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`-Zthreads` causes cycle errors in previously passing code
cargo new t
cd t
cargo add ppv-lite86
RUSTFLAGS="-Zthreads=16" ~/.cargo/bin/cargo +master build
Compiling ppv-lite86 v0.2.17
error[E0391]: cycle detected when type-checking `x86_64::sse2::<impl at /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.1>
--> /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/src/x86_64/sse2.rs:290:9
|
290 | fn $name(self) -> Self {
| ^^^^^^^^^^^^^^^^^^^^^^
...
313 | rotr_128!(rotate_each_word_right32, 32);
| --------------------------------------- in this macro invocation
|
note: ...which requires evaluating type-level constant...
--> /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/src/x86_64/sse2.rs:294:21
|
294 | _mm_slli_si128(self.x, 128 - $i as i32),
| ^^^^^^^^^^^^^^
...
313 | rotr_128!(rotate_each_word_right32, 32);
| --------------------------------------- in this macro invocation
note: ...which requires const-evaluating + checking `x86_64::sse2::<impl at /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0>
--> /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/src/x86_64/sse2.rs:294:21
|
294 | _mm_slli_si128(self.x, 128 - $i as i32),
| ^^^^^^^^^^^^^^
...
313 | rotr_128!(rotate_each_word_right32, 32);
| --------------------------------------- in this macro invocation
note: ...which requires caching mir of `x86_64::sse2::<impl at /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/src/x86>
--> /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/src/x86_64/sse2.rs:294:21
|
294 | _mm_slli_si128(self.x, 128 - $i as i32),
| ^^^^^^^^^^^^^^
...
313 | rotr_128!(rotate_each_word_right32, 32);
| --------------------------------------- in this macro invocation
note: ...which requires elaborating drops for `x86_64::sse2::<impl at /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/>
--> /home/matthias/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ppv-lite86-0.2.17/src/x86_64/sse2.rs:294:21
|
294 | _mm_slli_si128(self.x, 128 - $i as i32),
| ^^^^^^^^^^^^^^
...
313 | rotr_128!(rotate_each_word_right32, 32);
...
...
...
...
```
fun fact: this breaks the the bootstrap of parallel compiler with -Zthreads since ppv-lite86 is one of the dependencies lol
this bisects to #122140 cc @oli-obk
It’s being reverted in https://github.com/rust-lang/rust/pull/122347 — still something to fix when/if it relands of course, but at least the parallel WG won’t need to look at this issue until then.
