Currently the output should be almost identical to the one produced by CodeGen
to make the transition easier.
The only two differences I know of are:
* Some files get an extra advance loc of size 0. This will be fixed when
relaxations are enabled.
* The optimization of declaring an EH symbol as an external variable is not
implemented. This is a subset of adding the nounwind attribute, so we if really
this at -O0 we should probably do it at the IL level.
llvm-svn: 130623
actuall addresses in a .o file, so it is better to let the MachO writer compute
it.
This is good for two reasons. First, areas that shouldn't care about
addresses now don't have access to it. Second, the layout of each section
is independent. I should use this in a subsequent commit to speed it up.
Most of the patch is just removing the section address computation. The two
interesting parts are the change on how we handle padding in the end
of sections and how MachO can get the address of a-b when a and b are in
different sections.
Since now the expression evaluation normally doesn't know the section address,
it will think that a-b needs relocation and let the MachO writer know. Once
it has computed the section addresses, it calls back the expression evaluation
with the section addresses to resolve these expressions.
The remaining problem is the handling of padding. Currently it will create
a special alignment fragment at the end. Since that fragment doesn't update
the alignment of the section, it needs the real address to be computed.
Since now the layout will not compute a-b with a and b in different sections,
the only effect that the special alignment fragment has is update the
address size of the section. This can also be done by the MachO writer.
llvm-svn: 121076
MCStreamer instead of just MCObjectStreamer. Address changes cannot
be as efficient as we have to use DW_LNE_set_addres, but at least
most of the logic is shared.
This will be used so that, with CodeGen still using EmitDwarfLocDirective,
llvm-gcc is able to produce debug_line sections without needing an
assembler that supports .loc.
llvm-svn: 119777
where both symbols are "local", that is non-external symbols, and there is
no "base" for the symbols used in the expression, that is the section has
no non-temporary symbols. This case looks like this:
% cat local_reloc_A-B.s
.long 0
LB: .long 1
.long LA - LB - 4
.long 2
LA: .long 3
which llvm-mc will not encode without this patch, generates a "unsupported
local relocations in difference" error, but the Darwin assembler will
encode with relocation entries like this:
% otool -rv a.out l.out
a.out:
Relocation information (__TEXT,__text) 2 entries
address pcrel length extern type scattered symbolnum/value
00000008 False long False SUB False 1 (__TEXT,__text)
00000008 False long False UNSIGND False 1 (__TEXT,__text)
which is very similar to what is encoded when the symbols don't have the
leading 'L' and they are not temporary symbols. Which llvm-mc and the
Darwin assembler will encoded like this:
Relocation information (__TEXT,__text) 2 entries
address pcrel length extern type scattered symbolnum/value
00000008 False long True SUB False B
00000008 False long True UNSIGND False A
This is the missing relocation encoding needed to allow the Mach-O x86
Dwarf file and line table to be emitted. So this patch also removes the
TODO from the if() statement in MCMachOStreamer::Finish() that didn't
call MCDwarfFileTable::Emit() for 64-bit targets.
llvm-svn: 115389
and output the dwarf line number tables. This contains the code to emit and
encode the dwarf line tables from the previously gathered information in the
MCLineSection objects. This contains all the details to encode the line and
address deltas into the dwarf line table.
To do this an MCDwarfLineAddrFragment has been added.
Also this moves the interface code out of Mach-O streamer into
MCDwarf so it should be useable by other object file formats.
There is now one call to be made from an MCObjectStreamer
EmitInstruction() method:
MCLineEntry::Make(this, getCurrentSection());
to create a line entry after each instruction is assembled.
And one call call to be made from an MCObjectStreamer Finish() method:
MCDwarfFileTable::Emit(this, DwarfLineSection);
when getContext().hasDwarfFiles() is true and is passed a object file specific
MCSection where to emit the dwarf file and the line tables.
