sub-register of an "
"involved register, not recorded as involved!");
BBKillSet.set(ItRegId->second);
BBGen[ItRegId->second] = &MI;
}
BBGen[ItCurRegId->second] = &MI;
}
}
// If we restrict our analysis to basic block scope, conservatively add a
// dummy
// use for each generated value.
if (!ADRPMode && DummyOp && !MBB.succ_empty())
for (unsigned CurReg = 0; CurReg < NbReg; ++CurReg)
if (BBGen[CurReg])
getUses(ColorOpToReachedUses, CurReg, *BBGen[CurReg]).insert(DummyOp);
}
}
/// Reaching def core algorithm:
/// while an Out has changed
/// for each bb
/// for each color
/// In[bb][color] = U Out[bb.predecessors][color]
/// insert reachableUses[bb][color] in each in[bb][color]
/// op.reachedUses
///
/// Out[bb] = Gen[bb] U (In[bb] - Kill[bb])
static void reachingDefAlgorithm(MachineFunction &MF,
InstrToInstrs *ColorOpToReachedUses,
BlockToSetOfInstrsPerColor &In,
BlockToSetOfInstrsPerColor &Out,
BlockToInstrPerColor &Gen, BlockToRegSet &Kill,
BlockToSetOfInstrsPerColor &ReachableUses,
unsigned NbReg) {
bool HasChanged;
do {
HasChanged = false;
for (MachineBasicBlock &MBB : MF) {
unsigned CurReg;
for (CurReg = 0; CurReg < NbReg; ++CurReg) {
SetOfMachineInstr &BBInSet = getSet(In, MBB, CurReg, NbReg);
SetOfMachineInstr &BBReachableUses =
getSet(ReachableUses, MBB, CurReg, NbReg);
SetOfMachineInstr &BBOutSet = getSet(Out, MBB, CurReg, NbReg);
unsigned Size = BBOutSet.size();
// In[bb][color] = U Out[bb.predecessors][color]
for (MachineBasicBlock *PredMBB : MBB.predecessors()) {
SetOfMachineInstr &PredOutSet = getSet(Out, *PredMBB, CurReg, NbReg);
BBInSet.insert(PredOutSet.begin(), PredOutSet.end());
}
// insert reachableUses[bb][color] in each in[bb][color] op.reachedses
for (const MachineInstr *MI : BBInSet) {
SetOfMachineInstr &OpReachedUses =
getUses(ColorOpToReachedUses, CurReg, *MI);
OpReachedUses.insert(BBReachableUses.begin(), BBReachableUses.end());
}
// Out[bb] = Gen[bb] U (In[bb] - Kill[bb])
if (!Kill[&MBB].test(CurReg))
BBOutSet.insert(BBInSet.begin(), BBInSet.end());
if (Gen[&MBB][CurReg])
BBOutSet.insert(Gen[&MBB][CurReg]);
HasChanged |= BBOutSet.size() != Size;
}
}
} while (HasChanged);
}
/// Reaching definition algorithm.
/// \param MF function on which the algorithm will operate.
/// \param[out] ColorOpToReachedUses will contain the result of the reaching
/// def algorithm.
/// \param ADRPMode specify whether the reaching def algorithm should be tuned
/// for ADRP optimization. \see initReachingDef for more details.
/// \param DummyOp if not NULL, the algorithm will work at
/// basic block scope and will set for every exposed definition a use to
/// @p DummyOp.
/// \pre ColorOpToReachedUses is an array of at least number of registers of
/// InstrToInstrs.
static void reachingDef(MachineFunction &MF,
InstrToInstrs *ColorOpToReachedUses,
const MapRegToId &RegToId, bool ADRPMode = false,
const MachineInstr *DummyOp = nullptr) {
// structures:
// For each basic block.
// Out: a set per color of definitions that reach the
// out boundary of this block.
// In: Same as Out but for in boundary.
// Gen: generated color in this block (one operation per color).
// Kill: register set of killed color in this block.
// ReachableUses: a set per color of uses (operation) reachable
// for "In" definitions.
