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Fix PR18743.

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The IR
@foo = private constant i32 42

is valid, but before this patch we would produce an invalid MachO from it. It
was invalid because it would use an L label in a section where the liker needs
the labels in order to atomize it.

One way of fixing it would be to just reject this IR in the backend, but that
would not be very front end friendly.

What this patch does is use an 'l' prefix in sections that we know the linker
requires symbols for atomizing them. This allows frontends to just use
private and not worry about which sections they go to or how the linker handles
them.

One small issue with this strategy is that now a symbol name depends on the
section, which is not available before codegen. This is not a problem in
practice. The reason is that it only happens with private linkage, which will
be ignored by the non codegen users (llvm-nm and llvm-ar).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201608 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2014-02-18 22:24:57 +00:00
parent 1836fe5651
commit 6880f0e19f
30 changed files with 333 additions and 156 deletions
Download Patch File Download Diff File Expand all files Collapse all files

119
lib/CodeGen/TargetLoweringObjectFileImpl.cpp
View File

@ -36,6 +36,7 @@
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetLowering.h"
using namespace llvm;
using namespace dwarf;
@ -43,19 +44,18 @@ using namespace dwarf;
// ELF
//===----------------------------------------------------------------------===//
MCSymbol *
TargetLoweringObjectFileELF::getCFIPersonalitySymbol(const GlobalValue *GV,
Mangler &Mang,
MachineModuleInfo *MMI) const {
MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
unsigned Encoding = getPersonalityEncoding();
switch (Encoding & 0x70) {
default:
report_fatal_error("We do not support this DWARF encoding yet!");
case dwarf::DW_EH_PE_absptr:
return getSymbol(GV, Mang);
return TM.getTargetLowering()->getSymbol(GV, Mang);
case dwarf::DW_EH_PE_pcrel: {
return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
getSymbol(GV, Mang)->getName());
TM.getTargetLowering()->getSymbol(GV, Mang)->getName());
}
}
}
@ -89,18 +89,19 @@ void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
const TargetMachine &TM, MachineModuleInfo *MMI,
MCStreamer &Streamer) const {
if (Encoding & dwarf::DW_EH_PE_indirect) {
MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang);
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
// Add information about the stub reference to ELFMMI so that the stub
// gets emitted by the asmprinter.
MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
if (StubSym.getPointer() == 0) {
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
@ -109,8 +110,8 @@ const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
}
return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
MMI, Streamer);
return TargetLoweringObjectFile::
getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
}
static SectionKind
@ -195,10 +196,9 @@ getELFSectionFlags(SectionKind K) {
return Flags;
}
const MCSection *TargetLoweringObjectFileELF::
getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
StringRef SectionName = GV->getSection();
// Infer section flags from the section name if we can.
@ -248,7 +248,7 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Prefix = getSectionPrefixForGlobal(Kind);
SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
Name.append(Sym->getName().begin(), Sym->getName().end());
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
@ -487,9 +487,9 @@ emitModuleFlags(MCStreamer &Streamer,
Streamer.AddBlankLine();
}
const MCSection *TargetLoweringObjectFileMachO::
getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
// Parse the section specifier and create it if valid.
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
@ -526,6 +526,41 @@ getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
return S;
}
bool TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols(
const MCSection &Section) const {
const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
// Sections holding 1 byte strings are atomized based on the data
// they contain.
// Sections holding 2 byte strings require symbols in order to be
// atomized.
// There is no dedicated section for 4 byte strings.
if (SMO.getKind().isMergeable1ByteCString())
return false;
if (SMO.getSegmentName() == "__DATA" &&
SMO.getSectionName() == "__cfstring")
return false;
switch (SMO.getType()) {
default:
return true;
// These sections are atomized at the element boundaries without using
// symbols.
case MCSectionMachO::S_4BYTE_LITERALS:
case MCSectionMachO::S_8BYTE_LITERALS:
case MCSectionMachO::S_16BYTE_LITERALS:
case MCSectionMachO::S_LITERAL_POINTERS:
case MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS:
case MCSectionMachO::S_LAZY_SYMBOL_POINTERS:
case MCSectionMachO::S_MOD_INIT_FUNC_POINTERS:
case MCSectionMachO::S_MOD_TERM_FUNC_POINTERS:
case MCSectionMachO::S_INTERPOSING:
return false;
}
}
const MCSection *TargetLoweringObjectFileMachO::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
@ -606,21 +641,17 @@ TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
return ReadOnlySection; // .const
}
/// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
/// not to emit the UsedDirective for some symbols in llvm.used.
/// This hook allows targets to selectively decide not to emit the UsedDirective
/// for some symbols in llvm.used.
// FIXME: REMOVE this (rdar://7071300)
bool TargetLoweringObjectFileMachO::
shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler &Mang) const {
/// On Darwin, internally linked data beginning with "L" or "l" does not have
/// the directive emitted (this occurs in ObjC metadata).
if (!GV) return false;
bool TargetLoweringObjectFileMachO::shouldEmitUsedDirectiveFor(
const GlobalValue *GV, Mangler &Mang, TargetMachine &TM) const {
// Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
// FIXME: ObjC metadata is currently emitted as internal symbols that have
// \1L and \0l prefixes on them. Fix them to be Private/LinkerPrivate and
// this horrible hack can go away.
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
return false;
}
@ -630,14 +661,16 @@ shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler &Mang) const {
const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
const TargetMachine &TM, MachineModuleInfo *MMI,
MCStreamer &Streamer) const {
// The mach-o version of this method defaults to returning a stub reference.
if (Encoding & DW_EH_PE_indirect) {
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang);
MCSymbol *SSym =
getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
// Add information about the stub reference to MachOMMI so that the stub
// gets emitted by the asmprinter.
@ -645,7 +678,7 @@ const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
MachOMMI.getGVStubEntry(SSym);
if (StubSym.getPointer() == 0) {
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
@ -654,24 +687,24 @@ const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
}
return TargetLoweringObjectFile::
getTTypeGlobalReference(GV, Encoding, Mang, MMI, Streamer);
return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
TM, MMI, Streamer);
}
MCSymbol *TargetLoweringObjectFileMachO::
getCFIPersonalitySymbol(const GlobalValue *GV, Mangler &Mang,
MachineModuleInfo *MMI) const {
MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
// The mach-o version of this method defaults to returning a stub reference.
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang);
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
// Add information about the stub reference to MachOMMI so that the stub
// gets emitted by the asmprinter.
MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
if (StubSym.getPointer() == 0) {
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
@ -717,9 +750,9 @@ getCOFFSectionFlags(SectionKind K) {
return Flags;
}
const MCSection *TargetLoweringObjectFileCOFF::
getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
int Selection = 0;
unsigned Characteristics = getCOFFSectionFlags(Kind);
StringRef Name = GV->getSection();
@ -727,7 +760,7 @@ getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
if (GV->isWeakForLinker()) {
Selection = COFF::IMAGE_COMDAT_SELECT_ANY;
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
COMDATSymName = Sym->getName();
}
return getContext().getCOFFSection(Name,
@ -761,7 +794,7 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
unsigned Characteristics = getCOFFSectionFlags(Kind);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
MCSymbol *Sym = getSymbol(GV, Mang);
MCSymbol *Sym = TM.getTargetLowering()->getSymbol(GV, Mang);
return getContext().getCOFFSection(Name, Characteristics,
Kind, Sym->getName(),
COFF::IMAGE_COMDAT_SELECT_ANY);