[llvm-dev] Tablegen ridiculously slow when compiling for Debug

Joan Lluch via llvm-dev llvm-dev at lists.llvm.org
Sat Jun 29 13:00:12 PDT 2019

Hi Florian,

Ok, I ran this:


Compiled it again from clean, and the situation is worse than before. Incremental builds take an incredible amount of time stuck in running Tablegen scripts for all targets. Now this happens both in Release and Debug configurations. Just before this, at least Release compiled fine, but that’s no longer the case. 

Any other suggestions?  What could actually cause this? 


> On 29 Jun 2019, at 19:37, Florian Hahn <florian_hahn at apple.com> wrote:
> Hi,
>> On Jun 29, 2019, at 18:26, Joan Lluch via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> Hi all,
>> On LLVM version 7.0.1, incremental builds are very fast for both Release and Debug. I’m compiling with Xcode
>> I recently downloaded LLVM 9.0 from the LLVM-mirror Github repository and found that Incremental "Debug” builds take a ridiculously long time due to Tablegen taking ages (literally more than 10 minutes) to generate files. This makes it totally unusable for debug purposes. However, incremental ‘Release’ builds only take a few seconds.
>> Why is that?. Any suggestions?.
> You could give setting LLVM_OPTIMIZED_TABLEGEN a try (https://llvm.org/docs/CMake.html).
> Cheers,
> Florian

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