BlockToSetOfInstrsPerColor Out, In, ReachableUses;
BlockToInstrPerColor Gen;
BlockToRegSet Kill;
// Initialize Gen, kill and reachableUses.
initReachingDef(MF, ColorOpToReachedUses, Gen, Kill, ReachableUses, RegToId,
DummyOp, ADRPMode);
// Algo.
if (!DummyOp)
reachingDefAlgorithm(MF, ColorOpToReachedUses, In, Out, Gen, Kill,
ReachableUses, RegToId.size());
}
#ifndef NDEBUG
/// print the result of the reaching definition algorithm.
static void printReachingDef(const InstrToInstrs *ColorOpToReachedUses,
unsigned NbReg, const TargetRegisterInfo *TRI,
const MapIdToReg &IdToReg) {
unsigned CurReg;
for (CurReg = 0; CurReg < NbReg; ++CurReg) {
if (ColorOpToReachedUses[CurReg].empty())
continue;
DEBUG(dbgs() << "*** Reg " << PrintReg(IdToReg[CurReg], TRI) << " ***\n");
for (const auto &DefsIt : ColorOpToReachedUses[CurReg]) {
DEBUG(dbgs() << "Def:\n");
DEBUG(DefsIt.first->print(dbgs()));
DEBUG(dbgs() << "Reachable uses:\n");
for (const MachineInstr *MI : DefsIt.second) {
DEBUG(MI->print(dbgs()));
}
}
}
}
#endif // NDEBUG
/// Answer the following question: Can Def be one of the definition
/// involved in a part of a LOH?
static bool canDefBePartOfLOH(const MachineInstr *Def) {
unsigned Opc = Def->getOpcode();
// Accept ADRP, ADDLow and LOADGot.
switch (Opc) {
default:
return false;
case AArch64::ADRP:
return true;
case AArch64::ADDXri:
// Check immediate to see if the immediate is an address.
switch (Def->getOperand(2).getType()) {
default:
return false;
case MachineOperand::MO_GlobalAddress:
case MachineOperand::MO_JumpTableIndex:
case MachineOperand::MO_ConstantPoolIndex:
case MachineOperand::MO_BlockAddress:
return true;
}
case AArch64::LDRXui:
// Check immediate to see if the immediate is an address.
switch (Def->getOperand(2).getType()) {
default:
return false;
case MachineOperand::MO_GlobalAddress:
return true;
}
}
// Unreachable.
return false;
}
/// Check whether the given instruction can the end of a LOH chain involving a
/// store.
static bool isCandidateStore(const MachineInstr *Instr) {
switch (Instr->getOpcode()) {
default:
return false;
case AArch64::STRBui:
case AArch64::STRHui:
case AArch64::STRWui:
case AArch64::STRXui:
case AArch64::STRSui:
case AArch64::STRDui:
case AArch64::STRQui:
// In case we have str xA, [xA, #imm], this is two different uses
// of xA and we cannot fold, otherwise the xA stored may be wrong,
// even if #imm == 0.
if (Instr->getOperand(0).getReg() != Instr->getOperand(1).getReg())
return true;
}
return false;
}
/// Given the result of a reaching definition algorithm in ColorOpToReachedUses,
/// Build the Use to Defs information and filter out obvious non-LOH candidates.
/// In ADRPMode, non-LOH candidates are "uses" with non-ADRP definitions.
/// In non-ADRPMode, non-LOH candidates are "uses" with several definition,
/// i.e., no simple chain.
/// \param ADRPMode -- \see initReachingDef.
static void reachedUsesToDefs(InstrToInstrs &UseToReachingDefs,
const InstrToInstrs *ColorOpToReachedUses,
const MapRegToId &RegToId,
bool ADRPMode = false) {
SetOfMachineInstr NotCandidate;
unsigned NbReg = RegToId.size();
MapRegToId::const_iterator EndIt = RegToId.end();
for (unsigned CurReg = 0; CurReg < NbReg; ++CurReg) {
// If this color is never defined, continue.
if (ColorOpToReachedUses[CurReg].empty())
continue;
for (const auto &DefsIt : ColorOpToReachedUses[CurReg]) {
for (const MachineInstr *MI : DefsIt.second) {
const MachineInstr *Def = DefsIt.first;
MapRegToId::const_iterator It;
// if all the reaching defs are not adrp, this use will not be
// simplifiable.
if ((ADRPMode && Def->getOpcode() != AArch64::ADRP) ||
(!ADRPMode && !canDefBePartOfLOH(Def)) ||
(!ADRPMode && isCandidateStore(MI) &&
// store are LOH candidate iff the end of the chain is used as
// base.
