llvm dev - Apr 2021 - Pardon the newbie question

Hello,
Im trying to build trunk clang in debug version on oldish ubuntu with low
mem. Linking lli takes ages and fails on low mem. Is there a chance
building would succeed if i used lld instead of ld? If so is there an
option either to force lld or whole clang toolchain use in cmake instead of
default gcc (both gcc and clang are avail on system)? Otherwise I think ill
stick with release.

Best regards,
Pawel Kunio
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You can use `LLVM_USE_LINKER=lld` CMake variable to adopt LLD (to build LLVM).
And yes, LLD takes less memory and runs faster. Here are some other tips to save
memory:
1. You can use `LLVM_PARALLEL_LINK_JOBS=N` (also a cmake variable) to limit the
amount of parallel linker jobs to save some memory.

2. Build libraries as shared library via `BUILD_SHARED_LIBS=ON` CMake variable
can dramatically speed up the linking time and save you some memory.

3. Since you’re building a Debug build (and you’re building on Linux),
`LLVM_USE_SPLIT_DWARF` can dramatically reduce the size of debug info, which, to
some extend, also save you some memory during link time.

Best,
-Min
> On Apr 15, 2021, at 1:05 PM, pawel k. via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hello,
> Im trying to build trunk clang in debug version on oldish ubuntu with low
mem. Linking lli takes ages and fails on low mem. Is there a chance building
would succeed if i used lld instead of ld? If so is there an option either to
force lld or whole clang toolchain use in cmake instead of default gcc (both gcc
and clang are avail on system)? Otherwise I think ill stick with release.
> 
> Best regards,
> Pawel Kunio
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

On Thu, Apr 15, 2021 at 10:05:51PM +0200, pawel k. via llvm-dev
wrote:
> Hello,
> Im trying to build trunk clang in debug version on oldish ubuntu with low
> mem. Linking lli takes ages and fails on low mem. Is there a chance
> building would succeed if i used lld instead of ld? If so is there an
> option either to force lld or whole clang toolchain use in cmake instead of
> default gcc (both gcc and clang are avail on system)? Otherwise I think ill
> stick with release.
Your best options for that are using DWARF fusion
(-DLLVM_USE_SPLIT_DWARF) or as separate shared libraries
(-DBUILD_SHARED_LIBS). The former will punish the gdb load time and the
latter will penalize execution speed.

Joerg