Cherry-pick NoTrapAfterNoreturn fix for wasm backend #155
Conversation
In the WebAssembly back end, the TrapUnreachable option is currently load-bearing for correctness, inserting wasm `unreachable` instructions where needed to create valid wasm. There is another option, NoTrapAfterNoreturn, that removes some of those traps and causes incorrect wasm to be emitted. This turns off `NoTrapAfterNoreturn` for the Wasm backend and adds new tests.
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Can you propose this as an upstream llvm-17 backport? That's the preferred route if you can land it that way. |
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I think we should special case this on the rust side instead. That has the benefit that we don't need to make the behavior LLVM-version specific. |
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Which do we think is the best path here? Or maybe it's both? |
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@nikic It's not clear to me what you're suggesting. |
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@cuviper We can enable NoTrapAfterNoreturn for non-wasm targets only. This backport force-disables the option for wasm, but we can also not enable it in the first place in rustc. |
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OK, @majaha can you try that in |
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Okay, I've pushed a patch over at the other pull request. Let me know what you think. |
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Closing this, as we no longer need this backport with the updated implementation in rust-lang/rust#110494. |
Alloca serialisation tweaks.
In trying to enable the option NoTrapAfterNoreturn in rustc, we discovered a bug with that option in the WebAssembly back-end.
The fix was merged into llvm upstream: llvm#65876
And here's the relevant Rust issue, which I'll update when this PR is merged.
rust-lang/rust#110494