[all-commits] [llvm/llvm-project] c285a1: [WebAssembly] Make Emscripten EH work with Emscrip...

[Heejin Ahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c285a11efdb0821e6be9fcef695097890f44aa03
      https://github.com/llvm/llvm-project/commit/c285a11efdb0821e6be9fcef695097890f44aa03
  Author: Heejin Ahn <aheejin at gmail.com>
  Date:   2021-07-26 (Mon, 26 Jul 2021)

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

  Log Message:
  -----------
  [WebAssembly] Make Emscripten EH work with Emscripten SjLj

When Emscripten EH mixes with Emscripten SjLj, we are not currently
handling some of them correctly. There are three cases:
1. The current function calls `setjmp` and there is an `invoke` to a
   function that can either throw or longjmp. In this case, we have to
   check both for exception and longjmp. We are currently handling this
   case correctly:
   https://github.com/llvm/llvm-project/blob/0c0eb76782d5224b8d81a5afbb9a152bcf7c94c7/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp#L1058-L1090
   When inserting routines for functions that can longjmp, which we do
   only for setjmp-calling functions, we check if the function was
   previously an `invoke` and handle it correctly.

2. The current function does NOT call `setjmp` and there is an `invoke`
   to a function that can either throw or longjmp. Because there is no
   `setjmp` call, we haven't been doing any check for functions that can
   longjmp. But in that case, for `invoke`, we only check for an
   exception and if it is not an exception we reset `__THREW__` to 0,
   which can silently swallow the longjmp:
   https://github.com/llvm/llvm-project/blob/0c0eb76782d5224b8d81a5afbb9a152bcf7c94c7/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp#L70-L80
   This CL fixes this.

3. The current function calls `setjmp` and there is no `invoke`. Because
   it is not an `invoke`, we haven't been doing any check for functions
   that can throw, and only insert longjmp-checking routines for
   functions that can longjmp. But in that case, if a longjmpable
   function throws, we only check for a longjmp so if it is not a
   longjmp we reset `__THREW__` to 0, which can silently swallow the
   exception:
   https://github.com/llvm/llvm-project/blob/0c0eb76782d5224b8d81a5afbb9a152bcf7c94c7/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp#L156-L169
   This CL fixes this.

To do that, this moves around some code, so we register necessary
functions for both EH and SjLj and precompute some data (the set of
functions that contains `setjmp`) before doing actual EH or SjLj
transformation.

This CL makes 2nd and 3rd tests in
https://github.com/emscripten-core/emscripten/pull/14732 work.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D106525