RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-10-20 03:23:01 +02:00
Code Issues Projects Releases Wiki Activity
0f000465c2
llvm-mirror/lib/CodeGen/LiveDebugValues.cpp
Nikola Prica 27377535b8 [LiveDebugValues] Close range for previous variable's location when adding newly deduced location 
When LiveDebugValues deduces new variable's location from spill, restore or
register copy instruction it should close old variable's location. Otherwise
we can have multiple block output locations for same variable. That could lead
to inserting two DBG_VALUEs for same variable to the beginning of the successor
block which results to ignoring of first DBG_VALUE.

Reviewers: aprantl, jmorse, wolfgangp, dstenb

Reviewed By: aprantl

Subscribers: probinson, asowda, ivanbaev, petarj, djtodoro

Tags: #debug-info

Differential Revision: https://reviews.llvm.org/D62196

llvm-svn: 362373
2019-06-03 09:48:29 +00:00

982 lines
38 KiB
C++
Raw Blame History

//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// This pass implements a data flow analysis that propagates debug location
/// information by inserting additional DBG_VALUE instructions into the machine
/// instruction stream. The pass internally builds debug location liveness
/// ranges to determine the points where additional DBG_VALUEs need to be
/// inserted.
///
/// This is a separate pass from DbgValueHistoryCalculator to facilitate
/// testing and improve modularity.
///
//===----------------------------------------------------------------------===//
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/UniqueVector.h"
#include "llvm/CodeGen/LexicalScopes.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <functional>
#include <queue>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "livedebugvalues"
STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
// 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 isDbgValueDescribedByReg(const MachineInstr &MI) {
assert(MI.isDebugValue() && "expected a DBG_VALUE");
assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
// If location of variable is described using a register (directly
// or indirectly), this register is always a first operand.
return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
}
namespace {
class LiveDebugValues : public MachineFunctionPass {
private:
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
const TargetFrameLowering *TFI;
BitVector CalleeSavedRegs;
LexicalScopes LS;
enum struct TransferKind { TransferCopy, TransferSpill, TransferRestore };
/// Keeps track of lexical scopes associated with a user value's source
/// location.
class UserValueScopes {
DebugLoc DL;
LexicalScopes &LS;
SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
public:
UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {}
/// Return true if current scope dominates at least one machine
/// instruction in a given machine basic block.
bool dominates(MachineBasicBlock *MBB) {
if (LBlocks.empty())
LS.getMachineBasicBlocks(DL, LBlocks);
return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
}
};
/// Based on std::pair so it can be used as an index into a DenseMap.
using DebugVariableBase =
std::pair<const DILocalVariable *, const DILocation *>;
/// A potentially inlined instance of a variable.
struct DebugVariable : public DebugVariableBase {
DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt)
: DebugVariableBase(Var, InlinedAt) {}
const DILocalVariable *getVar() const { return this->first; }
const DILocation *getInlinedAt() const { return this->second; }
bool operator<(const DebugVariable &DV) const {
if (getVar() == DV.getVar())
return getInlinedAt() < DV.getInlinedAt();
return getVar() < DV.getVar();
}
};
/// A pair of debug variable and value location.
struct VarLoc {
// The location at which a spilled variable resides. It consists of a
// register and an offset.
struct SpillLoc {
unsigned SpillBase;
int SpillOffset;
bool operator==(const SpillLoc &Other) const {
return SpillBase == Other.SpillBase && SpillOffset == Other.SpillOffset;
}
};
const DebugVariable Var;
const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
mutable UserValueScopes UVS;
enum VarLocKind {
InvalidKind = 0,
RegisterKind,
SpillLocKind
} Kind = InvalidKind;
/// The value location. Stored separately to avoid repeatedly
/// extracting it from MI.
union {
uint64_t RegNo;
SpillLoc SpillLocation;
uint64_t Hash;
} Loc;
VarLoc(const MachineInstr &MI, LexicalScopes &LS)
: Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
UVS(MI.getDebugLoc(), LS) {
static_assert((sizeof(Loc) == sizeof(uint64_t)),
"hash does not cover all members of Loc");
assert(MI.isDebugValue() && "not a DBG_VALUE");
assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
if (int RegNo = isDbgValueDescribedByReg(MI)) {
Kind = RegisterKind;
Loc.RegNo = RegNo;
}
}
/// The constructor for spill locations.
