[PATCH] D150635: [clangd] Implement end-definition-comment inlay hints

[Sam McCall via Phabricator via cfe-commits]

sammccall added inline comments.


================
Comment at: clang-tools-extra/clangd/InlayHints.cpp:616
+    Position HintStart = sourceLocToPosition(SM, BraceRange.getEnd());
+    Position HintEnd = {HintStart.line,
+                        HintStart.character +
----------------
daiyousei-qz wrote:
> sammccall wrote:
> > please don't do this, call sourceLocToPosition unless you have benchmarks showing this is a bottleneck on real-world code.
> > 
> > `lspLength` and direct manipulation of line/character is unneccesarily subtle.
> > (If the performance matters, there's no need to be computing the LSP line of the lbrace at all - we never use it - this is one reason I think this function has the wrong signature)
> I argue performance does matter here. I eye-balled inlay hint compute time in clangd's output window from vscode. On "./clang/lib/Sema/SemaOpenMP.cpp" which is around 1MB, using `sourceLocToPosition` roughly takes around 1250~1350ms. However, using two `offsetLocToPosition` usually use 1400~1500ms.  I think 100ms delta is already a noticeable difference.
I'm unable to reproduce these results. After verifying EndBlock hints work in an editor:

```
$ bin/clangd --check=../clang/lib/Sema/SemaOpenMP.cpp
I[15:50:26.357] clangd version 17.0.0
I[15:50:26.358] Features: linux+debug-tidy
...
 I[15:50:26.358] Testing on source file /usr/local/google/home/sammccall/src/llvm-project/clang/lib/Sema/SemaOpenMP.cpp
...
I[15:50:26.428] Building preamble...
I[15:50:31.097] Indexing headers...
I[15:50:32.027] Built preamble of size 53468188 for file /usr/local/google/home/sammccall/src/llvm-project/clang/lib/Sema/SemaOpenMP.cpp version null in 5.60 seconds
I[15:50:32.032] Building AST...
I[15:50:38.857] Indexing AST...
I[15:50:38.975] Building inlay hints
I[15:50:38.993] Building semantic highlighting
I[15:50:39.050] Testing features at each token (may be slow in large files)
...
```

So that's 18ms for inlay hints after 5.6 seconds to parse the preamble and 6 seconds to parse the main file. (This is a debug build, opt must be faster).

This is on a fairly powerful machine, but surely it can't be 1000x faster than yours - something else must be going on.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150635/new/

https://reviews.llvm.org/D150635