Have the alignment intrinsics return ptr::Alignment directly

[scottmcm]

View all comments

Follow-up to #152605

Notably, a common case of align_of_val is to put it in Layout for allocator calls, so might as well have it just be an Alignment already to avoid the extra transmute.

No changes to rustc_const_eval because that's already writing a Scalar into a place, which does what we need since ptr::Alignment is repr(transparent) to a repr(usize).

[scottmcm]

I don't think anything in here should be more expensive, but in case...
@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 7121e2d (7121e2d136c08d87b9a5f3717916d4bec53334bb, parent: 2219766af622ad1f051ca96ae40650106b1bd9bd)

[rust-timer]

Finished benchmarking commit (7121e2d): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	4.5%	[0.2%, 16.2%]	4
Regressions ❌ (secondary)	0.6%	[0.3%, 0.9%]	2
Improvements ✅ (primary)	-0.4%	[-1.2%, -0.2%]	7
Improvements ✅ (secondary)	-1.0%	[-3.3%, -0.1%]	22
All ❌✅ (primary)	1.4%	[-1.2%, 16.2%]	11

Max RSS (memory usage)

Results (primary -3.9%, secondary 2.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	5.2%	[1.3%, 9.0%]	2
Improvements ✅ (primary)	-3.9%	[-5.4%, -1.6%]	5
Improvements ✅ (secondary)	-1.7%	[-1.7%, -1.7%]	1
All ❌✅ (primary)	-3.9%	[-5.4%, -1.6%]	5

Cycles

Results (primary 11.9%, secondary -1.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	11.9%	[11.9%, 11.9%]	1
Regressions ❌ (secondary)	4.0%	[4.0%, 4.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.1%	[-4.8%, -2.2%]	4
All ❌✅ (primary)	11.9%	[11.9%, 11.9%]	1

Binary size

Results (primary 0.3%, secondary -0.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.0%, 1.4%]	14
Regressions ❌ (secondary)	0.2%	[0.0%, 0.4%]	8
Improvements ✅ (primary)	-0.5%	[-0.7%, -0.1%]	4
Improvements ✅ (secondary)	-1.3%	[-2.2%, -0.4%]	17
All ❌✅ (primary)	0.3%	[-0.7%, 1.4%]	18

Bootstrap: 485.129s -> 482.811s (-0.48%)
Artifact size: 398.01 MiB -> 396.01 MiB (-0.50%)

[scottmcm]

r? @cjgillot
@rustbot ready

Those perf results are, I think, overall good. They're mostly green, and include things like -28% on rustc_mir_build, which is impressively good.

The one big regression is one of the LTO sub-jobs just going nuts for some reason:

TBH I'm not sure how this could possibly cause that. It's not the kind of "oh, inlining reshuffled everything" that we normally see from MIR changes. None of the other variants of that code show any material impact, and it's just so different from the results on everything else.

[rustbot]

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

This PR modifies tests/auxiliary/minicore.rs.

cc @jieyouxu

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

[scottmcm]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: a606286 (a60628660b41f808eeed74cac626bfc49b619ef6, parent: 4a997eeefbb8cf41617324bb6d08c72171c614e2)

[rust-timer]

Finished benchmarking commit (a606286): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	15.9%	[15.9%, 15.9%]	1
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	2
Improvements ✅ (primary)	-0.4%	[-0.5%, -0.3%]	3
Improvements ✅ (secondary)	-1.3%	[-3.9%, -0.2%]	17
All ❌✅ (primary)	3.7%	[-0.5%, 15.9%]	4

Max RSS (memory usage)

Results (primary -0.0%, secondary -3.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.3%, 2.7%]	3
Regressions ❌ (secondary)	0.9%	[0.9%, 0.9%]	1
Improvements ✅ (primary)	-2.0%	[-2.7%, -0.8%]	4
Improvements ✅ (secondary)	-4.9%	[-9.3%, -2.6%]	3
All ❌✅ (primary)	-0.0%	[-2.7%, 2.7%]	7

