llvm dev - Jan 2012 - [LLVMdev] generating ELF files on non-ELF platforms with MC

Hello,

We're currently working on MC-JIT, focusing on runtime generation and
loading of ELF object files, even on non-ELF platforms (i.e. Windows). However,
we run into a problem with MC insisting to generate COFF objects on Windows,
MachO on Macs and ELF only otherwise, based on the triple.

Is there an existing method to generate ELF objects with MC on Windows, without
modifying MC?

Thanks in advance,
Eli
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Hello
> Is there an existing method to generate ELF objects with MC on Windows,
> without modifying MC?
Here "on windows" you mean you want to generate the ELF file with
windows-specific code inside?

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

> Is there an existing method to generate ELF objects with MC on 
> Windows, without modifying MC?
Here "on windows" you mean you want to generate the ELF file with
windows-specific code inside?

--
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

--------------

Hi Anton,

Yes, what I mean is that I want to generate runnable Windows code, on Windows,
but package in ELF as the object file. Note that there's absolutely no
problem with this approach - in fact we have a functional prototype already.
The reason for this is that I currently want to employ MC-JIT on both Linux and
Windows, without implementing two separate runtime dynamic loaders. I want to
implement just RuntimeDyldELF, and use it on both Windows and Linux.

Eli

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Ping,
Apart from Anton's concerns (which I think are manageable) and Micah's
support, I received no reply on this.

Does there exist a way to tell MC to generate and ELF container for code on
Windows? If not, I'm willing to submit a patch to fix this, but would like
some opinions on the best direction to take here.

The proposed "llvm::TargetSpec class"
(http://nondot.org/sabre/LLVMNotes/TargetSpec.txt) seems to address this,
although AFAICS the current llvm::Triple does not explicitly specify the
object/container type. ELF is usually taken as "default" when no other
option is chosen. A representative example from X86MCTargetDesc.cpp:

---------------
static MCStreamer *createMCStreamer(const Target &T, StringRef TT,
                                    MCContext &Ctx, MCAsmBackend &MAB,
                                    raw_ostream &_OS,
                                    MCCodeEmitter *_Emitter,
                                    bool RelaxAll,
                                    bool NoExecStack) {
  Triple TheTriple(TT);

  if (TheTriple.isOSDarwin() || TheTriple.getEnvironment() == Triple::MachO)
    return createMachOStreamer(Ctx, MAB, _OS, _Emitter, RelaxAll);

  if (TheTriple.isOSWindows())
    return createWinCOFFStreamer(Ctx, MAB, *_Emitter, _OS, RelaxAll);

  return createELFStreamer(Ctx, MAB, _OS, _Emitter, RelaxAll, NoExecStack);
}
---------------

Would it be OK to add "ELF" to Triple::EnvironmentType? It seems like
a plausible choice since MachO is there. On the other hand, I'm not sure
whether it makes sense to make it mutually exclusive with the other members of
EnvironmentType (GNU, GNUEABI, EABI).

Eli




From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Bendersky, Eli
Sent: Wednesday, January 04, 2012 13:17
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] generating ELF files on non-ELF platforms with MC

Hello,

We're currently working on MC-JIT, focusing on runtime generation and
loading of ELF object files, even on non-ELF platforms (i.e. Windows). However,
we run into a problem with MC insisting to generate COFF objects on Windows,
MachO on Macs and ELF only otherwise, based on the triple.

Is there an existing method to generate ELF objects with MC on Windows, without
modifying MC?

Thanks in advance,
Eli
---------------------------------------------------------------------
Intel Israel (74) Limited

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.
---------------------------------------------------------------------
Intel Israel (74) Limited

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.

Hi,
> Would it be OK to add "ELF" to Triple::EnvironmentType? It seems
like a
plausible choice since MachO is there. On the other hand, I'm not sure
whether it makes sense to make it mutually exclusive with the other members
of EnvironmentType (GNU, GNUEABI, EABI).

EABI and GNUEABI imply ELF. GNU in practice does not need to imply ELF, but
is used in the ARM world as "the pre AAPCS ABI". I'm not certain,
but I
don't think EnvironmentType is even used on non-ARM platforms, so you could
add an extra enumerator without affecting anything.

That said, I don't think the container is a property of the triple or even
the target selection. For example, we could generate flat-binary or ELF
output on ELF systems.

Some solution that doesn't tie the output format to the target would be
better, IMHO.

Cheers,

James

-----Original Message-----
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Bendersky, Eli
Sent: 09 January 2012 10:10
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] FW: generating ELF files on non-ELF platforms with MC

Ping,
Apart from Anton's concerns (which I think are manageable) and Micah's
support, I received no reply on this.

Does there exist a way to tell MC to generate and ELF container for code on
Windows? If not, I'm willing to submit a patch to fix this, but would like
some opinions on the best direction to take here.

The proposed "llvm::TargetSpec class"
(http://nondot.org/sabre/LLVMNotes/TargetSpec.txt) seems to address this,
although AFAICS the current llvm::Triple does not explicitly specify the
object/container type. ELF is usually taken as "default" when no other
option is chosen. A representative example from X86MCTargetDesc.cpp:

---------------
static MCStreamer *createMCStreamer(const Target &T, StringRef TT,
                                    MCContext &Ctx, MCAsmBackend &MAB,
                                    raw_ostream &_OS,
                                    MCCodeEmitter *_Emitter,
                                    bool RelaxAll,
                                    bool NoExecStack) {
  Triple TheTriple(TT);

  if (TheTriple.isOSDarwin() || TheTriple.getEnvironment() == Triple::MachO)
    return createMachOStreamer(Ctx, MAB, _OS, _Emitter, RelaxAll);

  if (TheTriple.isOSWindows())
    return createWinCOFFStreamer(Ctx, MAB, *_Emitter, _OS, RelaxAll);

  return createELFStreamer(Ctx, MAB, _OS, _Emitter, RelaxAll, NoExecStack);
}
---------------

Would it be OK to add "ELF" to Triple::EnvironmentType? It seems like
a
plausible choice since MachO is there. On the other hand, I'm not sure
whether it makes sense to make it mutually exclusive with the other members
of EnvironmentType (GNU, GNUEABI, EABI).

Eli




From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Bendersky, Eli
Sent: Wednesday, January 04, 2012 13:17
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] generating ELF files on non-ELF platforms with MC

Hello,

We're currently working on MC-JIT, focusing on runtime generation and
loading of ELF object files, even on non-ELF platforms (i.e. Windows).
However, we run into a problem with MC insisting to generate COFF objects on
Windows, MachO on Macs and ELF only otherwise, based on the triple.

Is there an existing method to generate ELF objects with MC on Windows,
without modifying MC?

Thanks in advance,
Eli
---------------------------------------------------------------------
Intel Israel (74) Limited

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.
---------------------------------------------------------------------
Intel Israel (74) Limited

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
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recipient, please contact the sender and delete all copies.


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