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use rustc_index::{Idx, IndexVec};
use rustc_middle::mir::{BasicBlock, Body, Location};
/// Maps between a `Location` and a `PointIndex` (and vice versa).
pub struct DenseLocationMap {
/// For each basic block, how many points are contained within?
statements_before_block: IndexVec<BasicBlock, usize>,
/// Map backward from each point to the basic block that it
/// belongs to.
basic_blocks: IndexVec<PointIndex, BasicBlock>,
num_points: usize,
}
impl DenseLocationMap {
#[inline]
pub fn new(body: &Body<'_>) -> Self {
let mut num_points = 0;
let statements_before_block: IndexVec<BasicBlock, usize> = body
.basic_blocks
.iter()
.map(|block_data| {
let v = num_points;
num_points += block_data.statements.len() + 1;
v
})
.collect();
let mut basic_blocks = IndexVec::with_capacity(num_points);
for (bb, bb_data) in body.basic_blocks.iter_enumerated() {
basic_blocks.extend((0..=bb_data.statements.len()).map(|_| bb));
}
Self { statements_before_block, basic_blocks, num_points }
}
/// Total number of point indices
#[inline]
pub fn num_points(&self) -> usize {
self.num_points
}
/// Converts a `Location` into a `PointIndex`. O(1).
#[inline]
pub fn point_from_location(&self, location: Location) -> PointIndex {
let Location { block, statement_index } = location;
let start_index = self.statements_before_block[block];
PointIndex::new(start_index + statement_index)
}
/// Returns the `PointIndex` for the first statement in the given `BasicBlock`. O(1).
#[inline]
pub fn entry_point(&self, block: BasicBlock) -> PointIndex {
let start_index = self.statements_before_block[block];
PointIndex::new(start_index)
}
/// Return the PointIndex for the block start of this index.
#[inline]
pub fn to_block_start(&self, index: PointIndex) -> PointIndex {
PointIndex::new(self.statements_before_block[self.basic_blocks[index]])
}
/// Converts a `PointIndex` back to a location. O(1).
#[inline]
pub fn to_location(&self, index: PointIndex) -> Location {
assert!(index.index() < self.num_points);
let block = self.basic_blocks[index];
let start_index = self.statements_before_block[block];
let statement_index = index.index() - start_index;
Location { block, statement_index }
}
/// Sometimes we get point-indices back from bitsets that may be
/// out of range (because they round up to the nearest 2^N number
/// of bits). Use this function to filter such points out if you
/// like.
#[inline]
pub fn point_in_range(&self, index: PointIndex) -> bool {
index.index() < self.num_points
}
}
rustc_index::newtype_index! {
/// A single integer representing a `Location` in the MIR control-flow
/// graph. Constructed efficiently from `DenseLocationMap`.
#[orderable]
#[debug_format = "PointIndex({})"]
pub struct PointIndex {}
}
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