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Rollup merge of #98930 - tmiasko:pub-basic-blocks, r=oli-obk
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Make MIR basic blocks field public

This makes it possible to mutably borrow different fields of the MIR
body without resorting to methods like `basic_blocks_local_decls_mut_and_var_debug_info`.

To preserve validity of control flow graph caches in the presence of
modifications, a new struct `BasicBlocks` wraps together basic blocks
and control flow graph caches.

The `BasicBlocks` dereferences to `IndexVec<BasicBlock, BasicBlockData>`.
On the other hand a mutable access requires explicit `as_mut()` call.
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Dylan-DPC committed Jul 7, 2022
2 parents 66e47df + 17adfeb commit 8d8aa2c
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Showing 32 changed files with 229 additions and 230 deletions.
2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1628,7 +1628,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
location: Location,
) -> impl Iterator<Item = Location> + Captures<'tcx> + 'a {
if location.statement_index == 0 {
let predecessors = body.predecessors()[location.block].to_vec();
let predecessors = body.basic_blocks.predecessors()[location.block].to_vec();
Either::Left(predecessors.into_iter().map(move |bb| body.terminator_loc(bb)))
} else {
Either::Right(std::iter::once(Location {
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2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/invalidation.rs
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ pub(super) fn generate_invalidates<'tcx>(

if let Some(all_facts) = all_facts {
let _prof_timer = tcx.prof.generic_activity("polonius_fact_generation");
let dominators = body.dominators();
let dominators = body.basic_blocks.dominators();
let mut ig = InvalidationGenerator {
all_facts,
borrow_set,
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2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -334,7 +334,7 @@ fn do_mir_borrowck<'a, 'tcx>(
};
}

let dominators = body.dominators();
let dominators = body.basic_blocks.dominators();

let mut mbcx = MirBorrowckCtxt {
infcx,
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4 changes: 2 additions & 2 deletions compiler/rustc_borrowck/src/type_check/liveness/trace.rs
Original file line number Diff line number Diff line change
Expand Up @@ -258,7 +258,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {

let block = self.cx.elements.to_location(block_start).block;
self.stack.extend(
self.cx.body.predecessors()[block]
self.cx.body.basic_blocks.predecessors()[block]
.iter()
.map(|&pred_bb| self.cx.body.terminator_loc(pred_bb))
.map(|pred_loc| self.cx.elements.point_from_location(pred_loc)),
Expand Down Expand Up @@ -354,7 +354,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
}

let body = self.cx.body;
for &pred_block in body.predecessors()[block].iter() {
for &pred_block in body.basic_blocks.predecessors()[block].iter() {
debug!("compute_drop_live_points_for_block: pred_block = {:?}", pred_block,);

// Check whether the variable is (at least partially)
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2 changes: 1 addition & 1 deletion compiler/rustc_codegen_ssa/src/mir/analyze.rs
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ pub fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
fx: &FunctionCx<'a, 'tcx, Bx>,
) -> BitSet<mir::Local> {
let mir = fx.mir;
let dominators = mir.dominators();
let dominators = mir.basic_blocks.dominators();
let locals = mir
.local_decls
.iter()
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5 changes: 3 additions & 2 deletions compiler/rustc_const_eval/src/transform/promote_consts.rs
Original file line number Diff line number Diff line change
Expand Up @@ -856,7 +856,8 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
literal: ConstantKind::from_const(_const, tcx),
}))
};
let (blocks, local_decls) = self.source.basic_blocks_and_local_decls_mut();
let blocks = self.source.basic_blocks.as_mut();
let local_decls = &mut self.source.local_decls;
let loc = candidate.location;
let statement = &mut blocks[loc.block].statements[loc.statement_index];
match statement.kind {
Expand All @@ -865,7 +866,7 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
Rvalue::Ref(ref mut region, borrow_kind, ref mut place),
)) => {
// Use the underlying local for this (necessarily interior) borrow.
let ty = local_decls.local_decls()[place.local].ty;
let ty = local_decls[place.local].ty;
let span = statement.source_info.span;

let ref_ty = tcx.mk_ref(
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147 changes: 147 additions & 0 deletions compiler/rustc_middle/src/mir/basic_blocks.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,147 @@
use crate::mir::graph_cyclic_cache::GraphIsCyclicCache;
use crate::mir::predecessors::{PredecessorCache, Predecessors};
use crate::mir::switch_sources::{SwitchSourceCache, SwitchSources};
use crate::mir::traversal::PostorderCache;
use crate::mir::{BasicBlock, BasicBlockData, Successors, START_BLOCK};

use rustc_data_structures::graph;
use rustc_data_structures::graph::dominators::{dominators, Dominators};
use rustc_index::vec::IndexVec;

