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Inline String::into_raw_parts and reuse from_utf16 optimization - #160536

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rust-bors[bot] merged 2 commits into
rust-lang:mainfrom
fereidani:utf16_units
Aug 21, 2026
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Inline String::into_raw_parts and reuse from_utf16 optimization#160536
rust-bors[bot] merged 2 commits into
rust-lang:mainfrom
fereidani:utf16_units

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@fereidani

@fereidani fereidani commented Aug 5, 2026 •
edited by rustbot
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  1. I noticed that comment // This isn't done via collect::<Result<_, _>>() for performance reasons. explicitly states that this approach is wrong, but from_utf16le and from_utf16be are not using the same optimization.

  2. I believe into_raw_parts is missing the #[inline] as any other similar functions in the standard library are marked either with inline or inline(always).

This is also related to #48994; whenever that fix lands, optimizing from_utf16_units will results in these 3 functions getting optimized.

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Aug 5, 2026
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rustbot commented Aug 5, 2026

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r? @clarfonthey

rustbot has assigned @clarfonthey.
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@clarfonthey

clarfonthey commented Aug 21, 2026

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This seems reasonable to me. Thank you!

@bors r+ rollup

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rust-bors Bot commented Aug 21, 2026

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📌 Commit f741ac8 has been approved by clarfonthey

It is now in the queue for this repository.

@rust-bors rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 21, 2026
@jhpratt jhpratt mentioned this pull request Aug 21, 2026
Merged
rust-bors Bot pushed a commit that referenced this pull request Aug 21, 2026
@bors
Auto merge of #161458 - jhpratt:rollup-q1wVzyt, r=jhpratt
a872286 
Rollup of 20 pull requests

Successful merges:

 - #161259 (move some attribute related structs out of rustc_attr_ir)
 - #160853 (delegation: simplify matches on `FnKind`, minor refactorings)
 - #161161 (proc_macro: add support for 16-bit targets)
 - #159899 ( `GenericArgs::types` triage + possible fixes)
 - #160459 (Use attribute parser for `deprecated` attribute checking)
 - #160536 (Inline `String::into_raw_parts` and reuse `from_utf16` optimization)
 - #160563 (Make `BorrowedCursor<'a, T>` covariant in `'a` and drop an indirection)
 - #160595 (Clarify `str::split_at` docs)
 - #160813 (Optimize linked list iterator performance)
 - #161271 (doc: document safety requirements for core WTF-8)
 - #161317 (LLVM 24: configure float-abi via module flag)
 - #161320 (Only suggest `RUST_MIN_STACK` if maybe stack overflow)
 - #161369 (Add regression test for confusing lifetime error message issue)
 - #161393 (Configure LLM policy URL for triagebot)
 - #161403 (splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB)
 - #161409 (Add back `tests/rustdoc-gui/notable-trait.goml` test)
 - #161410 (Fix rustdoc remapping `documentation` scope documentation)
 - #161415 (Update expect messages in path docs to better follow guidelines)
 - #161438 (Change triagebot backport to ping T-libs-fcp)
 - #161442 (Add regression test for dead code on type alias used in impl self type)

Failed merges:

 - #160509 (Remove `RegionExt`; move methods to `Region` in `rustc_type_ir`)
@rust-bors
rust-bors Bot merged commit ca39ddb into rust-lang:main Aug 21, 2026
13 checks passed
@rustbot rustbot added this to the 1.100.0 milestone Aug 21, 2026
rust-bors Bot pushed a commit that referenced this pull request Aug 21, 2026
@bors
Unrolled build for #160536 in rollup 161458
839342e 
Rollup merge of #160536 - fereidani:utf16_units, r=clarfonthey

Inline `String::into_raw_parts` and reuse `from_utf16` optimization

1. I noticed that comment `// This isn't done via collect::<Result<_, _>>() for performance reasons.` explicitly states that this approach is wrong, but `from_utf16le` and `from_utf16be` are not using the same optimization.

2. I believe `into_raw_parts` is missing the `#[inline]` as any other similar functions in the standard library are marked either with `inline` or `inline(always)`.

This is also related to #48994; whenever that fix lands, optimizing `from_utf16_units` will results in these 3 functions getting optimized.
pull Bot pushed a commit to xtqqczze/rust-lang-miri that referenced this pull request Aug 22, 2026
@bors
Auto merge of #161458 - jhpratt:rollup-q1wVzyt, r=jhpratt
b4454c1 
Rollup of 20 pull requests

Successful merges:

 - rust-lang/rust#161259 (move some attribute related structs out of rustc_attr_ir)
 - rust-lang/rust#160853 (delegation: simplify matches on `FnKind`, minor refactorings)
 - rust-lang/rust#161161 (proc_macro: add support for 16-bit targets)
 - rust-lang/rust#159899 ( `GenericArgs::types` triage + possible fixes)
 - rust-lang/rust#160459 (Use attribute parser for `deprecated` attribute checking)
 - rust-lang/rust#160536 (Inline `String::into_raw_parts` and reuse `from_utf16` optimization)
 - rust-lang/rust#160563 (Make `BorrowedCursor<'a, T>` covariant in `'a` and drop an indirection)
 - rust-lang/rust#160595 (Clarify `str::split_at` docs)
 - rust-lang/rust#160813 (Optimize linked list iterator performance)
 - rust-lang/rust#161271 (doc: document safety requirements for core WTF-8)
 - rust-lang/rust#161317 (LLVM 24: configure float-abi via module flag)
 - rust-lang/rust#161320 (Only suggest `RUST_MIN_STACK` if maybe stack overflow)
 - rust-lang/rust#161369 (Add regression test for confusing lifetime error message issue)
 - rust-lang/rust#161393 (Configure LLM policy URL for triagebot)
 - rust-lang/rust#161403 (splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB)
 - rust-lang/rust#161409 (Add back `tests/rustdoc-gui/notable-trait.goml` test)
 - rust-lang/rust#161410 (Fix rustdoc remapping `documentation` scope documentation)
 - rust-lang/rust#161415 (Update expect messages in path docs to better follow guidelines)
 - rust-lang/rust#161438 (Change triagebot backport to ping T-libs-fcp)
 - rust-lang/rust#161442 (Add regression test for dead code on type alias used in impl self type)

