code review 10499043: runtime,cmd/ld: Merge TLS symbols and teach 5l about ARM TLS

runtime,cmd/ld: Merge TLS symbols and teach 5l about ARM TLS

This CL prepares for external linking support to ARM.

The pseudo-symbols runtime.g and runtime.m are merged into a single runtime.tlsgm symbol. When external linking, the offset of a thread local variable is stored at a memory location instead of being embedded into a offset of a ldr instruction. With a single runtime.tlsgm symbol for both g and m, only one such offset is needed.

The larger part of this CL moves TLS code from gcc compiled to internally compiled. The TLS code now uses the modern MRC instruction, and 5l is taught about TLS fallbacks in case the instruction is not available or appropriate.

This CL is needed by CL 10271047.

[elias.naur, 2013-06-24 14:12:58]

On 2013/06/24 14:12:28, elias.naur wrote:

This is ready for review, but because of the moratorium I won't mail it out.

[elias.naur, 2013-07-04 10:00:13]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[capnm, 2013-07-04 14:25:51]

The go binary crashes.
2bbca155a87f tip + this CL

# Testing packages.
run.bash: line 48: 17168 Segmentation fault
gdb output: https://github.com/capnm/golang/issues/2

[elias.naur, 2013-07-04 17:51:09]

On 2013/07/04 14:25:51, capnm wrote:
> The go binary crashes.
> 2bbca155a87f tip + this CL
> 
> # Testing packages.
> run.bash: line 48: 17168 Segmentation fault
> gdb output: https://github.com/capnm/golang/issues/2

Thanks for testing.

Somehow, the CL didn't include all my changes, and my testing didn't catch that
because the missing changes only applies to GOARM=5 builds. I've updated the CL
and verified that "GOARM=5 ./all.bash" completes successfully.

PTAL

[capnm, 2013-07-05 10:38:13]

On 2013/07/04 17:51:09, elias.naur wrote:
> Somehow, the CL didn't include all my changes, and my testing didn't catch
that
> because the missing changes only applies to GOARM=5 builds. I've updated the
CL
> and verified that "GOARM=5 ./all.bash" completes successfully.
> 
> PTAL

Works now (as well as the CL 10271047) on GOARM=6.
Thanks.

[bradfitz, 2013-07-29 20:43:05]

Did a comment get lost here?



On Mon, Jul 29, 2013 at 10:28 AM, <rsc@golang.org> wrote:

>
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[rsc, 2013-07-29 20:47:07]

No, I was adding myself to the Reviewers list. Sorry about the confusion.

[rsc, 2013-08-13 19:14:58]

LGTM

Lots of magic here but it seems modest enough.

[elias.naur, 2013-08-13 22:11:43]

On 2013/08/13 19:14:58, rsc wrote:
> LGTM
> 
> Lots of magic here but it seems modest enough.

Thanks a lot! As explained in 10271047, I'll update that CL when this CL is
submitted and finally update 9733044 for submission.