Use ptrdiff_t sized offsets for gvars_offsets to allow large sysimages

[gbaraldi]

Hopefully this fixes JuliaLang/PackageCompiler.jl#1019. This does mean a very slight size increase (each offset is twice as large but shouldn't make too much difference (it's an extra 32bit per gvar))

[topolarity]

Can you test that this is working before merging?

[giordano]

Does this work on 32-bit systems? Edit: ah, you skip the test below? Isn't it simpler to just exclude 32-bit systems together with Windows here?

[giordano]

x86_64 Darwin tests are systematically failing on this PR despite multiple retries.

[giordano]

This keeps failing: https://buildkite.com/julialang/julia-master/builds/45061#01952ab6-a051-466e-aa0a-49ff9c521962/758-1238

      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x47e): relocation SIGNED is out of range: 2402433694 is not in [-2147483648, 2147483647]; references _jl_globalYY.127339
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x40b): relocation SIGNED is out of range: 2402361361 is not in [-2147483648, 2147483647]; references _SUM.CoreDOT.GenericMemoryRefYY.43295
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x399): relocation SIGNED is out of range: 2402375627 is not in [-2147483648, 2147483647]; references _jl_globalYY.214098
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x38c): relocation SIGNED is out of range: 2402376008 is not in [-2147483648, 2147483647]; references _SUM.CoreDOT.TupleYY.50182
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x385): relocation SIGNED is out of range: 2402318159 is not in [-2147483648, 2147483647]; references _jl_globalYY.180619
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x34e): relocation SIGNED is out of range: 2402390694 is not in [-2147483648, 2147483647]; references _jl_globalYY.50155
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x347): relocation SIGNED is out of range: 2402312757 is not in [-2147483648, 2147483647]; references _jl_globalYY.43543
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x227): relocation SIGNED is out of range: 2402445277 is not in [-2147483648, 2147483647]; references _jl_globalYY.73842
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x194): relocation SIGNED is out of range: 2402405512 is not in [-2147483648, 2147483647]; references _SUM.CoreDOT.ArrayYY.45751
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x188): relocation SIGNED is out of range: 2402333196 is not in [-2147483648, 2147483647]; references _jl_globalYY.44727
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x161): relocation SIGNED is out of range: 2402419971 is not in [-2147483648, 2147483647]; references _SUM.CoreDOT.TupleYY.62458
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x14f): relocation SIGNED is out of range: 2402463005 is not in [-2147483648, 2147483647]; references _jl_small_typeof
      From worker 6:	lld: error: /private/var/tmp/agent-tempdirs/default-macmini-x64-4.0/tmp/jl_jFNgE1/sys.o.a(text#0.o):(symbol _japi1_reverse_273487+0x119): relocation SIGNED is out of range: 2402305235 is not in [-2147483648, 2147483647]; references _jl_globalYY.42860
[...]

[vtjnash]

I think you are relying on the .ldata section existing to be allowed to use large images like this, but that is an ELF-only feature. Since we use the Small or Medium CodeModels, individual object file relocations will only be able to reference a shared object smaller than about 2GB

[gbaraldi]

I guess we need to detect large images and switch to the large code model. (Maybe printing an info that the image is very large and will have lower performance. I think aarch64 is fine here because there the code model allows for 4GB relocations