Cycles

Results (primary 11.9%, secondary -3.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	11.9%	[11.9%, 11.9%]	1
Regressions ❌ (secondary)	3.2%	[3.2%, 3.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.0%	[-5.1%, -2.4%]	7
All ❌✅ (primary)	11.9%	[11.9%, 11.9%]	1

Binary size

Results (primary 0.2%, secondary -0.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.0%, 1.4%]	26
Regressions ❌ (secondary)	0.2%	[0.0%, 0.4%]	12
Improvements ✅ (primary)	-0.1%	[-0.4%, -0.0%]	16
Improvements ✅ (secondary)	-1.0%	[-2.6%, -0.0%]	18
All ❌✅ (primary)	0.2%	[-0.4%, 1.4%]	42

Bootstrap: 497.359s -> 498.748s (0.28%)
Artifact size: 397.13 MiB -> 397.19 MiB (0.02%)

[scottmcm]

@bors try @rust-timer queue

[rust-log-analyzer]

The job x86_64-gnu-miri failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

tests/pass/shims/x86/rounding-error.rs ... ok
tests/pass/shims/x86/intrinsics-x86-gfni.rs ... ok

FAILED TEST: tests/pass/alloc-access-tracking.rs
command: MIRI_ENV_VAR_TEST="0" MIRI_TEMP="/tmp/miri-uitest-8fGvbH" RUST_BACKTRACE="1" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/miri" "--error-format=json" "--sysroot=/checkout/obj/build/x86_64-unknown-linux-gnu/miri-sysroot" "-Dwarnings" "-Dunused" "-Ainternal_features" "-Zui-testing" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/tmp/miri_ui/0/tests/pass" "tests/pass/alloc-access-tracking.rs" "-Zmiri-track-alloc-accesses" "--edition" "2021"

error: actual output differed from expected
Execute `./miri test --bless` to update `tests/pass/alloc-access-tracking.stderr` to the actual output
--- tests/pass/alloc-access-tracking.stderr
+++ <stderr output>
---
   |
LL |         utils::miri_track_alloc(ptr);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ tracking was triggered here

note: write access at alloc199[0x0..0x1]
  --> tests/pass/alloc-access-tracking.rs:11:9
   |
LL |         *ptr = 42; // Crucially, only a write is printed here, no read!
   |         ^^^^^^^^^ tracking was triggered here

note: read access at alloc199[0x0..0x1]
  --> tests/pass/alloc-access-tracking.rs:12:9
   |
LL |         assert_eq!(*ptr, 42);
   |         ^^^^^^^^^^^^^^^^^^^^ tracking was triggered here

---
   |
   = note: stack backtrace:
           0: <std::boxed::Box<std::mem::MaybeUninit<[u8; 123]>> as std::ops::Drop>::drop
               at /checkout/library/alloc/src/boxed.rs:1956:17: 1956:79
           1: std::ptr::drop_glue::<std::boxed::Box<std::mem::MaybeUninit<[u8; 123]>>> - shim(Some(std::boxed::Box<std::mem::MaybeUninit<[u8; 123]>>))
               at /checkout/library/core/src/ptr/mod.rs:825:1: 827:25
           2: main
               at tests/pass/alloc-access-tracking.rs:13:5: 13:6


---
   |
LL |         utils::miri_track_alloc(ptr);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ tracking was triggered here

note: write access at alloc199[0x0..0x1]
  --> tests/pass/alloc-access-tracking.rs:11:9
   |
LL |         *ptr = 42; // Crucially, only a write is printed here, no read!
   |         ^^^^^^^^^ tracking was triggered here

note: read access at alloc199[0x0..0x1]
  --> tests/pass/alloc-access-tracking.rs:12:9
   |
LL |         assert_eq!(*ptr, 42);
   |         ^^^^^^^^^^^^^^^^^^^^ tracking was triggered here

