[clangd] Index reserved symbols from *intrin.h system headers

[jhuber6]

Summary:
clangd intentionally suppresses indexing symbols from system headers
as these are likely implementation details the user does not want.
Howver, there are plenty of system headers that provide extensions that
we want to index, such as vector intrinsic headers. This patch adds an
extra check for these commonly-named '*intrin.h' headers. This is not
fully inclusive for all symbols the user might want, but it's a good
start.

Fixes: #118684

[llvmbot]

@llvm/pr-subscribers-clang-tools-extra

@llvm/pr-subscribers-clangd

Author: Joseph Huber (jhuber6)

Changes

Summary:
clangd intentionally suppresses indexing symbols from system headers
as these are likely implementation details the user does not want.
Howver, there are plenty of system headers that provide extensions that
we want to index, such as vector intrinsic headers. This patch adds an
extra check for these commonly-named '*intrin.h' headers. This is not
fully inclusive for all symbols the user might want, but it's a good
start.

Fixes: #118684

---

Full diff: https://github.com/llvm/llvm-project/pull/119735.diff

1 Files Affected:

• (modified) clang-tools-extra/clangd/index/SymbolCollector.cpp (+6-1)

diff --git a/clang-tools-extra/clangd/index/SymbolCollector.cpp b/clang-tools-extra/clangd/index/SymbolCollector.cpp
index 81125dbb1aeafc..6d0af20e31260c 100644
--- a/clang-tools-extra/clangd/index/SymbolCollector.cpp
+++ b/clang-tools-extra/clangd/index/SymbolCollector.cpp
@@ -550,9 +550,14 @@ bool SymbolCollector::shouldCollectSymbol(const NamedDecl &ND,
   // Avoid indexing internal symbols in protobuf generated headers.
   if (isPrivateProtoDecl(ND))
     return false;
+
+  // System headers that end with `intrin.h` likely contain useful symbols.
   if (!Opts.CollectReserved &&
       (hasReservedName(ND) || hasReservedScope(*ND.getDeclContext())) &&
-      ASTCtx.getSourceManager().isInSystemHeader(ND.getLocation()))
+      ASTCtx.getSourceManager().isInSystemHeader(ND.getLocation()) &&
+      !ASTCtx.getSourceManager()
+           .getFilename(ND.getLocation())
+           .ends_with("intrin.h"))
     return false;
 
   return true;

[HighCommander4]

Thanks for the patch. I thought about whether it makes sense to have an additional check for the *intrin.h header being inside the resource directory specifically, but I don't see any headers with that name ending in any other system include directories, so I don't think we need to bother.

Would you mind adding a test case to SymbolCollectorTests.cpp as well? Here's an example of a test customizing a header file name, and here of exercising the "is system header" codepath.

[HighCommander4]

LGTM (I made a small tweak to the test name)