llvm-project/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp

376 lines
15 KiB
C++

//===- llvm/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/DbgEntityHistoryCalculator.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <map>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "dwarfdebug"
namespace {
using EntryIndex = DbgValueHistoryMap::EntryIndex;
}
// 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 Register isDescribedByReg(const MachineInstr &MI) {
assert(MI.isDebugValue());
assert(MI.getNumOperands() == 4);
// If the location of variable is an entry value (DW_OP_LLVM_entry_value)
// do not consider it as a register location.
if (MI.getDebugExpression()->isEntryValue())
return 0;
// 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() : Register();
}
bool DbgValueHistoryMap::startDbgValue(InlinedEntity Var,
const MachineInstr &MI,
EntryIndex &NewIndex) {
// Instruction range should start with a DBG_VALUE instruction for the
// variable.
assert(MI.isDebugValue() && "not a DBG_VALUE");
auto &Entries = VarEntries[Var];
if (!Entries.empty() && Entries.back().isDbgValue() &&
!Entries.back().isClosed() &&
Entries.back().getInstr()->isIdenticalTo(MI)) {
LLVM_DEBUG(dbgs() << "Coalescing identical DBG_VALUE entries:\n"
<< "\t" << Entries.back().getInstr() << "\t" << MI
<< "\n");
return false;
}
Entries.emplace_back(&MI, Entry::DbgValue);
NewIndex = Entries.size() - 1;
return true;
}
EntryIndex DbgValueHistoryMap::startClobber(InlinedEntity Var,
const MachineInstr &MI) {
auto &Entries = VarEntries[Var];
// If an instruction clobbers multiple registers that the variable is
// described by, then we may have already created a clobbering instruction.
if (Entries.back().isClobber() && Entries.back().getInstr() == &MI)
return Entries.size() - 1;
Entries.emplace_back(&MI, Entry::Clobber);
return Entries.size() - 1;
}
void DbgValueHistoryMap::Entry::endEntry(EntryIndex Index) {
// For now, instruction ranges are not allowed to cross basic block
// boundaries.
assert(isDbgValue() && "Setting end index for non-debug value");
assert(!isClosed() && "End index has already been set");
EndIndex = Index;
}
void DbgLabelInstrMap::addInstr(InlinedEntity Label, const MachineInstr &MI) {
assert(MI.isDebugLabel() && "not a DBG_LABEL");
LabelInstr[Label] = &MI;
}
namespace {
// Maps physreg numbers to the variables they describe.
using InlinedEntity = DbgValueHistoryMap::InlinedEntity;
using RegDescribedVarsMap = std::map<unsigned, SmallVector<InlinedEntity, 1>>;
// Keeps track of the debug value entries that are currently live for each
// inlined entity. As the history map entries are stored in a SmallVector, they
// may be moved at insertion of new entries, so store indices rather than
// pointers.
using DbgValueEntriesMap = std::map<InlinedEntity, SmallSet<EntryIndex, 1>>;
} // end anonymous namespace
// Claim that @Var is not described by @RegNo anymore.
static void dropRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo,
InlinedEntity Var) {
const auto &I = RegVars.find(RegNo);
assert(RegNo != 0U && I != RegVars.end());
auto &VarSet = I->second;
const auto &VarPos = llvm::find(VarSet, 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);
}
// Claim that @Var is now described by @RegNo.
static void addRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo,
InlinedEntity Var) {
assert(RegNo != 0U);
auto &VarSet = RegVars[RegNo];
assert(!is_contained(VarSet, Var));
VarSet.push_back(Var);
}
/// Create a clobbering entry and end all open debug value entries
/// for \p Var that are described by \p RegNo using that entry.
static void clobberRegEntries(InlinedEntity Var, unsigned RegNo,
const MachineInstr &ClobberingInstr,
DbgValueEntriesMap &LiveEntries,
DbgValueHistoryMap &HistMap) {
EntryIndex ClobberIndex = HistMap.startClobber(Var, ClobberingInstr);
// Close all entries whose values are described by the register.