VarLoc(const MachineInstr &MI, unsigned SpillBase, int SpillOffset,
LexicalScopes &LS)
: Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
UVS(MI.getDebugLoc(), LS) {
assert(MI.isDebugValue() && "not a DBG_VALUE");
assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
Kind = SpillLocKind;
Loc.SpillLocation = {SpillBase, SpillOffset};
}
/// If this variable is described by a register, return it,
/// otherwise return 0.
unsigned isDescribedByReg() const {
if (Kind == RegisterKind)
return Loc.RegNo;
return 0;
}
/// Determine whether the lexical scope of this value's debug location
/// dominates MBB.
bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); }
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void dump() const { MI.dump(); }
#endif
bool operator==(const VarLoc &Other) const {
return Var == Other.Var && Loc.Hash == Other.Loc.Hash;
}
/// This operator guarantees that VarLocs are sorted by Variable first.
bool operator<(const VarLoc &Other) const {
if (Var == Other.Var)
return Loc.Hash < Other.Loc.Hash;
return Var < Other.Var;
}
};
using VarLocMap = UniqueVector<VarLoc>;
using VarLocSet = SparseBitVector<>;
using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>;
struct TransferDebugPair {
MachineInstr *TransferInst;
MachineInstr *DebugInst;
};
using TransferMap = SmallVector<TransferDebugPair, 4>;
/// This holds the working set of currently open ranges. For fast
/// access, this is done both as a set of VarLocIDs, and a map of
/// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
/// previous open ranges for the same variable.
class OpenRangesSet {
VarLocSet VarLocs;
SmallDenseMap<DebugVariableBase, unsigned, 8> Vars;
public:
const VarLocSet &getVarLocs() const { return VarLocs; }
/// Terminate all open ranges for Var by removing it from the set.
void erase(DebugVariable Var) {
auto It = Vars.find(Var);
if (It != Vars.end()) {
unsigned ID = It->second;
VarLocs.reset(ID);
Vars.erase(It);
}
}
/// Terminate all open ranges listed in \c KillSet by removing
/// them from the set.
void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
VarLocs.intersectWithComplement(KillSet);
for (unsigned ID : KillSet)
Vars.erase(VarLocIDs[ID].Var);
}
/// Insert a new range into the set.
void insert(unsigned VarLocID, DebugVariableBase Var) {
VarLocs.set(VarLocID);
Vars.insert({Var, VarLocID});
}
/// Empty the set.
void clear() {
VarLocs.clear();
Vars.clear();
}
/// Return whether the set is empty or not.
bool empty() const {
assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
return VarLocs.empty();
}
};
bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
unsigned &Reg);
/// If a given instruction is identified as a spill, return the spill location
/// and set \p Reg to the spilled register.
Optional<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI,
MachineFunction *MF,
unsigned &Reg);
/// Given a spill instruction, extract the register and offset used to
/// address the spill location in a target independent way.
VarLoc::SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI);
void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
TransferMap &Transfers, VarLocMap &VarLocIDs,
unsigned OldVarID, TransferKind Kind,
unsigned NewReg = 0);
void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs);
void transferSpillOrRestoreInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs, TransferMap &Transfers);
void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs, TransferMap &Transfers);
void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
const VarLocMap &VarLocIDs);
bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
bool process(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
TransferMap &Transfers, bool transferChanges);
bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
const VarLocMap &VarLocIDs,
SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks);
bool ExtendRanges(MachineFunction &MF);
public:
static char ID;
/// Default construct and initialize the pass.
