[DEBUGINFO] Add flag for DWARF2 to use sections as references.
Summary:
Some targets does not support labels inside debug sections, but support
references in form `section+offset`. Patch adds initial support
for this.
Reviewers: echristo, probinson, jlebar
Subscribers: llvm-commits, JDevlieghere
Differential Revision: https://reviews.llvm.org/D43943
llvm-svn: 328314
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 2cee47c..b9e6a36 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -270,15 +270,20 @@
void DwarfCompileUnit::initStmtList() {
// Define start line table label for each Compile Unit.
- MCSymbol *LineTableStartSym =
- Asm->OutStreamer->getDwarfLineTableSymbol(getUniqueID());
+ MCSymbol *LineTableStartSym;
+ const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
+ if (DD->useSectionsAsReferences()) {
+ LineTableStartSym = TLOF.getDwarfLineSection()->getBeginSymbol();
+ } else {
+ LineTableStartSym =
+ Asm->OutStreamer->getDwarfLineTableSymbol(getUniqueID());
+ }
// DW_AT_stmt_list is a offset of line number information for this
// compile unit in debug_line section. For split dwarf this is
// left in the skeleton CU and so not included.
// The line table entries are not always emitted in assembly, so it
// is not okay to use line_table_start here.
- const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
StmtListValue =
addSectionLabel(getUnitDie(), dwarf::DW_AT_stmt_list, LineTableStartSym,
TLOF.getDwarfLineSection()->getBeginSymbol());
@@ -835,7 +840,7 @@
void DwarfCompileUnit::emitHeader(bool UseOffsets) {
// Don't bother labeling the .dwo unit, as its offset isn't used.
- if (!Skeleton) {
+ if (!Skeleton && !DD->useSectionsAsReferences()) {
LabelBegin = Asm->createTempSymbol("cu_begin");
Asm->OutStreamer->EmitLabel(LabelBegin);
}
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 58ef279..96481a8 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -133,6 +133,13 @@
cl::desc("Disable emission .debug_ranges section."),
cl::init(false));
+static cl::opt<DefaultOnOff> DwarfSectionsAsReferences(
+ "dwarf-sections-as-references", cl::Hidden,
+ cl::desc("Use sections+offset as references rather than labels."),
+ cl::values(clEnumVal(Default, "Default for platform"),
+ clEnumVal(Enable, "Enabled"), clEnumVal(Disable, "Disabled")),
+ cl::init(Default));
+
enum LinkageNameOption {
DefaultLinkageNames,
AllLinkageNames,
@@ -323,6 +330,9 @@
UsePubSections = !NoDwarfPubSections;
UseRangesSection = !NoDwarfRangesSection;
+ // Use sections as references.
+ UseSectionsAsReferences = DwarfSectionsAsReferences == Enable;
+
// Work around a GDB bug. GDB doesn't support the standard opcode;
// SCE doesn't support GNU's; LLDB prefers the standard opcode, which
// is defined as of DWARF 3.
@@ -1559,6 +1569,14 @@
}
}
+void DwarfDebug::emitSectionReference(const DwarfCompileUnit &CU) {
+ if (useSectionsAsReferences())
+ Asm->EmitDwarfOffset(CU.getSection()->getBeginSymbol(),
+ CU.getDebugSectionOffset());
+ else
+ Asm->emitDwarfSymbolReference(CU.getLabelBegin());
+}
+
void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name,
DwarfCompileUnit *TheU,
const StringMap<const DIE *> &Globals) {
@@ -1577,7 +1595,7 @@
Asm->EmitInt16(dwarf::DW_PUBNAMES_VERSION);
Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
- Asm->emitDwarfSymbolReference(TheU->getLabelBegin());
+ emitSectionReference(*TheU);
Asm->OutStreamer->AddComment("Compilation Unit Length");
Asm->EmitInt32(TheU->getLength());
@@ -1876,7 +1894,7 @@
Asm->OutStreamer->AddComment("DWARF Arange version number");
Asm->EmitInt16(dwarf::DW_ARANGES_VERSION);
Asm->OutStreamer->AddComment("Offset Into Debug Info Section");
- Asm->emitDwarfSymbolReference(CU->getLabelBegin());
+ emitSectionReference(*CU);
Asm->OutStreamer->AddComment("Address Size (in bytes)");
Asm->EmitInt8(PtrSize);
Asm->OutStreamer->AddComment("Segment Size (in bytes)");
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 4459a50..52b9206 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -264,6 +264,10 @@
/// Allow emission of .debug_ranges section.
bool UseRangesSection = true;
+ /// True if the sections itself must be used as references and don't create
+ /// temp symbols inside DWARF sections.
+ bool UseSectionsAsReferences = false;
+
/// DWARF5 Experimental Options
/// @{
bool HasDwarfAccelTables;
@@ -448,6 +452,9 @@
void collectVariableInfoFromMFTable(DwarfCompileUnit &TheCU,
DenseSet<InlinedVariable> &P);
+ /// Emit the reference to the section.
+ void emitSectionReference(const DwarfCompileUnit &CU);
+
protected:
/// Gather pre-function debug information.
void beginFunctionImpl(const MachineFunction *MF) override;
@@ -513,6 +520,11 @@
/// Returns whether ranges section should be emitted.
bool useRangesSection() const { return UseRangesSection; }
+ /// Returns whether to use sections as labels rather than temp symbols.
+ bool useSectionsAsReferences() const {
+ return UseSectionsAsReferences;
+ }
+
// Experimental DWARF5 features.
/// Returns whether or not to emit tables that dwarf consumers can