--- /dev/null
+//! A test for the logic that updates the state in a `ResultsCursor` during seek.
+
+use rustc::mir::{self, BasicBlock, Location};
+use rustc::ty;
+use rustc_index::bit_set::BitSet;
+use rustc_index::vec::IndexVec;
+
+use super::*;
+use crate::dataflow::BottomValue;
+
+/// Returns `true` if the given location points to a `Call` terminator that can return
+/// successfully.
+fn is_call_terminator_non_diverging(body: &mir::Body<'_>, loc: Location) -> bool {
+ loc == body.terminator_loc(loc.block)
+ && matches!(
+ body[loc.block].terminator().kind,
+ mir::TerminatorKind::Call { destination: Some(_), .. }
+ )
+}
+
+/// Creates a `mir::Body` with a few disconnected basic blocks.
+///
+/// This is the `Body` that will be used by the `MockAnalysis` below. The shape of its CFG is not
+/// important.
+fn mock_body() -> mir::Body<'static> {
+ let span = syntax_pos::DUMMY_SP;
+ let source_info = mir::SourceInfo { scope: mir::OUTERMOST_SOURCE_SCOPE, span };
+
+ let mut blocks = IndexVec::new();
+ let mut block = |n, kind| {
+ let nop = mir::Statement { source_info, kind: mir::StatementKind::Nop };
+
+ blocks.push(mir::BasicBlockData {
+ statements: std::iter::repeat(&nop).cloned().take(n).collect(),
+ terminator: Some(mir::Terminator { source_info, kind }),
+ is_cleanup: false,
+ })
+ };
+
+ let dummy_place = mir::Place { local: mir::RETURN_PLACE, projection: ty::List::empty() };
+
+ block(4, mir::TerminatorKind::Return);
+ block(1, mir::TerminatorKind::Return);
+ block(
+ 2,
+ mir::TerminatorKind::Call {
+ func: mir::Operand::Copy(dummy_place.clone()),
+ args: vec![],
+ destination: Some((dummy_place.clone(), mir::START_BLOCK)),
+ cleanup: None,
+ from_hir_call: false,
+ },
+ );
+ block(3, mir::TerminatorKind::Return);
+ block(0, mir::TerminatorKind::Return);
+ block(
+ 4,
+ mir::TerminatorKind::Call {
+ func: mir::Operand::Copy(dummy_place.clone()),
+ args: vec![],
+ destination: Some((dummy_place.clone(), mir::START_BLOCK)),
+ cleanup: None,
+ from_hir_call: false,
+ },
+ );
+
+ mir::Body::new_cfg_only(blocks)
+}
+
+/// A dataflow analysis whose state is unique at every possible `SeekTarget`.
+///
+/// Uniqueness is achieved by having a *locally* unique effect before and after each statement and
+/// terminator (see `effect_at_target`) while ensuring that the entry set for each block is
+/// *globally* unique (see `mock_entry_set`).
+///
+/// For example, a `BasicBlock` with ID `2` and a `Call` terminator has the following state at each
+/// location ("+x" indicates that "x" is added to the state).
+///
+/// | Location | Before | After |
+/// |------------------------|-------------------|--------|
+/// | (on_entry) | {102} ||
+/// | Statement 0 | +0 | +1 |
+/// | statement 1 | +2 | +3 |
+/// | `Call` terminator | +4 | +5 |
+/// | (on unwind) | {102,0,1,2,3,4,5} ||
+/// | (on successful return) | +6 ||
+///
+/// The `102` in the block's entry set is derived from the basic block index and ensures that the
+/// expected state is unique across all basic blocks. Remember, it is generated by
+/// `mock_entry_sets`, not from actually running `MockAnalysis` to fixpoint.
+struct MockAnalysis<'tcx> {
+ body: &'tcx mir::Body<'tcx>,
+}
+
+impl MockAnalysis<'tcx> {
+ const BASIC_BLOCK_OFFSET: usize = 100;
+
+ /// The entry set for each `BasicBlock` is the ID of that block offset by a fixed amount to
+ /// avoid colliding with the statement/terminator effects.
