[llvm-dev] debug build busts memory

[Alex Brachet-Mialot via llvm-dev]

The suggestion to just upgrade hardware isn't a constructive one in my
opinion, not everyone can do this. As for hardware, I've built llvm
with with a tiny 2 core pentium chip and 8gb of memory, (granted I
needed to increase my swap space) and I left it over night. Once it's
built you generally don't need to build it in full ever again and the
future strain on your machine will always be less.

These questions come up often enough maybe we should add a new section
about building with not enough memory to llvm/docs/CMake.rst. If 16gb
isn't enough then most people will have a hard time building. There
has been a lot of talk recently about making llvm development more
accessible to newcomers, being unable to even build has to be by far
the most egregious problem. How many people had a passing interest in
llvm but when their build failed didn't want to ask the mailing list
what other options they had and gave up?

On Tue, Nov 26, 2019 at 1:46 PM Keane, Erich via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> I believe it is pretty clear that the stock ld linker is basically unusable for our project without a sizable amount of hardware.  I’ve typically found that using gold or lld fixes this problem entirely.
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> Perhaps we need to start having CMake detect the presence of lld and use that if possible, else check for ‘gold’ and use it if possible, and only THEN fall back on ld.
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> Additionally, it is pretty rare for someone to need to debug TableGen (at least in my experience), and if they DO need it, they would know enough to know how to change the cmake variable.  I think we should have a serious discussion about making LLVM_OPTIMIZED_TABLEGEN=true be default.
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> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Reid Kleckner via llvm-dev
> Sent: Tuesday, November 26, 2019 10:41 AM
> To: David Jones <david.jones at metrics.ca>
> Cc: llvm-dev <llvm-dev at lists.llvm.org>; Bagel <bagel99 at gmail.com>
> Subject: Re: [llvm-dev] debug build busts memory
>
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> On Tue, Nov 26, 2019 at 10:31 AM David Jones via llvm-dev <llvm-dev at lists.llvm.org> wrote:
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> Throw hardware at it.
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> While I agree that this is good advice with the current state of affairs, I don't think we should consider the current situation acceptable.
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> LLVM has a lot of knobs that Tim alluded to, but first time users shouldn't have to search for them to get a working debug build of LLVM out of the box. As a community, we need to raise the bar here, and spend some time making first time build setup easier. I seem to recall that there were discussions at the dev meeting about simplifying our CMake build, and I think this can be part of that effort.
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