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[dsymutil] Fix handling of empty CUs in LTO links.

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r288399 introduced the DIEUnit class, and in the process broke
the corner case where dsymutil generates an empty CU during an
LTO link. This restores the logic and adds a test for the corner
case.

llvm-svn: 294618
This commit is contained in:
Frederic Riss 2017-02-09 19:41:55 +00:00
parent 812a2fc1c7
commit 097e532a63
2 changed files with 53 additions and 14 deletions
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33
test/tools/dsymutil/X86/generate-empty-CU.test Normal file
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@ -0,0 +1,33 @@
# RUN: llvm-dsymutil -f -o - -oso-prepend-path=%p/.. -y %s | llvm-dwarfdump - | FileCheck %s
# This test on links the Dwarf for an LTO binary and on purpose doesn't retain
# any symbol in the second CU out of 3. This is the only case where dsymutil
# will generate an empty CU and it requires special handling.
---
triple: 'x86_64-apple-darwin'
objects:
- filename: /Inputs/basic-lto.macho.x86_64.o
timestamp: 1417654896
symbols:
- { sym: _main, objAddr: 0x0000000000000000, binAddr: 0x0000000100000F40, size: 0x00000010 }
- { sym: _bar, objAddr: 0x0000000000000050, binAddr: 0x0000000100000F90, size: 0x00000024 }
...
.debug_info contents:
CHECK: Compile Unit: length = 0x0000007d version = 0x0002 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000081)
CHECK: DW_TAG_compile_unit
CHECK: DW_AT_name {{.*}} "basic1.c"
CHECK: DW_TAG_subprogram
DW_AT_name {{.*}} "main"
CHECK: Compile Unit: length = 0x00000007 version = 0x0002 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x0000008c)
CHECK: Compile Unit: length = 0x00000089 version = 0x0002 abbr_offset = 0x0000 addr_size = 0x08 (next unit at 0x00000119)
CHECK: DW_TAG_compile_unit
CHECK: DW_AT_name {{.*}} "basic3.c"
CHECK: DW_TAG_subprogram [7] *
CHECK: DW_AT_name {{.*}} = "bar"

34
tools/dsymutil/DwarfLinker.cpp
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@ -197,11 +197,8 @@ public:
CompileUnit(DWARFUnit &OrigUnit, unsigned ID, bool CanUseODR,
StringRef ClangModuleName)
: OrigUnit(OrigUnit), ID(ID), NewUnit(OrigUnit.getVersion(),
OrigUnit.getAddressByteSize(),
OrigUnit.getUnitDIE().getTag()),
LowPc(UINT64_MAX), HighPc(0), RangeAlloc(), Ranges(RangeAlloc),
ClangModuleName(ClangModuleName) {
: OrigUnit(OrigUnit), ID(ID), LowPc(UINT64_MAX), HighPc(0), RangeAlloc(),
Ranges(RangeAlloc), ClangModuleName(ClangModuleName) {
Info.resize(OrigUnit.getNumDIEs());
auto CUDie = OrigUnit.getUnitDIE(false);
@ -219,8 +216,15 @@ public:
unsigned getUniqueID() const { return ID; }
void createOutputDIE() {
NewUnit.emplace(OrigUnit.getVersion(), OrigUnit.getAddressByteSize(),
OrigUnit.getUnitDIE().getTag());
}
DIE *getOutputUnitDIE() const {
return &const_cast<DIEUnit &>(NewUnit).getUnitDie();
if (NewUnit)
return &const_cast<DIEUnit &>(*NewUnit).getUnitDie();
return nullptr;
}
bool hasODR() const { return HasODR; }
@ -329,7 +333,7 @@ private:
DWARFUnit &OrigUnit;
unsigned ID;
std::vector<DIEInfo> Info; ///< DIE info indexed by DIE index.
DIEUnit NewUnit;
Optional<DIEUnit> NewUnit;
uint64_t StartOffset;
uint64_t NextUnitOffset;
@ -397,7 +401,8 @@ uint64_t CompileUnit::computeNextUnitOffset() {
// The root DIE might be null, meaning that the Unit had nothing to
// contribute to the linked output. In that case, we will emit the
// unit header without any actual DIE.
NextUnitOffset += NewUnit.getUnitDie().getSize();
if (NewUnit)
NextUnitOffset += NewUnit->getUnitDie().getSize();
return NextUnitOffset;
}
@ -3357,12 +3362,13 @@ void DwarfLinker::DIECloner::cloneAllCompileUnits(
for (auto &CurrentUnit : CompileUnits) {
auto InputDIE = CurrentUnit->getOrigUnit().getUnitDIE();
CurrentUnit->setStartOffset(Linker.OutputDebugInfoSize);
// Clonse the InputDIE into your Unit DIE in our compile unit since it
// already has a DIE inside of it.
if (!cloneDIE(InputDIE, *CurrentUnit, 0 /* PC offset */,
11 /* Unit Header size */, 0,
CurrentUnit->getOutputUnitDIE()))
continue;
if (CurrentUnit->getInfo(0).Keep) {
// Clone the InputDIE into your Unit DIE in our compile unit since it
// already has a DIE inside of it.
CurrentUnit->createOutputDIE();
cloneDIE(InputDIE, *CurrentUnit, 0 /* PC offset */,
11 /* Unit Header size */, 0, CurrentUnit->getOutputUnitDIE());
}
Linker.OutputDebugInfoSize = CurrentUnit->computeNextUnitOffset();
if (Linker.Options.NoOutput)
continue;