[PATCH] D74340: [CodingStandards] Clarify C++ Standard Library usage

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert updated this revision to Diff 243651.
jdoerfert added a comment.

Use wording provided by @rjmccall


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74340/new/

https://reviews.llvm.org/D74340

Files:
  llvm/docs/CodingStandards.rst


Index: llvm/docs/CodingStandards.rst
===================================================================
--- llvm/docs/CodingStandards.rst
+++ llvm/docs/CodingStandards.rst
@@ -70,19 +70,27 @@
 C++ Standard Library
 --------------------
 
-Use the C++ standard library facilities whenever they are available for
-a particular task. LLVM and related projects emphasize and rely on the standard
-library facilities as much as possible.
-
-We avoid some standard facilities, like the I/O streams, and instead use LLVM's
-streams library (raw_ostream_). More detailed information on these subjects is
-available in the :doc:`ProgrammersManual`.
+Instead of implementing custom data structures we encourage the use of C++
+standard library facilities or LLVM support libraries whenever they are
+available for a particular task. LLVM and related projects emphasize and rely
+on the standard library facilities and the LLVM support libraries as much as
+possible.
 
 LLVM support libraries (for example, `ADT
 <https://github.com/llvm/llvm-project/tree/master/llvm/include/llvm/ADT>`_)
-implement functionality missing in the standard library. Such libraries are
-usually implemented in the ``llvm`` namespace and follow the expected standard
-interface, when there is one.
+implement specialized data structures or functionality missing in the standard
+library. Such libraries are usually implemented in the ``llvm`` namespace and
+follow the expected standard interface, when there is one.
+
+When both C++ and the LLVM support libraries provide similar functionality,
+and there isn't a specific reason to favor the C++ implementation, it is
+generally preferable to use the LLVM library. For example, `llvm::DenseMap`
+should almost always be used instead of `std::map` or `std::unordered_map`,
+and `llvm::SmallVector` should usually be used instead of `std::vector`.
+
+We explicitly avoid some standard facilities, like the I/O streams, and instead
+use LLVM's streams library (raw_ostream_). More detailed information on these
+subjects is available in the :doc:`ProgrammersManual`.
 
 Guidelines for Go code
 ----------------------


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