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[clangd] Use unique_function for config handlers (#203008)

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`ConfigYAML.cpp`'s `DictParser` owns its callbacks for one parse and
never copies them, so this replaces `std::function` with move-only
`llvm::unique_function` and removes the unused copy machinery for each
lambda.

In a matched Release AArch64 build, `ConfigYAML.cpp.o` shrank by 94,560
bytes, stripped clangd shrank by 16,848 bytes, unstripped clangd shrank
by 82,512 bytes, and dyld fixups fell by 336.

Validated with the 16 `ParseYAML` unit tests and `clangd --check`; 12
paired runs of 100,000 parses improved mean user CPU time by 3.46% (95%
CI: 1.31% to 5.61%).

Work towards #202616

AI tool disclosure: Co-authored with OpenAI Codex.
This commit is contained in:
David Zbarsky 2026-07-14 22:58:57 -07:00 committed by GitHub
parent 74822b4ee0
commit c4830afdbb
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1 changed files with 10 additions and 4 deletions
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14
clang-tools-extra/clangd/ConfigYAML.cpp
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@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//
#include "ConfigFragment.h"
#include "support/Logger.h"
#include "llvm/ADT/FunctionExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
@ -334,8 +335,11 @@ private:
// We don't use YamlIO as we want to control over unknown keys.
class DictParser {
llvm::StringRef Description;
std::vector<std::pair<llvm::StringRef, std::function<void(Node &)>>> Keys;
std::function<bool(Located<std::string>, Node &)> UnknownHandler;
std::vector<
std::pair<llvm::StringRef, llvm::unique_function<void(Node &) const>>>
Keys;
llvm::unique_function<bool(Located<std::string>, Node &) const>
UnknownHandler;
Parser *Outer;
public:
@ -345,7 +349,8 @@ private:
// Parse is called when Key is encountered, and passed the associated value.
// It should emit diagnostics if the value is invalid (e.g. wrong type).
// If Key is seen twice, Parse runs only once and an error is reported.
void handle(llvm::StringLiteral Key, std::function<void(Node &)> Parse) {
void handle(llvm::StringLiteral Key,
llvm::unique_function<void(Node &) const> Parse) {
for (const auto &Entry : Keys) {
(void)Entry;
assert(Entry.first != Key && "duplicate key handler");
@ -357,7 +362,8 @@ private:
// If this is unset or the Handler returns true, a warning is emitted for
// the unknown key.
void
unrecognized(std::function<bool(Located<std::string>, Node &)> Handler) {
unrecognized(llvm::unique_function<bool(Located<std::string>, Node &) const>
Handler) {
UnknownHandler = std::move(Handler);
}