Remove `box_new` intrinsic by cjgillot · Pull Request #147862 · rust-lang/rust

cjgillot · 2025-10-18T20:53:12Z

Draft to gauge the perf effect of the added move.

r? @ghost

cjgillot · 2025-10-18T20:53:44Z

@bors try @rust-timer queue

Remove `box_new` intrinsic

rust-bors · 2025-10-18T21:16:22Z

💔 Test for 9c292f4 failed: CI. Failed jobs:

try - dist-x86_64-linux (web logs, extended logs)

cjgillot · 2025-10-18T23:59:54Z

@bors try @rust-timer queue

Remove `box_new` intrinsic

rust-bors · 2025-10-19T02:15:48Z

☀️ Try build successful (CI)
Build commit: d4e488f (d4e488fd1cbd56d5ce97af9226cb30c35f3d8207, parent: 6380899f32599ea25615d4ccd708d0e8da652b0c)

rust-timer · 2025-10-19T03:27:08Z

Finished benchmarking commit (d4e488f): 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)	0.8%	[0.2%, 2.6%]	52
Regressions ❌ (secondary)	4.0%	[0.2%, 23.0%]	53
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.1%]	5
All ❌✅ (primary)	0.8%	[0.2%, 2.6%]	52

Max RSS (memory usage)

Results (primary 1.5%, secondary 4.4%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.4%, 2.1%]	6
Regressions ❌ (secondary)	4.4%	[2.3%, 7.0%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[0.4%, 2.1%]	6

Cycles

Results (primary 2.5%, secondary 4.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.2%, 3.0%]	4
Regressions ❌ (secondary)	7.2%	[1.9%, 24.4%]	25
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.9%	[-9.8%, -2.7%]	7
All ❌✅ (primary)	2.5%	[2.2%, 3.0%]	4

Binary size

Results (primary 1.2%, secondary 9.7%)

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

	mean	range	count
Regressions ❌ (primary)	1.4%	[0.0%, 6.1%]	76
Regressions ❌ (secondary)	10.5%	[0.5%, 45.5%]	36
Improvements ✅ (primary)	-0.1%	[-0.3%, -0.0%]	10
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	3
All ❌✅ (primary)	1.2%	[-0.3%, 6.1%]	86

Bootstrap: 471.955s -> 472.273s (0.07%)
Artifact size: 390.54 MiB -> 390.72 MiB (0.05%)

bors · 2025-10-19T11:20:18Z

☔ The latest upstream changes (presumably #147847) made this pull request unmergeable. Please resolve the merge conflicts.

cjgillot · 2025-10-19T23:19:36Z

@bors try @rust-timer queue

Remove `box_new` intrinsic

rust-bors · 2025-10-20T01:35:46Z

☀️ Try build successful (CI)
Build commit: 9203cf8 (9203cf8b58f999e8739690665622eca20e4cd85e, parent: 4ddbb6051271237f4192333e06b8129148995eef)

rust-timer · 2025-10-20T02:46:21Z

Finished benchmarking commit (9203cf8): comparison URL.

Overall result: ❌ regressions - 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)	0.8%	[0.2%, 2.8%]	58
Regressions ❌ (secondary)	3.8%	[0.1%, 22.2%]	55
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.1%]	5
All ❌✅ (primary)	0.8%	[0.2%, 2.8%]	58

Max RSS (memory usage)

Results (primary 1.3%, secondary 0.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[0.6%, 4.7%]	8
Regressions ❌ (secondary)	3.4%	[2.1%, 7.4%]	14
Improvements ✅ (primary)	-2.7%	[-3.1%, -2.3%]	2
Improvements ✅ (secondary)	-3.9%	[-4.5%, -3.1%]	8
All ❌✅ (primary)	1.3%	[-3.1%, 4.7%]	10

