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517 lines
18 KiB
517 lines
18 KiB
//===------ LiveDebugValues.cpp - Tracking Debug Value MIs ----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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///
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/// This pass implements a data flow analysis that propagates debug location
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/// information by inserting additional DBG_VALUE instructions into the machine
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/// instruction stream. The pass internally builds debug location liveness
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/// ranges to determine the points where additional DBG_VALUEs need to be
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/// inserted.
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///
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/// This is a separate pass from DbgValueHistoryCalculator to facilitate
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/// testing and improve modularity.
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SparseBitVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/UniqueVector.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/IR/DebugInfo.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Target/TargetSubtargetInfo.h"
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#include <list>
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#include <queue>
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using namespace llvm;
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#define DEBUG_TYPE "live-debug-values"
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STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
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namespace {
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// \brief If @MI is a DBG_VALUE with debug value described by a defined
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// register, returns the number of this register. In the other case, returns 0.
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static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) {
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assert(MI.isDebugValue() && "expected a DBG_VALUE");
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assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
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// If location of variable is described using a register (directly
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// or indirectly), this register is always a first operand.
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return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
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}
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class LiveDebugValues : public MachineFunctionPass {
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private:
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const TargetRegisterInfo *TRI;
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const TargetInstrInfo *TII;
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/// Based on std::pair so it can be used as an index into a DenseMap.
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typedef std::pair<const DILocalVariable *, const DILocation *>
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DebugVariableBase;
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/// A potentially inlined instance of a variable.
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struct DebugVariable : public DebugVariableBase {
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DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt)
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: DebugVariableBase(Var, InlinedAt) {}
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const DILocalVariable *getVar() const { return this->first; };
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const DILocation *getInlinedAt() const { return this->second; };
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bool operator<(const DebugVariable &DV) const {
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if (getVar() == DV.getVar())
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return getInlinedAt() < DV.getInlinedAt();
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return getVar() < DV.getVar();
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}
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};
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/// A pair of debug variable and value location.
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struct VarLoc {
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const DebugVariable Var;
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const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
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enum { InvalidKind = 0, RegisterKind } Kind;
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/// The value location. Stored separately to avoid repeatedly
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/// extracting it from MI.
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union {
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struct {
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uint32_t RegNo;
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uint32_t Offset;
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} RegisterLoc;
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uint64_t Hash;
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} Loc;
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VarLoc(const MachineInstr &MI)
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: Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
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Kind(InvalidKind) {
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static_assert((sizeof(Loc) == sizeof(uint64_t)),
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"hash does not cover all members of Loc");
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assert(MI.isDebugValue() && "not a DBG_VALUE");
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assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
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if (int RegNo = isDbgValueDescribedByReg(MI)) {
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Kind = RegisterKind;
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Loc.RegisterLoc.RegNo = RegNo;
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uint64_t Offset =
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MI.isIndirectDebugValue() ? MI.getOperand(1).getImm() : 0;
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// We don't support offsets larger than 4GiB here. They are
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// slated to be replaced with DIExpressions anyway.
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if (Offset >= (1ULL << 32))
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Kind = InvalidKind;
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else
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Loc.RegisterLoc.Offset = Offset;
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}
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}
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/// If this variable is described by a register, return it,
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/// otherwise return 0.
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unsigned isDescribedByReg() const {
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if (Kind == RegisterKind)
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return Loc.RegisterLoc.RegNo;
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return 0;
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}
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void dump() const { MI.dump(); }
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bool operator==(const VarLoc &Other) const {
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return Var == Other.Var && Loc.Hash == Other.Loc.Hash;
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}
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/// This operator guarantees that VarLocs are sorted by Variable first.
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bool operator<(const VarLoc &Other) const {
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if (Var == Other.Var)
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return Loc.Hash < Other.Loc.Hash;
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return Var < Other.Var;
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}
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};
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typedef UniqueVector<VarLoc> VarLocMap;
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typedef SparseBitVector<> VarLocSet;
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typedef SmallDenseMap<const MachineBasicBlock *, VarLocSet> VarLocInMBB;
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/// This holds the working set of currently open ranges. For fast
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/// access, this is done both as a set of VarLocIDs, and a map of
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/// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
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/// previous open ranges for the same variable.