SmallVector<EntryIndex, 4> IndicesToErase;
for (auto Index : LiveEntries[Var]) {
auto &Entry = HistMap.getEntry(Var, Index);
assert(Entry.isDbgValue() && "Not a DBG_VALUE in LiveEntries");
if (isDescribedByReg(*Entry.getInstr()) == RegNo) {
IndicesToErase.push_back(Index);
Entry.endEntry(ClobberIndex);
}
}
// Drop all entries that have ended.
for (auto Index : IndicesToErase)
LiveEntries[Var].erase(Index);
}
/// Add a new debug value for \p Var. Closes all overlapping debug values.
static void handleNewDebugValue(InlinedEntity Var, const MachineInstr &DV,
RegDescribedVarsMap &RegVars,
DbgValueEntriesMap &LiveEntries,
DbgValueHistoryMap &HistMap) {
EntryIndex NewIndex;
if (HistMap.startDbgValue(Var, DV, NewIndex)) {
SmallDenseMap<unsigned, bool, 4> TrackedRegs;
// If we have created a new debug value entry, close all preceding
// live entries that overlap.
SmallVector<EntryIndex, 4> IndicesToErase;
const DIExpression *DIExpr = DV.getDebugExpression();
for (auto Index : LiveEntries[Var]) {
auto &Entry = HistMap.getEntry(Var, Index);
assert(Entry.isDbgValue() && "Not a DBG_VALUE in LiveEntries");
const MachineInstr &DV = *Entry.getInstr();
bool Overlaps = DIExpr->fragmentsOverlap(DV.getDebugExpression());
if (Overlaps) {
IndicesToErase.push_back(Index);
Entry.endEntry(NewIndex);
}
if (Register Reg = isDescribedByReg(DV))
TrackedRegs[Reg] |= !Overlaps;
}
// If the new debug value is described by a register, add tracking of
// that register if it is not already tracked.
if (Register NewReg = isDescribedByReg(DV)) {
if (!TrackedRegs.count(NewReg))
addRegDescribedVar(RegVars, NewReg, Var);
LiveEntries[Var].insert(NewIndex);
TrackedRegs[NewReg] = true;
}
// Drop tracking of registers that are no longer used.
for (auto I : TrackedRegs)
if (!I.second)
dropRegDescribedVar(RegVars, I.first, Var);
// Drop all entries that have ended, and mark the new entry as live.
for (auto Index : IndicesToErase)
LiveEntries[Var].erase(Index);
LiveEntries[Var].insert(NewIndex);
}
}
// 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,
DbgValueEntriesMap &LiveEntries,
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)
clobberRegEntries(Var, I->first, ClobberingInstr, LiveEntries, HistMap);
RegVars.erase(I);
}
// 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,
DbgValueEntriesMap &LiveEntries,
const MachineInstr &ClobberingInstr) {
const auto &I = RegVars.find(RegNo);
if (I == RegVars.end())
return;
clobberRegisterUses(RegVars, I, HistMap, LiveEntries, ClobberingInstr);
}
void llvm::calculateDbgEntityHistory(const MachineFunction *MF,
const TargetRegisterInfo *TRI,
DbgValueHistoryMap &DbgValues,
DbgLabelInstrMap &DbgLabels) {
const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
Register FrameReg = TRI->getFrameRegister(*MF);
RegDescribedVarsMap RegVars;
DbgValueEntriesMap LiveEntries;
for (const auto &MBB : *MF) {
for (const auto &MI : MBB) {
if (MI.isDebugValue()) {
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");
InlinedEntity Var(RawVar, MI.getDebugLoc()->getInlinedAt());
handleNewDebugValue(Var, MI, RegVars, LiveEntries, DbgValues);
} else if (MI.isDebugLabel()) {
assert(MI.getNumOperands() == 1 && "Invalid DBG_LABEL instruction!");
const DILabel *RawLabel = MI.getDebugLabel();
assert(RawLabel->isValidLocationForIntrinsic(MI.getDebugLoc()) &&
"Expected inlined-at fields to agree");
// When collecting debug information for labels, there is no MCSymbol
// generated for it. So, we keep MachineInstr in DbgLabels in order
// to query MCSymbol afterward.
