tests/codegen/try_identity.rs

   1 // compile-flags: -C no-prepopulate-passes -O -Z mir-opt-level=3 -Zunsound-mir-opts
   2
   3 // Ensure that `x?` has no overhead on `Result<T, E>` due to identity `match`es in lowering.
   4 // This requires inlining to trigger the MIR optimizations in `SimplifyArmIdentity`.
   5
   6 #![crate_type = "lib"]
   7
   8 type R = Result<u64, i32>;
   9
  10 // This was written to the `?` from `try_trait`, but `try_trait_v2` uses a different structure,
  11 // so the relevant desugar is copied inline in order to keep the test testing the same thing.
  12 // FIXME(#85133): while this might be useful for `r#try!`, it would be nice to have a MIR
  13 // optimization that picks up the `?` desugaring, as `SimplifyArmIdentity` does not.
  14 #[no_mangle]
  15 pub fn try_identity(x: R) -> R {
  16 // CHECK: start:
  17 // FIXME(JakobDegen): Broken by deaggregation change CHECK-NOT\: br {{.*}}
  18 // CHECK ret void
  19     let y = match into_result(x) {
  20         Err(e) => return from_error(From::from(e)),
  21         Ok(v) => v,
  22     };
  23     Ok(y)
  24 }
  25
  26 #[inline]
  27 fn into_result<T, E>(r: Result<T, E>) -> Result<T, E> {
  28     r
  29 }
  30
  31 #[inline]
  32 fn from_error<T, E>(e: E) -> Result<T, E> {
  33     Err(e)
  34 }