[LLVMdev] Test Suite - Livermore Loops

Renato Golin renato.golin at linaro.org
Thu Jan 3 07:08:20 PST 2013

FYI, attached is a way to reproduce the error without the
test-suite paraphernalia.


On 3 January 2013 12:05, Renato Golin <renato.golin at linaro.org> wrote:

> David,
> I got some more work on the Livermore Loops and I found out that the issue
> is the difference in the parameters between a single step and a multi step
> compilation.
> When you compile "clang kernel06.c" it works fine, but when you get all
> steps (clang -emit-llvm + llvm-as + opt + llc etc), the defaults options of
> each and how they interact is showing a bug in the code generated.
> This difference is due to the fact that I'm running the test-suite using
> LNT, while the build bots are running it using Make directly. I'd expect
> them both to be the same, but apparently they're quite different in what
> kind of parameters they use, passes they test and results they get.
> I think there are two courses of action here:
> 1. Identify the issue, isolate the case and create a bug to resolve later.
> 2. Make sure LNT does exactly what the build bots are doing
> I'm working on item 1 right now, not sure how item 2 can be solved...
> Of course, the fact that it's the not same flow meant we caught a bug in
> LLVM, but that's bound to create more confusion and broken commits, which
> is worse in the long run.
> Also, if we're not running LNT as often as buildbots, the benefit of
> having them different is sporadic at best.
> When I set up some tests to run on ARM I have done both direct and
> multi-step, to make sure they were generating the same code and in many
> cases I found that the order in which the passes were executed was breaking
> some tests.
> We managed to get the EDG bridge to set it up in the same way as the
> multi-pass would, so we would get similar results, but it doesn't seem to
> be the case with clang.
> cheers,
> --renato
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