Don't update entries in TypedArena if T does not need drop
#78144
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rust-highfive
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Hmm, this makes me wonder whether we could make the This way we don't get into situations like this where we accidentally use a field that is never touched. Maybe this is overkill? But it feels kind of nice to me. What do you think? |
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I don't think I want to make TypedArena any more complicated, just to save 4-8 bytes in like 3 (well, the query system makes it actually hard to say, how many) places. I think I've already introduced enough complexity :) But I can try and think of a solution if complexity is not a huge concern. |
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The bytes aren't really the issue here, but the uses of the field. Though I guess you're right about complexity. So... I guess leave a comment on that |
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@bors r+ rollup Thanks! |
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📌 Commit 2705cae has been approved by |
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Don't update `entries` in `TypedArena` if T does not need drop As far as I can tell, `entries` is only used when dropping `TypedArenaChunk`s and their contents. It is already ignored there, if T is not `mem::needs_drop`, this PR just skips updating it's value. You can see `TypedArenaChunk` ignoring the entry count in L71. The reasoning is similar to what you can find in `DroplessArena`. r? @oli-obk
…laumeGomez Rollup of 9 pull requests Successful merges: - rust-lang#78046 (Add codegen test for issue rust-lang#73827) - rust-lang#78061 (Optimize const value interning for ZST types) - rust-lang#78070 (we can test std and core panic macros together) - rust-lang#78076 (Move orphan module-name/mod.rs files into module-name.rs files) - rust-lang#78129 (Wrapping intrinsics doc links update.) - rust-lang#78133 (Add some MIR-related regression tests) - rust-lang#78144 (Don't update `entries` in `TypedArena` if T does not need drop) - rust-lang#78145 (Drop unneeded `mut`) - rust-lang#78157 (Remove unused type from librustdoc) Failed merges: r? `@ghost`
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As far as I can tell,
entriesis only used when droppingTypedArenaChunks and their contents. It is already ignored there, if T is notmem::needs_drop, this PR just skips updating it's value.You can see
TypedArenaChunkignoring the entry count in L71. The reasoning is similar to what you can find inDroplessArena.r? @oli-obk