Speed up short key hashing

[dduan]

Use a packed 64-bit hash for keys up to 8 bytes, falling back to FNV for longer keys to reduce hashing work in hot paths.

[github-actions]

Comparing results between 'main' and 'pull_request'

Host 'runnervmh13bl' with 4 'x86_64' processors with 15 GB memory, running:
#18~24.04.1-Ubuntu SMP Sat Jun 28 04:46:03 UTC 2025

TOMLDecoderBenchmarks

Decode toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	67	68	68	68	72	89	222	7229
pull_request	67	68	68	69	72	85	146	7180
Δ	0	0	0	1	0	-4	-76	-49
Improvement %	0	0	0	-1	0	4	34	-49

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	626	626	626	627	627	627	627	7229
pull_request	625	625	625	625	625	625	625	7180
Δ	-1	-1	-1	-2	-2	-2	-2	-49
Improvement %	0	0	0	0	0	0	0	-49

Parse toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ns) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	6151	6283	6331	6383	6455	10135	29195	10000
pull_request	6091	6223	6255	6295	6355	8679	123230	10000
Δ	-60	-60	-76	-88	-100	-1456	94035	0
Improvement %	1	1	1	1	2	14	-322	0

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	9	10	10	10	10	10	10	10000
pull_request	9	10	10	10	10	10	10	10000
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	268	269	269	269	270	270	270	4
pull_request	266	266	268	268	268	268	268	4
Δ	-2	-3	-1	-1	-2	-2	-2	0
Improvement %	1	1	0	0	1	1	1	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	1674	1674	1674	1674	1674	1674	1674	4
pull_request	1674	1674	1674	1674	1674	1674	1674	4
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	8887	8937	8946	8970	9003	9232	9446	111
pull_request	8921	8962	8978	8995	9028	9290	9487	111
Δ	34	25	32	25	25	58	41	0
Improvement %	0	0	0	0	0	-1	0	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	66	66	66	66	66	66	66	111
pull_request	66	66	66	66	66	66	66	111
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

parse GitHub events archive metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	162	163	164	168	168	168	168	7
pull_request	164	165	166	170	176	176	176	6
Δ	2	2	2	2	8	8	8	-1
Improvement %	-1	-1	-1	-1	-5	-5	-5	-1

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	77	77	77	77	77	77	77	7
pull_request	77	77	77	77	77	77	77	6
Δ	0	0	0	0	0	0	0	-1
Improvement %	0	0	0	0	0	0	0	-1

parse canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	16	17	17	17	18	19	19	59
pull_request	16	16	17	17	18	19	19	60
Δ	0	-1	0	0	0	0	0	1
Improvement %	0	6	0	0	0	0	0	1

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	133	134	134	134	134	134	134	59
pull_request	133	134	134	134	134	134	134	60
Δ	0	0	0	0	0	0	0	1
Improvement %	0	0	0	0	0	0	0	1

parse twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	2697	2724	2730	2740	2757	3076	3854	358
pull_request	2718	2738	2753	2765	2777	2980	3347	356
Δ	21	14	23	25	20	-96	-507	-2
Improvement %	-1	-1	-1	-1	-1	3	13	-2

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	1293	1294	1294	1294	1294	1294	1294	358
pull_request	1293	1294	1294	1294	1294	1294	1294	356
Δ	0	0	0	0	0	0	0	-2
Improvement %	0	0	0	0	0	0	0	-2