Add new gas metering method: mutable global + local gas function (#34)

* fix misprints in doc comments

* added global gas tracker variable and local gas fn

* all exported functions of the module to accept a new param and to set the gas_left global to its value at their very start

* make module support both gas metering methods

* tests fixed for the old metering method

* better naming

* MutableGlobal metering method implemented, tests for the old method pass

* gas_metering::tests updated and pass

* all tests udpdated and pass

* emacs backup files to .gitignore

* docs updated

* clippy fix

* iff = if and only if

* more clippy

* docs misprints fixes

* refactored to have Backend trait and two implementations in separate sub-modules

* docs updated

* fixed old benches (updating them is coming next)

* added bench for an instrumented wasm-coremark

* updated benches: added them for both gas_metering instrumentations

* benches contest first ver

* added debug prints to the bench

* refactored to better fit frontend-backend pattern

* docs update

* updated benches

* design updated on feedback

* re-structured sub-modules

re-structured sub-modules & updated docs

* docs improved

* addressed latest feedback comments

* re-writed the local gas function

* coremark benches show ~20% performance improvement

* fix ci: test + clippy

* save before re-factoring prepare_in_wasm()

* bare_call_16 shows 16% worse perf

* + fibonacci recursive bench

* refactored benchmarks

* + factorial recursive bench

* benches on wasmi fixtures show no perf improvement, coremark runs ~20% faster being instrumented with mutable_global gas metering

* charge gas for local gas func isntructions execution

* replaced benchmark which requires multi_value feature

* save: optimized gas func a bit (benches work, fixture tests fail)

* 1033% overhead on many_blocks.wasm when mut_global gas_metering together with stack_height

* size overhead test for both gas metering methods + stack limiter

* added more benches

* improved print_size_overhead test

* test for comparing size overheads of two gas_metering injectors

* before optimization: benches + size overhead

* optimization try-1: inline part of gas func instructions: +benches +size overheads

* optimization try-2: inline hot path of gas fn:  +benches +size overheads

* opt try-3: count for gas fn cost on the caller side: +benches +size overhead

* revert to initial version but with static gas fn cost on the caller side: +benches +sizes

* tests fixed

* use newest wasmi 0.20: +benches +docs updated

* use if-else block instead of Return: +benches

* fix tests

* clippy fix

* addressed review comments

* Update changelog

Co-authored-by: Alexander Theißen <alex.theissen@me.com>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasm-instrument"
-version = "0.3.0"
+version = "0.4.0"
 edition = "2021"
 rust-version = "1.56.1"
 authors = ["Parity Technologies <admin@parity.io>"]
@@ -32,8 +32,12 @@ rand = "0.8"
 wat = "1"
 wasmparser = "0.94"
 wasmprinter = "0.2"
+wasmi = "0.20"
 
 [features]
 default = ["std"]
 std = ["parity-wasm/std"]
 sign_ext = ["parity-wasm/sign_ext"]
+
+[lib]
+bench = false