diff options
| -rw-r--r-- | compiler/rustc_middle/src/mir/mod.rs | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs index 12dc1c12264..8ff75bf392e 100644 --- a/compiler/rustc_middle/src/mir/mod.rs +++ b/compiler/rustc_middle/src/mir/mod.rs @@ -1077,6 +1077,25 @@ pub struct VarDebugInfo<'tcx> { // BasicBlock rustc_index::newtype_index! { + /// A node in the MIR [control-flow graph][CFG]. + /// + /// There are no branches (e.g., `if`s, function calls, etc.) within a basic block, which makes + /// it easier to do [data-flow analyses] and optimizations. Instead, branches are represented + /// as an edge in a graph between basic blocks. + /// + /// Basic blocks consist of a series of [statements][Statement], ending with a + /// [terminator][Terminator]. Basic blocks can have multiple predecessors and successors, + /// however there is a MIR pass ([`CriticalCallEdges`]) that removes *critical edges*, which + /// 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. + /// + /// Read more about basic blocks in the [rustc-dev-guide][guide-mir]. + /// + /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg + /// [data-flow analyses]: + /// https://rustc-dev-guide.rust-lang.org/appendix/background.html#what-is-a-dataflow-analysis + /// [`CriticalCallEdges`]: ../../rustc_mir/transform/add_call_guards/enum.AddCallGuards.html#variant.CriticalCallEdges + /// [guide-mir]: https://rustc-dev-guide.rust-lang.org/mir/ pub struct BasicBlock { derive [HashStable] DEBUG_FORMAT = "bb{}", @@ -1093,6 +1112,7 @@ impl BasicBlock { /////////////////////////////////////////////////////////////////////////// // BasicBlockData and Terminator +/// See [`BasicBlock`] for documentation on what basic blocks are at a high level. #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable)] pub struct BasicBlockData<'tcx> { /// List of statements in this block. |