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Reapply DW_AT_low/high_pc patch:

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Use the range machinery for DW_AT_ranges and DW_AT_high/lo_pc.

    This commit moves us from a single range per subprogram to extending
    ranges if we are:

    a) In the same section, and
    b) In the same enclosing CU.

    This means we have more fine grained ranges for compile units, and fewer
    ranges overall when we have multiple functions in the same CU
    adjacent to each other in the object file.

    Also remove all of the earlier hacks around this functionality for
    function sections etc. Also update all of the testcases to take into
    account the merging functionality.

with a fix for location entries in the debug_loc section:

Make sure that debug loc entries are relative to the low_pc
of the compile unit. This means that when we only have a single
range that the offset should be just relative to the low_pc
of the unit, for multiple ranges for a CU this means that we'll be
relative to 0 which we emit along with DW_AT_ranges.

This mostly shows up with linked binaries, so add a testcase with
multiple CUs so that our location is going to be offset of a CU
with a non-zero low_pc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204377 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Christopher
2014-03-20 19:16:16 +00:00
parent 0b087184ce
commit 8b97f004cb
11 changed files with 398 additions and 164 deletions
Download Patch File Download Diff File Expand all files Collapse all files

110
lib/CodeGen/AsmPrinter/DwarfDebug.cpp
View File

@ -178,7 +178,7 @@ static unsigned getDwarfVersionFromModule(const Module *M) {
DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
: Asm(A), MMI(Asm->MMI), FirstCU(0), PrevLabel(NULL), GlobalRangeCount(0),
InfoHolder(A, "info_string", DIEValueAllocator), HasCURanges(false),
InfoHolder(A, "info_string", DIEValueAllocator),
UsedNonDefaultText(false),
SkeletonHolder(A, "skel_string", DIEValueAllocator) {
@ -952,26 +952,34 @@ void DwarfDebug::finalizeModuleInfo() {
dwarf::DW_FORM_data8, ID);
}
// If we have code split among multiple sections or we've requested
// it then emit a DW_AT_ranges attribute on the unit that will remain
// in the .o file, otherwise add a DW_AT_low_pc.
// FIXME: Also add a high pc if we can.
// FIXME: We should use ranges if we have multiple compile units or
// allow reordering of code ala .subsections_via_symbols in mach-o.
// If we have code split among multiple sections or non-contiguous
// ranges of code then emit a DW_AT_ranges attribute on the unit that will
// remain in the .o file, otherwise add a DW_AT_low_pc.
// FIXME: We should use ranges allow reordering of code ala
// .subsections_via_symbols in mach-o. This would mean turning on
// ranges for all subprogram DIEs for mach-o.
DwarfCompileUnit *U = SkCU ? SkCU : static_cast<DwarfCompileUnit *>(TheU);
if (useCURanges() && TheU->getRanges().size()) {
addSectionLabel(Asm, U, U->getUnitDie(), dwarf::DW_AT_ranges,
Asm->GetTempSymbol("cu_ranges", U->getUniqueID()),
DwarfDebugRangeSectionSym);
unsigned NumRanges = TheU->getRanges().size();
if (NumRanges) {
if (NumRanges > 1) {
addSectionLabel(Asm, U, U->getUnitDie(), dwarf::DW_AT_ranges,
Asm->GetTempSymbol("cu_ranges", U->getUniqueID()),
DwarfDebugRangeSectionSym);
// A DW_AT_low_pc attribute may also be specified in combination with
// DW_AT_ranges to specify the default base address for use in location
// lists (see Section 2.6.2) and range lists (see Section 2.17.3).
U->addUInt(U->getUnitDie(), dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr,
0);
} else
U->addUInt(U->getUnitDie(), dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr,
0);
// A DW_AT_low_pc attribute may also be specified in combination with
// DW_AT_ranges to specify the default base address for use in
// location lists (see Section 2.6.2) and range lists (see Section
// 2.17.3).
U->addUInt(U->getUnitDie(), dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr,
0);
} else {
RangeSpan &Range = TheU->getRanges().back();
U->addLocalLabelAddress(U->getUnitDie(), dwarf::DW_AT_low_pc,
Range.getStart());
U->addLabelDelta(U->getUnitDie(), dwarf::DW_AT_high_pc,
Range.getEnd(), Range.getStart());
}
}
}
}
@ -1026,14 +1034,6 @@ void DwarfDebug::endSections() {
// Insert a final terminator.
SectionMap[Section].push_back(SymbolCU(NULL, Sym));
}
// For now only turn on CU ranges if we have -ffunction-sections enabled,
// we've emitted a function into a unique section, or we're using LTO. If
// we're using LTO then we can't know that any particular function in the
// module is correlated to a particular CU and so we need to be conservative.
// At this point all sections should be finalized except for dwarf sections.
HasCURanges = UsedNonDefaultText || (CUMap.size() > 1) ||
TargetMachine::getFunctionSections();
}
// Emit all Dwarf sections that should come after the content.
@ -1177,9 +1177,10 @@ static bool isDbgValueInDefinedReg(const MachineInstr *MI) {