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class OpenRangesSet {
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VarLocSet VarLocs;
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SmallDenseMap<DebugVariableBase, unsigned, 8> Vars;
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public:
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const VarLocSet &getVarLocs() const { return VarLocs; }
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/// Terminate all open ranges for Var by removing it from the set.
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void erase(DebugVariable Var) {
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auto It = Vars.find(Var);
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if (It != Vars.end()) {
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unsigned ID = It->second;
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VarLocs.reset(ID);
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Vars.erase(It);
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}
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}
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/// Terminate all open ranges listed in \c KillSet by removing
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/// them from the set.
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void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
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VarLocs.intersectWithComplement(KillSet);
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for (unsigned ID : KillSet)
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Vars.erase(VarLocIDs[ID].Var);
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}
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/// Insert a new range into the set.
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void insert(unsigned VarLocID, DebugVariableBase Var) {
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VarLocs.set(VarLocID);
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Vars.insert({Var, VarLocID});
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}
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/// Empty the set.
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void clear() {
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VarLocs.clear();
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Vars.clear();
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}
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/// Return whether the set is empty or not.
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bool empty() const {
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assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
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return VarLocs.empty();
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}
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};
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void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
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VarLocMap &VarLocIDs);
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void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
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const VarLocMap &VarLocIDs);
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bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
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VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
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bool transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
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VarLocInMBB &OutLocs, VarLocMap &VarLocIDs);
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bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
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const VarLocMap &VarLocIDs);
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bool ExtendRanges(MachineFunction &MF);
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public:
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static char ID;
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/// Default construct and initialize the pass.
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LiveDebugValues();
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/// Tell the pass manager which passes we depend on and what
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/// information we preserve.
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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MachineFunctionProperties getRequiredProperties() const override {
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return MachineFunctionProperties().set(
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MachineFunctionProperties::Property::AllVRegsAllocated);
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}
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/// Print to ostream with a message.
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void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
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const VarLocMap &VarLocIDs, const char *msg,
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raw_ostream &Out) const;
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/// Calculate the liveness information for the given machine function.
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bool runOnMachineFunction(MachineFunction &MF) override;
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};
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} // namespace
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//===----------------------------------------------------------------------===//
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// Implementation
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//===----------------------------------------------------------------------===//
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char LiveDebugValues::ID = 0;
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char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
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INITIALIZE_PASS(LiveDebugValues, "livedebugvalues", "Live DEBUG_VALUE analysis",
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false, false)
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/// Default construct and initialize the pass.
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LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
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initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
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}
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/// Tell the pass manager which passes we depend on and what information we
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/// preserve.
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void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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//===----------------------------------------------------------------------===//
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// Debug Range Extension Implementation
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//===----------------------------------------------------------------------===//
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void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
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const VarLocInMBB &V,
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const VarLocMap &VarLocIDs,
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const char *msg,
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raw_ostream &Out) const {
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for (const MachineBasicBlock &BB : MF) {
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const auto &L = V.lookup(&BB);
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Out << "MBB: " << BB.getName() << ":\n";
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for (unsigned VLL : L) {
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const VarLoc &VL = VarLocIDs[VLL];
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Out << " Var: " << VL.Var.getVar()->getName();
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Out << " MI: ";
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VL.dump();
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Out << "\n";
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}
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}
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Out << "\n";
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}
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/// End all previous ranges related to @MI and start a new range from @MI
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/// if it is a DBG_VALUE instr.
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void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
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OpenRangesSet &OpenRanges,
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VarLocMap &VarLocIDs) {
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if (!MI.isDebugValue())
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return;
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const DILocalVariable *Var = MI.getDebugVariable();
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const DILocation *DebugLoc = MI.getDebugLoc();
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const DILocation *InlinedAt = DebugLoc->getInlinedAt();
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assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
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"Expected inlined-at fields to agree");
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// End all previous ranges of Var.
