[llvm-dev] How to configure cmake to not rebuild .inc (tablegen) files?

Jie Zhou via llvm-dev llvm-dev at lists.llvm.org
Mon Oct 21 13:00:07 PDT 2019

On Oct 21, 2019, at 14:16, Mehdi AMINI <joker.eph at gmail.com<mailto:joker.eph at gmail.com>> wrote:

On Sun, Oct 20, 2019 at 4:21 PM Jie Zhou via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Dear all,

I’m developing Clang&LLVM on MacOS Catalina 10.15.
Now every time I "make clang", the building systems rebuilds
all the .inc files generated by cmake,

Are you saying that if you re-run `make clang` immediately after the first invocation complete you see these files rebuilt? You're not changing anything in the repo or running `git pull` (or equivalent)? This would really not be expected.

Yes the tablegen files get recompiled immediately after I run a `make clang`. I checked on a Ubuntu and did not see the same behavior.
But luckily Joan's suggestion works: the -DLLVM_OPTIMIZED_TABLEGEN for cmake will do the trick.

- Jie

which essentially
rebuilds all the tablegen files in llvm, although I did not
change any of the tablegen files. The building is unnecessary
and slow, especially when it builds the X86GenSubtargetInfo.inc.
Is there a way to prevent cmake generating Makefiles that
rebuilds all the tablegen files?

Here is my command line to run cmake for generating Makefiles:

cmake -G “Unix Makefiles” -DLLVM_TARGETS_TO_BUILD=“X86" -DCMAKE_BUILD_TYPE=Debug $(LLVM_SRC)

The cmake version is 3.13.4. And I did not experience the same behavior on a Linux.

- Jie
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llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>

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