// Get .debug_loc entry for the instruction range starting at MI.
static DebugLocEntry getDebugLocEntry(AsmPrinter *Asm,
const MCSymbol *FLabel,
const MCSymbol *SLabel,
const MachineInstr *MI) {
const MCSymbol *FLabel,
const MCSymbol *SLabel,
const MachineInstr *MI,
DwarfCompileUnit *Unit) {
const MDNode *Var = MI->getOperand(MI->getNumOperands() - 1).getMetadata();
assert(MI->getNumOperands() == 3);
@ -1191,14 +1192,14 @@ static DebugLocEntry getDebugLocEntry(AsmPrinter *Asm,
MLoc.set(MI->getOperand(0).getReg());
else
MLoc.set(MI->getOperand(0).getReg(), MI->getOperand(1).getImm());
return DebugLocEntry(FLabel, SLabel, MLoc, Var);
return DebugLocEntry(FLabel, SLabel, MLoc, Var, Unit);
}
if (MI->getOperand(0).isImm())
return DebugLocEntry(FLabel, SLabel, MI->getOperand(0).getImm());
return DebugLocEntry(FLabel, SLabel, MI->getOperand(0).getImm(), Unit);
if (MI->getOperand(0).isFPImm())
return DebugLocEntry(FLabel, SLabel, MI->getOperand(0).getFPImm());
return DebugLocEntry(FLabel, SLabel, MI->getOperand(0).getFPImm(), Unit);
if (MI->getOperand(0).isCImm())
return DebugLocEntry(FLabel, SLabel, MI->getOperand(0).getCImm());
return DebugLocEntry(FLabel, SLabel, MI->getOperand(0).getCImm(), Unit);
llvm_unreachable("Unexpected 3 operand DBG_VALUE instruction!");
}
@ -1288,8 +1289,10 @@ DwarfDebug::collectVariableInfo(SmallPtrSet<const MDNode *, 16> &Processed) {
}
// The value is valid until the next DBG_VALUE or clobber.
LexicalScope *FnScope = LScopes.getCurrentFunctionScope();
DwarfCompileUnit *TheCU = SPMap.lookup(FnScope->getScopeNode());
DotDebugLocEntries.push_back(
getDebugLocEntry(Asm, FLabel, SLabel, Begin));
getDebugLocEntry(Asm, FLabel, SLabel, Begin, TheCU));
}
DotDebugLocEntries.push_back(DebugLocEntry());
}
@ -1428,12 +1431,8 @@ void DwarfDebug::beginFunction(const MachineFunction *MF) {
// Grab the lexical scopes for the function, if we don't have any of those
// then we're not going to be able to do anything.
LScopes.initialize(*MF);
if (LScopes.empty()) {
// If we don't have a lexical scope for this function then there will
// be a hole in the range information. Keep note of this.
UsedNonDefaultText = true;
if (LScopes.empty())
return;
}
assert(UserVariables.empty() && DbgValues.empty() && "Maps weren't cleaned");
@ -1452,12 +1451,6 @@ void DwarfDebug::beginFunction(const MachineFunction *MF) {
else
Asm->OutStreamer.getContext().setDwarfCompileUnitID(TheCU->getUniqueID());
// Check the current section against the standard text section. If different
// keep track so that we will know when we're emitting functions into multiple
// sections.
if (Asm->getObjFileLowering().getTextSection() != Asm->getCurrentSection())
UsedNonDefaultText = true;
// Emit a label for the function so that we have a beginning address.
FunctionBeginSym = Asm->GetTempSymbol("func_begin", Asm->getFunctionNumber());
// Assumes in correct section after the entry point.
@ -1663,6 +1656,11 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
assert(CurFn != 0);
if (!MMI->hasDebugInfo() || LScopes.empty()) {
// If we don't have a lexical scope for this function then there will
// be a hole in the range information. Keep note of this by setting the
// previously used section to nullptr.
PrevSection = nullptr;
PrevCU = nullptr;
CurFn = 0;
return;
}
@ -1713,6 +1711,8 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
// Add the range of this function to the list of ranges for the CU.
RangeSpan Span(FunctionBeginSym, FunctionEndSym);
TheCU->addRange(std::move(Span));
PrevSection = Asm->getCurrentSection();
PrevCU = TheCU;
// Clear debug info
for (auto &I : ScopeVariables)
@ -2402,9 +2402,19 @@ void DwarfDebug::emitDebugLoc() {
Asm->OutStreamer.EmitIntValue(0, Size);
Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_loc", index));
} else {
// Set up the range.
Asm->OutStreamer.EmitSymbolValue(Entry.getBeginSym(), Size);
Asm->OutStreamer.EmitSymbolValue(Entry.getEndSym(), Size);
// Set up the range. This range is relative to the entry point of the
// compile unit. This is a hard coded 0 for low_pc when we're emitting
// ranges, or the DW_AT_low_pc on the compile unit otherwise.
const DwarfCompileUnit *CU = Entry.getCU();
if (CU->getRanges().size() == 1) {
// Grab the begin symbol from the first range as our base.
const MCSymbol *Base = CU->getRanges()[0].getStart();
Asm->EmitLabelDifference(Entry.getBeginSym(), Base, Size);
Asm->EmitLabelDifference(Entry.getEndSym(), Base, Size);
} else {
Asm->OutStreamer.EmitSymbolValue(Entry.getBeginSym(), Size);
Asm->OutStreamer.EmitSymbolValue(Entry.getEndSym(), Size);
}
Asm->OutStreamer.AddComment("Loc expr size");
MCSymbol *begin = Asm->OutStreamer.getContext().CreateTempSymbol();
MCSymbol *end = Asm->OutStreamer.getContext().CreateTempSymbol();
@ -2602,7 +2612,7 @@ void DwarfDebug::emitDebugRanges() {
}
// Now emit a range for the CU itself.
if (useCURanges() && TheCU->getRanges().size()) {
if (TheCU->getRanges().size() > 1) {
Asm->OutStreamer.EmitLabel(
Asm->GetTempSymbol("cu_ranges", TheCU->getUniqueID()));
for (const RangeSpan &Range : TheCU->getRanges()) {