InlinedEntity L(RawLabel, MI.getDebugLoc()->getInlinedAt());
DbgLabels.addInstr(L, MI);
}
if (MI.isDebugInstr())
continue;
// Not a DBG_VALUE instruction. It may clobber registers which describe
// some variables.
for (const MachineOperand &MO : MI.operands()) {
if (MO.isReg() && MO.isDef() && MO.getReg()) {
// Ignore call instructions that claim to clobber SP. The AArch64
// backend does this for aggregate function arguments.
if (MI.isCall() && MO.getReg() == SP)
continue;
// If this is a virtual register, only clobber it since it doesn't
// have aliases.
if (Register::isVirtualRegister(MO.getReg()))
clobberRegisterUses(RegVars, MO.getReg(), DbgValues, LiveEntries,
MI);
// If this is a register def operand, it may end a debug value
// range. Ignore frame-register defs in the epilogue and prologue,
// we expect debuggers to understand that stack-locations are
// invalid outside of the function body.
else if (MO.getReg() != FrameReg ||
(!MI.getFlag(MachineInstr::FrameDestroy) &&
!MI.getFlag(MachineInstr::FrameSetup))) {
for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
++AI)
clobberRegisterUses(RegVars, *AI, DbgValues, LiveEntries, MI);
}
} else if (MO.isRegMask()) {
// If this is a register mask operand, clobber all debug values in
// non-CSRs.
SmallVector<unsigned, 32> RegsToClobber;
// Don't consider SP to be clobbered by register masks.
for (auto It : RegVars) {
unsigned int Reg = It.first;
if (Reg != SP && Register::isPhysicalRegister(Reg) &&
MO.clobbersPhysReg(Reg))
RegsToClobber.push_back(Reg);
}
for (unsigned Reg : RegsToClobber) {
clobberRegisterUses(RegVars, Reg, DbgValues, LiveEntries, MI);
}
}
} // End MO loop.
} // End instr loop.
// Make sure locations for all 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()) {
// Iterate over all variables that have open debug values.
for (auto &Pair : LiveEntries) {
if (Pair.second.empty())
continue;
// Create a clobbering entry.
EntryIndex ClobIdx = DbgValues.startClobber(Pair.first, MBB.back());
// End all entries.
for (EntryIndex Idx : Pair.second) {
DbgValueHistoryMap::Entry &Ent = DbgValues.getEntry(Pair.first, Idx);
assert(Ent.isDbgValue() && !Ent.isClosed());
Ent.endEntry(ClobIdx);
}
}
LiveEntries.clear();
RegVars.clear();
}
}
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void DbgValueHistoryMap::dump() const {
dbgs() << "DbgValueHistoryMap:\n";
for (const auto &VarRangePair : *this) {
const InlinedEntity &Var = VarRangePair.first;
const Entries &Entries = VarRangePair.second;
const DILocalVariable *LocalVar = cast<DILocalVariable>(Var.first);
const DILocation *Location = Var.second;
dbgs() << " - " << LocalVar->getName() << " at ";
if (Location)
dbgs() << Location->getFilename() << ":" << Location->getLine() << ":"
<< Location->getColumn();
else
dbgs() << "<unknown location>";
dbgs() << " --\n";
for (const auto &E : enumerate(Entries)) {
const auto &Entry = E.value();
dbgs() << " Entry[" << E.index() << "]: ";
if (Entry.isDbgValue())
dbgs() << "Debug value\n";
else
dbgs() << "Clobber\n";
dbgs() << " Instr: " << *Entry.getInstr();
if (Entry.isDbgValue()) {
if (Entry.getEndIndex() == NoEntry)
dbgs() << " - Valid until end of function\n";
else
dbgs() << " - Closed by Entry[" << Entry.getEndIndex() << "]\n";
}
dbgs() << "\n";
}
}
}
#endif