[PATCH] D39555: Introduce llvm-opt-fuzzer for fuzzing optimization passes

[Kostya Serebryany via Phabricator via llvm-commits]

kcc added a comment.

First trophy: 
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=4210
Looks real. Did you see it?

> Thanks for doing that! My original thought was to start instcombine runs with the IR corpus. In my local experiments I found that using simple corpus gathered from the llvm-lit tests proves to be way more productive than non corpus runs.

No surprise here!

>   I found zero issues in about 10 hour runs without the corpus and with the corpus there were couple of failures during the first two minutes.

Nice!

> However I also observed couple of crashes in the FuzzMutate itself, which I planned to fix first.
> 
> So the short answer to your question - next step is to use reasonable corpus for the instcombine, but first to fix all the immediate issues.

Good strategy.

Ideally, a fuzz target would have an optional extra build rule. 
that will create ${FUZZ_TARGET_NAME}_seed_corpus.zip so that 
in https://github.com/google/oss-fuzz/blob/master/projects/llvm/build.sh
we just copy all such files to $OUT


Repository:
  rL LLVM

https://reviews.llvm.org/D39555