#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/Target/TargetRegisterInfo.h"
#include <algorithm>
#include <map>
+#include <set>
#define DEBUG_TYPE "dwarfdebug"
namespace llvm {
-namespace {
-// Maps physreg numbers to the variables they describe.
-typedef std::map<unsigned, SmallVector<const MDNode *, 1>> RegDescribedVarsMap;
-}
-
// \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() == 3);
+ 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(const MDNode *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(const MDNode *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(const MDNode *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 std::map<unsigned, SmallVector<const MDNode *, 1>> RegDescribedVarsMap;
+}
+
// \brief Claim that @Var is not described by @RegNo anymore.
static void dropRegDescribedVar(RegDescribedVarsMap &RegVars,
unsigned RegNo, const MDNode *Var) {
static void addRegDescribedVar(RegDescribedVarsMap &RegVars,
unsigned RegNo, const MDNode *Var) {
assert(RegNo != 0U);
- RegVars[RegNo].push_back(Var);
-}
-
-static void clobberVariableLocation(SmallVectorImpl<const MachineInstr *> &VarHistory,
- const MachineInstr &ClobberingInstr) {
- assert(!VarHistory.empty());
- // DBG_VALUE we're clobbering should belong to the same MBB.
- assert(VarHistory.back()->isDebugValue());
- assert(VarHistory.back()->getParent() == ClobberingInstr.getParent());
- VarHistory.push_back(&ClobberingInstr);
+ 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
// Iterate over all variables described by this register and add this
// instruction to their history, clobbering it.
for (const auto &Var : I->second)
- clobberVariableLocation(HistMap[Var], ClobberingInstr);
+ HistMap.endInstrRange(Var, ClobberingInstr);
RegVars.erase(I);
}
-// \brief Terminate the location range for all variables, described by registers
-// clobbered by @MI.
-static void clobberRegisterUses(RegDescribedVarsMap &RegVars,
- const MachineInstr &MI,
- const TargetRegisterInfo *TRI,
- DbgValueHistoryMap &HistMap) {
+// \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) {
- unsigned RegNo = *AI;
- clobberRegisterUses(RegVars, RegNo, HistMap, MI);
- }
+ for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid(); ++AI)
+ Func(*AI);
}
}
-// \brief Terminate the location range for all register-described variables
-// by inserting @ClobberingInstr to their history.
-static void clobberAllRegistersUses(RegDescribedVarsMap &RegVars,
- DbgValueHistoryMap &HistMap,
- const MachineInstr &ClobberingInstr) {
- for (const auto &I : RegVars)
- for (const auto &Var : I.second)
- clobberVariableLocation(HistMap[Var], ClobberingInstr);
- RegVars.clear();
+// \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)); I != MBB.rend();
+ ++I) {
+ if (I->getDebugLoc() != LastLoc)
+ return Res;
+ Res = std::prev(I.base());
+ }
+ // If all instructions have the same debug location, assume whole MBB is
+ // an epilogue.
+ return MBB.begin();
}
-// \brief Update the register that describes location of @Var in @RegVars map.
-static void
-updateRegForVariable(RegDescribedVarsMap &RegVars, const MDNode *Var,
- const SmallVectorImpl<const MachineInstr *> &VarHistory,
- const MachineInstr &MI) {
- if (!VarHistory.empty()) {
- const MachineInstr &Prev = *VarHistory.back();
- // Check if Var is currently described by a register by instruction in the
- // same basic block.
- if (Prev.isDebugValue() && Prev.getDebugVariable() == Var &&
- Prev.getParent() == MI.getParent()) {
- if (unsigned PrevReg = isDescribedByReg(Prev))
- dropRegDescribedVar(RegVars, PrevReg, Var);
- }
- }
+// \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,
+ std::set<unsigned> &Regs) {
+ for (const auto &MBB : *MF) {
+ auto FirstEpilogueInst = getFirstEpilogueInst(MBB);
- assert(MI.getDebugVariable() == Var);
- if (unsigned MIReg = isDescribedByReg(MI))
- addRegDescribedVar(RegVars, MIReg, Var);
+ for (const auto &MI : MBB) {
+ if (&MI == FirstEpilogueInst)
+ break;
+ if (!MI.getFlag(MachineInstr::FrameSetup))
+ applyToClobberedRegisters(MI, TRI, [&](unsigned r) { Regs.insert(r); });
+ }
+ }
}
void calculateDbgValueHistory(const MachineFunction *MF,
const TargetRegisterInfo *TRI,
DbgValueHistoryMap &Result) {
- RegDescribedVarsMap RegVars;
+ std::set<unsigned> ChangingRegs;
+ 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.
- clobberRegisterUses(RegVars, MI, TRI, Result);
+ applyToClobberedRegisters(MI, TRI, [&](unsigned RegNo) {
+ if (ChangingRegs.count(RegNo))
+ clobberRegisterUses(RegVars, RegNo, Result, MI);
+ });
continue;
}
- const MDNode *Var = MI.getDebugVariable();
- auto &History = Result[Var];
+ 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.
+ DIVariable Var = MI.getDebugVariable();
- if (!History.empty() && History.back()->isIdenticalTo(&MI)) {
- DEBUG(dbgs() << "Coalescing identical DBG_VALUE entries:\n"
- << "\t" << History.back() << "\t" << MI << "\n");
- continue;
- }
+ if (unsigned PrevReg = Result.getRegisterForVar(Var))
+ dropRegDescribedVar(RegVars, PrevReg, Var);
- updateRegForVariable(RegVars, Var, History, MI);
- History.push_back(&MI);
+ 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())
- clobberAllRegistersUses(RegVars, Result, MBB.back());
+ if (!MBB.empty() && &MBB != &MF->back()) {
+ for (unsigned RegNo : ChangingRegs)
+ clobberRegisterUses(RegVars, RegNo, Result, MBB.back());
+ }
}
}
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