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IR: Add COMDATs to the IR

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This new IR facility allows us to represent the object-file semantic of
a COMDAT group.

COMDATs allow us to tie together sections and make the inclusion of one
dependent on another. This is required to implement features like MS
ABI VFTables and optimizing away certain kinds of initialization in C++.

This functionality is only representable in COFF and ELF, Mach-O has no
similar mechanism.

Differential Revision: http://reviews.llvm.org/D4178

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211920 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-06-27 18:19:56 +00:00
parent 4a295dfbf9
commit c8a1169c93
56 changed files with 1511 additions and 104 deletions
Download Patch File Download Diff File Expand all files Collapse all files

133
lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View File

@ -192,6 +192,18 @@ getELFSectionFlags(SectionKind K) {
return Flags;
}
static const Comdat *getELFComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return nullptr;
if (C->getSelectionKind() != Comdat::Any)
report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
C->getName() + "' cannot be lowered.");
return C;
}
const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
@ -200,9 +212,15 @@ const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
if (const Comdat *C = getELFComdat(GV)) {
Group = C->getName();
Flags |= ELF::SHF_GROUP;
}
return getContext().getELFSection(SectionName,
getELFSectionType(SectionName, Kind),
getELFSectionFlags(Kind), Kind);
getELFSectionType(SectionName, Kind), Flags,
Kind, /*EntrySize=*/0, Group);
}
/// getSectionPrefixForGlobal - Return the section prefix name used by options
@ -224,7 +242,6 @@ static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
return ".data.rel.ro.";
}
const MCSection *TargetLoweringObjectFileELF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
@ -238,7 +255,7 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
// If this global is linkonce/weak and the target handles this by emitting it
// into a 'uniqued' section name, create and return the section now.
if ((GV->isWeakForLinker() || EmitUniquedSection) &&
if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
!Kind.isCommon()) {
StringRef Prefix = getSectionPrefixForGlobal(Kind);
@ -247,8 +264,11 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
if (GV->isWeakForLinker()) {
Group = Name.substr(Prefix.size());
if (GV->isWeakForLinker() || GV->hasComdat()) {
if (const Comdat *C = getELFComdat(GV))
Group = C->getName();
else
Group = Name.substr(Prefix.size());
Flags |= ELF::SHF_GROUP;
}
@ -482,6 +502,15 @@ emitModuleFlags(MCStreamer &Streamer,
Streamer.AddBlankLine();
}
static void checkMachOComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return;
report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
"' cannot be lowered.");
}
const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
@ -489,6 +518,9 @@ const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
checkMachOComdat(GV);
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
TAA, TAAParsed, StubSize);
@ -559,6 +591,7 @@ bool TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols(
const MCSection *TargetLoweringObjectFileMachO::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
checkMachOComdat(GV);
// Handle thread local data.
if (Kind.isThreadBSS()) return TLSBSSSection;
@ -727,6 +760,50 @@ getCOFFSectionFlags(SectionKind K) {
return Flags;
}
const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
assert(C && "expected GV to have a Comdat!");
StringRef ComdatGVName = C->getName();
const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
if (!ComdatGV)
report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
"' does not exist.");
if (ComdatGV->getComdat() != C)
report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
"' is not a key for it's COMDAT.");
return ComdatGV;
}
static int getSelectionForCOFF(const GlobalValue *GV) {
if (const Comdat *C = GV->getComdat()) {
const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
ComdatKey = GA->getBaseObject();
if (ComdatKey == GV) {
switch (C->getSelectionKind()) {
case Comdat::Any:
return COFF::IMAGE_COMDAT_SELECT_ANY;
case Comdat::ExactMatch:
return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
case Comdat::Largest:
return COFF::IMAGE_COMDAT_SELECT_LARGEST;
case Comdat::NoDuplicates:
return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
case Comdat::SameSize:
return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
}
} else {
return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
}
} else if (GV->isWeakForLinker()) {
return COFF::IMAGE_COMDAT_SELECT_ANY;
}
return 0;
}
const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
@ -734,11 +811,21 @@ const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
unsigned Characteristics = getCOFFSectionFlags(Kind);
StringRef Name = GV->getSection();
StringRef COMDATSymName = "";
if (GV->isWeakForLinker()) {
Selection = COFF::IMAGE_COMDAT_SELECT_ANY;
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
MCSymbol *Sym = TM.getSymbol(GV, Mang);
COMDATSymName = Sym->getName();
if ((GV->isWeakForLinker() || GV->hasComdat()) && !Kind.isCommon()) {
Selection = getSelectionForCOFF(GV);
const GlobalValue *ComdatGV;
if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
ComdatGV = getComdatGVForCOFF(GV);
else
ComdatGV = GV;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
COMDATSymName = Sym->getName();
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
} else {
Selection = 0;
}
}
return getContext().getCOFFSection(Name,
Characteristics,
@ -775,17 +862,27 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
// into a 'uniqued' section name, create and return the section now.
// Section names depend on the name of the symbol which is not feasible if the
// symbol has private linkage.
if ((GV->isWeakForLinker() || EmitUniquedSection) &&
!GV->hasPrivateLinkage() && !Kind.isCommon()) {
if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
!Kind.isCommon()) {
const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
unsigned Characteristics = getCOFFSectionFlags(Kind);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
MCSymbol *Sym = TM.getSymbol(GV, Mang);
return getContext().getCOFFSection(
Name, Characteristics, Kind, Sym->getName(),
GV->isWeakForLinker() ? COFF::IMAGE_COMDAT_SELECT_ANY
: COFF::IMAGE_COMDAT_SELECT_NODUPLICATES);
int Selection = getSelectionForCOFF(GV);
if (!Selection)
Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
const GlobalValue *ComdatGV;
if (GV->hasComdat())
ComdatGV = getComdatGVForCOFF(GV);
else
ComdatGV = GV;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
StringRef COMDATSymName = Sym->getName();
return getContext().getCOFFSection(Name, Characteristics, Kind,
COMDATSymName, Selection);
}
}
if (Kind.isText())