[all-commits] [llvm/llvm-project] f5cff2: [WebAssembly] Fix PHI when relaying longjmps

[Heejin Ahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f5cff292e297ad5094f35d6223a199e389adcd99
      https://github.com/llvm/llvm-project/commit/f5cff292e297ad5094f35d6223a199e389adcd99
  Author: Heejin Ahn <aheejin at gmail.com>
  Date:   2021-08-26 (Thu, 26 Aug 2021)

  Changed paths:
    M llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
    M llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj.ll

  Log Message:
  -----------
  [WebAssembly] Fix PHI when relaying longjmps

When doing Emscritpen EH, if SjLj is also enabled and used and if the
thrown exception has a possiblity being a longjmp instead of an
exception, we shouldn't swallow it; we should rethrow, or relay it. It
was done in D106525 and the code is here:
https://github.com/llvm/llvm-project/blob/8441a8eea8007b9eaaaabf76055949180a702d6d/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp#L858-L898

Here is the pseudocode of that part: (copied from comments)
```
if (%__THREW__.val == 0 || %__THREW__.val == 1)
  goto %tail
else
  goto %longjmp.rethrow

longjmp.rethrow: ;; This is longjmp. Rethrow it
  %__threwValue.val = __threwValue
  emscripten_longjmp(%__THREW__.val, %__threwValue.val);

tail: ;; Nothing happened or an exception is thrown
  ... Continue exception handling ...
```

If the current BB (where the `invoke` is created) has successors that
has the current BB as its PHI incoming node, now that has to change to
`tail` in the pseudocode, because `tail` is the latest BB that is
connected with the next BB, but this was missing.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D108785