Auto merge of #96867 - michaelwoerister:path-prefix-fixes-2, r=davidtwco

--remap-path-prefix: Fix duplicated path components in debuginfo

This PR fixes an issue with `--remap-path-prefix` where path components could appear twice in the remapped version of the path (e.g. https://github.com/rust-lang/rust/issues/78479). The underlying problem was that `--remap-path-prefix` is often used to map an absolute path to something that looks like a relative path, e.g.:

```
--remap-path-prefix=/home/calvin/.cargo/registry/src/github.com-1ecc6299db9ec823=crates.io",
```

and relative paths in debuginfo are interpreted as being relative to the compilation directory. So if Cargo invokes the compiler with `/home/calvin/.cargo/registry/src/github.com-1ecc6299db9ec823/some_crate-0.1.0/src/lib.rs` as input and `/home/calvin/.cargo/registry/src/github.com-1ecc6299db9ec823/some_crate-0.1.0` as the compiler's working directory, then debuginfo will state that the working directory was `crates.io/some_crate-0.1.0` and the file is question was `crates.io/some_crate-0.1.0/src/lib.rs`, which combined gives the path:

```
crates.io/some_crate-0.1.0/crates.io/some_crate-0.1.0/src/lib.rs
```

With this PR the compiler will detect this situation and set up debuginfo in LLVM in a way that makes it strip the duplicated path components when emitting DWARF.

The PR also extracts the logic for making remapped paths absolute into a common helper function that is now used by debuginfo too (instead of just during crate metadata generation).

1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/codegen/remap_path_prefix/main.rs b/src/test/codegen/remap_path_prefix/main.rs
index b13d576295c..381f11ff1ef 100644
--- a/src/test/codegen/remap_path_prefix/main.rs
+++ b/src/test/codegen/remap_path_prefix/main.rs
@@ -22,7 +22,7 @@ fn main() {
 }
 
 // Here we check that local debuginfo is mapped correctly.
-// CHECK: !DIFile(filename: "/the/src/remap_path_prefix/main.rs", directory: "/the/cwd"
+// CHECK: !DIFile(filename: "/the/src/remap_path_prefix/main.rs", directory: ""
 
 // And here that debuginfo from other crates are expanded to absolute paths.
 // CHECK: !DIFile(filename: "/the/aux-src/remap_path_prefix_aux.rs", directory: ""