llvm dev - Apr 2017 - Help with setting up ARM embedded clang + lld

Hi all,
I've been doing a ton of embedded work (bare metal ARM Cortex M0+ and
M4, hopefully RISCV in the future) in the last year and would love to
start using and hacking on the llvm toolchain. I've tried setting up
clang + lld but can't get lld to work because clang tries to launch gcc.
I realize support is early but I'd love to have a dev setup so I can
help fix things.

Could some help me setup my Makefiles in this project:
https://github.com/tannewt/circuitpython/tree/clang to use dev builds of
clang and lld? Thanks!
~Scott

Did you read http://lld.llvm.org/#using-lld? In short, you want to pass
-use-ld=lld to clang to use ld.lld instead of ld.

On Sun, Apr 30, 2017 at 3:18 PM, Scott Shawcroft via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
> I've been doing a ton of embedded work (bare metal ARM Cortex M0+ and
> M4, hopefully RISCV in the future) in the last year and would love to
> start using and hacking on the llvm toolchain. I've tried setting up
> clang + lld but can't get lld to work because clang tries to launch
gcc.
> I realize support is early but I'd love to have a dev setup so I can
> help fix things.
>
> Could some help me setup my Makefiles in this project:
> https://github.com/tannewt/circuitpython/tree/clang to use dev builds of
> clang and lld? Thanks!
> ~Scott
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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On Sun, Apr 30, 2017 at 03:18:35PM -0700, Scott Shawcroft via llvm-dev
wrote:
> Hi all,
> I've been doing a ton of embedded work (bare metal ARM Cortex M0+ and
> M4, hopefully RISCV in the future) in the last year and would love to
> start using and hacking on the llvm toolchain. I've tried setting up
> clang + lld but can't get lld to work because clang tries to launch
gcc.
> I realize support is early but I'd love to have a dev setup so I can
> help fix things.
clang doesn't know how to call a linker for baremetal, so it tries to
fallback to gcc. Just call the linker directly.

Joerg

I did look at that and it doesn't work. Here is the line from the
Makefile:
https://github.com/tannewt/circuitpython/blob/clang/atmel-samd/Makefile#L300
And here is it as output from make:
clang version 5.0.0 (trunk 301735)
Target: armv6m-none--eabi
Thread model: posix
InstalledDir: /Users/tannewt/repos/llvm/build/bin
"gcc" -flto -v -fuse-ld=lld -march=thumb...
clang-5.0: error: unable to execute command: Executable "gcc"
doesn't
exist!clang-5.0: error: linker (via gcc) command failed with exit code 1
(use -v to see invocation)
On Sun, Apr 30, 2017, at 03:28 PM, Rui Ueyama wrote:
> Did you read http://lld.llvm.org/#using-lld? In short, you want to
> pass -use-ld=lld to clang to use ld.lld instead of ld.> 
> On Sun, Apr 30, 2017 at 3:18 PM, Scott Shawcroft via llvm-dev <llvm-
> dev at lists.llvm.org> wrote:>> Hi all,
>> I've been doing a ton of embedded work (bare metal ARM Cortex M0+
and>> M4, hopefully RISCV in the future) in the last year and would love
to>> start using and hacking on the llvm toolchain. I've tried setting
up>> clang + lld but can't get lld to work because clang tries to
>> launch gcc.>> I realize support is early but I'd love to have
a dev setup so I can>> help fix things.
>> 
>> Could some help me setup my Makefiles in this project:
>> https://github.com/tannewt/circuitpython/tree/clang to use dev
>> builds of>> clang and lld? Thanks!
>> ~Scott
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Ok, thanks! I got it going that way. I'd still love to hear from anyone
off list working on similar stuff.
~Scott

On Sun, Apr 30, 2017, at 03:32 PM, Joerg Sonnenberger
wrote:
> On Sun, Apr 30, 2017 at 03:18:35PM -0700, Scott Shawcroft via llvm-dev
> wrote:
> > Hi all,
> > I've been doing a ton of embedded work (bare metal ARM Cortex M0+
and
> > M4, hopefully RISCV in the future) in the last year and would love to
> > start using and hacking on the llvm toolchain. I've tried setting
up
> > clang + lld but can't get lld to work because clang tries to
launch gcc.
> > I realize support is early but I'd love to have a dev setup so I
can
> > help fix things.
> 
> clang doesn't know how to call a linker for baremetal, so it tries to
> fallback to gcc. Just call the linker directly.
> 
> Joerg