---

yaml
---
r: 272103
b: refs/heads/master
c: a5236e9
h: refs/heads/master
i:
  272101: f977488
  272099: 0a9dff7
  272095: f935abe

Author: nikomatsakis

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 068142a2e6d8a72e52091ccebd3368ffaf267643
+refs/heads/master: a5236e9da03fe58c4db8f011880c74a6911ed5e7
 refs/heads/snap-stage3: 235d77457d80b549dad3ac36d94f235208a1eafb
 refs/heads/try: 49312a405e14a449b98fe0056b12a40ac128be4a
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105

trunk/src/librustc_incremental/persist/README.md

@@ -0,0 +1,13 @@
+This is the code to load/save the dependency graph. Loading is assumed
+to run early in compilation, and saving at the very end. When loading,
+the basic idea is that we will load up the dependency graph from the
+previous compilation and compare the hashes of our HIR nodes to the
+hashes of the HIR nodes that existed at the time. For each node whose
+hash has changed, or which no longer exists in the new HIR, we can
+remove that node from the old graph along with any nodes that depend
+on it. Then we add what's left to the new graph (if any such nodes or
+edges already exist, then there would be no effect, but since we do
+this first thing, they do not).
+
+
+

trunk/src/librustc_incremental/persist/load.rs

@@ -10,7 +10,6 @@
 
 //! Code to save/load the dep-graph from files.
 
-
 use calculate_svh::SvhCalculate;
 use rbml::{self, Doc};
 use rbml::reader::{self, DecodeResult, Decoder};
@@ -32,6 +31,12 @@ type DirtyNodes = FnvHashSet<DepNode<DefId>>;
 
 type CleanEdges = Vec<(DepNode<DefId>, DepNode<DefId>)>;
 
+/// If we are in incremental mode, and a previous dep-graph exists,
+/// then load up those nodes/edges that are still valid into the
+/// dep-graph for this session. (This is assumed to be running very
+/// early in compilation, before we've really done any work, but
+/// actually it doesn't matter all that much.) See `README.md` for
+/// more general overview.
 pub fn load_dep_graph<'tcx>(tcx: &ty::TyCtxt<'tcx>) {
     let _ignore = tcx.dep_graph.in_ignore();