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[compiler-rt] Enable building builtins using top-level CMake file
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Authored by phosek on Oct 15 2020, 12:16 PM.



When building builtins separately as part of the runtime build, we
also want to include crt. To enable that, enable building builtins
together with crt using the top-level CMake file with a new option

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phosek created this revision.Oct 15 2020, 12:16 PM
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phosek requested review of this revision.Oct 15 2020, 12:16 PM

This is an alternative to D70744. I'm not a fan of introducing compiler-rt/builtins as a new top-level CMake, so I was trying to come up with an alternative and this is what I came up with, let me know what you think.

This is an alternative to D70744. I'm not a fan of introducing compiler-rt/builtins as a new top-level CMake, so I was trying to come up with an alternative and this is what I came up with, let me know what you think.

I think this is an improvement, it was awkward to have two top-level entry points to the cmake anyway. This probably allows for some further de-duplication down the road as well.


It would be nice to print the list of supported crt arch here as well.


OS_NAME doesn't currently get set in builtin-config-ix, we'll need to duplicate the setup from config-ix.


We probably should retain the new cmake minimum


We should probably disable the crt build here now.


Ditto the other comment

phosek updated this revision to Diff 298559.Oct 16 2020, 12:22 AM
phosek marked 6 inline comments as done.
daltenty accepted this revision.Oct 19 2020, 3:11 PM

LGTM, with slight adjustment. Though I will note that this requires a clean build because CMake will complain about the change in source directory in cache:

CMake Error: The source “../compiler-rt/CMakeLists.txt" does not match the source ../compiler-rt/lib/builtins/CMakeLists.txt" used to generate cache. Re-run cmake with a different source directory.


fyi, this needs a slight adjustments because D87120 has landed

This revision is now accepted and ready to land.Oct 19 2020, 3:11 PM
daltenty requested changes to this revision.Oct 23 2020, 7:43 AM
daltenty added inline comments.

The problem we have here is that the scope for these variables has changed, builtin-config-ix.cmake is only included in the builtins CMakeList.tx, so when we go to check COMPILER_RT_HAS_CRT it's out of scope.

Perhaps it would be cleaner to split the CRT checks into it's own crt-config-ix.cmake that can be included at the appropriate scope?

This revision now requires changes to proceed.Oct 23 2020, 7:43 AM
phosek updated this revision to Diff 330160.Mar 11 2021, 11:58 PM
phosek marked 2 inline comments as done.
phosek edited the summary of this revision. (Show Details)
phosek updated this revision to Diff 330162.Mar 12 2021, 12:04 AM
kaz7 added a comment.Dec 3 2021, 7:35 PM

Hi. Thank you for trying to achieve pre-compiling of crtbegin/crtend and builtins. Our architecture, SX-Aurora VE, doesn't have freely distributed crtbegin/crtend, so a mechanism like this is really important as I mentioned in D115038.

I take a look. I think the way to isolate each modules are good way to do. So, basically, it's fine to land in my opinion. However, we have been updating runtimes tramendously. So, it's better to rebase to recent main. We already have compiler-rt/cmake/Modules/AllSupportedArchDefs.cmake. Scope is changed like @daltenty suggested.

After that, we can review it and run it. Thank you for your efforts.

kaz7 added a comment.Dec 3 2021, 8:00 PM

I also think separating this patch to following 3 parts makes applying this patch easy.

  1. moving AIX related definitions
  2. isolating crt-config-ix.cmake
  3. supporting bootstrap build of crtbegin/crtend and builtins
kaz7 added a comment.Dec 7 2021, 4:51 AM

I've tested this patch after rebasing it by hand. It works great. So, I really want to contribute whatever I can. @phosek , please let me know what ever I can help. Thanks!

simoll added a subscriber: simoll.Dec 9 2021, 4:45 AM
kaz7 added a comment.Dec 17 2021, 5:08 AM

Hi, is there anything I can help to merge this patch? We need this modification to compile crtbegin/crtend before runtime libraries in order to compile LLVM for VE using bootstrapping build,

kaz7 added a comment.Feb 11 2022, 3:28 PM

Hi @phosek

I understand you are very busy. But, is there any way to push forward this patch since the ability of runtime standalone build has been removed at D119255. We, VE, badly need this feature, compiling crtbegin.o and crtend.o before runtimes. I previously posted similar patch, D115038, but it is recommended to remove since you already post this patch. But, this patch is not merged yet. Now, this patch is blocking VE runtime build from my point of view. Is it OK to make a similar patch if you don't have time to work on this? Please let me know what you think. Thanks.

q66 added a subscriber: q66.Apr 11 2022, 7:35 PM

are there any plans to get this or an equivalent in? currently in my distribution i have to ship a version of this patch rebased to llvm 14 ( because if i don't, i can't build llvm at all (my system is fully llvm-based, therefore does not come with a gcc crt; an llvm crt is needed in order to build the rest of the runtimes, as otherwise invoking the in-tree clang used to build compiler-rt will try to find crtbeginS.o etc. which do not exist in my system)

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q66 added a comment.Apr 11 2022, 7:37 PM

considering the old way of doing things is deprecated and as far as i can tell scheduled for removal in llvm 15, not having something equivalent to this means llvm will no longer build out of box in gcc-less linux systems...

smeenai resigned from this revision.Thu, Apr 28, 2:05 PM