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by xena 2 days ago
This might be the first time in my career I have genuinely found a compiler bug. I've been operating under the axiom of "don't assume it's a compiler bug, assume you're fucking it up somehow". When you get to the point that disabling ASLR makes it consistent intra-host I think I've won the right to at least suspect a compiler bug is at play.

I'll go file it upstream after work today.
1 comments
ammar2 2 days ago
If you feel like increasing your power as per your post, this is a somewhat decent first LLVM issue, take a look at WebAssemblyCFGStackify.cpp :)

llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll and friends are existing tests that you can kinda mangle if you want to get a good reproducer.

Also take a look at https://discourse.llvm.org/t/reverse-iteration-bots/72224

Otherwise, happy to put my reproducer/patch on the bug after you file it!

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xena 2 days ago
I'm gonna have to file the bug without a minimal reproduction case. The issue seems to be those try_table blocks getting nondeterministically reordered at link time (is it using machine pointers for iteration order?). Sadly I'm observing this with a local checkout of binaryen, so it may take a while for you to find the minimal reproduction case.
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xena 1 day ago
I filed the bug: https://github.com/llvm/llvm-project/issues/204883
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