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Auto merge of #123441 - saethlin:fixed-len-file-names, r=oli-obk

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Stabilize the size of incr comp object file names

The current implementation does not produce stable-length paths, and we create the paths in a way that makes our allocation behavior is nondeterministic. I think `@eddyb` fixed a number of other cases like this in the past, and this PR fixes another one. Whether that actually matters I have no idea, but we still have bimodal behavior in rustc-perf and the non-uniformity in `find` and `ls` was bothering me.

I've also removed the truncation of the mangled CGU names. Before this PR incr comp paths look like this:
```
target/debug/incremental/scratch-38izrrq90cex7/s-gux6gz0ow8-1ph76gg-ewe1xj434l26w9up5bedsojpd/261xgo1oqnd90ry5.o
```
And after, they look like this:
```
target/debug/incremental/scratch-035omutqbfkbw/s-gux6borni0-16r3v1j-6n64tmwqzchtgqzwwim5amuga/55v2re42sztc8je9bva6g8ft3.o
```

On the one hand, I'm sure this will break some people's builds because they're on Windows and only a few bytes from the path length limit. But if we're that seriously worried about the length of our file names, I have some other ideas on how to make them smaller. And last time I deleted some hash truncations from the compiler, there was a huge drop in the number if incremental compilation ICEs that were reported: https://github.com/rust-lang/rust/pull/110367https://github.com/rust-lang/rust/pull/110367

---

Upon further reading, this PR actually fixes a bug. This comment says the CGU names are supposed to be a fixed-length hash, and before this PR they aren't: ca7d34efa9/compiler/rustc_monomorphize/src/partitioning.rs (L445-L448)
This commit is contained in:
bors 2024-05-03 17:41:48 +00:00
commit efa15ebfef
1 changed files with 3 additions and 2 deletions
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5
src/context.rs
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@ -6,7 +6,8 @@
use rustc_codegen_ssa::base::wants_msvc_seh;
use rustc_codegen_ssa::errors as ssa_errors;
use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeMethods, MiscMethods};
use rustc_data_structures::base_n;
use rustc_data_structures::base_n::ToBaseN;
use rustc_data_structures::base_n::ALPHANUMERIC_ONLY;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_middle::mir::mono::CodegenUnit;
use rustc_middle::span_bug;
@ -621,7 +622,7 @@ pub fn generate_local_symbol_name(&self, prefix: &str) -> String {
let mut name = String::with_capacity(prefix.len() + 6);
name.push_str(prefix);
name.push_str(".");
base_n::push_str(idx as u128, base_n::ALPHANUMERIC_ONLY, &mut name);
name.push_str(&(idx as u64).to_base(ALPHANUMERIC_ONLY));
name
}
}