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[PECOFF] Support yet another new type of weak symbol. 

COMDAT_SELECT_LARGEST is a COMDAT type that make linker to choose the largest
definition from among all of the definition of a symbol. If the size is the
same, the choice is arbitrary.

Differential Revision: http://llvm-reviews.chandlerc.com/D3011

llvm-svn: 204172
This commit is contained in:
Rui Ueyama 2014-03-18 19:37:50 +00:00
parent 4e39f717ff
commit 7ad72ebc5e
7 changed files with 124 additions and 15 deletions
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1
lld/include/lld/Core/DefinedAtom.h
View File

@ -99,6 +99,7 @@ public:
mergeAsWeakAndAddressUsed, // Is C++ definition inline definition whose
// address was taken.
mergeSameNameAndSize, // Another atom with different size is error
mergeByLargestSection, // Choose an atom whose section is the largest.
mergeByContent, // Merge with other constants with same content.
};

59
lld/lib/Core/SymbolTable.cpp
View File

@ -102,13 +102,14 @@ enum MergeResolution {
MCR_Error
};
static MergeResolution mergeCases[][5] = {
// no tentative weak weakAddress sameNameAndSize
{MCR_Error, MCR_First, MCR_First, MCR_First, MCR_SameSize}, // no
{MCR_Second, MCR_Largest, MCR_Second, MCR_Second, MCR_SameSize}, // tentative
{MCR_Second, MCR_First, MCR_First, MCR_Second, MCR_SameSize}, // weak
{MCR_Second, MCR_First, MCR_First, MCR_First, MCR_SameSize}, // weakAddress
{MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize}, // sameSize
static MergeResolution mergeCases[][6] = {
// no tentative weak weakAddress sameNameAndSize largest
{MCR_Error, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // no
{MCR_Second, MCR_Largest, MCR_Second, MCR_Second, MCR_SameSize, MCR_Largest}, // tentative
{MCR_Second, MCR_First, MCR_First, MCR_Second, MCR_SameSize, MCR_Largest}, // weak
{MCR_Second, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // weakAddress
{MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize}, // sameSize
{MCR_Largest, MCR_Largest, MCR_Largest, MCR_Largest, MCR_SameSize, MCR_Largest}, // largest
};
static MergeResolution mergeSelect(DefinedAtom::Merge first,
@ -118,6 +119,33 @@ static MergeResolution mergeSelect(DefinedAtom::Merge first,
return mergeCases[first][second];
}
static uint64_t getSizeFollowReferences(const DefinedAtom *atom, uint32_t kind) {
uint64_t size = 0;
redo:
while (atom) {
for (const Reference *r : *atom) {
if (r->kindNamespace() == Reference::KindNamespace::all &&
r->kindArch() == Reference::KindArch::all &&
r->kindValue() == kind) {
atom = cast<DefinedAtom>(r->target());
size += atom->size();
goto redo;
}
}
break;
}
return size;
}
// Returns the size of the section containing the given atom. Atoms in the same
// section are connected by layout-before and layout-after edges, so this
// function traverses them to get the total size of atoms in the same section.
static uint64_t sectionSize(const DefinedAtom *atom) {
return atom->size()
+ getSizeFollowReferences(atom, lld::Reference::kindLayoutBefore)
+ getSizeFollowReferences(atom, lld::Reference::kindLayoutAfter);
}
void SymbolTable::addByName(const Atom &newAtom) {
StringRef name = newAtom.name();
assert(!name.empty());
@ -148,19 +176,22 @@ void SymbolTable::addByName(const Atom &newAtom) {
case MCR_Second:
useNew = true;
break;
case MCR_Largest:
useNew = true;
case MCR_Largest: {
uint64_t existingSize = sectionSize((DefinedAtom*)existing);
uint64_t newSize = sectionSize((DefinedAtom*)&newAtom);
useNew = (newSize >= existingSize);
break;
}
case MCR_SameSize: {
uint64_t sa = ((DefinedAtom*)existing)->size();
uint64_t sb = ((DefinedAtom*)&newAtom)->size();
if (sa == sb) {
uint64_t existingSize = sectionSize((DefinedAtom*)existing);
uint64_t newSize = sectionSize((DefinedAtom*)&newAtom);
if (existingSize == newSize) {
useNew = true;
break;
}
llvm::errs() << "Size mismatch: "
<< existing->name() << " (" << sa << ") "
<< newAtom.name() << " (" << sb << ")\n";
<< existing->name() << " (" << existingSize << ") "
<< newAtom.name() << " (" << newSize << ")\n";
// fallthrough
}
case MCR_Error:

4
lld/lib/ReaderWriter/PECOFF/ReaderCOFF.cpp
View File

@ -250,11 +250,13 @@ DefinedAtom::Merge getMerge(const coff_aux_section_definition *auxsym) {
case llvm::COFF::IMAGE_COMDAT_SELECT_ANY:
return DefinedAtom::mergeAsWeakAndAddressUsed;
case llvm::COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH:
// TODO: This mapping is wrong. Fix it.
return DefinedAtom::mergeByContent;
case llvm::COFF::IMAGE_COMDAT_SELECT_SAME_SIZE:
return DefinedAtom::mergeSameNameAndSize;
case llvm::COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE:
case llvm::COFF::IMAGE_COMDAT_SELECT_LARGEST:
return DefinedAtom::mergeByLargestSection;
case llvm::COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE:
case llvm::COFF::IMAGE_COMDAT_SELECT_NEWEST:
// FIXME: These attributes has more complicated semantics than the regular
// weak symbol. These are mapped to mergeAsWeakAndAddressUsed for now

1
lld/lib/ReaderWriter/YAML/ReaderWriterYAML.cpp
View File

@ -340,6 +340,7 @@ template <> struct ScalarEnumerationTraits<lld::DefinedAtom::Merge> {
io.enumCase(value, "by-content", lld::DefinedAtom::mergeByContent);
io.enumCase(value, "same-name-and-size",
lld::DefinedAtom::mergeSameNameAndSize);
io.enumCase(value, "largest", lld::DefinedAtom::mergeByLargestSection);
}
};

25
lld/test/pecoff/Inputs/merge-largest1.obj.yaml Normal file
View File

@ -0,0 +1,25 @@
---
header:
Machine: IMAGE_FILE_MACHINE_I386
Characteristics: [ ]
sections:
- Name: .text
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 16
SectionData: 00112233
symbols:
- Name: .text
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
NumberOfAuxSymbols: 1
AuxiliaryData: 0700000000000000C979F796000006000000
- Name: "_foo"
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_FUNCTION
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
...

25
lld/test/pecoff/Inputs/merge-largest2.obj.yaml Normal file
View File

@ -0,0 +1,25 @@
---
header:
Machine: IMAGE_FILE_MACHINE_I386
Characteristics: [ ]
sections:
- Name: .text
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 16
SectionData: 0011223344556677
symbols:
- Name: .text
Value: 0
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
NumberOfAuxSymbols: 1
AuxiliaryData: 0700000000000000C979F796000006000000
- Name: "_foo"
Value: 6
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_FUNCTION
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
...

24
lld/test/pecoff/merge-largest.test Normal file
View File

@ -0,0 +1,24 @@
# RUN: yaml2obj %p/Inputs/merge-largest1.obj.yaml > %t1.obj
# RUN: yaml2obj %p/Inputs/merge-largest2.obj.yaml > %t2.obj
#
# RUN: lld -flavor link /out:%t.exe /subsystem:console /opt:noref /force \
# RUN: -- %t1.obj %t2.obj 2>&1 > %t.log
#
# FileCheck complains if the input files is empty, so add a dummy line.
# RUN: echo foo >> %t.log
# RUN: FileCheck -check-prefix=STDERR %s < %t.log
#
# RUN: llvm-readobj -sections %t.exe | FileCheck -check-prefix=READOBJ %s
STDERR-NOT: duplicate symbol error
READOBJ: Format: COFF-i386
READOBJ-NEXT: Arch: i386
READOBJ-NEXT: AddressSize: 32bit
READOBJ-NEXT: Sections [
READOBJ-NEXT: Section {
READOBJ-NEXT: Number: 1
READOBJ-NEXT: Name: .text (2E 74 65 78 74 00 00 00)
READOBJ-NEXT: VirtualSize: 0x8
READOBJ-NEXT: VirtualAddress: 0x1000
READOBJ-NEXT: RawDataSize: 8