Cycles

Results (primary 2.7%, secondary 4.1%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[1.8%, 3.5%]	2
Regressions ❌ (secondary)	6.1%	[1.2%, 23.9%]	30
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.6%	[-8.6%, -1.7%]	7
All ❌✅ (primary)	2.7%	[1.8%, 3.5%]	2

Binary size

Results (primary 1.2%, secondary 8.7%)

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

	mean	range	count
Regressions ❌ (primary)	1.3%	[0.0%, 6.4%]	76
Regressions ❌ (secondary)	9.4%	[0.4%, 43.8%]	39
Improvements ✅ (primary)	-0.1%	[-0.3%, -0.0%]	10
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	3
All ❌✅ (primary)	1.2%	[-0.3%, 6.4%]	86

Bootstrap: 471.841s -> 473.148s (0.28%)
Artifact size: 388.67 MiB -> 390.76 MiB (0.54%)

bors · 2025-10-22T14:43:11Z

☔ The latest upstream changes (presumably #147687) made this pull request unmergeable. Please resolve the merge conflicts.

rust-log-analyzer · 2025-10-23T01:25:34Z

The job aarch64-gnu-llvm-20-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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

---- [ui] tests/ui/limits/issue-17913.rs stdout ----
Saved the actual stderr to `/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/limits/issue-17913/issue-17913.stderr`
diff of stderr:

5 note: inside `std::mem::size_of::<[&usize; usize::MAX]>`
6   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
7 
+ note: the above error was encountered while instantiating `fn Box::<[&usize; usize::MAX]>::new_in`
+   --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
+ 
8 error[E0080]: values of the type `[&usize; usize::MAX]` are too big for the target architecture
9   --> $SRC_DIR/core/src/ptr/alignment.rs:LL:COL
10    |

Note: some mismatched output was normalized before being compared
- note: the above error was encountered while instantiating `fn Box::<[&usize; 17293822569102704640]>::new_in`
-   --> /rustc/FAKE_PREFIX/library/alloc/src/boxed.rs:253:16
+ note: the above error was encountered while instantiating `fn Box::<[&usize; usize::MAX]>::new_in`
+   --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
+ 


The actual stderr differed from the expected stderr
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args limits/issue-17913.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/limits/issue-17913.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/limits/issue-17913" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error[E0080]: values of the type `[&usize; 17293822569102704640]` are too big for the target architecture
##[error]  --> /rustc/FAKE_PREFIX/library/core/src/mem/mod.rs:1266:26
   |
   = note: evaluation of `<[&usize; 17293822569102704640] as std::mem::SizedTypeProperties>::IS_ZST` failed inside this call
note: inside `std::mem::size_of::<[&usize; 17293822569102704640]>`
  --> /rustc/FAKE_PREFIX/library/core/src/mem/mod.rs:336:5

note: the above error was encountered while instantiating `fn Box::<[&usize; 17293822569102704640]>::new_in`
  --> /rustc/FAKE_PREFIX/library/alloc/src/boxed.rs:253:16

error[E0080]: values of the type `[&usize; 17293822569102704640]` are too big for the target architecture
##[error]  --> /rustc/FAKE_PREFIX/library/core/src/ptr/alignment.rs:50:32
   |
   = note: evaluation of `std::ptr::Alignment::of::<std::mem::MaybeUninit<[&usize; 17293822569102704640]>>::{constant#0}` failed inside this call
note: inside `std::mem::align_of::<MaybeUninit<[&usize; 17293822569102704640]>>`
  --> /rustc/FAKE_PREFIX/library/core/src/mem/mod.rs:491:5

note: the above error was encountered while instantiating `fn Box::<[&usize; 17293822569102704640]>::try_new_uninit_in`
  --> /rustc/FAKE_PREFIX/library/alloc/src/boxed.rs:470:15

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0080`.

bors · 2025-10-23T09:45:55Z

☔ The latest upstream changes (presumably #147793) made this pull request unmergeable. Please resolve the merge conflicts.