Auto merge of #47954 - eddyb:copy-elision, r=<try>

[WIP] Implement a "place unification" MIR optimization (aka source/destination propagation).

*nothing to see here* (PR open for testing purposes)

note to self: **DO NOT MERGE** without inspecting all `FIXME` / `HACK` comments

src/librustc_mir/dataflow/at_location.rs → src/librustc_mir/analysis/dataflow/at_location.rs

@@ -15,8 +15,8 @@ use rustc::mir::{BasicBlock, Location};
 use rustc_data_structures::indexed_set::{self, IdxSetBuf};
 use rustc_data_structures::indexed_vec::Idx;
 
-use dataflow::{BitDenotation, BlockSets, DataflowResults};
-use dataflow::move_paths::{HasMoveData, MovePathIndex};
+use analysis::dataflow::{BitDenotation, BlockSets, DataflowResults};
+use analysis::dataflow::move_paths::{HasMoveData, MovePathIndex};
 
 use std::iter;
 

src/librustc_mir/dataflow/impls/borrowed_locals.rs → src/librustc_mir/analysis/dataflow/impls/borrowed_locals.rs

@@ -12,7 +12,7 @@ pub use super::*;
 
 use rustc::mir::*;
 use rustc::mir::visit::Visitor;
-use dataflow::BitDenotation;
+use analysis::dataflow::BitDenotation;
 
 /// This calculates if any part of a MIR local could have previously been borrowed.
 /// This means that once a local has been borrowed, its bit will always be set

src/librustc_mir/dataflow/impls/borrows.rs → src/librustc_mir/analysis/dataflow/impls/borrows.rs

@@ -23,8 +23,8 @@ use rustc_data_structures::bitslice::{BitwiseOperator};
 use rustc_data_structures::indexed_set::{IdxSet};
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 
-use dataflow::{BitDenotation, BlockSets, InitialFlow};
-pub use dataflow::indexes::{BorrowIndex, ReserveOrActivateIndex};
+use analysis::dataflow::{BitDenotation, BlockSets, InitialFlow};
+pub use analysis::dataflow::indexes::{BorrowIndex, ReserveOrActivateIndex};
 use borrow_check::nll::region_infer::RegionInferenceContext;
 use borrow_check::nll::ToRegionVid;
 

src/librustc_mir/dataflow/impls/storage_liveness.rs → src/librustc_mir/analysis/dataflow/impls/storage_liveness.rs

@@ -11,7 +11,7 @@
 pub use super::*;
 
 use rustc::mir::*;
-use dataflow::BitDenotation;
+use analysis::dataflow::BitDenotation;
 
 #[derive(Copy, Clone)]
 pub struct MaybeStorageLive<'a, 'tcx: 'a> {

src/librustc_mir/dataflow/mod.rs → src/librustc_mir/analysis/dataflow/mod.rs

@@ -121,14 +121,14 @@ pub struct MoveDataParamEnv<'gcx, 'tcx> {
     pub(crate) param_env: ty::ParamEnv<'gcx>,
 }
 
-pub(crate) fn do_dataflow<'a, 'gcx, 'tcx, BD, P>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
-                                                 mir: &'a Mir<'tcx>,
-                                                 node_id: ast::NodeId,
-                                                 attributes: &[ast::Attribute],
-                                                 dead_unwinds: &IdxSet<BasicBlock>,
-                                                 bd: BD,
-                                                 p: P)
-                                                 -> DataflowResults<BD>
+pub(crate) fn do_dataflow<BD, P>(tcx: TyCtxt,
+                                 mir: &Mir,
+                                 node_id: ast::NodeId,
+                                 attributes: &[ast::Attribute],
+                                 dead_unwinds: &IdxSet<BasicBlock>,
+                                 bd: BD,
+                                 p: P)
+                                 -> DataflowResults<BD>
     where BD: BitDenotation + InitialFlow,
           P: Fn(&BD, BD::Idx) -> DebugFormatted
 {
@@ -139,7 +139,7 @@ pub(crate) fn do_dataflow<'a, 'gcx, 'tcx, BD, P>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
 impl<'a, 'gcx: 'tcx, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
 {
     pub(crate) fn run<P>(self,
-                         tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                         tcx: TyCtxt,
                          node_id: ast::NodeId,
                          attributes: &[ast::Attribute],
                          p: P) -> DataflowResults<BD>
@@ -513,7 +513,7 @@ pub struct BlockSets<'a, E: Idx> {
 }
 
 impl<'a, E:Idx> BlockSets<'a, E> {
-    fn gen(&mut self, e: &E) {
+    pub(crate) fn gen(&mut self, e: &E) {
         self.gen_set.add(e);
         self.kill_set.remove(e);
     }
@@ -538,7 +538,7 @@ impl<'a, E:Idx> BlockSets<'a, E> {
         }
     }
 
-    fn kill(&mut self, e: &E) {
+    pub(crate) fn kill(&mut self, e: &E) {
         self.gen_set.remove(e);
         self.kill_set.add(e);
     }