((It = RegToId.find((MI)->getOperand(1).getReg())) == EndIt ||
It->second != CurReg))) {
NotCandidate.insert(MI);
continue;
}
// Do not consider self reaching as a simplifiable case for ADRP.
if (!ADRPMode || MI != DefsIt.first) {
UseToReachingDefs[MI].insert(DefsIt.first);
// If UsesIt has several reaching definitions, it is not
// candidate for simplificaton in non-ADRPMode.
if (!ADRPMode && UseToReachingDefs[MI].size() > 1)
NotCandidate.insert(MI);
}
}
}
}
for (const MachineInstr *Elem : NotCandidate) {
DEBUG(dbgs() << "Too many reaching defs: " << *Elem << "\n");
// It would have been better if we could just remove the entry
// from the map. Because of that, we have to filter the garbage
// (second.empty) in the subsequence analysis.
UseToReachingDefs[Elem].clear();
}
}
/// Based on the use to defs information (in ADRPMode), compute the
/// opportunities of LOH ADRP-related.
static void computeADRP(const InstrToInstrs &UseToDefs,
AArch64FunctionInfo &AArch64FI,
const MachineDominatorTree *MDT) {
DEBUG(dbgs() << "*** Compute LOH for ADRP\n");
for (const auto &Entry : UseToDefs) {
unsigned Size = Entry.second.size();
if (Size == 0)
continue;
if (Size == 1) {
const MachineInstr *L2 = *Entry.second.begin();
const MachineInstr *L1 = Entry.first;
if (!MDT->dominates(L2, L1)) {
DEBUG(dbgs() << "Dominance check failed:\n" << *L2 << '\n' << *L1
<< '\n');
continue;
}
DEBUG(dbgs() << "Record AdrpAdrp:\n" << *L2 << '\n' << *L1 << '\n');
SmallVector<const MachineInstr *, 2> Args;
Args.push_back(L2);
Args.push_back(L1);
AArch64FI.addLOHDirective(MCLOH_AdrpAdrp, Args);
++NumADRPSimpleCandidate;
}
#ifdef DEBUG
else if (Size == 2)
++NumADRPComplexCandidate2;
else if (Size == 3)
++NumADRPComplexCandidate3;
else
++NumADRPComplexCandidateOther;
#endif
// if Size < 1, the use should have been removed from the candidates
assert(Size >= 1 && "No reaching defs for that use!");
}
}
/// Check whether the given instruction can be the end of a LOH chain
/// involving a load.
static bool isCandidateLoad(const MachineInstr *Instr) {
switch (Instr->getOpcode()) {
default:
return false;
case AArch64::LDRSBWui:
case AArch64::LDRSBXui:
case AArch64::LDRSHWui:
case AArch64::LDRSHXui:
case AArch64::LDRSWui:
case AArch64::LDRBui:
case AArch64::LDRHui:
case AArch64::LDRWui:
case AArch64::LDRXui:
case AArch64::LDRSui:
case AArch64::LDRDui:
case AArch64::LDRQui:
if (Instr->getOperand(2).getTargetFlags() & AArch64II::MO_GOT)
return false;
return true;
}
// Unreachable.
return false;
}
/// Check whether the given instruction can load a litteral.
static bool supportLoadFromLiteral(const MachineInstr *Instr) {
switch (Instr->getOpcode()) {
default:
return false;
case AArch64::LDRSWui:
case AArch64::LDRWui:
case AArch64::LDRXui:
case AArch64::LDRSui:
case AArch64::LDRDui:
case AArch64::LDRQui:
return true;
}
// Unreachable.
return false;
}
/// Check whether the given instruction is a LOH candidate.
/// \param UseToDefs is used to check that Instr is at the end of LOH supported
/// chain.
