[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.

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index b4f9273..3477e2b 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -5227,10 +5227,12 @@ void Verifier::visitInstruction(Instruction &I) {
                 F->getIntrinsicID() == Intrinsic::experimental_patchpoint ||
                 F->getIntrinsicID() == Intrinsic::fake_use ||
                 F->getIntrinsicID() == Intrinsic::experimental_gc_statepoint ||
+                F->getIntrinsicID() == Intrinsic::wasm_throw ||
                 F->getIntrinsicID() == Intrinsic::wasm_rethrow ||
                 IsAttachedCallOperand(F, CBI, i),
             "Cannot invoke an intrinsic other than donothing, patchpoint, "
-            "statepoint, coro_resume, coro_destroy or clang.arc.attachedcall",
+            "statepoint, coro_resume, coro_destroy, clang.arc.attachedcall or "
+            "wasm.(re)throw",
             &I);
       Check(F->getParent() == &M, "Referencing function in another module!", &I,
             &M, F, F->getParent());