Auto merge of rust-lang#122597 - pacak:master, r=bjorn3

Show files produced by `--emit foo` in json artifact notifications

Right now it is possible to ask `rustc` to save some intermediate representation into one or more files with `--emit=foo`, but figuring out what exactly was produced is difficult. This pull request adds information about `llvm_ir` and `asm` intermediate files into notifications produced by `--json=artifacts`.

Related discussion: https://internals.rust-lang.org/t/easier-access-to-files-generated-by-emit-foo/20477

Motivation - `cargo-show-asm` parses those intermediate files and presents them in a user friendly way, but right now I have to apply some dirty hacks. Hacks make behavior confusing: hintron/computer-enhance#35

This pull request introduces a new behavior: now `rustc` will emit a new artifact notification for every artifact type user asked to `--emit`, for example for `--emit asm` those will include all the `.s` files.

Most users won't notice this behavior, to be affected by it all of the following must hold:
- user must use `rustc` binary directly (when `cargo` invokes `rustc` - it consumes artifact notifications and doesn't emit anything)
- user must specify both `--emit xxx` and `--json artifacts`
- user must refuse to handle unknown artifact types
- user must disable incremental compilation (or deal with it better than cargo does, or use a workaround like `save-temps`) in order not to hit rust-lang#88829 / rust-lang#89149

Author: bors

src/driver/aot.rs

@@ -288,6 +288,29 @@ fn produce_final_output_artifacts(
         }
     }
 
+    if sess.opts.json_artifact_notifications {
+        if codegen_results.modules.len() == 1 {
+            codegen_results.modules[0].for_each_output(|_path, ty| {
+                if sess.opts.output_types.contains_key(&ty) {
+                    let descr = ty.shorthand();
+                    // for single cgu file is renamed to drop cgu specific suffix
+                    // so we regenerate it the same way
+                    let path = crate_output.path(ty);
+                    sess.dcx().emit_artifact_notification(path.as_path(), descr);
+                }
+            });
+        } else {
+            for module in &codegen_results.modules {
+                module.for_each_output(|path, ty| {
+                    if sess.opts.output_types.contains_key(&ty) {
+                        let descr = ty.shorthand();
+                        sess.dcx().emit_artifact_notification(&path, descr);
+                    }
+                });
+            }
+        }
+    }
+
     // We leave the following files around by default:
     //  - #crate#.o
     //  - #crate#.crate.metadata.o