/// \pre UseToDefs contains only on def per use, i.e., obvious non candidate are
/// already been filtered out.
static bool isCandidate(const MachineInstr *Instr,
const InstrToInstrs &UseToDefs,
const MachineDominatorTree *MDT) {
if (!isCandidateLoad(Instr) && !isCandidateStore(Instr))
return false;
const MachineInstr *Def = *UseToDefs.find(Instr)->second.begin();
if (Def->getOpcode() != AArch64::ADRP) {
// At this point, Def is ADDXri or LDRXui of the right type of
// symbol, because we filtered out the uses that were not defined
// by these kind of instructions (+ ADRP).
// Check if this forms a simple chain: each intermediate node must
// dominates the next one.
if (!MDT->dominates(Def, Instr))
return false;
// Move one node up in the simple chain.
if (UseToDefs.find(Def) ==
UseToDefs.end()
// The map may contain garbage we have to ignore.
||
UseToDefs.find(Def)->second.empty())
return false;
Instr = Def;
Def = *UseToDefs.find(Def)->second.begin();
}
// Check if we reached the top of the simple chain:
// - top is ADRP.
// - check the simple chain property: each intermediate node must
// dominates the next one.
if (Def->getOpcode() == AArch64::ADRP)
return MDT->dominates(Def, Instr);
return false;
}
static bool registerADRCandidate(const MachineInstr &Use,
const InstrToInstrs &UseToDefs,
const InstrToInstrs *DefsPerColorToUses,
AArch64FunctionInfo &AArch64FI,
SetOfMachineInstr *InvolvedInLOHs,
const MapRegToId &RegToId) {
// Look for opportunities to turn ADRP -> ADD or
// ADRP -> LDR GOTPAGEOFF into ADR.
// If ADRP has more than one use. Give up.
if (Use.getOpcode() != AArch64::ADDXri &&
(Use.getOpcode() != AArch64::LDRXui ||
!(Use.getOperand(2).getTargetFlags() & AArch64II::MO_GOT)))
return false;
InstrToInstrs::const_iterator It = UseToDefs.find(&Use);
// The map may contain garbage that we need to ignore.
if (It == UseToDefs.end() || It->second.empty())
return false;
const MachineInstr &Def = **It->second.begin();
if (Def.getOpcode() != AArch64::ADRP)
return false;
// Check the number of users of ADRP.
const SetOfMachineInstr *Users =
getUses(DefsPerColorToUses,
RegToId.find(Def.getOperand(0).getReg())->second, Def);
if (Users->size() > 1) {
++NumADRComplexCandidate;
return false;
}
++NumADRSimpleCandidate;
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(&Def)) &&
"ADRP already involved in LOH.");
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(&Use)) &&
"ADD already involved in LOH.");
DEBUG(dbgs() << "Record AdrpAdd\n" << Def << '\n' << Use << '\n');
SmallVector<const MachineInstr *, 2> Args;
Args.push_back(&Def);
Args.push_back(&Use);
AArch64FI.addLOHDirective(Use.getOpcode() == AArch64::ADDXri ? MCLOH_AdrpAdd
: MCLOH_AdrpLdrGot,
Args);
return true;
}
/// Based on the use to defs information (in non-ADRPMode), compute the
/// opportunities of LOH non-ADRP-related
static void computeOthers(const InstrToInstrs &UseToDefs,
const InstrToInstrs *DefsPerColorToUses,
AArch64FunctionInfo &AArch64FI, const MapRegToId &RegToId,
const MachineDominatorTree *MDT) {
SetOfMachineInstr *InvolvedInLOHs = nullptr;
#ifdef DEBUG
SetOfMachineInstr InvolvedInLOHsStorage;
InvolvedInLOHs = &InvolvedInLOHsStorage;
#endif // DEBUG
DEBUG(dbgs() << "*** Compute LOH for Others\n");
// ADRP -> ADD/LDR -> LDR/STR pattern.
// Fall back to ADRP -> ADD pattern if we fail to catch the bigger pattern.
// FIXME: When the statistics are not important,
// This initial filtering loop can be merged into the next loop.
// Currently, we didn't do it to have the same code for both DEBUG and
// NDEBUG builds. Indeed, the iterator of the second loop would need
// to be changed.
