llvm dev - Oct 2016 - [cfe-dev] Using lld in ELLCC for different targets

With all the talk about using lld on the list, I thought it would be 
interesting to try using it in my clang based ELLCC cross compilation 
tool chain. http://ellcc.org

The change was simple, since I use configuration files to tell clang how 
to compile, where to find libraries, etc. I described the config files 
here: http://ellcc.org/blog/?p=13246

All I had to do was change the linker executable definition for each target:

linker:

   #exe: $E/ecc-ld$X

   exe: $E/ld.lld$x

(where $E is the executable directory where the compiler was found and 
$X is the executable extension, "" under Linux)

Here are the results of linking a program for Linux:

ARM32 v6: Good

ARM32 v7: Good

ARM32 big endian: Not supported by lld, no armelfb_linux_eabi emulation 
mode.

Aarch64: Good

MIPS 32 little and big endian: Good

MIPS64 big endian: Good

PPC32: lld failed with a bad relocation type.

PPC64 little endian: Not supported by lld, no elf64lppc emulation mode.

X86 32 and 64: Good

As a test I built clang to run native on ARMv6, ARMv7, Aarch64, MIPS32, 
MIPS64, and x86_84 Linux: Good

Very cool!

I use ld for mingw-w64 targets. Is there a mode for the COFF lld that 
makes it also act like ld?

Now I have to look into how lld supports Linker scripts for my non-Linux 
targets.

-Rich

On Fri, Oct 28, 2016 at 2:56 PM, Richard Pennington via cfe-dev <
cfe-dev at lists.llvm.org> wrote:
> With all the talk about using lld on the list, I thought it would be
> interesting to try using it in my clang based ELLCC cross compilation tool
> chain. http://ellcc.org
>
> The change was simple, since I use configuration files to tell clang how
> to compile, where to find libraries, etc. I described the config files
> here: http://ellcc.org/blog/?p=13246
>
> All I had to do was change the linker executable definition for each
> target:
>
> linker:
>
>   #exe: $E/ecc-ld$X
>
>   exe: $E/ld.lld$x
>
> (where $E is the executable directory where the compiler was found and $X
> is the executable extension, "" under Linux)
>
> Here are the results of linking a program for Linux:
>
> ARM32 v6: Good
>
> ARM32 v7: Good
>
> ARM32 big endian: Not supported by lld, no armelfb_linux_eabi emulation
> mode.
>
> Aarch64: Good
>
> MIPS 32 little and big endian: Good
>
> MIPS64 big endian: Good
>
> PPC32: lld failed with a bad relocation type.
>
> PPC64 little endian: Not supported by lld, no elf64lppc emulation mode.
>
> X86 32 and 64: Good
>
> As a test I built clang to run native on ARMv6, ARMv7, Aarch64, MIPS32,
> MIPS64, and x86_84 Linux: Good
>
> Very cool!
>
Awesome results!

I wonder if ARM32 BE is a real thing. I know that the processor is
bi-endian, but is there any system that uses ARM32 in big-endian mode?

> I use ld for mingw-w64 targets. Is there a mode for the COFF lld that
> makes it also act like ld?
>
Unfortunately, no. You can use the GNU compatible driver on Windows, but it
always produces ELF.

Now I have to look into how lld supports Linker scripts for my
non-Linux
> targets.
>
> -Rich
>
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
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On 28 October 2016 at 23:02, Rui Ueyama via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Awesome results!
I'm surprised! LLD is barely working on ARM at the moment. :)

> I wonder if ARM32 BE is a real thing. I know that the processor is
> bi-endian, but is there any system that uses ARM32 in big-endian mode?
Yes... it is "a thing". :)

ARM has two modes: BE32 and BE8 (mixed) and they can be enabled via
CP15 registers.

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0290g/ch06s05s01.html


cheers,
--renato