Re-add a way to specify initial state

Author: nagisa

src/librustc_mir/transform/const_propagate.rs

@@ -48,7 +48,7 @@ impl Pass for ConstPropagate {}
 
 impl<'tcx> MirPass<'tcx> for ConstPropagate {
     fn run_pass<'a>(&mut self, tcx: TyCtxt<'a, 'tcx, 'tcx>, _: MirSource, mir: &mut Mir<'tcx>) {
-        *mir = Dataflow::forward(mir,
+        *mir = Dataflow::forward(mir, ConstLattice::new(),
                                  ConstTransfer { tcx: tcx },
                                  ConstRewrite { tcx: tcx }.and_then(SimplifyRewrite));
     }

src/librustc_mir/transform/dataflow/mod.rs

@@ -111,7 +111,7 @@ where L: Lattice,
       R: Rewrite<'tcx, T>
 {
     /// Execute dataflow in forward direction
-    pub fn forward(mir: &'a Mir<'tcx>, transfer: T, rewrite: R) -> Mir<'tcx> {
+    pub fn forward(mir: &'a Mir<'tcx>, initial: L, transfer: T, rewrite: R) -> Mir<'tcx> {
         let block_count = mir.basic_blocks().len();
         let mut queue = BitVector::new(block_count);
         queue.insert(START_BLOCK.index());
@@ -123,6 +123,7 @@ where L: Lattice,
             transfer: transfer,
         };
         dataflow.knowledge.extend(::std::iter::repeat(None).take(block_count));
+        dataflow.update_fact(START_BLOCK, initial);
         dataflow.fixpoint(Self::forward_block);
         dataflow.construct_mir()
     }
@@ -169,18 +170,25 @@ where L: Lattice,
       R: Rewrite<'tcx, T>
 {
     /// Execute dataflow in backward direction.
-    pub fn backward(mir: &'a Mir<'tcx>, transfer: T, rewrite: R) -> Mir<'tcx> {
+    pub fn backward(mir: &'a Mir<'tcx>, initial: L, transfer: T, rewrite: R) -> Mir<'tcx> {
         let block_count = mir.basic_blocks().len();
         let mut queue = BitVector::new(block_count);
         mir_exits(mir, &mut queue);
+        let mut knowledge = IndexVec::with_capacity(block_count);
+        knowledge.extend(::std::iter::repeat(None).take(block_count));
+        for block in queue.iter() {
+            knowledge[BasicBlock::new(block)] = Some(Knowledge {
+                fact: initial.clone(),
+                new_block: None,
+            });
+        }
         let mut dataflow = Dataflow {
             mir: mir,
             queue: queue,
-            knowledge: IndexVec::with_capacity(block_count),
+            knowledge: knowledge,
             rewrite: rewrite,
             transfer: transfer,
         };
-        dataflow.knowledge.extend(::std::iter::repeat(None).take(block_count));
         dataflow.fixpoint(Self::backward_block);
         dataflow.construct_mir()
     }

src/librustc_mir/transform/deadcode.rs

@@ -22,7 +22,8 @@ impl Pass for DeadCode {}
 
 impl<'tcx> MirPass<'tcx> for DeadCode {
     fn run_pass<'a>(&mut self, _: TyCtxt<'a, 'tcx, 'tcx>, _: MirSource, mir: &mut Mir<'tcx>) {
-        let new_mir = Dataflow::backward(mir, DeadCodeTransfer, DeadCodeRewrite);
+        let new_mir = Dataflow::backward(mir, DeadCodeLattice::bottom(),
+                                         DeadCodeTransfer, DeadCodeRewrite);
         *mir = new_mir;
     }
 }

src/librustc_mir/transform/mod.rs

@@ -20,5 +20,5 @@ pub mod promote_consts;
 pub mod qualify_consts;
 pub mod dump_mir;
 pub mod deaggregator;
-pub mod liveness;
-pub mod cs_propagate;
+pub mod deadcode;
+pub mod const_propagate;