[cfe-dev] [llvm-dev] Who wants faster LLVM/Clang builds?

Robinson, Paul via cfe-dev cfe-dev at lists.llvm.org
Mon Dec 11 14:36:07 PST 2017


There are known problems with running IWYU over LLVM/Clang -- Zachary
Turner made an attempt a while back to get it up and running. Since
the LLVM tree uses all sorts of modern and moderately complex
patterns, we're struggling to keep up

Re-implementing IWYU based on Clang tooling seems like it would help a lot with that kind of problem.
--paulr

From: cfe-dev [mailto:cfe-dev-bounces at lists.llvm.org] On Behalf Of Mikhail Zolotukhin via cfe-dev
Sent: Monday, December 11, 2017 12:37 PM
To: Kim Gräsman
Cc: llvm-dev; Clang Dev; Chris Lattner
Subject: Re: [cfe-dev] [llvm-dev] Who wants faster LLVM/Clang builds?

Hi Kim,

On Dec 10, 2017, at 7:39 AM, Kim Gräsman <kim.grasman at gmail.com<mailto:kim.grasman at gmail.com>> wrote:

Hi Michael,

On Thu, Dec 7, 2017 at 3:16 AM, Michael Zolotukhin
<mzolotukhin at apple.com<mailto:mzolotukhin at apple.com>> wrote:


Nice to IWYU developers here:) I wonder how hard it would be to run IWYU on
LLVM/Clang (or, if it’s supposed to work, I wonder what I did wrong).

There are known problems with running IWYU over LLVM/Clang -- Zachary
Turner made an attempt a while back to get it up and running. Since
the LLVM tree uses all sorts of modern and moderately complex
patterns, we're struggling to keep up.
I see.



If we also can tweak it a bit to make it choose more human-like (~more
conservative) decisions, we would be able to just apply what it suggests!

Different humans appear to have different preferences :)
True, what I meant hear is to make the changes more conservative: e.g. if we can replace
#include "MyClass.h"
with
class MyClass;
then this change is probably desirable in every way: it documents the code better, it decreases coupling, it improves compile time.

But if for instance we suggest replacing it with
#include "BaseClass1.h"           // previously included from MyClass.h
#include "ExtraStuffForMyClass.h"
then it's less straight-forward, at least from the code-selfdocumentation point of view.

If we could make IWYU to only suggest changes of the first type, then we probably could've just blindly apply all the suggested changes.


It'd be great to hear more about specifics, maybe you can bring them
up on the IWYU list:
https://groups.google.com/forum/#!forum/include-what-you-use?
Will do, thanks.

Michael


Some of IWYU's controversial changes are by design, but some are just
bugs, and if you have ideas for a more principled design, we
appreciate all the input we can get.

Thanks,
- Kim

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