| //===-- llvm/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp -------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "DbgValueHistoryCalculator.h" |
| #include "llvm/ADT/BitVector.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/IR/DebugInfo.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetRegisterInfo.h" |
| #include <algorithm> |
| #include <map> |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "dwarfdebug" |
| |
| // \brief If @MI is a DBG_VALUE with debug value described by a |
| // defined register, returns the number of this register. |
| // In the other case, returns 0. |
| static unsigned isDescribedByReg(const MachineInstr &MI) { |
| assert(MI.isDebugValue()); |
| assert(MI.getNumOperands() == 4); |
| // If location of variable is described using a register (directly or |
| // indirecltly), this register is always a first operand. |
| return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0; |
| } |
| |
| void DbgValueHistoryMap::startInstrRange(InlinedVariable Var, |
| const MachineInstr &MI) { |
| // Instruction range should start with a DBG_VALUE instruction for the |
| // variable. |
| assert(MI.isDebugValue() && "not a DBG_VALUE"); |
| auto &Ranges = VarInstrRanges[Var]; |
| if (!Ranges.empty() && Ranges.back().second == nullptr && |
| Ranges.back().first->isIdenticalTo(&MI)) { |
| DEBUG(dbgs() << "Coalescing identical DBG_VALUE entries:\n" |
| << "\t" << Ranges.back().first << "\t" << MI << "\n"); |
| return; |
| } |
| Ranges.push_back(std::make_pair(&MI, nullptr)); |
| } |
| |
| void DbgValueHistoryMap::endInstrRange(InlinedVariable Var, |
| const MachineInstr &MI) { |
| auto &Ranges = VarInstrRanges[Var]; |
| // Verify that the current instruction range is not yet closed. |
| assert(!Ranges.empty() && Ranges.back().second == nullptr); |
| // For now, instruction ranges are not allowed to cross basic block |
| // boundaries. |
| assert(Ranges.back().first->getParent() == MI.getParent()); |
| Ranges.back().second = &MI; |
| } |
| |
| unsigned DbgValueHistoryMap::getRegisterForVar(InlinedVariable Var) const { |
| const auto &I = VarInstrRanges.find(Var); |
| if (I == VarInstrRanges.end()) |
| return 0; |
| const auto &Ranges = I->second; |
| if (Ranges.empty() || Ranges.back().second != nullptr) |
| return 0; |
| return isDescribedByReg(*Ranges.back().first); |
| } |
| |
| namespace { |
| // Maps physreg numbers to the variables they describe. |
| typedef DbgValueHistoryMap::InlinedVariable InlinedVariable; |
| typedef std::map<unsigned, SmallVector<InlinedVariable, 1>> RegDescribedVarsMap; |
| } |
| |
| // \brief Claim that @Var is not described by @RegNo anymore. |
| static void dropRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo, |
| InlinedVariable Var) { |
| const auto &I = RegVars.find(RegNo); |
| assert(RegNo != 0U && I != RegVars.end()); |
| auto &VarSet = I->second; |
| const auto &VarPos = std::find(VarSet.begin(), VarSet.end(), Var); |
| assert(VarPos != VarSet.end()); |
| VarSet.erase(VarPos); |
| // Don't keep empty sets in a map to keep it as small as possible. |
| if (VarSet.empty()) |
| RegVars.erase(I); |
| } |
| |
| // \brief Claim that @Var is now described by @RegNo. |
| static void addRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo, |
| InlinedVariable Var) { |
| assert(RegNo != 0U); |
| auto &VarSet = RegVars[RegNo]; |
| assert(std::find(VarSet.begin(), VarSet.end(), Var) == VarSet.end()); |
| VarSet.push_back(Var); |
| } |
| |
| // \brief Terminate the location range for variables described by register at |
| // @I by inserting @ClobberingInstr to their history. |
| static void clobberRegisterUses(RegDescribedVarsMap &RegVars, |
| RegDescribedVarsMap::iterator I, |
| DbgValueHistoryMap &HistMap, |
| const MachineInstr &ClobberingInstr) { |
| // Iterate over all variables described by this register and add this |
| // instruction to their history, clobbering it. |
| for (const auto &Var : I->second) |
| HistMap.endInstrRange(Var, ClobberingInstr); |
| RegVars.erase(I); |
| } |
| |
| // \brief Terminate the location range for variables described by register |
| // @RegNo by inserting @ClobberingInstr to their history. |
| static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo, |
| DbgValueHistoryMap &HistMap, |
| const MachineInstr &ClobberingInstr) { |
