dwarfgen: Add support for generating the debug_str_offsets section, take 3
Previous version of this patch failed on darwin targets because of
different handling of cross-debug-section relocations. This fixes the
tests to emit the DW_AT_str_offsets_base attribute correctly in both
cases. Since doing this is a non-trivial amount of code, and I'm going
to need it in more than one test, I've added a helper function to the
dwarfgen DIE class to do it.
Original commit message follows:
The motivation for this is D49493, where we'd like to test details of
debug_str_offsets behavior which is difficult to trigger from a
traditional test.
This adds the plubming necessary for dwarfgen to generate this section.
The more interesting changes are:
- I've moved emitStringOffsetsTableHeader function from DwarfFile to
DwarfStringPool, so I can generate the section header more easily from
the unit test.
- added a new addAttribute overload taking an MCExpr*. This is used to
generate the DW_AT_str_offsets_base, which links a compile unit to the
offset table.
I've also added a basic test for reading and writing DW_form_strx forms.
Reviewers: dblaikie, JDevlieghere, probinson
Subscribers: llvm-commits, aprantl
Differential Revision: https://reviews.llvm.org/D49670
llvm-svn: 338031
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index f1e61b4..d2f123c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1506,8 +1506,9 @@
void DwarfDebug::emitStringOffsetsTableHeader() {
DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
- Holder.emitStringOffsetsTableHeader(
- Asm->getObjFileLowering().getDwarfStrOffSection());
+ Holder.getStringPool().emitStringOffsetsTableHeader(
+ *Asm, Asm->getObjFileLowering().getDwarfStrOffSection(),
+ Holder.getStringOffsetsStartSym());
}
template <typename AccelTableT>
@@ -2292,8 +2293,9 @@
void DwarfDebug::emitStringOffsetsTableHeaderDWO() {
assert(useSplitDwarf() && "No split dwarf?");
- InfoHolder.emitStringOffsetsTableHeader(
- Asm->getObjFileLowering().getDwarfStrOffDWOSection());
+ InfoHolder.getStringPool().emitStringOffsetsTableHeader(
+ *Asm, Asm->getObjFileLowering().getDwarfStrOffDWOSection(),
+ InfoHolder.getStringOffsetsStartSym());
}
// Emit the .debug_str.dwo section for separated dwarf. This contains the
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp
index f3a3cbd..c90bd56 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp
@@ -28,26 +28,6 @@
CUs.push_back(std::move(U));
}
-void DwarfFile::emitStringOffsetsTableHeader(MCSection *Section) {
- if (StrPool.empty())
- return;
- Asm->OutStreamer->SwitchSection(Section);
- unsigned EntrySize = 4;
- // FIXME: DWARF64
- // We are emitting the header for a contribution to the string offsets
- // table. The header consists of an entry with the contribution's
- // size (not including the size of the length field), the DWARF version and
- // 2 bytes of padding.
- Asm->emitInt32(StrPool.size() * EntrySize + 4);
- Asm->emitInt16(Asm->getDwarfVersion());
- Asm->emitInt16(0);
- // Define the symbol that marks the start of the contribution. It is
- // referenced by most unit headers via DW_AT_str_offsets_base.
- // Split units do not use the attribute.
- if (StringOffsetsStartSym)
- Asm->OutStreamer->EmitLabel(StringOffsetsStartSym);
-}
-
// Emit the various dwarf units to the unit section USection with
// the abbreviations going into ASection.
void DwarfFile::emitUnits(bool UseOffsets) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfFile.h b/llvm/lib/CodeGen/AsmPrinter/DwarfFile.h
index 272a268..8dfbc4e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfFile.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfFile.h
@@ -91,9 +91,6 @@
/// Add a unit to the list of CUs.
void addUnit(std::unique_ptr<DwarfCompileUnit> U);
- /// Emit the string table offsets header.
- void emitStringOffsetsTableHeader(MCSection *Section);
-
/// Emit all of the units to the section listed with the given
/// abbreviation section.
void emitUnits(bool UseOffsets);
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp
index f296467..a61fa83 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp
@@ -39,6 +39,28 @@
return EntryRef(*I.first);
}
+void DwarfStringPool::emitStringOffsetsTableHeader(AsmPrinter &Asm,
+ MCSection *Section,
+ MCSymbol *StartSym) {
+ if (empty())
+ return;
+ Asm.OutStreamer->SwitchSection(Section);
+ unsigned EntrySize = 4;
+ // FIXME: DWARF64
+ // We are emitting the header for a contribution to the string offsets
+ // table. The header consists of an entry with the contribution's
+ // size (not including the size of the length field), the DWARF version and
+ // 2 bytes of padding.
+ Asm.emitInt32(size() * EntrySize + 4);
+ Asm.emitInt16(Asm.getDwarfVersion());
+ Asm.emitInt16(0);
+ // Define the symbol that marks the start of the contribution. It is
+ // referenced by most unit headers via DW_AT_str_offsets_base.
+ // Split units do not use the attribute.
+ if (StartSym)
+ Asm.OutStreamer->EmitLabel(StartSym);
+}
+
void DwarfStringPool::emit(AsmPrinter &Asm, MCSection *StrSection,
MCSection *OffsetSection, bool UseRelativeOffsets) {
if (Pool.empty())
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h b/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h
index 069c124..6e6988e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h
@@ -19,6 +19,7 @@
class AsmPrinter;
class MCSection;
+class MCSymbol;
// Collection of strings for this unit and assorted symbols.
// A String->Symbol mapping of strings used by indirect
@@ -36,6 +37,9 @@
DwarfStringPool(BumpPtrAllocator &A, AsmPrinter &Asm, StringRef Prefix);
+ void emitStringOffsetsTableHeader(AsmPrinter &Asm, MCSection *OffsetSection,
+ MCSymbol *StartSym);
+
void emit(AsmPrinter &Asm, MCSection *StrSection,
MCSection *OffsetSection = nullptr,
bool UseRelativeOffsets = false);