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perf: reduce llvm-lines by removing .extend([_; 2]) #308

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dtolnay merged 1 commit into from
Nov 3, 2025
Merged

perf: reduce llvm-lines by removing .extend([_; 2]) #308

dtolnay merged 1 commit into from
Nov 3, 2025

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@dishmaker
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@dishmaker dishmaker commented Nov 3, 2025

Before:

quote$ cargo llvm-lines --release | head -n 3
  Lines               Copies             Function name
  -----               ------             -------------
  8959                447                (TOTAL)

After:

quote$ cargo llvm-lines --release | head -n 3
  Lines               Copies             Function name
  -----               ------             -------------
  8495                424                (TOTAL)

@dtolnay dtolnay merged commit 1253e29 into dtolnay:master Nov 3, 2025
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dishmaker commented Nov 3, 2025 •
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Weird. On latest master total lines actually increased.

quote$ git log
commit 1253e2919ee22d51c94b61494c7e2de9e9392a3c (HEAD -> master, origin/master, origin/HEAD)
Merge: 6280f98 be59ab1
Author: David Tolnay <[email protected]>
Date:   Mon Nov 3 13:05:13 2025 -0800

    Merge pull request #308 from dishmaker/dishmaker/perf_llvml_runtime_append_arr
    
    perf: reduce llvm-lines by removing `.extend([_; 2])`

quote$ cargo llvm-lines --release | head -n 3
  Lines               Copies             Function name
  -----               ------             -------------
  8658                365                (TOTAL)

quote$ cargo -V
cargo 1.93.0-nightly (636800288 2025-10-31)

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dtolnay commented Nov 3, 2025

Related to <TokenStream as TokenStreamExt>::append from #305.

// 8662 lines

do_append(self, token.into());
fn do_append(stream: &mut TokenStream, tree: TokenTree) {
    stream.extend(Some(tree));
}
// 8672 lines

do_append(self, token.into());
fn do_append(stream: &mut TokenStream, tree: TokenTree) {
    stream.extend(iter::once(tree));
}
// 7768 lines

self.extend(iter::once(token.into()));
// 9376 lines

self.extend(Some(token.into()));

@dtolnay dtolnay mentioned this pull request Nov 6, 2025
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@dishmaker @dtolnay