From 23b4db227a391b8c64a54c863846c0f8a8168426 Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Sun, 12 Aug 2018 20:49:43 +0200
Subject: [PATCH] Implement basic incremental compilation

---
 build.sh   |  2 +-
 src/lib.rs | 25 +++++++++++++++++++++----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/build.sh b/build.sh
index c0bc1978300..3d9bcbd1919 100755
--- a/build.sh
+++ b/build.sh
@@ -20,6 +20,6 @@ $RUSTC mini_core.rs --crate-name mini_core --crate-type lib &&
 $RUSTC example.rs --crate-type lib &&
 $RUSTC mini_core_hello_world.rs --crate-type bin &&
 
-$RUSTC ../target/libcore/src/libcore/lib.rs --color=always --crate-type lib 2>&1 | (head -n 20; echo "===="; tail -n 1000)
+$RUSTC ../target/libcore/src/libcore/lib.rs --color=always --crate-type lib -Cincremental=../target/libcore/incremental 2>&1 | (head -n 20; echo "===="; tail -n 1000)
 cat ../target/log.txt | sort | uniq -c | grep -v "rval unsize move" | grep -v "rval len"
 rm *.rlib ../target/log.txt
diff --git a/src/lib.rs b/src/lib.rs
index bec98bf5863..bb51ba659c3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -68,7 +68,7 @@ mod prelude {
         self, subst::Substs, FnSig, Instance, InstanceDef, ParamEnv, PolyFnSig, Ty, TyCtxt,
         TypeAndMut, TypeFoldable, TypeVariants,
     };
-    pub use rustc_data_structures::{indexed_vec::Idx, sync::Lrc};
+    pub use rustc_data_structures::{indexed_vec::Idx, sync::Lrc, fx::FxHashMap};
     pub use rustc_mir::monomorphize::{collector, MonoItem};
     pub use syntax::ast::{FloatTy, IntTy, UintTy};
     pub use syntax::codemap::DUMMY_SP;
@@ -186,6 +186,13 @@ impl CodegenBackend for CraneliftCodegenBackend {
         providers.target_features_whitelist = |_tcx, _cnum| Lrc::new(Default::default());
         providers.is_reachable_non_generic = |_tcx, _defid| true;
         providers.exported_symbols = |_tcx, _crate| Arc::new(Vec::new());
+        providers.upstream_monomorphizations = |_tcx, _cnum| Lrc::new(FxHashMap());
+        providers.upstream_monomorphizations_for = |tcx, def_id| {
+            debug_assert!(!def_id.is_local());
+            tcx.upstream_monomorphizations(LOCAL_CRATE)
+                .get(&def_id)
+                .cloned()
+        };
     }
     fn provide_extern(&self, providers: &mut Providers) {
         providers.is_reachable_non_generic = |_tcx, _defid| true;
@@ -251,9 +258,13 @@ impl CodegenBackend for CraneliftCodegenBackend {
             let mut log = ::std::fs::File::create("../target/log.txt").unwrap();
 
             let before = ::std::time::Instant::now();
-            for mono_item in
-                collector::collect_crate_mono_items(tcx, collector::MonoItemCollectionMode::Eager).0
-            {
+            let mono_items = collector::collect_crate_mono_items(tcx, collector::MonoItemCollectionMode::Eager).0;
+
+            // TODO: move to the end of this function when compiling libcore doesn't have unimplemented stuff anymore
+            save_incremental(tcx);
+            tcx.sess.warn("Saved incremental data");
+
+            for mono_item in mono_items {
                 let cx = &mut cx;
                 let context = &mut context;
                 let res = ::std::panic::catch_unwind(::std::panic::AssertUnwindSafe(move || {
@@ -371,6 +382,12 @@ impl CodegenBackend for CraneliftCodegenBackend {
     }
 }
 
+fn save_incremental<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
+    rustc_incremental::assert_dep_graph(tcx);
+    rustc_incremental::save_dep_graph(tcx);
+    rustc_incremental::finalize_session_directory(tcx.sess, tcx.crate_hash(LOCAL_CRATE));
+}
+
 /// This is the entrypoint for a hot plugged rustc_codegen_cranelift
 #[no_mangle]
 pub fn __rustc_codegen_backend() -> Box<CodegenBackend> {