LiveDebugValues();
/// Tell the pass manager which passes we depend on and what
/// information we preserve.
void getAnalysisUsage(AnalysisUsage &AU) const override;
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().set(
MachineFunctionProperties::Property::NoVRegs);
}
/// Print to ostream with a message.
void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
const VarLocMap &VarLocIDs, const char *msg,
raw_ostream &Out) const;
/// Calculate the liveness information for the given machine function.
bool runOnMachineFunction(MachineFunction &MF) override;
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Implementation
//===----------------------------------------------------------------------===//
char LiveDebugValues::ID = 0;
char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
false, false)
/// Default construct and initialize the pass.
LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
}
/// Tell the pass manager which passes we depend on and what information we
/// preserve.
void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
//===----------------------------------------------------------------------===//
// Debug Range Extension Implementation
//===----------------------------------------------------------------------===//
#ifndef NDEBUG
void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
const VarLocInMBB &V,
const VarLocMap &VarLocIDs,
const char *msg,
raw_ostream &Out) const {
Out << '\n' << msg << '\n';
for (const MachineBasicBlock &BB : MF) {
const VarLocSet &L = V.lookup(&BB);
if (L.empty())
continue;
Out << "MBB: " << BB.getNumber() << ":\n";
for (unsigned VLL : L) {
const VarLoc &VL = VarLocIDs[VLL];
Out << " Var: " << VL.Var.getVar()->getName();
Out << " MI: ";
VL.dump();
}
}
Out << "\n";
}
#endif
LiveDebugValues::VarLoc::SpillLoc
LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
assert(MI.hasOneMemOperand() &&
"Spill instruction does not have exactly one memory operand?");
auto MMOI = MI.memoperands_begin();
const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
assert(PVal->kind() == PseudoSourceValue::FixedStack &&
"Inconsistent memory operand in spill instruction");
int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
const MachineBasicBlock *MBB = MI.getParent();
unsigned Reg;
int Offset = TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
return {Reg, Offset};
}
/// End all previous ranges related to @MI and start a new range from @MI
/// if it is a DBG_VALUE instr.
void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs) {
if (!MI.isDebugValue())
return;
const DILocalVariable *Var = MI.getDebugVariable();
const DILocation *DebugLoc = MI.getDebugLoc();
const DILocation *InlinedAt = DebugLoc->getInlinedAt();
assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
"Expected inlined-at fields to agree");
// End all previous ranges of Var.
DebugVariable V(Var, InlinedAt);
OpenRanges.erase(V);
// Add the VarLoc to OpenRanges from this DBG_VALUE.
// TODO: Currently handles DBG_VALUE which has only reg as location.
if (isDbgValueDescribedByReg(MI)) {
VarLoc VL(MI, LS);
unsigned ID = VarLocIDs.insert(VL);
OpenRanges.insert(ID, VL.Var);
}
}
/// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc
/// with \p OldVarID should be deleted form \p OpenRanges and replaced with
/// new VarLoc. If \p NewReg is different than default zero value then the
/// new location will be register location created by the copy like instruction,
/// otherwise it is variable's location on the stack.
void LiveDebugValues::insertTransferDebugPair(
MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
VarLocMap &VarLocIDs, unsigned OldVarID, TransferKind Kind,
unsigned NewReg) {
const MachineInstr *DebugInstr = &VarLocIDs[OldVarID].MI;
MachineFunction *MF = MI.getParent()->getParent();
MachineInstr *NewDebugInstr;
auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr,
&VarLocIDs](VarLoc &VL, MachineInstr *NewDebugInstr) {
unsigned LocId = VarLocIDs.insert(VL);
// Close this variable's previous location range.
DebugVariable V(DebugInstr->getDebugVariable(),
DebugInstr->getDebugLoc()->getInlinedAt());
OpenRanges.erase(V);
OpenRanges.insert(LocId, VL.Var);
// The newly created DBG_VALUE instruction NewDebugInstr must be inserted
// after MI. Keep track of the pairing.
TransferDebugPair MIP = {&MI, NewDebugInstr};
Transfers.push_back(MIP);
};
// End all previous ranges of Var.
OpenRanges.erase(VarLocIDs[OldVarID].Var);
switch (Kind) {
case TransferKind::TransferCopy: {
assert(NewReg &&
"No register supplied when handling a copy of a debug value");
// Create a DBG_VALUE instruction to describe the Var in its new
// register location.