This appears to now be correct for 32-bit targets, at least x86. But the
relocation entries for 64-bit Darwin needs some further work which is next
up to work on. So for now the 64-bit Mach-O target does not output the
dwarf file and line tables.
llvm-svn: 115157
The ELF implementation now creates text, data and bss to match the gnu as
behavior.
The text streamer still has the old MachO specific behavior since
the testsuite checks that it will error when a directive is given
before a setting the current section for example.
A nice benefit is that -n is not required anymore when producing
ELF files.
llvm-svn: 114027
and output the dwarf line number tables. This takes the current loc info after
an instruction is assembled and saves the needed info into an object that has
vector and for each section. These objects will be used for the final patch to
build and emit the encoded dwarf line number tables. Again for now this is only
in the Mach-O streamer but at some point will move to a more generic place.
llvm-svn: 112668
previously collected info from the .file directives and outputs the encoded
bytes for it. For now this is only in the Mach-O streamer but at some point
will move to a more generic place.
llvm-svn: 110617
- Don't clear weak reference flag, 'as' was only "trying" to do this, it wasn't
actually succeeding.
- Clear the "lazy bound" bit when we mark something external. This corresponds
roughly to the lazy clearing of the bit that 'as' implements in
symbol_table_lookup.
- The exact meaning of these flags appears pretty loose, since 'as' isn't very
consistent. For now we just try to match 'as', we will clean this up one day
hopefully.
llvm-svn: 103964
to be aligned with optimal nops. This patch does not change any functionality
and when the compiler is changed to use EmitCodeAlignment() it should also not
change the resulting output. Once the compiler change is made and everything
looks good the next patch with the table of optimal X86 nops will be added to
WriteNopData() changing the output. There are many FIXMEs in this patch which
will be removed when we have better target hooks (coming soon I hear).
llvm-svn: 96963
- I'm still trying to figure out the cleanest way to implement this and match the assembler, currently there are some substantial differences.
llvm-svn: 80347
- The indirect table itself isn't being filled in yet.
- This isn't factored properly and is rather FIXMEd, but at the moment I'm more
focused on figuring out what it needs to do.
llvm-svn: 79910
- This is mostly complete, the main thing missing is .indirect_symbol support
(which would be straight-forward, except that the way it is implemented in
'as' makes getting an exact .o match interesting).
llvm-svn: 79899
- Honor .globl.
- Set symbol type and section correctly ('nm' now works), and order symbols
appropriately.
- Take care to the string table so that the .o matches 'as' exactly (for ease
of testing).
llvm-svn: 79740
- The only .s syntax this honors right now is emitting labels, and some parts
of the symbol table generation are wrong or faked.
- This is enough to get nm to report such symbols... incorrectly, but still.
Also, fixed byte emission to extend the previous fragment if possible.
llvm-svn: 79739
(external was really undefined and there wasn't an explicit representation for
absolute symbols).
- This still needs some cleanup to how the absolute "pseudo" section is dealt
with, but I haven't figured out the nicest approach yet.
llvm-svn: 79733
- Together these form the (Mach-O) back end of the assembler.
- MCAssembler is the actual assembler backend, which is designed to have a
reasonable API. This will eventually grow to support multiple object file
implementations, but for now its Mach-O/i386 only.
- MCMachOStreamer adapts the MCStreamer "actions" API to the MCAssembler API,
e.g. converting the various directives into fragments, managing state like
the current section, and so on.
- llvm-mc will use the new backend via '-filetype=obj', which may eventually
be, but is not yet, since I hear that people like assemblers which actually
assemble.
- The only thing that works at the moment is changing sections. For the time
being I have a Python Mach-O dumping tool in test/scripts so this stuff can
be easily tested, eventually I expect to replace this with a real LLVM tool.
- More doxyments to come.
I assume that since this stuff doesn't touch any of the things which are part of
2.6 that it is ok to put this in not so long before the freeze, but if someone
objects let me know, I can pull it.
llvm-svn: 79612
Rafael Espindola