| const auto &I = RegVars.find(RegNo); |
| if (I == RegVars.end()) |
| return; |
| clobberRegisterUses(RegVars, I, HistMap, ClobberingInstr); |
| } |
| |
| // \brief Collect all registers clobbered by @MI and apply the functor |
| // @Func to their RegNo. |
| // @Func should be a functor with a void(unsigned) signature. We're |
| // not using std::function here for performance reasons. It has a |
| // small but measurable impact. By using a functor instead of a |
| // std::set& here, we can avoid the overhead of constructing |
| // temporaries in calculateDbgValueHistory, which has a significant |
| // performance impact. |
| template<typename Callable> |
| static void applyToClobberedRegisters(const MachineInstr &MI, |
| const TargetRegisterInfo *TRI, |
| Callable Func) { |
| for (const MachineOperand &MO : MI.operands()) { |
| if (!MO.isReg() || !MO.isDef() || !MO.getReg()) |
| continue; |
| for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid(); ++AI) |
| Func(*AI); |
| } |
| } |
| |
| // \brief Returns the first instruction in @MBB which corresponds to |
| // the function epilogue, or nullptr if @MBB doesn't contain an epilogue. |
| static const MachineInstr *getFirstEpilogueInst(const MachineBasicBlock &MBB) { |
| auto LastMI = MBB.getLastNonDebugInstr(); |
| if (LastMI == MBB.end() || !LastMI->isReturn()) |
| return nullptr; |
| // Assume that epilogue starts with instruction having the same debug location |
| // as the return instruction. |
| DebugLoc LastLoc = LastMI->getDebugLoc(); |
| auto Res = LastMI; |
| for (MachineBasicBlock::const_reverse_iterator I(std::next(LastMI)), |
| E = MBB.rend(); |
| I != E; ++I) { |
| if (I->getDebugLoc() != LastLoc) |
| return Res; |
| Res = &*I; |
| } |
| // If all instructions have the same debug location, assume whole MBB is |
| // an epilogue. |
| return MBB.begin(); |
| } |
| |
| // \brief Collect registers that are modified in the function body (their |
| // contents is changed outside of the prologue and epilogue). |
| static void collectChangingRegs(const MachineFunction *MF, |
| const TargetRegisterInfo *TRI, |
| BitVector &Regs) { |
| for (const auto &MBB : *MF) { |
| auto FirstEpilogueInst = getFirstEpilogueInst(MBB); |
| |
| for (const auto &MI : MBB) { |
| if (&MI == FirstEpilogueInst) |
| break; |
| if (!MI.getFlag(MachineInstr::FrameSetup)) |
| applyToClobberedRegisters(MI, TRI, [&](unsigned r) { Regs.set(r); }); |
| } |
| } |
| } |
| |
| void llvm::calculateDbgValueHistory(const MachineFunction *MF, |
| const TargetRegisterInfo *TRI, |
| DbgValueHistoryMap &Result) { |
| BitVector ChangingRegs(TRI->getNumRegs()); |
| collectChangingRegs(MF, TRI, ChangingRegs); |
| |
| RegDescribedVarsMap RegVars; |
| for (const auto &MBB : *MF) { |
| for (const auto &MI : MBB) { |
| if (!MI.isDebugValue()) { |
| // Not a DBG_VALUE instruction. It may clobber registers which describe |
| // some variables. |
| applyToClobberedRegisters(MI, TRI, [&](unsigned RegNo) { |
| if (ChangingRegs.test(RegNo)) |
| clobberRegisterUses(RegVars, RegNo, Result, MI); |
| }); |
| continue; |
| } |
| |
| assert(MI.getNumOperands() > 1 && "Invalid DBG_VALUE instruction!"); |
| // Use the base variable (without any DW_OP_piece expressions) |
| // as index into History. The full variables including the |
| // piece expressions are attached to the MI. |
| const DILocalVariable *RawVar = MI.getDebugVariable(); |
| assert(RawVar->isValidLocationForIntrinsic(MI.getDebugLoc()) && |
| "Expected inlined-at fields to agree"); |
| InlinedVariable Var(RawVar, MI.getDebugLoc()->getInlinedAt()); |
| |
| if (unsigned PrevReg = Result.getRegisterForVar(Var)) |
| dropRegDescribedVar(RegVars, PrevReg, Var); |
| |
| Result.startInstrRange(Var, MI); |
| |
| if (unsigned NewReg = isDescribedByReg(MI)) |
| addRegDescribedVar(RegVars, NewReg, Var); |
| } |
| |
| // Make sure locations for register-described variables are valid only |
| // until the end of the basic block (unless it's the last basic block, in |
| // which case let their liveness run off to the end of the function). |
| if (!MBB.empty() && &MBB != &MF->back()) { |
| for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) { |
| auto CurElem = I++; // CurElem can be erased below. |
| if (ChangingRegs.test(CurElem->first)) |
| clobberRegisterUses(RegVars, CurElem, Result, MBB.back()); |
| } |
| } |
| } |
| } |