NewDebugInstr = BuildMI(
*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(),
DebugInstr->isIndirectDebugValue(), NewReg,
DebugInstr->getDebugVariable(), DebugInstr->getDebugExpression());
if (DebugInstr->isIndirectDebugValue())
NewDebugInstr->getOperand(1).setImm(DebugInstr->getOperand(1).getImm());
VarLoc VL(*NewDebugInstr, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: ";
NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
/*SkipOpers*/false, /*SkipDebugLoc*/false,
/*AddNewLine*/true, TII));
return;
}
case TransferKind::TransferSpill: {
// Create a DBG_VALUE instruction to describe the Var in its spilled
// location.
VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
auto *SpillExpr = DIExpression::prepend(DebugInstr->getDebugExpression(),
DIExpression::ApplyOffset,
SpillLocation.SpillOffset);
NewDebugInstr = BuildMI(
*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), true,
SpillLocation.SpillBase, DebugInstr->getDebugVariable(), SpillExpr);
VarLoc VL(*NewDebugInstr, SpillLocation.SpillBase,
SpillLocation.SpillOffset, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
/*SkipOpers*/false, /*SkipDebugLoc*/false,
/*AddNewLine*/true, TII));
return;
}
case TransferKind::TransferRestore: {
assert(NewReg &&
"No register supplied when handling a restore of a debug value");
MachineFunction *MF = MI.getMF();
DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent());
NewDebugInstr =
BuildMI(*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), false,
NewReg, DebugInstr->getDebugVariable(), DIB.createExpression());
VarLoc VL(*NewDebugInstr, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: ";
NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
/*SkipOpers*/false, /*SkipDebugLoc*/false,
/*AddNewLine*/true, TII));
return;
}
}
llvm_unreachable("Invalid transfer kind");
}
/// A definition of a register may mark the end of a range.
void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
OpenRangesSet &OpenRanges,
const VarLocMap &VarLocIDs) {
MachineFunction *MF = MI.getMF();
const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
SparseBitVector<> KillSet;
for (const MachineOperand &MO : MI.operands()) {
// Determine whether the operand is a register def. Assume that call
// instructions never clobber SP, because some backends (e.g., AArch64)
// never list SP in the regmask.
if (MO.isReg() && MO.isDef() && MO.getReg() &&
TRI->isPhysicalRegister(MO.getReg()) &&
!(MI.isCall() && MO.getReg() == SP)) {
// Remove ranges of all aliased registers.
for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
for (unsigned ID : OpenRanges.getVarLocs())
if (VarLocIDs[ID].isDescribedByReg() == *RAI)
KillSet.set(ID);
} else if (MO.isRegMask()) {
// Remove ranges of all clobbered registers. Register masks don't usually
// list SP as preserved. While the debug info may be off for an
// instruction or two around callee-cleanup calls, transferring the
// DEBUG_VALUE across the call is still a better user experience.
for (unsigned ID : OpenRanges.getVarLocs()) {
unsigned Reg = VarLocIDs[ID].isDescribedByReg();
if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
KillSet.set(ID);
}
}
}
OpenRanges.erase(KillSet, VarLocIDs);
}
/// Decide if @MI is a spill instruction and return true if it is. We use 2
/// criteria to make this decision:
/// - Is this instruction a store to a spill slot?
/// - Is there a register operand that is both used and killed?
/// TODO: Store optimization can fold spills into other stores (including
/// other spills). We do not handle this yet (more than one memory operand).
bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
MachineFunction *MF, unsigned &Reg) {
SmallVector<const MachineMemOperand*, 1> Accesses;
// TODO: Handle multiple stores folded into one.
if (!MI.hasOneMemOperand())
return false;
if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII))
return false; // This is not a spill instruction, since no valid size was
// returned from either function.
auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
if (!MO.isReg() || !MO.isUse()) {
Reg = 0;
return false;
}
Reg = MO.getReg();
return MO.isKill();
};
for (const MachineOperand &MO : MI.operands()) {
// In a spill instruction generated by the InlineSpiller the spilled
// register has its kill flag set.
if (isKilledReg(MO, Reg))
return true;
if (Reg != 0) {
// Check whether next instruction kills the spilled register.
