Merge two different equality specialization traits in core

[scottmcm]

Arrays and slices each had their own version of this, without a matching set of impls.

Merge them into one (still-pub(crate)) cmp::BytewiseEq trait, so we can stop doing all these things twice.

And that means that the [T]::eq → memcmp specialization picks up a bunch of types where that previously only worked for arrays, so examples like https://rust.godbolt.org/z/KjsG8MGGT will use it now instead of emitting loops.

r? the8472

[scottmcm]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 17eb9a4119fa8a997e23a9550aa4c61a32448c96 with merge 9c05d441ef24374b0550066c86e1aaa9c88bb046...

[bors]

☀️ Try build successful - checks-actions
Build commit: 9c05d441ef24374b0550066c86e1aaa9c88bb046 (9c05d441ef24374b0550066c86e1aaa9c88bb046)

[bors]

☀️ Try build successful - checks-actions
Build commit: 9c05d441ef24374b0550066c86e1aaa9c88bb046 (9c05d441ef24374b0550066c86e1aaa9c88bb046)

[rust-timer]

Finished benchmarking commit (9c05d441ef24374b0550066c86e1aaa9c88bb046): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

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

Instruction count

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

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.3%	[-3.5%, -3.1%]	2
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-2.0%	[-2.0%, -2.0%]	1
All ❌✅ (primary)	-2.5%	[-2.5%, -2.5%]	1

[the8472]

@bors r+

[bors]

📌 Commit 6e74bd72ffe5746d0d06c3c4bc9b7473f15926f5 has been approved by the8472

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6e74bd72ffe5746d0d06c3c4bc9b7473f15926f5 with merge 57b9057b23a1f72d33865c45b4b204f94cd25096...

[bors]

💔 Test failed - checks-actions

[scottmcm]

@bors r-

Looks like the noundef flag isn't always there in calls. Will fix.

@rustbot author

[bors]

⌛ Testing commit a6fe3a067f52cd65d5319322849957524a4c1ae9 with merge eed0ee1c58e10efdd617800c5e0c9043eba8df4b...

[bors]

💔 Test failed - checks-actions

[scottmcm]

@bors retry SSL read failure installing awscli

curl: (56) OpenSSL SSL_read: Connection reset by peer, errno 104
tar: Unexpected EOF in archive
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now

[bors]

⌛ Testing commit a6fe3a067f52cd65d5319322849957524a4c1ae9 with merge ac25a0161f301c029fba11896272744c0799b612...

[bors]

💔 Test failed - checks-actions

[scottmcm]

Oh, weird, bcmp doesn't get noundef on its arguments.

@bors r=the8472

[bors]

📌 Commit 44eec1d has been approved by the8472

It is now in the queue for this repository.

[bors]

⌛ Testing commit 44eec1d with merge 0b4ba4c...

[bors]

☀️ Test successful - checks-actions
Approved by: the8472
Pushing 0b4ba4c to master...

[rust-timer]

Finished benchmarking commit (0b4ba4c): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.7%	[1.4%, 2.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

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