Auto merge of #69295 - ecstatic-morse:unified-dataflow-generators, r=tmandry

Use new dataflow framework for generators

#65672 introduced a new dataflow framework that can handle arbitrarily complex transfer functions as well as ones expressed as a series of gen/kill operations. This PR ports the analyses used to implement generators to the new framework so that we can remove the old one. See #68241 for a prior example of this. The new framework has some superficial API changes, but this shouldn't alter the generator passes in any way.

r? @tmandry

2 files changed, 105 insertions, 88 deletions

diff --git a/src/librustc_mir/dataflow/impls/mod.rs b/src/librustc_mir/dataflow/impls/mod.rs
index 59aa91ab824..87d8e9e411c 100644
--- a/src/librustc_mir/dataflow/impls/mod.rs
+++ b/src/librustc_mir/dataflow/impls/mod.rs
@@ -14,7 +14,7 @@ use crate::util::elaborate_drops::DropFlagState;
 
 use super::generic::{AnalysisDomain, GenKill, GenKillAnalysis};
 use super::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex};
-use super::{BottomValue, GenKillSet};
+use super::BottomValue;
 
 use super::drop_flag_effects_for_function_entry;
 use super::drop_flag_effects_for_location;
diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs
index 659b66823c2..fabe562e68a 100644
--- a/src/librustc_mir/dataflow/impls/storage_liveness.rs
+++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs
@@ -1,47 +1,39 @@
 pub use super::*;
 
-use crate::dataflow::generic::{Results, ResultsRefCursor};
-use crate::dataflow::BitDenotation;
-use crate::dataflow::MaybeBorrowedLocals;
+use crate::dataflow::generic::{self as dataflow, GenKill, Results, ResultsRefCursor};
+use crate::dataflow::BottomValue;
 use rustc::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc::mir::*;
 use std::cell::RefCell;
 
 #[derive(Copy, Clone)]
-pub struct MaybeStorageLive<'a, 'tcx> {
-    body: &'a Body<'tcx>,
-}
+pub struct MaybeStorageLive;
 
-impl<'a, 'tcx> MaybeStorageLive<'a, 'tcx> {
-    pub fn new(body: &'a Body<'tcx>) -> Self {
-        MaybeStorageLive { body }
-    }
+impl dataflow::AnalysisDomain<'tcx> for MaybeStorageLive {
+    type Idx = Local;
 
-    pub fn body(&self) -> &Body<'tcx> {
-        self.body
-    }
-}
+    const NAME: &'static str = "maybe_storage_live";
 
-impl<'a, 'tcx> BitDenotation<'tcx> for MaybeStorageLive<'a, 'tcx> {
-    type Idx = Local;
-    fn name() -> &'static str {
-        "maybe_storage_live"
-    }
-    fn bits_per_block(&self) -> usize {
-        self.body.local_decls.len()
+    fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
+        body.local_decls.len()
     }
 
-    fn start_block_effect(&self, on_entry: &mut BitSet<Local>) {
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut BitSet<Self::Idx>) {
         // The resume argument is live on function entry (we don't care about
         // the `self` argument)
-        for arg in self.body.args_iter().skip(1) {
+        for arg in body.args_iter().skip(1) {
             on_entry.insert(arg);
         }
     }
+}
 
-    fn statement_effect(&self, trans: &mut GenKillSet<Local>, loc: Location) {
-        let stmt = &self.body[loc.block].statements[loc.statement_index];
-
+impl dataflow::GenKillAnalysis<'tcx> for MaybeStorageLive {
+    fn statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        stmt: &mir::Statement<'tcx>,
+        _: Location,
+    ) {
         match stmt.kind {
             StatementKind::StorageLive(l) => trans.gen(l),
             StatementKind::StorageDead(l) => trans.kill(l),
@@ -49,22 +41,28 @@ impl<'a, 'tcx> BitDenotation<'tcx> for MaybeStorageLive<'a, 'tcx> {
         }
     }
 
-    fn terminator_effect(&self, _trans: &mut GenKillSet<Local>, _loc: Location) {
+    fn terminator_effect(
+        &self,
+        _trans: &mut impl GenKill<Self::Idx>,
+        _: &mir::Terminator<'tcx>,
+        _: Location,
+    ) {
         // Terminators have no effect
     }
 