---
   |
   = note: stack backtrace:
           0: <std::boxed::Box<std::mem::MaybeUninit<[u8; 123]>> as std::ops::Drop>::drop
               at /checkout/library/alloc/src/boxed.rs:1956:17: 1956:79
           1: std::ptr::drop_glue::<std::boxed::Box<std::mem::MaybeUninit<[u8; 123]>>> - shim(Some(std::boxed::Box<std::mem::MaybeUninit<[u8; 123]>>))
               at /checkout/library/core/src/ptr/mod.rs:825:1: 827:25
           2: main
               at tests/pass/alloc-access-tracking.rs:13:5: 13:6


---
Location:
   /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ui_test-0.30.4/src/lib.rs:365

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   1: <color_eyre[3baf1ac4a67c392b]::config::EyreHook>::into_eyre_hook::{closure#0}<unknown>
      at <unknown source file>:<unknown line>
   2: eyre[750f75771dd51b5c]::capture_handler<unknown>
      at <unknown source file>:<unknown line>
   3: eyre[750f75771dd51b5c]::private::format_err<unknown>
      at <unknown source file>:<unknown line>
   4: ui_test[2db925eb1bf77098]::run_tests_generic::<ui_test[2db925eb1bf77098]::default_file_filter, ui[85ef28d17faeaf69]::run_tests::{closure#1}, alloc[6f3730ed6c509d98]::boxed::Box<dyn ui_test[2db925eb1bf77098]::status_emitter::StatusEmitter>><unknown>
      at <unknown source file>:<unknown line>
   5: ui[85ef28d17faeaf69]::ui<unknown>
      at <unknown source file>:<unknown line>
   6: ui[85ef28d17faeaf69]::main<unknown>
      at <unknown source file>:<unknown line>
   7: std[ce2e4a3fcfbc8ce7]::sys::backtrace::__rust_begin_short_backtrace::<fn() -> core[1f398f8c6d30aea1]::result::Result<(), eyre[750f75771dd51b5c]::Report>, core[1f398f8c6d30aea1]::result::Result<(), eyre[750f75771dd51b5c]::Report>><unknown>
      at <unknown source file>:<unknown line>
   8: std[ce2e4a3fcfbc8ce7]::rt::lang_start::<core[1f398f8c6d30aea1]::result::Result<(), eyre[750f75771dd51b5c]::Report>>::{closure#0}<unknown>
      at <unknown source file>:<unknown line>
   9: std[ce2e4a3fcfbc8ce7]::rt::lang_start_internal<unknown>
      at <unknown source file>:<unknown line>
  10: main<unknown>
      at <unknown source file>:<unknown line>
  11: __libc_start_main<unknown>
      at <unknown source file>:<unknown line>
  12: _start<unknown>
      at <unknown source file>:<unknown line>

Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
Run with RUST_BACKTRACE=full to include source snippets.
error: test failed, to rerun pass `--test ui`

Caused by:
  process didn't exit successfully: `/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/release/deps/ui-c1d1550a3ddadc4f` (exit status: 1)
Bootstrap failed while executing `test --stage 2 src/tools/miri src/tools/miri/cargo-miri`
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo test -Zwarnings --target x86_64-unknown-linux-gnu -Zbinary-dep-depinfo -j 4 -Zroot-dir=/checkout --locked --color=always --profile=release --manifest-path /checkout/src/tools/miri/Cargo.toml -- [workdir=/checkout]` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:191:21
Executed at: src/bootstrap/src/core/build_steps/test.rs:740:19