SetOfMachineInstr PotentialCandidates;
SetOfMachineInstr PotentialADROpportunities;
for (auto &Use : UseToDefs) {
// If no definition is available, this is a non candidate.
if (Use.second.empty())
continue;
// Keep only instructions that are load or store and at the end of
// a ADRP -> ADD/LDR/Nothing chain.
// We already filtered out the no-chain cases.
if (!isCandidate(Use.first, UseToDefs, MDT)) {
PotentialADROpportunities.insert(Use.first);
continue;
}
PotentialCandidates.insert(Use.first);
}
// Make the following distinctions for statistics as the linker does
// know how to decode instructions:
// - ADD/LDR/Nothing make there different patterns.
// - LDR/STR make two different patterns.
// Hence, 6 - 1 base patterns.
// (because ADRP-> Nothing -> STR is not simplifiable)
// The linker is only able to have a simple semantic, i.e., if pattern A
// do B.
// However, we want to see the opportunity we may miss if we were able to
// catch more complex cases.
// PotentialCandidates are result of a chain ADRP -> ADD/LDR ->
// A potential candidate becomes a candidate, if its current immediate
// operand is zero and all nodes of the chain have respectively only one user
#ifdef DEBUG
SetOfMachineInstr DefsOfPotentialCandidates;
#endif
for (const MachineInstr *Candidate : PotentialCandidates) {
// Get the definition of the candidate i.e., ADD or LDR.
const MachineInstr *Def = *UseToDefs.find(Candidate)->second.begin();
// Record the elements of the chain.
const MachineInstr *L1 = Def;
const MachineInstr *L2 = nullptr;
unsigned ImmediateDefOpc = Def->getOpcode();
if (Def->getOpcode() != AArch64::ADRP) {
// Check the number of users of this node.
const SetOfMachineInstr *Users =
getUses(DefsPerColorToUses,
RegToId.find(Def->getOperand(0).getReg())->second, *Def);
if (Users->size() > 1) {
#ifdef DEBUG
// if all the uses of this def are in potential candidate, this is
// a complex candidate of level 2.
bool IsLevel2 = true;
for (const MachineInstr *MI : *Users) {
if (!PotentialCandidates.count(MI)) {
++NumTooCplxLvl2;
IsLevel2 = false;
break;
}
}
if (IsLevel2)
++NumCplxLvl2;
#endif // DEBUG
PotentialADROpportunities.insert(Def);
continue;
}
L2 = Def;
Def = *UseToDefs.find(Def)->second.begin();
L1 = Def;
} // else the element in the middle of the chain is nothing, thus
// Def already contains the first element of the chain.
// Check the number of users of the first node in the chain, i.e., ADRP
const SetOfMachineInstr *Users =
getUses(DefsPerColorToUses,
RegToId.find(Def->getOperand(0).getReg())->second, *Def);
if (Users->size() > 1) {
#ifdef DEBUG
// if all the uses of this def are in the defs of the potential candidate,
// this is a complex candidate of level 1
if (DefsOfPotentialCandidates.empty()) {
// lazy init
DefsOfPotentialCandidates = PotentialCandidates;
for (const MachineInstr *Candidate : PotentialCandidates) {
if (!UseToDefs.find(Candidate)->second.empty())
DefsOfPotentialCandidates.insert(
*UseToDefs.find(Candidate)->second.begin());
}
}
bool Found = false;
for (auto &Use : *Users) {
if (!DefsOfPotentialCandidates.count(Use)) {
++NumTooCplxLvl1;
Found = true;
break;
}
}
if (!Found)
++NumCplxLvl1;
#endif // DEBUG
continue;
}
bool IsL2Add = (ImmediateDefOpc == AArch64::ADDXri);
// If the chain is three instructions long and ldr is the second element,
// then this ldr must load form GOT, otherwise this is not a correct chain.
if (L2 && !IsL2Add && L2->getOperand(2).getTargetFlags() != AArch64II::MO_GOT)
continue;
SmallVector<const MachineInstr *, 3> Args;
MCLOHType Kind;
if (isCandidateLoad(Candidate)) {
if (!L2) {
// At this point, the candidate LOH indicates that the ldr instruction
// may use a direct access to the symbol. There is not such encoding
// for loads of byte and half.
