Rollup merge of #131418 - coolreader18:wasm-exc-use-stdarch, r=bjorn3 · qinheping/verify-rust-std@b6c0376 (original) (raw)
`@@ -40,29 +40,25 @@ pub unsafe fn _Unwind_DeleteException(exception: *mut _Unwind_Exception) {
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`}
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`pub unsafe fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code {
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``
`-
#[cfg(panic = "unwind")]
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``
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extern "C" {
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``
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/// LLVM lowers this intrinsic to the throw instruction.
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``
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// FIXME(coolreader18): move to stdarch
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``
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#[link_name = "llvm.wasm.throw"]
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``
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fn wasm_throw(tag: i32, ptr: *mut u8) -> !;
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``
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}
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``
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`` // The wasm throw instruction takes a "tag", which differentiates certain
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`// types of exceptions from others. LLVM currently just identifies these
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`// via integers, with 0 corresponding to C++ exceptions and 1 to C setjmp()/longjmp().
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`// Ideally, we'd be able to choose something unique for Rust, but for now,
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`// we pretend to be C++ and implement the Itanium exception-handling ABI.
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` cfg_if::cfg_if! {
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``
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// for now, unless we're -Zbuild-std with panic=unwind, never codegen a throw.
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`+
// panic=abort is default for wasm targets. Because an unknown instruction is a load-time
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// error on wasm, instead of a runtime error like on traditional architectures, we never
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// want to codegen a throw instruction, as that would break users using runtimes that
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// don't yet support exceptions. The only time this first branch would be selected is if
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// the user explicitly opts in to wasm exceptions, via -Zbuild-std with -Cpanic=unwind.
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`if #[cfg(panic = "unwind")] {
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``
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wasm_throw(0, exception.cast())
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`+
// corresponds with llvm::WebAssembly::Tag::CPP_EXCEPTION
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`+
// in llvm-project/llvm/include/llvm/CodeGen/WasmEHFuncInfo.h
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`+
const CPP_EXCEPTION_TAG: i32 = 0;
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`+
core::arch::wasm::throw::(exception.cast())
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`} else {
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`let _ = exception;
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``
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#[cfg(target_arch = "wasm32")]
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``
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core::arch::wasm32::unreachable();
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``
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#[cfg(target_arch = "wasm64")]
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``
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core::arch::wasm64::unreachable();
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`+
core::arch::wasm::unreachable()
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`}
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`}
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`}
`