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Invalid codegen for wasm at opt-level=0 #51986

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alexcrichton opened this issue Jul 2, 2018 · 0 comments
Closed

Invalid codegen for wasm at opt-level=0 #51986

alexcrichton opened this issue Jul 2, 2018 · 0 comments
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A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. O-wasm Target: WASM (WebAssembly), http://webassembly.org/

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@alexcrichton
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I've reported an upstream LLVM bug for this but I want to track it on our side as well to track pulling in the fix. The gist of the issue is that this code:

extern {
    fn return_one() -> u32;
    fn panic() -> !;
}

#[no_mangle]
pub unsafe extern fn test() {
    let tmp: bool = !(return_one() == 1);
    if tmp { panic() }
    if !tmp { panic() }
}

will execute successfully when compiled at O0:

<html>
  <head>
    <script>
const imports = {
  env: {
    return_one: function() { return 1; },
    panic: function() { throw 'bad'; }
  }
};
fetch('foo.wasm')
  .then(r => r.arrayBuffer())
  .then(r => WebAssembly.instantiate(r, imports))
  .then(m => {
    console.log('start');
    m.instance.exports.test()
    console.log('end');
  })
  .catch(e => console.error(e));
    </script>
  </head>
  <body>
  </body>
</html>

And it should certainly panic!

I'm currently hoping we can fix this upstream in LLVM before we need to work around it in rustc!
@alexcrichton alexcrichton added A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. O-wasm Target: WASM (WebAssembly), http://webassembly.org/ labels Jul 2, 2018
alexcrichton referenced this issue in rustwasm/wasm-bindgen Jul 2, 2018
@ohanar
change some asserts to assert_(eq|ne)s
d123bed
alexcrichton added a commit to alexcrichton/rust that referenced this issue Jul 2, 2018
@alexcrichton
Update LLVM to bring in a wasm codegen fix
c4f6f90 
Closes rust-lang#51986
@alexcrichton alexcrichton mentioned this issue Jul 2, 2018
Merged
kennytm added a commit to kennytm/rust that referenced this issue Jul 6, 2018
@kennytm
Rollup merge of rust-lang#52005 - alexcrichton:update-llvm-for-wasm, …
1568b5e 
…r=kennytm

Update LLVM to bring in a wasm codegen fix

Closes rust-lang#51986
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