[circt-verilog-lsp] Avoid recursing into other buffers when indexing #9055
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uenoku
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Oct 6, 2025
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Cool! I think this totally makes sense.
lib/Tools/circt-verilog-lsp-server/VerilogServerImpl/VerilogIndex.cpp
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Profiling showed `visitDefault` dominated indexing time (~99.99% of runtime in larger projects) due
to deep traversal into non-relevant buffers. This patch keeps correctness while
greatly reducing unnecessary recursion. In a SoC-scale System verilog project, this change reduces
indexing time from 6.6 s to 4 ms.
- Added `definitelyOutsideMainBuffer()` helper to detect whether an AST node’s
source range, syntax range, or location belongs to the main buffer.
- Integrated this check into the templated `visit<T>` function:
- Skips recursion (`visitDefault`) when a node is clearly outside the main file.
- Uses a new `ASTBase` alias for clarity and correctness when calling
`visitDefault<T>()`.
- Removed redundant `visitDefault()` calls from individual symbol visitors
(`NetSymbol`, `VariableSymbol`, `ImportSymbol`, etc.) that no longer need to
recurse manually.
- Result: traversal remains correct but prunes large off-buffer branches early,
improving indexing time for multi-file compilations.
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Profiling showed
visitDefaultdominated indexing time (~99.99% of runtime in larger projects) due to deep traversal into non-relevant buffers. This patch keeps correctness while greatly reducing unnecessary recursion. In a SoC-scale System verilog project, this change reduces indexing time from 6.6 s to 4 ms.definitelyOutsideMainBuffer()helper to detect whether an AST node’s source range, syntax range, or location belongs to the main buffer.visit<T>function:visitDefault) when a node is clearly outside the main file.ASTBasealias for clarity and correctness when callingvisitDefault<T>().visitDefault()calls from individual symbol visitors (NetSymbol,VariableSymbol,ImportSymbol, etc.) that no longer need to recurse manually.