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DebugVariable V(Var, InlinedAt);
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OpenRanges.erase(V);
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// Add the VarLoc to OpenRanges from this DBG_VALUE.
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// TODO: Currently handles DBG_VALUE which has only reg as location.
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if (isDbgValueDescribedByReg(MI)) {
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VarLoc VL(MI);
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unsigned ID = VarLocIDs.insert(VL);
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OpenRanges.insert(ID, VL.Var);
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}
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}
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/// A definition of a register may mark the end of a range.
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void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
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OpenRangesSet &OpenRanges,
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const VarLocMap &VarLocIDs) {
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MachineFunction *MF = MI.getParent()->getParent();
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const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
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unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
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SparseBitVector<> KillSet;
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for (const MachineOperand &MO : MI.operands()) {
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if (MO.isReg() && MO.isDef() && MO.getReg() &&
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TRI->isPhysicalRegister(MO.getReg())) {
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// Remove ranges of all aliased registers.
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for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
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for (unsigned ID : OpenRanges.getVarLocs())
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if (VarLocIDs[ID].isDescribedByReg() == *RAI)
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KillSet.set(ID);
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} else if (MO.isRegMask()) {
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// Remove ranges of all clobbered registers. Register masks don't usually
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// list SP as preserved. While the debug info may be off for an
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// instruction or two around callee-cleanup calls, transferring the
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// DEBUG_VALUE across the call is still a better user experience.
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for (unsigned ID : OpenRanges.getVarLocs()) {
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unsigned Reg = VarLocIDs[ID].isDescribedByReg();
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if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
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KillSet.set(ID);
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}
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}
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}
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OpenRanges.erase(KillSet, VarLocIDs);
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}
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/// Terminate all open ranges at the end of the current basic block.
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bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
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OpenRangesSet &OpenRanges,
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VarLocInMBB &OutLocs,
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const VarLocMap &VarLocIDs) {
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bool Changed = false;
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const MachineBasicBlock *CurMBB = MI.getParent();
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if (!(MI.isTerminator() || (&MI == &CurMBB->instr_back())))
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return false;
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if (OpenRanges.empty())
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return false;
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DEBUG(for (unsigned ID : OpenRanges.getVarLocs()) {
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// Copy OpenRanges to OutLocs, if not already present.
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dbgs() << "Add to OutLocs: "; VarLocIDs[ID].dump();
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});
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VarLocSet &VLS = OutLocs[CurMBB];
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Changed = VLS |= OpenRanges.getVarLocs();
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OpenRanges.clear();
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return Changed;
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}
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/// This routine creates OpenRanges and OutLocs.
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bool LiveDebugValues::transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
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VarLocInMBB &OutLocs, VarLocMap &VarLocIDs) {
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bool Changed = false;
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transferDebugValue(MI, OpenRanges, VarLocIDs);
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transferRegisterDef(MI, OpenRanges, VarLocIDs);
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Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
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return Changed;
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}
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/// This routine joins the analysis results of all incoming edges in @MBB by
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/// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
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/// source variable in all the predecessors of @MBB reside in the same location.
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bool LiveDebugValues::join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs,
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VarLocInMBB &InLocs, const VarLocMap &VarLocIDs) {
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DEBUG(dbgs() << "join MBB: " << MBB.getName() << "\n");
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bool Changed = false;
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VarLocSet InLocsT; // Temporary incoming locations.
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// For all predecessors of this MBB, find the set of VarLocs that
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// can be joined.
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for (auto p : MBB.predecessors()) {
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auto OL = OutLocs.find(p);
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// Join is null in case of empty OutLocs from any of the pred.
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if (OL == OutLocs.end())
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return false;
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// Just copy over the Out locs to incoming locs for the first predecessor.
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if (p == *MBB.pred_begin()) {
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InLocsT = OL->second;
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continue;
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}
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// Join with this predecessor.