-    fn propagate_call_return(
+    fn call_return_effect(
         &self,
-        _in_out: &mut BitSet<Local>,
-        _call_bb: mir::BasicBlock,
-        _dest_bb: mir::BasicBlock,
-        _dest_place: &mir::Place<'tcx>,
+        _trans: &mut impl GenKill<Self::Idx>,
+        _block: BasicBlock,
+        _func: &mir::Operand<'tcx>,
+        _args: &[mir::Operand<'tcx>],
+        _return_place: &mir::Place<'tcx>,
     ) {
         // Nothing to do when a call returns successfully
     }
 }
 
-impl<'a, 'tcx> BottomValue for MaybeStorageLive<'a, 'tcx> {
+impl BottomValue for MaybeStorageLive {
     /// bottom = dead
     const BOTTOM_VALUE: bool = false;
 }
@@ -73,60 +71,62 @@ type BorrowedLocalsResults<'a, 'tcx> = ResultsRefCursor<'a, 'a, 'tcx, MaybeBorro
 
 /// Dataflow analysis that determines whether each local requires storage at a
 /// given location; i.e. whether its storage can go away without being observed.
-pub struct RequiresStorage<'mir, 'tcx> {
+pub struct MaybeRequiresStorage<'mir, 'tcx> {
     body: ReadOnlyBodyAndCache<'mir, 'tcx>,
     borrowed_locals: RefCell<BorrowedLocalsResults<'mir, 'tcx>>,
 }
 
-impl<'mir, 'tcx: 'mir> RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> {
     pub fn new(
         body: ReadOnlyBodyAndCache<'mir, 'tcx>,
         borrowed_locals: &'mir Results<'tcx, MaybeBorrowedLocals>,
     ) -> Self {
-        RequiresStorage {
+        MaybeRequiresStorage {
             body,
             borrowed_locals: RefCell::new(ResultsRefCursor::new(*body, borrowed_locals)),
         }
     }
-
-    pub fn body(&self) -> &Body<'tcx> {
-        &self.body
-    }
 }
 
-impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> dataflow::AnalysisDomain<'tcx> for MaybeRequiresStorage<'mir, 'tcx> {
     type Idx = Local;
-    fn name() -> &'static str {
-        "requires_storage"
-    }
-    fn bits_per_block(&self) -> usize {
-        self.body.local_decls.len()
+
+    const NAME: &'static str = "requires_storage";
+
+    fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
+        body.local_decls.len()
     }
 
-    fn start_block_effect(&self, on_entry: &mut BitSet<Local>) {
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut BitSet<Self::Idx>) {
         // The resume argument is live on function entry (we don't care about
         // the `self` argument)
-        for arg in self.body.args_iter().skip(1) {
+        for arg in body.args_iter().skip(1) {
             on_entry.insert(arg);
         }
     }
+}
 
-    fn before_statement_effect(&self, sets: &mut GenKillSet<Self::Idx>, loc: Location) {
-        let stmt = &self.body[loc.block].statements[loc.statement_index];
-
+impl<'mir, 'tcx> dataflow::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'mir, 'tcx> {
+    fn before_statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        stmt: &mir::Statement<'tcx>,
+        loc: Location,
+    ) {
         // If a place is borrowed in a statement, it needs storage for that statement.
-        self.borrowed_locals.borrow().analysis().statement_effect(sets, stmt, loc);
+        self.borrowed_locals.borrow().analysis().statement_effect(trans, stmt, loc);
 
-        // If a place is assigned to in a statement, it needs storage for that statement.
         match &stmt.kind {
-            StatementKind::StorageDead(l) => sets.kill(*l),
+            StatementKind::StorageDead(l) => trans.kill(*l),
+
+            // If a place is assigned to in a statement, it needs storage for that statement.
             StatementKind::Assign(box (place, _))
             | StatementKind::SetDiscriminant { box place, .. } => {
-                sets.gen(place.local);
+                trans.gen(place.local);
             }
-            StatementKind::InlineAsm(box InlineAsm { outputs, .. }) => {
-                for place in &**outputs {
-                    sets.gen(place.local);
+            StatementKind::InlineAsm(asm) => {
+                for place in &*asm.outputs {
+                    trans.gen(place.local);
                 }
             }
 
@@ -140,22 +140,30 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
         }
     }
 
-    fn statement_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
+    fn statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _: &mir::Statement<'tcx>,
+        loc: Location,
+    ) {
         // If we move from a place then only stops needing storage *after*
         // that statement.
-        self.check_for_move(sets, loc);
+        self.check_for_move(trans, loc);
     }
 
