Optimize for common drop_keep cases in wasmi executor

[Robbepop]

This is a result of an observation that we could speed-up execution of branch and return instructions that keep no values or just a single value upon jump. Especially in the Wasm MVP those two cases are the common ones.

This is take 2 after the first experiment yielded really bad results: #492

[Robbepop]

On my local machine I am observing speed ups up to 10% especially for call intense workloads. Unfortunately our benchmarking CI cannot confirm this right now.

[paritytech-cicd-pr]

BENCHMARKS

	NATIVE			WASMTIME
BENCHMARK	MASTER	PR	DIFF	MASTER	PR	DIFF	WASMTIME OVERHEAD
execute/ count_until	2.36ms	2.19ms	🟢 -8.36%	9.20ms	9.36ms	🔴 1.82%	🔴 327%
execute/ factorial_iterative	1.52µs	1.66µs	🔴 9.41%	3.34µs	3.32µs	⚪ -0.58%	🟡 100%
execute/ factorial_recursive	2.10µs	2.12µs	⚪ 0.80%	4.13µs	4.16µs	⚪ 0.58%	🟡 96%
execute/ fib_iterative	10.58ms	10.04ms	🟢 -5.24%	15.62ms	15.56ms	⚪ -0.24%	🟡 55%
execute/ fib_recursive	17.20ms	19.00ms	🔴 10.86%	39.47ms	38.74ms	🟢 -1.87%	🔴 104%
execute/ global_bump	3.50ms	3.64ms	🔴 4.89%	12.73ms	13.39ms	🔴 4.89%	🔴 268%
execute/ host_calls	33.07µs	33.54µs	⚪ 0.05%	108.36µs	106.68µs	🟢 -1.41%	🔴 218%
execute/ memory_fill	8.19ms	8.61ms	🔴 5.18%	14.75ms	14.82ms	⚪ 0.55%	🟡 72%
execute/ memory_sum	8.28ms	7.91ms	🟢 -5.41%	15.15ms	14.99ms	🟢 -1.14%	🟡 89%
execute/ memory_vec_add	14.79ms	15.14ms	🔴 2.39%	30.11ms	30.36ms	⚪ 0.92%	🟡 100%
execute/ recursive_is_even	2.69ms	2.75ms	🔴 2.13%	6.65ms	6.62ms	⚪ -0.33%	🔴 141%
execute/ recursive_ok	369.29µs	416.49µs	🔴 12.64%	924.43µs	916.21µs	⚪ -0.72%	🔴 120%
execute/ recursive_scan	476.63µs	488.60µs	🔴 2.63%	1.30ms	1.30ms	⚪ 0.33%	🔴 167%
execute/ recursive_trap	37.21µs	43.73µs	🔴 17.78%	96.06µs	97.76µs	🔴 1.85%	🔴 124%
execute/ regex_redux	3.36ms	3.44ms	🔴 2.38%	5.12ms	5.07ms	⚪ -0.80%	🟢 48%
execute/ rev_complement	3.06ms	3.13ms	🔴 2.46%	4.95ms	4.96ms	⚪ 0.23%	🟡 58%
execute/ tiny_keccak	2.62ms	2.63ms	⚪ 0.60%	4.14ms	4.17ms	⚪ 0.61%	🟡 58%
execute/ trunc_f2i	3.51ms	3.60ms	🔴 2.64%	8.97ms	9.12ms	🔴 1.59%	🔴 153%
instantiate/ wasm_kernel	76.87µs	78.16µs	🔴 1.68%	136.80µs	103.29µs	🟢 -24.44%	🟢 32%
translate/ wasm_kernel	6.27ms	6.09ms	⚪ -1.10%	11.77ms	11.77ms	⚪ 0.05%	🟡 93%

Link to pipeline

[codecov-commenter]

Codecov Report

Merging #493 (967fdb8) into master (1fbc2d3) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #493      +/-   ##
==========================================
+ Coverage   79.18%   79.20%   +0.01%     
==========================================
  Files          74       74              
  Lines        6309     6314       +5     
==========================================
+ Hits         4996     5001       +5     
  Misses       1313     1313              

Impacted Files	Coverage Δ
crates/wasmi/src/engine/executor.rs	98.27% <100.00%> (+<0.01%)	⬆️
crates/wasmi/src/engine/stack/values/vref.rs	98.52% <100.00%> (+0.09%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more