optimize next_chunk impls for Filter and FilterMap

[the8472]

OLD:

benchmarks:
    iter::bench_next_chunk_filter_even                 104.00ns/iter  +/- 1.00ns
    iter::bench_next_chunk_filter_map_even             101.00ns/iter  +/- 1.00ns
    iter::bench_next_chunk_filter_map_mostly_false       1.99µs/iter +/- 10.00ns
    iter::bench_next_chunk_filter_map_predictably_true  56.00ns/iter  +/- 0.00ns
    iter::bench_next_chunk_filter_mostly_false           1.15µs/iter  +/- 6.00ns
    iter::bench_next_chunk_filter_predictably_true      65.00ns/iter  +/- 1.00ns


NEW:

benchmarks:
    iter::bench_next_chunk_filter_even                  42.00ns/iter  +/- 0.00ns
    iter::bench_next_chunk_filter_map_even              49.00ns/iter  +/- 1.00ns
    iter::bench_next_chunk_filter_map_mostly_false     501.00ns/iter  +/- 3.00ns
    iter::bench_next_chunk_filter_map_predictably_true  31.00ns/iter  +/- 0.00ns
    iter::bench_next_chunk_filter_mostly_false         534.00ns/iter +/- 13.00ns
    iter::bench_next_chunk_filter_predictably_true      28.00ns/iter  +/- 1.00ns

[rustbot]

r? @thomcc

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[thomcc]

Nice improvement. The code is pretty complex, but seems correct and the benchmarks definitely justify it.

@bors r+ rollup=never

[bors]

📌 Commit b40896d has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit b40896d with merge 7ca94f2...

[bors]

☀️ Test successful - checks-actions
Approved by: thomcc
Pushing 7ca94f2 to master...

[rust-timer]

Finished benchmarking commit (7ca94f2): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	1
All ❌✅ (primary)	-	-	0

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-	-	0

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)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 644.637s -> 643.892s (-0.12%)