-    fn before_terminator_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
-        let terminator = self.body[loc.block].terminator();
-
+    fn before_terminator_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        terminator: &mir::Terminator<'tcx>,
+        loc: Location,
+    ) {
         // If a place is borrowed in a terminator, it needs storage for that terminator.
-        self.borrowed_locals.borrow().analysis().terminator_effect(sets, terminator, loc);
+        self.borrowed_locals.borrow().analysis().terminator_effect(trans, terminator, loc);
 
         match &terminator.kind {
-            TerminatorKind::Call { destination: Some((Place { local, .. }, _)), .. }
-            | TerminatorKind::Yield { resume_arg: Place { local, .. }, .. } => {
-                sets.gen(*local);
+            TerminatorKind::Call { destination: Some((place, _)), .. }
+            | TerminatorKind::Yield { resume_arg: place, .. } => {
+                trans.gen(place.local);
             }
 
             // Nothing to do for these. Match exhaustively so this fails to compile when new
@@ -176,14 +184,19 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
         }
     }
 
-    fn terminator_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
-        match &self.body[loc.block].terminator().kind {
+    fn terminator_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        terminator: &mir::Terminator<'tcx>,
+        loc: Location,
+    ) {
+        match &terminator.kind {
             // For call terminators the destination requires storage for the call
             // and after the call returns successfully, but not after a panic.
             // Since `propagate_call_unwind` doesn't exist, we have to kill the
-            // destination here, and then gen it again in `propagate_call_return`.
-            TerminatorKind::Call { destination: Some((Place { local, .. }, _)), .. } => {
-                sets.kill(*local);
+            // destination here, and then gen it again in `call_return_effect`.
+            TerminatorKind::Call { destination: Some((place, _)), .. } => {
+                trans.kill(place.local);
             }
 
             // Nothing to do for these. Match exhaustively so this fails to compile when new
@@ -204,45 +217,49 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
             | TerminatorKind::Unreachable => {}
         }
 
-        self.check_for_move(sets, loc);
+        self.check_for_move(trans, loc);
     }
 
-    fn propagate_call_return(
+    fn call_return_effect(
         &self,
-        in_out: &mut BitSet<Local>,
-        _call_bb: mir::BasicBlock,
-        _dest_bb: mir::BasicBlock,
-        dest_place: &mir::Place<'tcx>,
+        trans: &mut impl GenKill<Self::Idx>,
+        _block: BasicBlock,
+        _func: &mir::Operand<'tcx>,
+        _args: &[mir::Operand<'tcx>],
+        return_place: &mir::Place<'tcx>,
     ) {
-        in_out.insert(dest_place.local);
+        trans.gen(return_place.local);
     }
 }
 
-impl<'mir, 'tcx> RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> {
     /// Kill locals that are fully moved and have not been borrowed.
-    fn check_for_move(&self, sets: &mut GenKillSet<Local>, loc: Location) {
-        let mut visitor = MoveVisitor { sets, borrowed_locals: &self.borrowed_locals };
+    fn check_for_move(&self, trans: &mut impl GenKill<Local>, loc: Location) {
+        let mut visitor = MoveVisitor { trans, borrowed_locals: &self.borrowed_locals };
         visitor.visit_location(self.body, loc);
     }
 }
 
-impl<'mir, 'tcx> BottomValue for RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> BottomValue for MaybeRequiresStorage<'mir, 'tcx> {
     /// bottom = dead
     const BOTTOM_VALUE: bool = false;
 }
 
-struct MoveVisitor<'a, 'mir, 'tcx> {
+struct MoveVisitor<'a, 'mir, 'tcx, T> {
     borrowed_locals: &'a RefCell<BorrowedLocalsResults<'mir, 'tcx>>,
-    sets: &'a mut GenKillSet<Local>,
+    trans: &'a mut T,
 }
 
-impl<'a, 'mir: 'a, 'tcx> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx> {
+impl<'a, 'mir, 'tcx, T> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx, T>
+where
+    T: GenKill<Local>,
+{
     fn visit_local(&mut self, local: &Local, context: PlaceContext, loc: Location) {
         if PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) == context {
             let mut borrowed_locals = self.borrowed_locals.borrow_mut();
             borrowed_locals.seek_before(loc);
             if !borrowed_locals.contains(*local) {
-                self.sets.kill(*local);
+                self.trans.kill(*local);
             }
         }
     }