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>

tests/diff.rs

@@ -1,10 +1,9 @@
-use parity_wasm::elements::Module;
 use std::{
 	fs,
 	io::{self, Read, Write},
 	path::{Path, PathBuf},
 };
-use wasm_instrument::{self as instrument, parity_wasm::elements};
+use wasm_instrument::{self as instrument, gas_metering, parity_wasm::elements};
 use wasmparser::validate;
 
 fn slurp<P: AsRef<Path>>(path: P) -> io::Result<Vec<u8>> {
@@ -20,18 +19,23 @@ fn dump<P: AsRef<Path>>(path: P, buf: &[u8]) -> io::Result<()> {
 	Ok(())
 }
 
-fn run_diff_test<F: FnOnce(&[u8]) -> Vec<u8>>(test_dir: &str, name: &str, test: F) {
+fn run_diff_test<F: FnOnce(&[u8]) -> Vec<u8>>(
+	test_dir: &str,
+	in_name: &str,
+	out_name: &str,
+	test: F,
+) {
 	let mut fixture_path = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
 	fixture_path.push("tests");
 	fixture_path.push("fixtures");
 	fixture_path.push(test_dir);
-	fixture_path.push(name);
+	fixture_path.push(in_name);
 
 	let mut expected_path = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
 	expected_path.push("tests");
 	expected_path.push("expectations");
 	expected_path.push(test_dir);
-	expected_path.push(name);
+	expected_path.push(out_name);
 
 	let fixture_wasm = wat::parse_file(&fixture_path).expect("Failed to read fixture");
 	validate(&fixture_wasm).expect("Fixture is invalid");
@@ -48,7 +52,7 @@ fn run_diff_test<F: FnOnce(&[u8]) -> Vec<u8>>(test_dir: &str, name: &str, test:
 	if actual_wat != expected_wat {
 		println!("difference!");
 		println!("--- {}", expected_path.display());
-		println!("+++ {} test {}", test_dir, name);
+		println!("+++ {} test {}", test_dir, out_name);
 		for diff in diff::lines(expected_wat, &actual_wat) {
 			match diff {
 				diff::Result::Left(l) => println!("-{}", l),
@@ -72,13 +76,18 @@ mod stack_height {
 		( $name:ident ) => {
 			#[test]
 			fn $name() {
-				run_diff_test("stack-height", concat!(stringify!($name), ".wat"), |input| {
-					let module =
-						elements::deserialize_buffer(input).expect("Failed to deserialize");
-					let instrumented = instrument::inject_stack_limiter(module, 1024)
-						.expect("Failed to instrument with stack counter");
-					elements::serialize(instrumented).expect("Failed to serialize")
-				});
+				run_diff_test(
+					"stack-height",
+					concat!(stringify!($name), ".wat"),
+					concat!(stringify!($name), ".wat"),
+					|input| {
+						let module =
+							elements::deserialize_buffer(input).expect("Failed to deserialize");
+						let instrumented = instrument::inject_stack_limiter(module, 1024)
+							.expect("Failed to instrument with stack counter");
+						elements::serialize(instrumented).expect("Failed to serialize")
+					},
+				);
 			}
 		};
 	}
@@ -96,27 +105,53 @@ mod gas {
 	use super::*;
 
 	macro_rules! def_gas_test {
-		( $name:ident ) => {
+		( ($input:ident, $name1:ident, $name2:ident) ) => {
 			#[test]
-			fn $name() {
-				run_diff_test("gas", concat!(stringify!($name), ".wat"), |input| {
-					let rules = instrument::gas_metering::ConstantCostRules::default();
+			fn $name1() {
+				run_diff_test(
+					"gas",
+					concat!(stringify!($input), ".wat"),
+					concat!(stringify!($name1), ".wat"),
+					|input| {
+						let rules = gas_metering::ConstantCostRules::default();
 
-					let module: Module =
-						elements::deserialize_buffer(input).expect("Failed to deserialize");
-					let module = module.parse_names().expect("Failed to parse names");
+						let module: elements::Module =
+							elements::deserialize_buffer(input).expect("Failed to deserialize");
+						let module = module.parse_names().expect("Failed to parse names");
+						let backend = gas_metering::host_function::Injector::new("env", "gas");
 
-					let instrumented = instrument::gas_metering::inject(module, &rules, "env")
-						.expect("Failed to instrument with gas metering");
-					elements::serialize(instrumented).expect("Failed to serialize")
-				});
+						let instrumented = gas_metering::inject(module, backend, &rules)
+							.expect("Failed to instrument with gas metering");
+						elements::serialize(instrumented).expect("Failed to serialize")
+					},
+				);
+			}
+
+			#[test]
+			fn $name2() {
+				run_diff_test(
+					"gas",
+					concat!(stringify!($input), ".wat"),
+					concat!(stringify!($name2), ".wat"),
+					|input| {
+						let rules = gas_metering::ConstantCostRules::default();
+
+						let module: elements::Module =
+							elements::deserialize_buffer(input).expect("Failed to deserialize");
+						let module = module.parse_names().expect("Failed to parse names");
+						let backend = gas_metering::mutable_global::Injector::new("gas_left");
+						let instrumented = gas_metering::inject(module, backend, &rules)
+							.expect("Failed to instrument with gas metering");
+						elements::serialize(instrumented).expect("Failed to serialize")
+					},
+				);
 			}
 		};
 	}
 
-	def_gas_test!(ifs);
-	def_gas_test!(simple);
-	def_gas_test!(start);
-	def_gas_test!(call);
-	def_gas_test!(branch);
+	def_gas_test!((ifs, ifs_host_fn, ifs_mut_global));
+	def_gas_test!((simple, simple_host_fn, simple_mut_global));
+	def_gas_test!((start, start_host_fn, start_mut_global));
+	def_gas_test!((call, call_host_fn, call_mut_global));
+	def_gas_test!((branch, branch_host_fn, branch_mut_global));
 }