rename and document NLL MIR dump entry point

Author: lqd

compiler/rustc_borrowck/src/lib.rs

@@ -229,7 +229,7 @@ fn do_mir_borrowck<'tcx>(
 
     // Dump MIR results into a file, if that is enabled. This let us
     // write unit-tests, as well as helping with debugging.
-    nll::dump_mir_results(&infcx, body, &regioncx, &opt_closure_req);
+    nll::dump_nll_mir(&infcx, body, &regioncx, &opt_closure_req);
 
     // We also have a `#[rustc_regions]` annotation that causes us to dump
     // information.

compiler/rustc_borrowck/src/nll.rs

@@ -209,7 +209,16 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
     }
 }
 
-pub(super) fn dump_mir_results<'tcx>(
+/// `-Zdump-mir=nll` dumps MIR annotated with NLL specific information:
+/// - free regions
+/// - inferred region values
+/// - region liveness
+/// - inference constraints and their causes
+///
+/// As well as graphviz `.dot` visualizations of:
+/// - the region constraints graph
+/// - the region SCC graph
+pub(super) fn dump_nll_mir<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,