[PATCH] D94039: [WebAssembly] Update WasmEHPrepare for the new spec

[Heejin Ahn via Phabricator via cfe-commits]

aheejin created this revision.
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Clang generates `wasm.get.exception` and `wasm.get.ehselector`
intrinsics, which respectively return a caught exception value (a
pointer to some C++ exception struct) and a selector (an integer value
that tells which C++ `catch` clause the current exception matches, or
does not match any).

WasmEHPrepare is a pass that does some IR-level preparation before
instruction selection. Previously one of things we did in this pass was
to convert `wasm.get.exception` intrinsic calls to
`wasm.extract.exception` intrinsics. Their semantics were the same
except `wasm.extract.exception` did not have a token argument. We
maintained these two separate intrinsics with the same semantics because
instruction selection couldn't handle token arguments. This
`wasm.extract.exception` intrinsic was later converted to
`extract_exception` instruction in instruction selection, which was a
pseudo instruction to implement `br_on_exn`. Because `br_on_exn` pushed
an extracted value onto the value stack after the `end` instruction of a
`block`, but LLVM does not have a way of that kind of behavior, so this
pseudo instruction was used to pull an extracted value out of thin air,
like this:

  block $l0
    ...
    br_on_exn $cpp_exception $l0
    ...
  end
  extract_exception ;; pushes values onto the stack

In the new spec, we don't need this pseudo instruction anymore because
`catch` itself returns a value and we don't have `br_on_exn` anymore. In
the spec `catch` returns multiple values (like `br_on_exn`), but here we
assume it only returns a single i32, which is sufficient to support C++.

So this renames `wasm.get.exception` intrinsic to `wasm.catch`. Because
this CL does not yet contain instruction selection for `wasm.catch`
intrinsic, all `RUN` lines in exception.ll, eh-lsda.ll, and
cfg-stackify-eh.ll, and a single `RUN` line in wasm-eh.cpp (which is an
end-to-end test from C++ source to assembly) fail. So this CL
temporarily disables those `RUN` lines, and for those test files without
any valid remaining `RUN` lines, adds a dummy `RUN` line to make them
pass. These tests will be reenabled in later CLs.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94039

Files:
  clang/test/CodeGenCXX/wasm-eh.cpp
  llvm/include/llvm/CodeGen/WasmEHFuncInfo.h
  llvm/include/llvm/IR/IntrinsicsWebAssembly.td
  llvm/lib/CodeGen/WasmEHPrepare.cpp
  llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
  llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
  llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
  llvm/test/CodeGen/WebAssembly/eh-lsda.ll
  llvm/test/CodeGen/WebAssembly/exception.ll
  llvm/test/CodeGen/WebAssembly/wasmehprepare.ll

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