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MC/Mach-O: Lift relocation emission logic a bit higher to separate evaluation / relocation handling from the actual .o writing. 

llvm-svn: 98942
This commit is contained in:
Daniel Dunbar 2010-03-19 07:09:18 +00:00
parent 22a411ff5b
commit 563d40eda6
1 changed files with 77 additions and 56 deletions
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133
llvm/lib/MC/MCAssembler.cpp
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@ -170,6 +170,27 @@ class MachObjectWriter {
unsigned Is64Bit : 1;
unsigned IsLSB : 1;
/// @name Relocation Data
/// @{
struct MachRelocationEntry {
uint32_t Word0;
uint32_t Word1;
};
llvm::DenseMap<const MCSectionData*,
std::vector<MachRelocationEntry> > Relocations;
/// @}
/// @name Symbol Table Data
SmallString<256> StringTable;
std::vector<MachSymbolData> LocalSymbolData;
std::vector<MachSymbolData> ExternalSymbolData;
std::vector<MachSymbolData> UndefinedSymbolData;
/// @}
public:
MachObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool _IsLSB = true)
: OS(_OS), Is64Bit(_Is64Bit), IsLSB(_IsLSB) {
@ -464,14 +485,9 @@ public:
Write32(Address);
}
struct MachRelocationEntry {
uint32_t Word0;
uint32_t Word1;
};
void ComputeScatteredRelocationInfo(MCAssembler &Asm, MCFragment &Fragment,
MCAsmFixup &Fixup,
const MCValue &Target,
std::vector<MachRelocationEntry> &Relocs) {
void RecordScatteredRelocation(MCAssembler &Asm, MCFragment &Fragment,
const MCAsmFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
uint32_t Address = Fragment.getOffset() + Fixup.Offset;
unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
@ -504,15 +520,7 @@ public:
Value2 = B_SD->getAddress();
}
MachRelocationEntry MRE;
MRE.Word0 = ((Address << 0) |
(Type << 24) |
(Log2Size << 28) |
(IsPCRel << 30) |
RF_Scattered);
MRE.Word1 = Value;
Relocs.push_back(MRE);
// Relocations are written out in reverse order, so the PAIR comes first.
if (Type == RIT_Difference || Type == RIT_LocalDifference) {
MachRelocationEntry MRE;
MRE.Word0 = ((0 << 0) |
@ -521,24 +529,25 @@ public:
(IsPCRel << 30) |
RF_Scattered);
MRE.Word1 = Value2;
Relocs.push_back(MRE);
Relocations[Fragment.getParent()].push_back(MRE);
}
MachRelocationEntry MRE;
MRE.Word0 = ((Address << 0) |
(Type << 24) |
(Log2Size << 28) |
(IsPCRel << 30) |
RF_Scattered);
MRE.Word1 = Value;
Relocations[Fragment.getParent()].push_back(MRE);
}
void ComputeRelocationInfo(MCAssembler &Asm, MCDataFragment &Fragment,
MCAsmFixup &Fixup,
std::vector<MachRelocationEntry> &Relocs) {
void RecordRelocation(MCAssembler &Asm, MCDataFragment &Fragment,
const MCAsmFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
// FIXME: Share layout object.
MCAsmLayout Layout(Asm);
// Evaluate the fixup; if the value was resolved, no relocation is needed.
MCValue Target;
if (Asm.EvaluateFixup(Layout, Fixup, &Fragment, Target, Fixup.FixedValue))
return;
// If this is a difference or a defined symbol plus an offset, then we need
// a scattered relocation entry.
uint32_t Offset = Target.getConstant();
@ -546,9 +555,10 @@ public:
Offset += 1 << Log2Size;
if (Target.getSymB() ||
(Target.getSymA() && !Target.getSymA()->getSymbol().isUndefined() &&
Offset))
return ComputeScatteredRelocationInfo(Asm, Fragment, Fixup, Target,
Relocs);
Offset)) {
RecordScatteredRelocation(Asm, Fragment, Fixup, Target, FixedValue);
return;
}
// See <reloc.h>.
uint32_t Address = Fragment.getOffset() + Fixup.Offset;
@ -596,7 +606,20 @@ public:
(Log2Size << 25) |
(IsExtern << 27) |
(Type << 28));
Relocs.push_back(MRE);
Relocations[Fragment.getParent()].push_back(MRE);
}
void ComputeRelocationInfo(MCAssembler &Asm, MCDataFragment &Fragment,
MCAsmFixup &Fixup) {
// FIXME: Share layout object.
MCAsmLayout Layout(Asm);
// Evaluate the fixup; if the value was resolved, no relocation is needed.
MCValue Target;
if (Asm.EvaluateFixup(Layout, Fixup, &Fragment, Target, Fixup.FixedValue))
return;
RecordRelocation(Asm, Fragment, Fixup, Target, Fixup.FixedValue);
}
void BindIndirectSymbols(MCAssembler &Asm) {
@ -820,32 +843,24 @@ public:
WriteSegmentLoadCommand(NumSections, VMSize,
SectionDataStart, SectionDataSize);
// ... and then the section headers.
//
// We also compute the section relocations while we do this. Note that
// computing relocation info will also update the fixup to have the correct
// value; this will overwrite the appropriate data in the fragment when it
// is written.
std::vector<MachRelocationEntry> RelocInfos;
uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
for (MCAssembler::iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it) {
MCSectionData &SD = *it;
// The assembler writes relocations in the reverse order they were seen.
//
// FIXME: It is probably more complicated than this.
unsigned NumRelocsStart = RelocInfos.size();
for (MCSectionData::reverse_iterator it2 = SD.rbegin(),
ie2 = SD.rend(); it2 != ie2; ++it2)
for (MCSectionData::iterator it2 = SD.begin(),
ie2 = SD.end(); it2 != ie2; ++it2)
if (MCDataFragment *DF = dyn_cast<MCDataFragment>(&*it2))
for (unsigned i = 0, e = DF->fixup_size(); i != e; ++i)
ComputeRelocationInfo(Asm, *DF, DF->getFixups()[e - i - 1],
RelocInfos);
ComputeRelocationInfo(Asm, *DF, DF->getFixups()[i]);
}
unsigned NumRelocs = RelocInfos.size() - NumRelocsStart;
uint64_t SectionStart = SectionDataStart + SD.getAddress();
WriteSection(SD, SectionStart, RelocTableEnd, NumRelocs);
// ... and then the section headers.
uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
for (MCAssembler::iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it) {
std::vector<MachRelocationEntry> &Relocs = Relocations[it];
unsigned NumRelocs = Relocs.size();
uint64_t SectionStart = SectionDataStart + it->getAddress();
WriteSection(*it, SectionStart, RelocTableEnd, NumRelocs);
RelocTableEnd += NumRelocs * RelocationInfoSize;
}
@ -891,9 +906,15 @@ public:
WriteZeros(SectionDataPadding);
// Write the relocation entries.
for (unsigned i = 0, e = RelocInfos.size(); i != e; ++i) {
Write32(RelocInfos[i].Word0);
Write32(RelocInfos[i].Word1);
for (MCAssembler::iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it) {
// Write the section relocation entries, in reverse order to match 'as'
// (approximately, the exact algorithm is more complicated than this).
std::vector<MachRelocationEntry> &Relocs = Relocations[it];
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
Write32(Relocs[e - i - 1].Word0);
Write32(Relocs[e - i - 1].Word1);
}
}
// Write the symbol table data, if used.