// FIXME: Current solution does not cover search for killed register in
// bundles and instructions further down the chain.
auto NextI = std::next(MI.getIterator());
// Skip next instruction that points to basic block end iterator.
if (MI.getParent()->end() == NextI)
continue;
unsigned RegNext;
for (const MachineOperand &MONext : NextI->operands()) {
// Return true if we came across the register from the
// previous spill instruction that is killed in NextI.
if (isKilledReg(MONext, RegNext) && RegNext == Reg)
return true;
}
}
}
// Return false if we didn't find spilled register.
return false;
}
Optional<LiveDebugValues::VarLoc::SpillLoc>
LiveDebugValues::isRestoreInstruction(const MachineInstr &MI,
MachineFunction *MF, unsigned &Reg) {
if (!MI.hasOneMemOperand())
return None;
// FIXME: Handle folded restore instructions with more than one memory
// operand.
if (MI.getRestoreSize(TII)) {
Reg = MI.getOperand(0).getReg();
return extractSpillBaseRegAndOffset(MI);
}
return None;
}
/// A spilled register may indicate that we have to end the current range of
/// a variable and create a new one for the spill location.
/// A restored register may indicate the reverse situation.
/// We don't want to insert any instructions in process(), so we just create
/// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
/// It will be inserted into the BB when we're done iterating over the
/// instructions.
void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs,
TransferMap &Transfers) {
MachineFunction *MF = MI.getMF();
TransferKind TKind;
unsigned Reg;
Optional<VarLoc::SpillLoc> Loc;
LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump(););
if (isSpillInstruction(MI, MF, Reg)) {
TKind = TransferKind::TransferSpill;
LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump(););
LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
<< "\n");
} else {
if (!(Loc = isRestoreInstruction(MI, MF, Reg)))
return;
TKind = TransferKind::TransferRestore;
LLVM_DEBUG(dbgs() << "Recognized as restore: "; MI.dump(););
LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
<< "\n");
}
// Check if the register or spill location is the location of a debug value.
for (unsigned ID : OpenRanges.getVarLocs()) {
if (TKind == TransferKind::TransferSpill &&
VarLocIDs[ID].isDescribedByReg() == Reg) {
LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
<< VarLocIDs[ID].Var.getVar()->getName() << ")\n");
} else if (TKind == TransferKind::TransferRestore &&
VarLocIDs[ID].Loc.SpillLocation == *Loc) {
LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
<< VarLocIDs[ID].Var.getVar()->getName() << ")\n");
} else
continue;
insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, TKind,
Reg);
return;
}
}
/// If \p MI is a register copy instruction, that copies a previously tracked
/// value from one register to another register that is callee saved, we
/// create new DBG_VALUE instruction described with copy destination register.
void LiveDebugValues::transferRegisterCopy(MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocMap &VarLocIDs,
TransferMap &Transfers) {
const MachineOperand *SrcRegOp, *DestRegOp;
if (!TII->isCopyInstr(MI, SrcRegOp, DestRegOp) || !SrcRegOp->isKill() ||
!DestRegOp->isDef())
return;
auto isCalleSavedReg = [&](unsigned Reg) {
for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
if (CalleeSavedRegs.test(*RAI))
return true;
return false;
};
unsigned SrcReg = SrcRegOp->getReg();
unsigned DestReg = DestRegOp->getReg();
// We want to recognize instructions where destination register is callee
// saved register. If register that could be clobbered by the call is
// included, there would be a great chance that it is going to be clobbered
// soon. It is more likely that previous register location, which is callee
// saved, is going to stay unclobbered longer, even if it is killed.
if (!isCalleSavedReg(DestReg))
return;
for (unsigned ID : OpenRanges.getVarLocs()) {
if (VarLocIDs[ID].isDescribedByReg() == SrcReg) {
insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID,
TransferKind::TransferCopy, DestReg);
return;
}
}
}
/// Terminate all open ranges at the end of the current basic block.
bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs,
const VarLocMap &VarLocIDs) {
bool Changed = false;
const MachineBasicBlock *CurMBB = MI.getParent();
if (!(MI.isTerminator() || (&MI == &CurMBB->back())))
return false;
if (OpenRanges.empty())
return false;
LLVM_DEBUG(for (unsigned ID
: OpenRanges.getVarLocs()) {
// Copy OpenRanges to OutLocs, if not already present.
dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ": ";
VarLocIDs[ID].dump();
});
VarLocSet &VLS = OutLocs[CurMBB];
Changed = VLS |= OpenRanges.getVarLocs();
// New OutLocs set may be different due to spill, restore or register
// copy instruction processing.
if (Changed)
VLS = OpenRanges.getVarLocs();
OpenRanges.clear();
return Changed;
}
/// This routine creates OpenRanges and OutLocs.
bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
TransferMap &Transfers, bool transferChanges) {
bool Changed = false;
transferDebugValue(MI, OpenRanges, VarLocIDs);
transferRegisterDef(MI, OpenRanges, VarLocIDs);
if (transferChanges) {
transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers);
}
Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
return Changed;
}
/// This routine joins the analysis results of all incoming edges in @MBB by
/// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
/// source variable in all the predecessors of @MBB reside in the same location.
bool LiveDebugValues::join(
MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
const VarLocMap &VarLocIDs,
SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) {
LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
bool Changed = false;
VarLocSet InLocsT; // Temporary incoming locations.
// For all predecessors of this MBB, find the set of VarLocs that
// can be joined.
int NumVisited = 0;
for (auto p : MBB.predecessors()) {
// Ignore unvisited predecessor blocks. As we are processing
// the blocks in reverse post-order any unvisited block can
// be considered to not remove any incoming values.
if (!Visited.count(p)) {
LLVM_DEBUG(dbgs() << " ignoring unvisited pred MBB: " << p->getNumber()
<< "\n");
continue;
}
auto OL = OutLocs.find(p);
// Join is null in case of empty OutLocs from any of the pred.
if (OL == OutLocs.end())
return false;
// Just copy over the Out locs to incoming locs for the first visited
// predecessor, and for all other predecessors join the Out locs.
if (!NumVisited)
InLocsT = OL->second;
else
InLocsT &= OL->second;
LLVM_DEBUG({
if (!InLocsT.empty()) {
for (auto ID : InLocsT)
dbgs() << " gathered candidate incoming var: "
<< VarLocIDs[ID].Var.getVar()->getName() << "\n";
}
});
NumVisited++;
}
// Filter out DBG_VALUES that are out of scope.
VarLocSet KillSet;
bool IsArtificial = ArtificialBlocks.count(&MBB);
if (!IsArtificial) {
for (auto ID : InLocsT) {
if (!VarLocIDs[ID].dominates(MBB)) {
KillSet.set(ID);
LLVM_DEBUG({
auto Name = VarLocIDs[ID].Var.getVar()->getName();
dbgs() << " killing " << Name << ", it doesn't dominate MBB\n";
});
}
}
}
InLocsT.intersectWithComplement(KillSet);
// As we are processing blocks in reverse post-order we
// should have processed at least one predecessor, unless it
// is the entry block which has no predecessor.
assert((NumVisited || MBB.pred_empty()) &&
"Should have processed at least one predecessor");
if (InLocsT.empty())
return false;
VarLocSet &ILS = InLocs[&MBB];
// Insert DBG_VALUE instructions, if not already inserted.