Failed merges:

 - rust-lang/rust#160509 (Remove `RegionExt`; move methods to `Region` in `rustc_type_ir`)
malezjaa pushed a commit to malezjaa/rust that referenced this pull request Aug 23, 2026
@bors @malezjaa
Auto merge of rust-lang#161458 - jhpratt:rollup-q1wVzyt, r=jhpratt
b8b3ef3 
Rollup of 20 pull requests

Successful merges:

 - rust-lang#161259 (move some attribute related structs out of rustc_attr_ir)
 - rust-lang#160853 (delegation: simplify matches on `FnKind`, minor refactorings)
 - rust-lang#161161 (proc_macro: add support for 16-bit targets)
 - rust-lang#159899 ( `GenericArgs::types` triage + possible fixes)
 - rust-lang#160459 (Use attribute parser for `deprecated` attribute checking)
 - rust-lang#160536 (Inline `String::into_raw_parts` and reuse `from_utf16` optimization)
 - rust-lang#160563 (Make `BorrowedCursor<'a, T>` covariant in `'a` and drop an indirection)
 - rust-lang#160595 (Clarify `str::split_at` docs)
 - rust-lang#160813 (Optimize linked list iterator performance)
 - rust-lang#161271 (doc: document safety requirements for core WTF-8)
 - rust-lang#161317 (LLVM 24: configure float-abi via module flag)
 - rust-lang#161320 (Only suggest `RUST_MIN_STACK` if maybe stack overflow)
 - rust-lang#161369 (Add regression test for confusing lifetime error message issue)
 - rust-lang#161393 (Configure LLM policy URL for triagebot)
 - rust-lang#161403 (splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB)
 - rust-lang#161409 (Add back `tests/rustdoc-gui/notable-trait.goml` test)
 - rust-lang#161410 (Fix rustdoc remapping `documentation` scope documentation)
 - rust-lang#161415 (Update expect messages in path docs to better follow guidelines)
 - rust-lang#161438 (Change triagebot backport to ping T-libs-fcp)
 - rust-lang#161442 (Add regression test for dead code on type alias used in impl self type)

Failed merges:

 - rust-lang#160509 (Remove `RegionExt`; move methods to `Region` in `rustc_type_ir`)

implement [u8]::split_ascii_whitespace

format

fix
malezjaa pushed a commit to malezjaa/rust that referenced this pull request Aug 23, 2026
@bors @malezjaa
Auto merge of rust-lang#161458 - jhpratt:rollup-q1wVzyt, r=jhpratt
fa79d8f 
Rollup of 20 pull requests

Successful merges:

 - rust-lang#161259 (move some attribute related structs out of rustc_attr_ir)
 - rust-lang#160853 (delegation: simplify matches on `FnKind`, minor refactorings)
 - rust-lang#161161 (proc_macro: add support for 16-bit targets)
 - rust-lang#159899 ( `GenericArgs::types` triage + possible fixes)
 - rust-lang#160459 (Use attribute parser for `deprecated` attribute checking)
 - rust-lang#160536 (Inline `String::into_raw_parts` and reuse `from_utf16` optimization)
 - rust-lang#160563 (Make `BorrowedCursor<'a, T>` covariant in `'a` and drop an indirection)
 - rust-lang#160595 (Clarify `str::split_at` docs)
 - rust-lang#160813 (Optimize linked list iterator performance)
 - rust-lang#161271 (doc: document safety requirements for core WTF-8)
 - rust-lang#161317 (LLVM 24: configure float-abi via module flag)
 - rust-lang#161320 (Only suggest `RUST_MIN_STACK` if maybe stack overflow)
 - rust-lang#161369 (Add regression test for confusing lifetime error message issue)
 - rust-lang#161393 (Configure LLM policy URL for triagebot)
 - rust-lang#161403 (splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB)
 - rust-lang#161409 (Add back `tests/rustdoc-gui/notable-trait.goml` test)
 - rust-lang#161410 (Fix rustdoc remapping `documentation` scope documentation)
 - rust-lang#161415 (Update expect messages in path docs to better follow guidelines)
 - rust-lang#161438 (Change triagebot backport to ping T-libs-fcp)
 - rust-lang#161442 (Add regression test for dead code on type alias used in impl self type)

Failed merges:

 - rust-lang#160509 (Remove `RegionExt`; move methods to `Region` in `rustc_type_ir`)

implement [u8]::split_ascii_whitespace

format

fix
@rust-timer

rust-timer commented Sep 14, 2026

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Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (839342e): comparison URL.

Overall result: no relevant changes - BENCHMARK(S) FAILED

@rustbot label: -perf-regression

❗ ❗ ❗ ❗ ❗
Warning ⚠️: The following benchmark(s) failed to build:

  • Job failure

❗ ❗ ❗ ❗ ❗

Instruction count

This perf run didn't have relevant results for this metric.

Max RSS (memory usage)

This perf run didn't have relevant results for this metric.

Cycles

This perf run didn't have relevant results for this metric.

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: missing data
Artifact size: 400.02 MiB -> 400.14 MiB (0.03%)

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