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InLocsT &= OL->second;
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}
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if (InLocsT.empty())
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return false;
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VarLocSet &ILS = InLocs[&MBB];
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// Insert DBG_VALUE instructions, if not already inserted.
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VarLocSet Diff = InLocsT;
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Diff.intersectWithComplement(ILS);
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for (auto ID : Diff) {
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// This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
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// new range is started for the var from the mbb's beginning by inserting
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// a new DBG_VALUE. transfer() will end this range however appropriate.
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const VarLoc &DiffIt = VarLocIDs[ID];
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const MachineInstr *DMI = &DiffIt.MI;
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MachineInstr *MI =
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BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(),
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DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(), 0,
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DMI->getDebugVariable(), DMI->getDebugExpression());
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if (DMI->isIndirectDebugValue())
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MI->getOperand(1).setImm(DMI->getOperand(1).getImm());
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DEBUG(dbgs() << "Inserted: "; MI->dump(););
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ILS.set(ID);
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++NumInserted;
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Changed = true;
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}
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return Changed;
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}
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/// Calculate the liveness information for the given machine function and
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/// extend ranges across basic blocks.
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bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
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DEBUG(dbgs() << "\nDebug Range Extension\n");
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bool Changed = false;
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bool OLChanged = false;
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bool MBBJoined = false;
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VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
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OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
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VarLocInMBB OutLocs; // Ranges that exist beyond bb.
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VarLocInMBB InLocs; // Ranges that are incoming after joining.
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DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
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DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
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std::priority_queue<unsigned int, std::vector<unsigned int>,
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std::greater<unsigned int>>
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Worklist;
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std::priority_queue<unsigned int, std::vector<unsigned int>,
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std::greater<unsigned int>>
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Pending;
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// Initialize every mbb with OutLocs.
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for (auto &MBB : MF)
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for (auto &MI : MBB)
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transfer(MI, OpenRanges, OutLocs, VarLocIDs);
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DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after initialization",
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dbgs()));
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ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
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unsigned int RPONumber = 0;
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for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
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OrderToBB[RPONumber] = *RI;
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BBToOrder[*RI] = RPONumber;
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Worklist.push(RPONumber);
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++RPONumber;
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}
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// This is a standard "union of predecessor outs" dataflow problem.
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// To solve it, we perform join() and transfer() using the two worklist method
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// until the ranges converge.
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// Ranges have converged when both worklists are empty.
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while (!Worklist.empty() || !Pending.empty()) {
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// We track what is on the pending worklist to avoid inserting the same
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// thing twice. We could avoid this with a custom priority queue, but this
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// is probably not worth it.
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SmallPtrSet<MachineBasicBlock *, 16> OnPending;
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while (!Worklist.empty()) {
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MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
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Worklist.pop();
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MBBJoined = join(*MBB, OutLocs, InLocs, VarLocIDs);
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if (MBBJoined) {
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MBBJoined = false;
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Changed = true;
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for (auto &MI : *MBB)
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OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs);
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DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
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"OutLocs after propagating", dbgs()));
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|
DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
|
|
"InLocs after propagating", dbgs()));
|
|
|
|
if (OLChanged) {
|
|
OLChanged = false;
|
|
for (auto s : MBB->successors())
|
|
if (OnPending.insert(s).second) {
|
|
Pending.push(BBToOrder[s]);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
Worklist.swap(Pending);
|
|
// At this point, pending must be empty, since it was just the empty
|
|
// worklist
|
|
assert(Pending.empty() && "Pending should be empty");
|
|
}
|
|
|
|
DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
|
|
DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
|
|
return Changed;
|
|
}
|
|
|
|
bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
|
|
TRI = MF.getSubtarget().getRegisterInfo();
|
|
TII = MF.getSubtarget().getInstrInfo();
|
|
|
|
bool Changed = false;
|
|
|
|
Changed |= ExtendRanges(MF);
|
|
|
|
return Changed;
|
|
}
|