Auto merge of #128506 - compiler-errors:by-move-body, r=cjgillot

Stop storing a special inner body for the coroutine by-move body for async closures

...and instead, just synthesize an item which is treated mostly normally by the MIR pipeline.

This PR does a few things:
* We synthesize a new `DefId` for the by-move body of a closure, which has its `mir_built` fed with the output of the `ByMoveBody` MIR transformation, and some other relevant queries.
* This has the `DefKind::ByMoveBody`, which we use to distinguish it from "real" bodies (that come from HIR) which need to be borrowck'd. Introduce `TyCtxt::is_synthetic_mir` to skip over `mir_borrowck` which is called by `mir_promoted`; borrowck isn't really possible to make work ATM since it heavily relies being called on a body generated from HIR, and is redundant by the construction of the by-move-body.
* Remove the special `PassManager` hacks for handling the inner `by_move_body` stored within the coroutine's mir body. Instead, this body is fed like a regular MIR body, so it's goes through all of the `tcx.*_mir` stages normally (build -> promoted -> ...etc... -> optimized) ✨.
* Remove the `InstanceKind::ByMoveBody` shim, since now we have a "regular" def id, we can just use `InstanceKind::Item`. This also allows us to remove the corresponding hacks from codegen, such as in `fn_sig_for_fn_abi` ✨.

Notable remarks:
* ~~I know it's kind of weird to be using `DefKind::Closure` here, since it's not a distinct closure but just a new MIR body. I don't believe it really matters, but I could also use a different `DefKind`... maybe one that we could use for synthetic MIR bodies in general?~~ edit: We're doing this now.

1 files changed, 14 insertions, 0 deletions

diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 96a6f52d60b..779b98d073d 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -784,7 +784,20 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
             }
         );
     });
+
     rustc_hir_analysis::check_crate(tcx);
+    sess.time("MIR_coroutine_by_move_body", || {
+        tcx.hir().par_body_owners(|def_id| {
+            if tcx.needs_coroutine_by_move_body_def_id(def_id) {
+                tcx.ensure_with_value().coroutine_by_move_body_def_id(def_id);
+            }
+        });
+    });
+    // Freeze definitions as we don't add new ones at this point.
+    // We need to wait until now since we synthesize a by-move body
+    // This improves performance by allowing lock-free access to them.
+    tcx.untracked().definitions.freeze();
+
     sess.time("MIR_borrow_checking", || {
         tcx.hir().par_body_owners(|def_id| {
             // Run unsafety check because it's responsible for stealing and
@@ -816,6 +829,7 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
             );
         }
     });
+
     sess.time("layout_testing", || layout_test::test_layout(tcx));
     sess.time("abi_testing", || abi_test::test_abi(tcx));