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Note that BasicBlock is just an index #78035

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Oct 18, 2020
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Note that BasicBlock is just an index #78035

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5 changes: 4 additions & 1 deletion compiler/rustc_middle/src/mir/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -146,7 +146,7 @@ impl<'tcx> MirSource<'tcx> {
/// The lowered representation of a single function.
#[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable)]
pub struct Body<'tcx> {
/// A list of basic blocks. References to basic block use a newtyped index type `BasicBlock`
/// A list of basic blocks. References to basic block use a newtyped index type [`BasicBlock`]
/// that indexes into this vector.
basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,

Expand Down Expand Up @@ -1106,6 +1106,9 @@ rustc_index::newtype_index! {
/// are edges that go from a multi-successor node to a multi-predecessor node. This pass is
/// needed because some analyses require that there are no critical edges in the CFG.
///
/// Note that this type is just an index into [`Body.basic_blocks`](Body::basic_blocks);
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Are there other places where BasicBlock is an index?

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I don't really understand the question?

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I wasn’t sure if there are other places where it is an index into a vector of blocks and I want to make sure I don’t mislead people by saying that it’s an index into specifically Body when in fact there are other places that hold a vector of blocks that are indexed by BasicBlock. Hope that was clearer!

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Ah I see, thanks for clarifying.

I don't think there are other lists this is an index into, but you can audit all IndexVec<BasicBlock, _> if you want to be sure.

/// the actual data that a basic block holds is in [`BasicBlockData`].
///
/// Read more about basic blocks in the [rustc-dev-guide][guide-mir].
///
/// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
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