Guillaume Gomez b917753d79 Rollup merge of #120116 - the8472:only-same-alignments, r=cuviper ... Remove alignment-changing in-place collect This removes the alignment-changing in-place collect optimization introduced in #110353 Currently stable users can't benefit from the optimization because GlobaAlloc doesn't support alignment-changing realloc and neither do most posix allocators. So in practice it has a negative impact on performance. Explanation from https://github.com/rust-lang/rust/issues/120091#issuecomment-1899071681: > > You mention that in case of alignment mismatch -- when the new alignment is less than the old -- the implementation calls `mremap`. > > I was trying to note that this isn't really the case in practice, due to the semantics of Rust's allocator APIs. The only use of the allocator within the `in_place_collect` implementation itself is [a call to `Allocator::shrink()`](db7125f008/library/alloc/src/vec/in_place_collect.rs (L299-L303)), which per its documentation [allows decreasing the required alignment](https://doc.rust-lang.org/1.75.0/core/alloc/trait.Allocator.html). However, in stable Rust, the only available `Allocator` is [`Global`](https://doc.rust-lang.org/1.75.0/alloc/alloc/struct.Global.html), which delegates to the registered `GlobalAlloc`. Since `GlobalAlloc::realloc()` [cannot change the required alignment](https://doc.rust-lang.org/1.75.0/core/alloc/trait.GlobalAlloc.html#method.realloc), the implementation of [`<Global as Allocator>::shrink()`](db7125f008/library/alloc/src/alloc.rs (L280-L321)) must fall back to creating a brand-new allocation, `memcpy`ing the data into it, and freeing the old allocation, whenever the alignment doesn't remain exactly the same. > > Therefore, the underlying allocator, provided by libc or some other source, has no opportunity to internally `mremap()` the data when the alignment is changed, since it has no way of knowing that the allocation is the same.		2024-01-20 20:06:35 +01:00
..
alloc	Rollup merge of #120116 - the8472:only-same-alignments, r=cuviper	2024-01-20 20:06:35 +01:00
backtrace@6145fe6bac	Update backtrace submodule	2023-11-21 16:33:42 +01:00
core	Rollup merge of #118799 - GKFX:stabilize-simple-offsetof, r=wesleywiser	2024-01-20 09:37:26 +01:00
panic_abort	add teeos std impl	2023-12-07 10:33:03 +08:00
panic_unwind	Update test for E0796 and static_mut_ref lint	2024-01-07 17:29:25 +03:00
portable-simd	Fix target_feature config in portable-simd	2023-12-14 14:50:32 +01:00
proc_macro	proc_macro_c_str_literals: Implement Literal::c_string constructor	2024-01-16 13:27:58 -08:00
profiler_builtins	Bump cfg(bootstrap)	2023-08-23 20:05:14 -04:00
rtstartup	library: Fix warnings in rtstartup	2024-01-06 01:32:03 +03:00
rustc-std-workspace-alloc	Replace libstd, libcore, liballoc in line comments.	2022-12-30 14:00:42 +01:00
rustc-std-workspace-core
rustc-std-workspace-std
std	Rollup merge of #120150 - Jules-Bertholet:stabilize-round-ties-even, r=cuviper	2024-01-20 09:37:29 +01:00
stdarch@f4528dd6e8	Bump stdarch submodule	2023-10-12 11:11:29 +02:00
sysroot	Expose compiler-builtins-weak-intrinsics feature for -Zbuild-std	2023-06-23 11:15:34 +01:00
test	Auto merge of #118548 - Enselic:bench-padding, r=thomcc,ChrisDenton	2024-01-12 05:06:03 +00:00
unwind	Enable Static Builds for FreeBSD	2024-01-11 15:26:16 +00:00