When not using subsections via symbols, the assembler can resolve
symbol differences (including pcrel references) to non-local
labels at assembly time, not just those in the same atom.
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If the fixup is out of range for the Thumb1 instruction, relax it
to the Thumb2 encoding instead.
rdar://10711829
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When the non-local symbol in the expression is in the same fragment
as the second symbol, the assembler can still evaluate the expression
without needing a relocation.
For example, on ARM:
_foo:
ldr lr, (_foo - 4)
rdar://10348687
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assembly source when it generates the TAG_subprogram dwarf debug info for
the labels that have nothing between them as in this bit of assembly source:
% cat ZeroLength.s
_func1:
_func2:
nop
One solution would be to not emit the subsequent labels with the same address
and use the next label with a different address or the end of the section for
the AT_high_pc value of the TAG_subprogram.
Turns out in llvm-mc it is not possible in all cases to determine of two
symbols have the same value at the point we put out the TAG_subprogram dwarf
debug info.
So we will have llvm-mc instead of putting out TAG_subprogram's put out
DW_TAG_label's. And the DW_TAG_label does not have a AT_high_pc value which
avoids the problem.
This commit is only the functional change to make the diffs clear as to what is
really being changed. The next commit will be to clean up the names of such
things like MCGenDwarfSubprogramEntry to something like MCGenDwarfLabelEntry.
rdar://10666925
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generates the dwarf Compile Unit DIE and a dwarf subprogram DIE for each
non-temporary label.
The next part will be to get the clang driver to enable this when assembling
a .s file. rdar://9275556
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When the file isn't being built with subsections-via-symbols, symbol
differences involving non-local symbols can be resolved more aggressively.
Needed for gas compatibility.
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it is separating the directory part from the basename of the FileName. Noticed
that this:
.file 1 "dir/foo"
when assembled got the two parts switched. Using the Mac OS X dwarfdump tool
it can be seen easily:
% dwarfdump -a a.out
include_directories[ 1] = 'foo'
Dir Mod Time File Len File Name
---- ---------- ---------- ---------------------------
file_names[ 1] 1 0x00000000 0x00000000 dir
...
Which should be:
...
include_directories[ 1] = 'dir'
Dir Mod Time File Len File Name
---- ---------- ---------- ---------------------------
file_names[ 1] 1 0x00000000 0x00000000 foo
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.cfi_startproc. e.g. libffi:
$ cat confopt.c
asm (".cfi_startproc\n\t.cfi_endproc");
int main () { return 0; }
Teach MC / dwarf emission to handle these cfi directives which essentially
create an empty frame.
rdar://10017184
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With this we don't need the EffectiveSize field anymore. Without that field
LayoutFragment only updates offsets and we don't need to invalidate the
current fragment when it is relaxed (only the ones following it).
This is also a very small improvement in the accuracy of the layout info as
we now use the after relaxation size immediately.
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Since we now don't update addresses so early, we might relax a bit more than
we need to. This is simillar to the issue in PR8467.
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as llc + llvm-mc. This time ELF is not changed and I tested that llvm-gcc
bootstrap on darwin10 using darwin9's assembler and linker.
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foo = a - b
.long foo
instead of just
.long a - b
First, on darwin9 64 bits the assembler produces the wrong result. Second,
if "a" is the end of the section all darwin assemblers (9, 10 and mc) will not
consider a - b to be a constant but will if the dummy foo is created.
Split how we handle these cases. The first one is something MC should take care
of. The second one has to be handled by the caller.
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doing that if the target is darwin10 or newer.
This fixes
*) Direct object emission was producing objects without the workaround on
darwin9.
*) Assembly printing was producing objects with the workaround on linux.
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correctly. The Lexer was incorrectly eating the newline casusing it to branch
to address 0. Updated the test case to use a "0:" label and a branch to "0b".
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- This fixes a string table mismatch with 'as' when two new symbols are defined
in a single instruction.
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- 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.
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be diced into atoms, and adjust getAtom() to take this into account.
- This fixes relocations to symbols in fixed size literal sections, for
example.
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- This eliminates getAtomForAddress() (which was a linear search) and
simplifies getAtom().
- This also fixes some correctness problems where local labels at the same
address as non-local labels could be assigned to the wrong atom.
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override prefix and only the r/m16 forms should have had that. Also for variant
one, the AT&T syntax, added suffixes to all forms. Also added the missing
64-bit form for 'CRC32 r64, r/m8'. Plus added test cases for all forms and
tweaked one test case to add the needed suffixes.
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- This is "extraordinarily" Darwin 'as' compatible. See the litany of FIXMEs littered about for more information.
- There are a few cases which seem to clearly be 'as' bugs which I have left unsupported, and there is one cases where we diverge but should fix if it blocks diffing .o files (Darwin 'as' ends up widening a jump unnecessarily).
- 403.gcc build, runs, and diffs equivalently to the 'as' built version now (using llvm-mc). However, it builds so slowly that I wouldn't recommend trying it quite yet. :)
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relative to the fragment address, not its offset. This was masked by the text
section normally being at address 0.
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- The implementation is currently very brain dead and inefficient, but I have a
clear plan on how to fix it.
- The good news is, it works and correctly assembles 403.gcc (when built with
Clang, at '-Os', '-Os -g', and '-O3'). Even better, at '-Os' and '-Os -g',
the resulting binary is exactly equivalent to that when built with the system
assembler. So it probably works! :)
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section with TextAlignFillValue and calls EmitCodeAlignment() instead of
calling EmitValueToAlignment(). This allows x86 assembly code to be aligned
with optimal nops.
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that a symbol stub section with no attributes can be parsed as in:
.section __TEXT,__picsymbolstub4,symbol_stubs,none,16
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- I'm still trying to figure out the cleanest way to implement this and match the assembler, currently there are some substantial differences.
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sections, etc.
- The quick and dirty way, just clone the TargetLoweringObjectFile
code. Eventually this should be shared... somehow.
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- I moved section creation back into AsmParser. I think policy decisions like
this should be pushed higher, not lower, when possible (in addition the
assembler has flags which change this behavior, for example).
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- I haven't really tried to find the "right" way to store the fixups or apply
them, yet. This works, but isn't particularly elegant or fast.
- Still no evaluation support, so we don't actually ever not turn a fixup into
a relocation entry.
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- 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).
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- 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).
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(e.g., .objc_message_refs).
- Just emit a .align when we see the directive; this isn't exactly what 'as'
does but in practice it should be ok, at least for now. See FIXME.
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- 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.
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