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MachO: Add linker-optimisation hint framework to MC.

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Another part of the ARM64 backend (so tests will be following soon).
This is currently used by the linker to relax adrp/ldr pairs into nops
where possible, though could well be more broadly applicable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205084 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover
2014-03-29 07:34:53 +00:00
parent 0301154c0e
commit 1330ee3189
10 changed files with 325 additions and 3 deletions
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29
lib/MC/MachObjectWriter.cpp
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@ -761,6 +761,14 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
LoadCommandsSize += sizeof(MachO::linkedit_data_command);
}
// Add the loh load command size, if used.
uint64_t LOHRawSize = Asm.getLOHContainer().getEmitSize(*this, Layout);
uint64_t LOHSize = RoundUpToAlignment(LOHRawSize, is64Bit() ? 8 : 4);
if (LOHSize) {
++NumLoadCommands;
LoadCommandsSize += sizeof(MachO::linkedit_data_command);
}
// Add the symbol table load command sizes, if used.
unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
UndefinedSymbolData.size();
@ -849,6 +857,12 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
DataRegionsSize);
}
// Write the loh load command, if used.
uint64_t LOHTableEnd = DataInCodeTableEnd + LOHSize;
if (LOHSize)
WriteLinkeditLoadCommand(MachO::LC_LINKER_OPTIMIZATION_HINT,
DataInCodeTableEnd, LOHSize);
// Write the symbol table load command, if used.
if (NumSymbols) {
unsigned FirstLocalSymbol = 0;
@ -865,10 +879,10 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
// If used, the indirect symbols are written after the section data.
if (NumIndirectSymbols)
IndirectSymbolOffset = DataInCodeTableEnd;
IndirectSymbolOffset = LOHTableEnd;
// The symbol table is written after the indirect symbol data.
uint64_t SymbolTableOffset = DataInCodeTableEnd + IndirectSymbolSize;
uint64_t SymbolTableOffset = LOHTableEnd + IndirectSymbolSize;
// The string table is written after symbol table.
uint64_t StringTableOffset =
@ -935,6 +949,17 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
Write16(Data->Kind);
}
// Write out the loh commands, if there is one.
if (LOHSize) {
#ifndef NDEBUG
unsigned Start = OS.tell();
#endif
Asm.getLOHContainer().Emit(*this, Layout);
// Pad to a multiple of the pointer size.
WriteBytes("", OffsetToAlignment(LOHRawSize, is64Bit() ? 8 : 4));
assert(OS.tell() - Start == LOHSize);
}
// Write the symbol table data, if used.
if (NumSymbols) {
// Write the indirect symbol entries.