rust/src/test/codegen/non-terminate/infinite-loop-2.rs, branch 1.44.0https://github.com/rust-lang/rust
http://git.dreamy.place/mirrors/rust/atom?h=1.44.02019-09-27T23:13:53+00:00Gate llvm.sideeffect under -Z insert-sideeffect2019-09-27T23:13:53+00:00Xiang Fansfanxiang@gmail.com2019-09-27T23:13:53+00:00urn:sha1:10c668190cb419b539a36214237382c6689f7dafAdd llvm.sideeffect to potential infinite loops and recursions2019-09-27T20:45:08+00:00Xiang Fansfanxiang@gmail.com2019-06-06T00:39:20+00:00urn:sha1:f71e0daa29b232d8f689f77fecb84dcb87fce6da
LLVM assumes that a thread will eventually cause side effect. This is
not true in Rust if a loop or recursion does nothing in its body,
causing undefined behavior even in common cases like `loop {}`.
Inserting llvm.sideeffect fixes the undefined behavior.
As a micro-optimization, only insert llvm.sideeffect when jumping back
in blocks or calling a function.
A patch for LLVM is expected to allow empty non-terminate code by
default and fix this issue from LLVM side.
https://github.com/rust-lang/rust/issues/28728