Remove no-op reinterpret wasmi instructions

[Robbepop]

This removes the 4 reinterpret wasmi bytecode instructions since they are doing nothing at runtime anyways.
Turns out that for some weird reason removing those 4 instructions significantly regresses performance of the wasmi interpreter ...
Until this is fixed or we know why that happens I won't merge this PR.

[paritytech-cicd-pr]

BENCHMARKS

	NATIVE			WASMTIME
BENCHMARK	MASTER	PR	DIFF	MASTER	PR	DIFF	WASMTIME OVERHEAD
execute/ bare_call_0	1.23ms	1.20ms	🟢 -1.98%	902.71µs	908.39µs	🔴 0.65%	🟢 -25%
execute/ bare_call_0/typed	652.44µs	651.51µs	⚪ 0.02%	389.28µs	408.21µs	🔴 4.85%	🟢 -37%
execute/ bare_call_1	1.33ms	1.32ms	🟢 -0.73%	1.11ms	1.22ms	🔴 10.07%	🟢 -8%
execute/ bare_call_16	3.07ms	2.85ms	🟢 -7.35%	4.60ms	4.64ms	⚪ 0.07%	🟡 63%
execute/ bare_call_16/typed	1.53ms	1.36ms	🟢 -11.26%	2.00ms	2.02ms	⚪ 0.68%	🟢 48%
execute/ bare_call_1/typed	776.18µs	764.30µs	🟢 -1.43%	699.57µs	697.45µs	⚪ -0.45%	🟢 -9%
execute/ bare_call_4	1.65ms	1.64ms	🟢 -0.70%	1.72ms	1.75ms	🔴 1.56%	🟢 7%
execute/ bare_call_4/typed	876.78µs	857.93µs	🟢 -2.09%	824.43µs	802.98µs	🟢 -2.70%	🟢 -6%
execute/ br_table	830.81µs	890.46µs	⚪ 5.23%	878.53µs	920.41µs	🔴 4.49%	🟢 3%
execute/ count_until	1.15ms	772.43µs	🟢 -33.07%	1.98ms	2.37ms	🔴 19.67%	🔴 207%
execute/ factorial_iterative	500.72µs	364.59µs	🟢 -27.17%	801.11µs	842.85µs	🔴 5.38%	🔴 131%
execute/ factorial_recursive	761.11µs	700.12µs	🟢 -8.19%	1.23ms	1.27ms	🔴 3.64%	🟡 82%
execute/ fib_iterative	2.54ms	1.67ms	🟢 -34.17%	4.33ms	4.48ms	🔴 3.69%	🔴 168%
execute/ fib_recursive	7.98ms	6.64ms	🟢 -16.87%	11.19ms	11.29ms	⚪ 0.86%	🟡 70%
execute/ global_bump	2.00ms	1.17ms	🟢 -41.59%	3.00ms	3.17ms	🔴 5.57%	🔴 171%
execute/ global_const	1.21ms	898.46µs	🟢 -26.18%	2.21ms	2.33ms	🔴 5.80%	🔴 159%
execute/ host_calls	32.42µs	31.52µs	🟢 -2.72%	35.79µs	37.24µs	🔴 4.00%	🟢 18%
execute/ memory_fill	2.04ms	1.50ms	🟢 -26.73%	3.74ms	3.99ms	🔴 6.75%	🔴 166%
execute/ memory_sum	2.02ms	1.50ms	🟢 -25.87%	3.80ms	3.97ms	🔴 4.58%	🔴 165%
execute/ memory_vec_add	4.42ms	3.16ms	🟢 -28.56%	7.72ms	8.22ms	🔴 6.48%	🔴 161%
execute/ recursive_is_even	1.33ms	1.28ms	🟢 -4.21%	2.02ms	2.10ms	🔴 4.08%	🟡 64%
execute/ recursive_ok	171.82µs	165.80µs	🟢 -3.33%	282.62µs	295.25µs	🔴 4.46%	🟡 78%
execute/ recursive_scan	219.00µs	200.94µs	🟢 -8.34%	359.73µs	375.06µs	🔴 4.10%	🟡 87%
execute/ recursive_trap	16.95µs	16.19µs	🟢 -4.29%	28.84µs	28.87µs	⚪ 0.13%	🟡 78%
execute/ regex_redux	815.50µs	660.73µs	🟢 -18.75%	1.40ms	1.45ms	🔴 3.17%	🔴 119%
execute/ rev_complement	890.52µs	620.62µs	🟢 -30.32%	1.39ms	1.43ms	🔴 2.87%	🔴 130%
execute/ tiny_keccak	784.55µs	470.76µs	🟢 -39.94%	1.09ms	1.19ms	🔴 9.96%	🔴 153%
execute/ trunc_f2i	1.33ms	1.09ms	🟢 -17.77%	2.22ms	2.44ms	🔴 9.77%	🔴 123%
instantiate/ wasm_kernel	70.63µs	70.61µs	⚪ 1.16%	71.43µs	95.52µs	🔴 32.71%	🟢 35%
translate/ erc1155	239.75µs	246.43µs	🔴 2.37%	373.63µs	380.49µs	🔴 1.99%	🟡 54%
translate/ erc20	117.87µs	119.29µs	⚪ 1.45%	181.39µs	185.79µs	🔴 2.23%	🟡 56%
translate/ erc721	167.93µs	169.41µs	🔴 1.44%	264.59µs	270.11µs	🔴 1.97%	🟡 59%
translate/ spidermonkey	0.00ns	0.00ns	⚪ 0.53%	0.00ns	0.00ns	🔴 1.99%	🟢 0%
translate/ wasm_kernel	4.26ms	4.19ms	🟢 -1.92%	7.07ms	7.19ms	🔴 2.16%	🟡 72%

Link to pipeline

[Robbepop]

I used the cargo-asm tool to inspect the Executor::execute function on an assembly level to understand if Rust and LLVM somehow fail to properly optimize the function after removal of the 4 unnecessary instructions. The result is: There is a huge difference in the assembly output!

See yourself:

• master: https://gist.github.com/Robbepop/cde5a25f00b78259a11170a6614aca90
  • Roughly 3.8k lines of assembly
• PR: https://gist.github.com/Robbepop/9df0eb661c5fcab9aa8391221fda7196
  • Roughly 5.9k lines of assembly

[codecov-commenter]

Codecov Report

Merging #518 (4b3d74d) into master (f5e1c46) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #518      +/-   ##
==========================================
- Coverage   79.73%   79.65%   -0.08%     
==========================================
  Files          75       75              
  Lines        6291     6267      -24     
==========================================
- Hits         5016     4992      -24     
  Misses       1275     1275              

Impacted Files	Coverage Δ
crates/wasmi/src/engine/bytecode/mod.rs	100.00% <ø> (ø)
crates/wasmi/src/engine/executor.rs	98.04% <ø> (-0.05%)	⬇️
crates/wasmi/src/engine/bytecode/tests.rs	100.00% <100.00%> (ø)
crates/wasmi/src/engine/func_builder/mod.rs	89.72% <100.00%> (-0.13%)	⬇️

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[Robbepop]

While the changes introduces in this PR were a regression to performance for wasmi with Rust 1.64 they are now significantly improving wasmi performance with Rust 1.65. Therefore it is now ready to merge.