#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
pub struct BasicBlocks<'tcx> {
basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
predecessor_cache: PredecessorCache,
switch_source_cache: SwitchSourceCache,
is_cyclic: GraphIsCyclicCache,
postorder_cache: PostorderCache,
}

impl<'tcx> BasicBlocks<'tcx> {
#[inline]
pub fn new(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
BasicBlocks {
basic_blocks,
predecessor_cache: PredecessorCache::new(),
switch_source_cache: SwitchSourceCache::new(),
is_cyclic: GraphIsCyclicCache::new(),
postorder_cache: PostorderCache::new(),
}
}

/// Returns true if control-flow graph contains a cycle reachable from the `START_BLOCK`.
#[inline]
pub fn is_cfg_cyclic(&self) -> bool {
self.is_cyclic.is_cyclic(self)
}

#[inline]
pub fn dominators(&self) -> Dominators<BasicBlock> {
dominators(&self)
}

/// Returns predecessors for each basic block.
#[inline]
pub fn predecessors(&self) -> &Predecessors {
self.predecessor_cache.compute(&self.basic_blocks)
}

/// Returns basic blocks in a postorder.
#[inline]
pub fn postorder(&self) -> &[BasicBlock] {
self.postorder_cache.compute(&self.basic_blocks)
}

/// `switch_sources()[&(target, switch)]` returns a list of switch
/// values that lead to a `target` block from a `switch` block.
#[inline]
pub fn switch_sources(&self) -> &SwitchSources {
self.switch_source_cache.compute(&self.basic_blocks)
}

/// Returns mutable reference to basic blocks. Invalidates CFG cache.
#[inline]
pub fn as_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
self.invalidate_cfg_cache();
&mut self.basic_blocks
}

/// Get mutable access to basic blocks without invalidating the CFG cache.
///
/// By calling this method instead of e.g. [`BasicBlocks::as_mut`] you promise not to change
/// the CFG. This means that
///
/// 1) The number of basic blocks remains unchanged
/// 2) The set of successors of each terminator remains unchanged.
/// 3) For each `TerminatorKind::SwitchInt`, the `targets` remains the same and the terminator
/// kind is not changed.
///
/// If any of these conditions cannot be upheld, you should call [`BasicBlocks::invalidate_cfg_cache`].
#[inline]
pub fn as_mut_preserves_cfg(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
&mut self.basic_blocks
}

/// Invalidates cached information about the CFG.
///
/// You will only ever need this if you have also called [`BasicBlocks::as_mut_preserves_cfg`].
/// All other methods that allow you to mutate the basic blocks also call this method
/// themselves, thereby avoiding any risk of accidentaly cache invalidation.
pub fn invalidate_cfg_cache(&mut self) {
self.predecessor_cache.invalidate();
self.switch_source_cache.invalidate();
self.is_cyclic.invalidate();
self.postorder_cache.invalidate();
}
}

impl<'tcx> std::ops::Deref for BasicBlocks<'tcx> {
type Target = IndexVec<BasicBlock, BasicBlockData<'tcx>>;

#[inline]
fn deref(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
&self.basic_blocks
}
}

impl<'tcx> graph::DirectedGraph for BasicBlocks<'tcx> {
type Node = BasicBlock;
}

impl<'tcx> graph::WithNumNodes for BasicBlocks<'tcx> {
#[inline]
fn num_nodes(&self) -> usize {
self.basic_blocks.len()
}
}

impl<'tcx> graph::WithStartNode for BasicBlocks<'tcx> {
#[inline]
fn start_node(&self) -> Self::Node {
START_BLOCK
}
}

impl<'tcx> graph::WithSuccessors for BasicBlocks<'tcx> {
#[inline]
fn successors(&self, node: Self::Node) -> <Self as graph::GraphSuccessors<'_>>::Iter {
self.basic_blocks[node].terminator().successors()
}
}

impl<'a, 'b> graph::GraphSuccessors<'b> for BasicBlocks<'a> {
type Item = BasicBlock;
type Iter = Successors<'b>;
}

impl<'tcx, 'graph> graph::GraphPredecessors<'graph> for BasicBlocks<'tcx> {
type Item = BasicBlock;
type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicBlock>>;
}

impl<'tcx> graph::WithPredecessors for BasicBlocks<'tcx> {
#[inline]
fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter {
self.predecessors()[node].iter().copied()
}
}
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