VarLocSet Diff = InLocsT;
Diff.intersectWithComplement(ILS);
for (auto ID : Diff) {
// This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
// new range is started for the var from the mbb's beginning by inserting
// a new DBG_VALUE. process() will end this range however appropriate.
const VarLoc &DiffIt = VarLocIDs[ID];
const MachineInstr *DebugInstr = &DiffIt.MI;
MachineInstr *MI = BuildMI(
MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(),
DebugInstr->getDesc(), DebugInstr->isIndirectDebugValue(),
DebugInstr->getOperand(0).getReg(), DebugInstr->getDebugVariable(),
DebugInstr->getDebugExpression());
if (DebugInstr->isIndirectDebugValue())
MI->getOperand(1).setImm(DebugInstr->getOperand(1).getImm());
LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump(););
ILS.set(ID);
++NumInserted;
Changed = true;
}
return Changed;
}
/// Calculate the liveness information for the given machine function and
/// extend ranges across basic blocks.
bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
LLVM_DEBUG(dbgs() << "\nDebug Range Extension\n");
bool Changed = false;
bool OLChanged = false;
bool MBBJoined = false;
VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
VarLocInMBB OutLocs; // Ranges that exist beyond bb.
VarLocInMBB InLocs; // Ranges that are incoming after joining.
TransferMap Transfers; // DBG_VALUEs associated with spills.
// Blocks which are artificial, i.e. blocks which exclusively contain
// instructions without locations, or with line 0 locations.
SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
std::priority_queue<unsigned int, std::vector<unsigned int>,
std::greater<unsigned int>>
Worklist;
std::priority_queue<unsigned int, std::vector<unsigned int>,
std::greater<unsigned int>>
Pending;
enum : bool { dontTransferChanges = false, transferChanges = true };
// Initialize every mbb with OutLocs.
// We are not looking at any spill instructions during the initial pass
// over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
// instructions for spills of registers that are known to be user variables
// within the BB in which the spill occurs.
for (auto &MBB : MF)
for (auto &MI : MBB)
process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
dontTransferChanges);
auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
if (const DebugLoc &DL = MI.getDebugLoc())
return DL.getLine() != 0;
return false;
};
for (auto &MBB : MF)
if (none_of(MBB.instrs(), hasNonArtificialLocation))
ArtificialBlocks.insert(&MBB);
LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
"OutLocs after initialization", dbgs()));
ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
unsigned int RPONumber = 0;
for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
OrderToBB[RPONumber] = *RI;
BBToOrder[*RI] = RPONumber;
Worklist.push(RPONumber);
++RPONumber;
}
// This is a standard "union of predecessor outs" dataflow problem.
// To solve it, we perform join() and process() using the two worklist method
// until the ranges converge.
// Ranges have converged when both worklists are empty.
SmallPtrSet<const MachineBasicBlock *, 16> Visited;
while (!Worklist.empty() || !Pending.empty()) {
// We track what is on the pending worklist to avoid inserting the same
// thing twice. We could avoid this with a custom priority queue, but this
// is probably not worth it.
SmallPtrSet<MachineBasicBlock *, 16> OnPending;
LLVM_DEBUG(dbgs() << "Processing Worklist\n");
while (!Worklist.empty()) {
MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
Worklist.pop();
MBBJoined =
join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, ArtificialBlocks);
Visited.insert(MBB);
if (MBBJoined) {
MBBJoined = false;
Changed = true;
// Now that we have started to extend ranges across BBs we need to
// examine spill instructions to see whether they spill registers that
// correspond to user variables.
for (auto &MI : *MBB)
OLChanged |= process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
transferChanges);
// Add any DBG_VALUE instructions necessitated by spills.
for (auto &TR : Transfers)
MBB->insertAfter(MachineBasicBlock::iterator(*TR.TransferInst),
TR.DebugInst);
Transfers.clear();
LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
"OutLocs after propagating", dbgs()));
LLVM_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");
}
LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
return Changed;
}
bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
if (!MF.getFunction().getSubprogram())
// LiveDebugValues will already have removed all DBG_VALUEs.
return false;
// Skip functions from NoDebug compilation units.
if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
DICompileUnit::NoDebug)
return false;
TRI = MF.getSubtarget().getRegisterInfo();
TII = MF.getSubtarget().getInstrInfo();
TFI = MF.getSubtarget().getFrameLowering();
TFI->determineCalleeSaves(MF, CalleeSavedRegs,
make_unique<RegScavenger>().get());
LS.initialize(MF);
bool Changed = ExtendRanges(MF);
return Changed;
}
Reference in New Issue View Git Blame Copy Permalink