[PATCH] D88408: [docs] Revise loop terminology reference.

[Michael Kruse via Phabricator via llvm-commits]

Meinersbur created this revision.
Meinersbur added reviewers: baziotis, reames, fhahn, jdoerfert, Whitney, kbarton, etiotto, hfinkel, bmahjour.
Herald added a project: LLVM.
Meinersbur requested review of this revision.

Motivated by D88183 <https://reviews.llvm.org/D88183>, this seeks to clarify the current loop nomenclature with added illustrations, examples for possibly unexpected situations (infinite loops not part of the "parent" loop, logical loops sharing the same header, ...), and clarification on what other sources may consider a loop. The current document also has multiple errors that are fixed here.

Some selected errors:

- Loops a defined as strongly-connected components. A component a partition of all nodes, i.e. a subloop can never be a component. That is, the document as it currently is only covers top-level loops, even it also uses the term SCC for subloops.
- "a block can be the header of two separate loops at the same time" (it is considered a single loop by LoopInfo)
- "execute before some interesting event happens" (some interesting event is not well-defined)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D88408

Files:
  llvm/docs/LoopTerminology.rst
  llvm/docs/loop-guard.svg
  llvm/docs/loop-irreducible.svg
  llvm/docs/loop-merge.svg
  llvm/docs/loop-nested.svg
  llvm/docs/loop-nonmaximal.svg
  llvm/docs/loop-separate.svg
  llvm/docs/loop-single.svg
  llvm/docs/loop-terminology.svg