+ fn mock_entry_set(self, bb: BasicBlock) -> BitSet<usize> {
+ let mut ret = BitSet::new_empty(self.bits_per_block(body));
+ ret.insert(Self::BASIC_BLOCK_OFFSET + bb.index());
+ ret
+ }
+
+ fn mock_entry_sets(&self) -> IndexVec<BasicBlock, BitSet<usize>> {
+ let empty = BitSet::new_empty(self.bits_per_block(body));
+ let mut ret = IndexVec::from_elem(empty, &self.body.basic_blocks());
+
+ for (bb, _) in self.body.basic_blocks().iter_enumerated() {
+ ret[bb] = self.mock_entry_set(bb);
+ }
+
+ ret
+ }
+
+ /// Returns the index that should be added to the dataflow state at the given target.
+ ///
+ /// This index is only unique within a given basic block. `SeekAfter` and
+ /// `SeekAfterAssumeCallReturns` have the same effect unless `target` is a `Call` terminator.
+ fn effect_at_target(&self, target: SeekTarget) -> Option<usize> {
+ use SeekTarget::*;
+
+ let idx = match target {
+ BlockStart(_) => return None,
+
+ AfterAssumeCallReturns(loc) if is_call_terminator_non_diverging(self.body, loc) => {
+ loc.statement_index * 2 + 2
+ }
+
+ Before(loc) => loc.statement_index * 2,
+ After(loc) | AfterAssumeCallReturns(loc) => loc.statement_index * 2 + 1,
+ };
+
+ assert!(idx < Self::BASIC_BLOCK_OFFSET, "Too many statements in basic block");
+ Some(idx)
+ }
+
+ /// Returns the expected state at the given `SeekTarget`.
+ ///
+ /// This is the union of index of the target basic block, the index assigned to the
+ /// target statement or terminator, and the indices of all preceding statements in the target
+ /// basic block.
+ ///
+ /// For example, the expected state when calling
+ /// `seek_before(Location { block: 2, statement_index: 2 })` would be `[102, 0, 1, 2, 3, 4]`.
+ fn expected_state_at_target(&self, target: SeekTarget) -> BitSet<usize> {
+ let mut ret = BitSet::new_empty(self.bits_per_block(self.body));
+ ret.insert(Self::BASIC_BLOCK_OFFSET + target.block().index());
+
+ if let Some(target_effect) = self.effect_at_target(target) {
+ for i in 0..=target_effect {
+ ret.insert(i);
+ }
+ }
+
+ ret
+ }
+}
+
+impl BottomValue for MockAnalysis<'tcx> {
+ const BOTTOM_VALUE: bool = false;
+}
+
+impl AnalysisDomain<'tcx> for MockAnalysis<'tcx> {
+ type Idx = usize;
+
+ const NAME: &'static str = "mock";
+
+ fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
+ Self::BASIC_BLOCK_OFFSET + body.basic_blocks().len()
+ }
+
+ fn initialize_start_block(&self, _: &mir::Body<'tcx>, _: &mut BitSet<Self::Idx>) {
+ unimplemented!("This is never called since `MockAnalysis` is never iterated to fixpoint");
+ }
+}
+
+impl Analysis<'tcx> for MockAnalysis<'tcx> {
+ fn apply_statement_effect(
+ &self,
+ state: &mut BitSet<Self::Idx>,
+ _statement: &mir::Statement<'tcx>,
+ location: Location,
+ ) {
+ let idx = SeekTarget::After(location).effect(self.body).unwrap();
+ assert!(state.insert(idx));
+ }
+
+ fn apply_before_statement_effect(
+ &self,
+ state: &mut BitSet<Self::Idx>,
+ _statement: &mir::Statement<'tcx>,
+ location: Location,
+ ) {
+ let idx = SeekTarget::Before(location).effect(self.body).unwrap();
+ assert!(state.insert(idx));
+ }
+
+ fn apply_terminator_effect(
+ &self,
+ state: &mut BitSet<Self::Idx>,
+ _terminator: &mir::Terminator<'tcx>,
+ location: Location,
+ ) {
+ let idx = SeekTarget::After(location).effect(self.body).unwrap();
+ assert!(state.insert(idx));
+ }
+
+ fn apply_before_terminator_effect(
+ &self,
+ state: &mut BitSet<Self::Idx>,
+ _terminator: &mir::Terminator<'tcx>,
+ location: Location,
+ ) {
+ let idx = SeekTarget::Before(location).effect(self.body).unwrap();
+ assert!(state.insert(idx));
+ }
+
+ fn apply_call_return_effect(
+ &self,
+ state: &mut BitSet<Self::Idx>,
+ block: BasicBlock,
+ _func: &mir::Operand<'tcx>,
+ _args: &[mir::Operand<'tcx>],
+ _return_place: &mir::Place<'tcx>,
+ ) {
+ let location = self.body.terminator_loc(block);
+ let idx = SeekTarget::AfterAssumeCallReturns(location).effect(self.body).unwrap();
+ assert!(state.insert(idx));
+ }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum SeekTarget {
+ BlockStart(BasicBlock),
+ Before(Location),
+ After(Location),
+ AfterAssumeCallReturns(Location),
+}
+
+impl SeekTarget {
+ fn block(&self) -> BasicBlock {
+ use SeekTarget::*;
+
+ match *self {
+ BlockStart(block) => block,
+ Before(loc) | After(loc) | AfterAssumeCallReturns(loc) => loc.block,
+ }
+ }
+
+ /// An iterator over all possible `SeekTarget`s in a given block in order, starting with
+ /// `BlockStart`.