--- BACKTRACE vvv
   0: <bootstrap::utils::exec::DeferredCommand>::finish_process
             at /checkout/src/bootstrap/src/utils/exec.rs:939:17
   1: <bootstrap::utils::exec::DeferredCommand>::wait_for_output::<&bootstrap::utils::exec::ExecutionContext>
             at /checkout/src/bootstrap/src/utils/exec.rs:831:21
   2: <bootstrap::utils::exec::ExecutionContext>::run
             at /checkout/src/bootstrap/src/utils/exec.rs:741:45
   3: <bootstrap::utils::exec::BootstrapCommand>::run::<&bootstrap::core::builder::Builder>
             at /checkout/src/bootstrap/src/utils/exec.rs:339:27
   4: <bootstrap::core::build_steps::test::Miri as bootstrap::core::builder::Step>::run
             at /checkout/src/bootstrap/src/core/build_steps/test.rs:740:19
   5: <bootstrap::core::builder::Builder>::ensure::<bootstrap::core::build_steps::test::Miri>
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1595:36
   6: <bootstrap::core::build_steps::test::Miri as bootstrap::core::builder::Step>::make_run
             at /checkout/src/bootstrap/src/core/build_steps/test.rs:666:21
   7: <bootstrap::core::builder::StepDescription>::maybe_run
             at /checkout/src/bootstrap/src/core/builder/mod.rs:476:13
   8: bootstrap::core::builder::cli_paths::match_paths_to_steps_and_run
             at /checkout/src/bootstrap/src/core/builder/cli_paths.rs:232:18
   9: <bootstrap::core::builder::Builder>::run_step_descriptions
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1138:9
  10: <bootstrap::core::builder::Builder>::execute_cli
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1117:14
  11: <bootstrap::Build>::build
             at /checkout/src/bootstrap/src/lib.rs:803:25
  12: bootstrap::main
             at /checkout/src/bootstrap/src/bin/main.rs:130:11
  13: <fn() as core::ops::function::FnOnce<()>>::call_once
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/ops/function.rs:250:5
  14: std::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/sys/backtrace.rs:166:18
  15: std::rt::lang_start::<()>::{closure#0}
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/rt.rs:206:18
  16: <&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe as core::ops::function::FnOnce<()>>::call_once
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/core/src/ops/function.rs:287:21
  17: std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:581:40
  18: std::panicking::catch_unwind::<i32, &dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:544:19
  19: std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe, i32>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panic.rs:359:14
  20: std::rt::lang_start_internal::{closure#0}
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/rt.rs:175:24
  21: std::panicking::catch_unwind::do_call::<std::rt::lang_start_internal::{closure#0}, isize>
             at /rustc/ef0fb8a2563200e322fa4419f09f65a63742038c/library/std/src/panicking.rs:581:40
---
  28: __libc_start_main
  29: _start


Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:48:29
  local time: Sun May 10 06:01:39 UTC 2026
  network time: Sun, 10 May 2026 06:01:39 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"

[rust-bors]

☀️ Try build successful (CI)
Build commit: a1b0fb1 (a1b0fb110184ac3bacbafba05300db9eccadb311, parent: ce89c898570852a1bb441d77570596e50bf362c2)

[rust-timer]

Finished benchmarking commit (a1b0fb1): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	8.2%	[0.1%, 16.3%]	2
Regressions ❌ (secondary)	0.1%	[0.1%, 0.2%]	5
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	2
Improvements ✅ (secondary)	-1.1%	[-3.9%, -0.1%]	19
All ❌✅ (primary)	3.9%	[-0.4%, 16.3%]	4

Max RSS (memory usage)

Results (primary 0.4%, secondary -1.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	5.3%	[2.3%, 10.2%]	3
Regressions ❌ (secondary)	1.7%	[0.9%, 2.4%]	2
Improvements ✅ (primary)	-2.5%	[-3.7%, -1.0%]	5
Improvements ✅ (secondary)	-8.8%	[-8.8%, -8.8%]	1
All ❌✅ (primary)	0.4%	[-3.7%, 10.2%]	8

Cycles

Results (primary 12.1%, secondary -1.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	12.1%	[12.1%, 12.1%]	1
Regressions ❌ (secondary)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-4.5%, -1.2%]	6
All ❌✅ (primary)	12.1%	[12.1%, 12.1%]	1

Binary size

Results (primary 0.2%, secondary -0.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.0%, 1.4%]	34
Regressions ❌ (secondary)	0.2%	[0.0%, 0.4%]	12
Improvements ✅ (primary)	-0.2%	[-0.6%, -0.0%]	16
Improvements ✅ (secondary)	-1.0%	[-2.6%, -0.0%]	19
All ❌✅ (primary)	0.2%	[-0.6%, 1.4%]	50

Bootstrap: 498.161s -> 498.108s (-0.01%)
Artifact size: 397.12 MiB -> 397.26 MiB (0.04%)