if (!supportLoadFromLiteral(Candidate))
continue;
DEBUG(dbgs() << "Record AdrpLdr:\n" << *L1 << '\n' << *Candidate
<< '\n');
Kind = MCLOH_AdrpLdr;
Args.push_back(L1);
Args.push_back(Candidate);
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L1)) &&
"L1 already involved in LOH.");
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(Candidate)) &&
"Candidate already involved in LOH.");
++NumADRPToLDR;
} else {
DEBUG(dbgs() << "Record Adrp" << (IsL2Add ? "Add" : "LdrGot")
<< "Ldr:\n" << *L1 << '\n' << *L2 << '\n' << *Candidate
<< '\n');
Kind = IsL2Add ? MCLOH_AdrpAddLdr : MCLOH_AdrpLdrGotLdr;
Args.push_back(L1);
Args.push_back(L2);
Args.push_back(Candidate);
PotentialADROpportunities.remove(L2);
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L1)) &&
"L1 already involved in LOH.");
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L2)) &&
"L2 already involved in LOH.");
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(Candidate)) &&
"Candidate already involved in LOH.");
#ifdef DEBUG
// get the immediate of the load
if (Candidate->getOperand(2).getImm() == 0)
if (ImmediateDefOpc == AArch64::ADDXri)
++NumADDToLDR;
else
++NumLDRToLDR;
else if (ImmediateDefOpc == AArch64::ADDXri)
++NumADDToLDRWithImm;
else
++NumLDRToLDRWithImm;
#endif // DEBUG
}
} else {
if (ImmediateDefOpc == AArch64::ADRP)
continue;
else {
DEBUG(dbgs() << "Record Adrp" << (IsL2Add ? "Add" : "LdrGot")
<< "Str:\n" << *L1 << '\n' << *L2 << '\n' << *Candidate
<< '\n');
Kind = IsL2Add ? MCLOH_AdrpAddStr : MCLOH_AdrpLdrGotStr;
Args.push_back(L1);
Args.push_back(L2);
Args.push_back(Candidate);
PotentialADROpportunities.remove(L2);
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L1)) &&
"L1 already involved in LOH.");
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L2)) &&
"L2 already involved in LOH.");
assert((!InvolvedInLOHs || InvolvedInLOHs->insert(Candidate)) &&
"Candidate already involved in LOH.");
#ifdef DEBUG
// get the immediate of the store
if (Candidate->getOperand(2).getImm() == 0)
if (ImmediateDefOpc == AArch64::ADDXri)
++NumADDToSTR;
else
++NumLDRToSTR;
else if (ImmediateDefOpc == AArch64::ADDXri)
++NumADDToSTRWithImm;
else
++NumLDRToSTRWithImm;
#endif // DEBUG
}
}
AArch64FI.addLOHDirective(Kind, Args);
}
// Now, we grabbed all the big patterns, check ADR opportunities.
for (const MachineInstr *Candidate : PotentialADROpportunities)
registerADRCandidate(*Candidate, UseToDefs, DefsPerColorToUses, AArch64FI,
InvolvedInLOHs, RegToId);
}
/// Look for every register defined by potential LOHs candidates.
/// Map these registers with dense id in @p RegToId and vice-versa in
/// @p IdToReg. @p IdToReg is populated only in DEBUG mode.
