Auto merge of #74967 - Aaron1011:feature/incr-def-path-table, r=pnkfelix

Implement lazy decoding of DefPathTable during incremental compilation

PR https://github.com/rust-lang/rust/pull/75813 implemented lazy decoding of the `DefPathTable` from crate metadata. However, it requires decoding the entire `DefPathTable` when incremental compilation is active, so that we can map a decoded `DefPathHash` to a `DefId` from an arbitrary crate.

This PR adds support for lazy decoding of dependency `DefPathTable`s when incremental compilation si active.

When we load the incremental cache and dep
graph, we need the ability to map a `DefPathHash` to a `DefId` in the
current compilation session (if the corresponding definition still
exists).

This is accomplished by storing the old `DefId` (that is, the `DefId`
from the previous compilation session) for each `DefPathHash` we need to
remap. Since a `DefPathHash` includes the owning crate, the old crate is
guaranteed to be the right one (if the definition still exists). We then
use the old `DefIndex` as an initial guess, which we validate by
comparing the expected and actual `DefPathHash`es. In most cases,
foreign crates will be completely unchanged, which means that we our
guess will be correct. If our guess is wrong, we fall back to decoding
the entire `DefPathTable` for the foreign crate. This still represents
an improvement over the status quo, since we can skip decoding the
entire `DefPathTable` for other crates (where all of our guesses were
correct).

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 1f820024f77..c13d26c79d7 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -747,7 +747,7 @@ pub fn create_global_ctxt<'tcx>(
         Definitions::new(crate_name, sess.local_crate_disambiguator()),
     ));
 
-    let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess);
+    let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess, defs);
 
     let codegen_backend = compiler.codegen_backend();
     let mut local_providers = *DEFAULT_QUERY_PROVIDERS;