Simplify size/align_of_val<T: Sized> to size/align_of<T> instead

[scottmcm]

This is relevant to things like Box<[u8; 1024]> where the drop looks at the size_of_val (since obviously it might be DST in general) but where we don't actually need to do that since it's always that same value for the Sized type.

(Equivalent to #152681, but flipped in the rebase so it can land before #152641 instead of depending on it.)

[scottmcm]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 85c1367 (85c13679ed60d98f876a8f50c0b7505fb1ea3260, parent: 139651428df86cf88443295542c12ea617cbb587)

[rust-timer]

Finished benchmarking commit (85c1367): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-0.5%	[-0.5%, -0.5%]	2
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	1

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results (primary -2.4%, secondary 2.7%)

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)	2.7%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-2.4%	[-2.8%, -2.0%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.4%	[-2.8%, -2.0%]	2

Binary size

Results (primary -0.3%)

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)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.6%, -0.0%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.6%, -0.0%]	2

Bootstrap: 482.657s -> 485.908s (0.67%)
Artifact size: 397.96 MiB -> 397.86 MiB (-0.03%)

[scottmcm]

r? @cjgillot

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[cjgillot]

@bors r+

[rust-bors]

📌 Commit 649e027 has been approved by cjgillot

It is now in the queue for this repository.