static void collectInvolvedReg(MachineFunction &MF, MapRegToId &RegToId,
MapIdToReg &IdToReg,
const TargetRegisterInfo *TRI) {
unsigned CurRegId = 0;
if (!PreCollectRegister) {
unsigned NbReg = TRI->getNumRegs();
for (; CurRegId < NbReg; ++CurRegId) {
RegToId[CurRegId] = CurRegId;
DEBUG(IdToReg.push_back(CurRegId));
DEBUG(assert(IdToReg[CurRegId] == CurRegId && "Reg index mismatches"));
}
return;
}
DEBUG(dbgs() << "** Collect Involved Register\n");
for (const auto &MBB : MF) {
for (const MachineInstr &MI : MBB) {
if (!canDefBePartOfLOH(&MI))
continue;
// Process defs
for (MachineInstr::const_mop_iterator IO = MI.operands_begin(),
IOEnd = MI.operands_end();
IO != IOEnd; ++IO) {
if (!IO->isReg() || !IO->isDef())
continue;
unsigned CurReg = IO->getReg();
for (MCRegAliasIterator AI(CurReg, TRI, true); AI.isValid(); ++AI)
if (RegToId.find(*AI) == RegToId.end()) {
DEBUG(IdToReg.push_back(*AI);
assert(IdToReg[CurRegId] == *AI &&
"Reg index mismatches insertion index."));
RegToId[*AI] = CurRegId++;
DEBUG(dbgs() << "Register: " << PrintReg(*AI, TRI) << '\n');
}
}
}
}
}
bool AArch64CollectLOH::runOnMachineFunction(MachineFunction &MF) {
const TargetMachine &TM = MF.getTarget();
const TargetRegisterInfo *TRI = TM.getSubtargetImpl()->getRegisterInfo();
const MachineDominatorTree *MDT = &getAnalysis<MachineDominatorTree>();
MapRegToId RegToId;
MapIdToReg IdToReg;
AArch64FunctionInfo *AArch64FI = MF.getInfo<AArch64FunctionInfo>();
assert(AArch64FI && "No MachineFunctionInfo for this function!");
DEBUG(dbgs() << "Looking for LOH in " << MF.getName() << '\n');
collectInvolvedReg(MF, RegToId, IdToReg, TRI);
if (RegToId.empty())
return false;
MachineInstr *DummyOp = nullptr;
if (BasicBlockScopeOnly) {
const AArch64InstrInfo *TII = static_cast<const AArch64InstrInfo *>(
TM.getSubtargetImpl()->getInstrInfo());
// For local analysis, create a dummy operation to record uses that are not
// local.
DummyOp = MF.CreateMachineInstr(TII->get(AArch64::COPY), DebugLoc());
}
unsigned NbReg = RegToId.size();
bool Modified = false;
// Start with ADRP.
InstrToInstrs *ColorOpToReachedUses = new InstrToInstrs[NbReg];
// Compute the reaching def in ADRP mode, meaning ADRP definitions
// are first considered as uses.
reachingDef(MF, ColorOpToReachedUses, RegToId, true, DummyOp);
DEBUG(dbgs() << "ADRP reaching defs\n");
DEBUG(printReachingDef(ColorOpToReachedUses, NbReg, TRI, IdToReg));
// Translate the definition to uses map into a use to definitions map to ease
// statistic computation.
InstrToInstrs ADRPToReachingDefs;
reachedUsesToDefs(ADRPToReachingDefs, ColorOpToReachedUses, RegToId, true);
// Compute LOH for ADRP.
computeADRP(ADRPToReachingDefs, *AArch64FI, MDT);
delete[] ColorOpToReachedUses;
// Continue with general ADRP -> ADD/LDR -> LDR/STR pattern.
ColorOpToReachedUses = new InstrToInstrs[NbReg];
// first perform a regular reaching def analysis.
reachingDef(MF, ColorOpToReachedUses, RegToId, false, DummyOp);
DEBUG(dbgs() << "All reaching defs\n");
DEBUG(printReachingDef(ColorOpToReachedUses, NbReg, TRI, IdToReg));
// Turn that into a use to defs to ease statistic computation.
InstrToInstrs UsesToReachingDefs;
reachedUsesToDefs(UsesToReachingDefs, ColorOpToReachedUses, RegToId, false);
// Compute other than AdrpAdrp LOH.
computeOthers(UsesToReachingDefs, ColorOpToReachedUses, *AArch64FI, RegToId,
MDT);
delete[] ColorOpToReachedUses;
if (BasicBlockScopeOnly)
MF.DeleteMachineInstr(DummyOp);
return Modified;
}
/// createAArch64CollectLOHPass - returns an instance of the Statistic for
/// linker optimization pass.
FunctionPass *llvm::createAArch64CollectLOHPass() {
return new AArch64CollectLOH();
}
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