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Support SHF_MERGE sections in COMDATs. 

This patch unifies the comdat and non-comdat code paths. By doing this
it add missing features to the comdat side and removes the fixed
section assumptions from the non-comdat side.

In ELF there is no one true section for "4 byte mergeable" constants.
We are better off computing the required properties of the section
and asking the context for it.

llvm-svn: 230411
This commit is contained in:
Rafael Espindola 2015-02-25 00:52:15 +00:00
parent 7b0281089e
commit 8bc9ccc60a
2 changed files with 57 additions and 86 deletions
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137
llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View File

@ -164,9 +164,7 @@ static unsigned getELFSectionType(StringRef Name, SectionKind K) {
return ELF::SHT_PROGBITS;
}
static unsigned
getELFSectionFlags(SectionKind K, bool InCOMDAT) {
static unsigned getELFSectionFlags(SectionKind K) {
unsigned Flags = 0;
if (!K.isMetadata())
@ -181,10 +179,7 @@ getELFSectionFlags(SectionKind K, bool InCOMDAT) {
if (K.isThreadLocal())
Flags |= ELF::SHF_TLS;
// FIXME: There is nothing in ELF preventing an SHF_MERGE from being
// in a comdat. We just avoid it for now because we don't print
// those .sections correctly.
if (!InCOMDAT && (K.isMergeableCString() || K.isMergeableConst()))
if (K.isMergeableCString() || K.isMergeableConst())
Flags |= ELF::SHF_MERGE;
if (K.isMergeableCString())
@ -214,7 +209,7 @@ const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
Kind = getELFKindForNamedSection(SectionName, Kind);
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind, GV->hasComdat());
unsigned Flags = getELFSectionFlags(Kind);
if (const Comdat *C = getELFComdat(GV)) {
Group = C->getName();
Flags |= ELF::SHF_GROUP;
@ -249,97 +244,74 @@ static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
return ".data.rel.ro";
}
static const MCSection *
getUniqueELFSection(MCContext &Ctx, const GlobalValue &GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM, unsigned Flags) {
StringRef Prefix = getSectionPrefixForGlobal(Kind);
const MCSection *TargetLoweringObjectFileELF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
unsigned Flags = getELFSectionFlags(Kind);
SmallString<128> Name(Prefix);
bool UniqueSectionNames = TM.getUniqueSectionNames();
if (UniqueSectionNames) {
Name.push_back('.');
TM.getNameWithPrefix(Name, &GV, Mang, true);
// If we have -ffunction-section or -fdata-section then we should emit the
// global value to a uniqued section specifically for it.
bool EmitUniqueSection = false;
if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
if (Kind.isText())
EmitUniqueSection = TM.getFunctionSections();
else
EmitUniqueSection = TM.getDataSections();
}
EmitUniqueSection |= GV->hasComdat();
unsigned EntrySize = 0;
if (Kind.isMergeableCString()) {
if (Kind.isMergeable2ByteCString()) {
EntrySize = 2;
} else if (Kind.isMergeable4ByteCString()) {
EntrySize = 4;
} else {
EntrySize = 1;
assert(Kind.isMergeable1ByteCString() && "unknown string width");
}
} else if (Kind.isMergeableConst()) {
if (Kind.isMergeableConst4()) {
EntrySize = 4;
} else if (Kind.isMergeableConst8()) {
EntrySize = 8;
} else {
assert(Kind.isMergeableConst16() && "unknown data width");
EntrySize = 16;
}
}
StringRef Group = "";
if (const Comdat *C = getELFComdat(&GV)) {
if (const Comdat *C = getELFComdat(GV)) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
}
return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags, 0, Group,
!UniqueSectionNames);
}
const MCSection *TargetLoweringObjectFileELF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
unsigned Flags = getELFSectionFlags(Kind, GV->hasComdat());
// If we have -ffunction-section or -fdata-section then we should emit the
// global value to a uniqued section specifically for it.
bool EmitUniquedSection = false;
if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
if (Kind.isText())
EmitUniquedSection = TM.getFunctionSections();
else
EmitUniquedSection = TM.getDataSections();
}
if (EmitUniquedSection || GV->hasComdat())
return getUniqueELFSection(getContext(), *GV, Kind, Mang, TM, Flags);
if (Kind.isText()) return TextSection;
bool UniqueSectionNames = TM.getUniqueSectionNames();
SmallString<128> Name;
if (Kind.isMergeableCString()) {
// We also need alignment here.
// FIXME: this is getting the alignment of the character, not the
// alignment of the global!
unsigned Align =
TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
unsigned EntrySize = 1;
if (Kind.isMergeable2ByteCString())
EntrySize = 2;
else if (Kind.isMergeable4ByteCString())
EntrySize = 4;
else
assert(Kind.isMergeable1ByteCString() && "unknown string width");
std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
std::string Name = SizeSpec + utostr(Align);
return getContext().getELFSection(
Name, ELF::SHT_PROGBITS,
ELF::SHF_ALLOC | ELF::SHF_MERGE | ELF::SHF_STRINGS, EntrySize, "");
Name = SizeSpec + utostr(Align);
} else if (Kind.isMergeableConst()) {
Name = ".rodata.cst";
Name += utostr(EntrySize);
} else {
Name = getSectionPrefixForGlobal(Kind);
}
if (Kind.isMergeableConst()) {
if (Kind.isMergeableConst4() && MergeableConst4Section)
return MergeableConst4Section;
if (Kind.isMergeableConst8() && MergeableConst8Section)
return MergeableConst8Section;
if (Kind.isMergeableConst16() && MergeableConst16Section)
return MergeableConst16Section;
return ReadOnlySection; // .const
if (EmitUniqueSection && UniqueSectionNames) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GV, Mang, true);
}
if (Kind.isReadOnly()) return ReadOnlySection;
if (Kind.isThreadData()) return TLSDataSection;
if (Kind.isThreadBSS()) return TLSBSSSection;
// Note: we claim that common symbols are put in BSSSection, but they are
// really emitted with the magic .comm directive, which creates a symbol table
// entry but not a section.
if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
if (Kind.isDataNoRel()) return DataSection;
if (Kind.isDataRelLocal()) return DataRelLocalSection;
if (Kind.isDataRel()) return DataRelSection;
if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return DataRelROSection;
return getContext().getELFSection(Name, getELFSectionType(Name, Kind), Flags,
EntrySize, Group,
EmitUniqueSection && !UniqueSectionNames);
}
const MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
@ -351,8 +323,7 @@ const MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
if (!EmitUniqueSection)
return ReadOnlySection;
return getUniqueELFSection(getContext(), F, SectionKind::getReadOnly(), Mang,
TM, ELF::SHF_ALLOC);
return SelectSectionForGlobal(&F, SectionKind::getReadOnly(), Mang, TM);
}
bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(

6
llvm/test/CodeGen/X86/global-sections-comdat.ll
View File

@ -41,6 +41,6 @@ bb5:
$G16 = comdat any
@G16 = unnamed_addr constant i32 42, comdat
; LINUX: .section .rodata.G16,"aG",@progbits,G16,comdat
; LINUX-SECTIONS: .section .rodata.G16,"aG",@progbits,G16,comdat
; LINUX-SECTIONS-SHORT: .section .rodata,"aG",@progbits,G16,comdat
; LINUX: .section .rodata.cst4.G16,"aGM",@progbits,4,G16,comdat
; LINUX-SECTIONS: .section .rodata.cst4.G16,"aGM",@progbits,4,G16,comdat
; LINUX-SECTIONS-SHORT: .section .rodata.cst4,"aGM",@progbits,4,G16,comdat