[all-commits] [llvm/llvm-project] d2d469: [WebAssembly] Make llvm.wasm.throw invokable (#128...

[Heejin Ahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d2d469eb7981885eac188bf7988c72d7e85b2d4e
      https://github.com/llvm/llvm-project/commit/d2d469eb7981885eac188bf7988c72d7e85b2d4e
  Author: Heejin Ahn <aheejin at gmail.com>
  Date:   2025-02-25 (Tue, 25 Feb 2025)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
    M llvm/lib/CodeGen/WasmEHPrepare.cpp
    M llvm/lib/IR/Verifier.cpp
    M llvm/test/CodeGen/WebAssembly/exception.ll
    M llvm/test/Verifier/invoke.ll

  Log Message:
  -----------
  [WebAssembly] Make llvm.wasm.throw invokable (#128104)

`llvm.wasm.throw` intrinsic can throw but it was not invokable. Not sure
what the rationale was when it was first written that way, but I think
at least in Emscripten's C++ exception support with the Wasm port of
libunwind, `__builtin_wasm_throw`, which is lowered down to
`llvm.wasm.rethrow`, is used only within `_Unwind_RaiseException`, which
is an one-liner and thus does not need an `invoke`:
https://github.com/emscripten-core/emscripten/blob/720e97f76d6f19e0c6a2d6988988cfe23f0517fb/system/lib/libunwind/src/Unwind-wasm.c#L69
(`_Unwind_RaiseException` is called by `__cxa_throw`, which is generated
by the `throw` C++ keyword)

But this does not address other direct uses of the builtin in C++, whose
use I'm not sure about but is not prohibited. Also other language
frontends may need to use the builtin in different functions, which has
`try`-`catch`es or destructors.

This makes `llvm.wasm.throw` invokable in the backend. To do that, this
adds a custom lowering routine to `SelectionDAGBuilder::visitInvoke`,
like we did for `llvm.wasm.rethrow`.

This does not generate `invoke`s for `__builtin_wasm_throw` yet, which
will be done by a follow-up PR.

Addresses #124710.



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