+ ///
+ /// This includes both `After` and `AfterAssumeCallReturns` for every `Location`.
+ fn iter_in_block(body: &mir::Body<'_>, block: BasicBlock) -> impl Iterator<Item = Self> {
+ let statements_and_terminator = (0..=body[block].statements.len())
+ .flat_map(|i| (0..3).map(move |j| (i, j)))
+ .map(move |(i, kind)| {
+ let loc = Location { block, statement_index: i };
+ match kind {
+ 0 => SeekTarget::Before(loc),
+ 1 => SeekTarget::After(loc),
+ 2 => SeekTarget::AfterAssumeCallReturns(loc),
+ _ => unreachable!(),
+ }
+ });
+
+ std::iter::once(SeekTarget::BlockStart(block)).chain(statements_and_terminator)
+ }
+}
+
+#[test]
+fn cursor_seek() {
+ let body = mock_body();
+ let body = &body;
+ let analysis = MockAnalysis { body };
+
+ let mut cursor = Results { entry_sets: analysis.mock_entry_sets(), analysis }.into_cursor(body);
+
+ // Sanity check: the mock call return effect is unique and actually being applied.
+ let call_terminator_loc = Location { block: BasicBlock::from_usize(2), statement_index: 2 };
+ assert!(is_call_terminator_non_diverging(body, call_terminator_loc));
+
+ let call_return_effect = cursor
+ .analysis()
+ .effect_at_target(SeekTarget::AfterAssumeCallReturns(call_terminator_loc))
+ .unwrap();
+ assert_ne!(call_return_effect, SeekTarget::After(call_terminator_loc).effect(body).unwrap());
+
+ cursor.seek_after(call_terminator_loc);
+ assert!(!cursor.get().contains(call_return_effect));
+ cursor.seek_after_assume_call_returns(call_terminator_loc);
+ assert!(cursor.get().contains(call_return_effect));
+
+ let every_target = || {
+ body.basic_blocks()
+ .iter_enumerated()
+ .flat_map(|(bb, _)| SeekTarget::iter_in_block(body, bb))
+ };
+
+ let mut seek_to_target = |targ| {
+ use SeekTarget::*;
+
+ match targ {
+ BlockStart(block) => cursor.seek_to_block_start(block),
+ Before(loc) => cursor.seek_before(loc),
+ After(loc) => cursor.seek_after(loc),
+ AfterAssumeCallReturns(loc) => cursor.seek_after_assume_call_returns(loc),
+ }
+
+ assert_eq!(cursor.get(), &cursor.analysis().expected_state_at_target(targ));
+ };
+
+ // Seek *to* every possible `SeekTarget` *from* every possible `SeekTarget`.
+ //
+ // By resetting the cursor to `from` each time it changes, we end up checking some edges twice.
+ // What we really want is an Eulerian cycle for the complete digraph over all possible
+ // `SeekTarget`s, but it's not worth spending the time to compute it.
+ for from in every_target() {
+ seek_to_target(from);
+
+ for to in every_target() {
+ seek_to_target(to);
+ seek_to_target(from);
+ }
+ }
+}
projects / rust.git / commitdiff