Switch to Wasmtime for parachain execution (#2265)

* Switch to Wasmtime for parachain execution

* Fix the signature for halt's validate_block

* wasmtime feature enabled from cli

* Adds missing feature

Co-authored-by: Sergei Shulepov <sergei@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>

polkadot/cli/Cargo.toml

@@ -40,7 +40,7 @@ substrate-build-script-utils = { git = "https://github.com/paritytech/substrate"
 
 [features]
 default = [ "wasmtime", "db", "cli", "full-node", "trie-memory-tracker", "polkadot-parachain" ]
-wasmtime = [ "sc-cli/wasmtime" ]
+wasmtime = [ "sc-cli/wasmtime", "polkadot-parachain/wasmtime" ]
 db = [ "service/db" ]
 cli = [
 	"structopt",

polkadot/parachain/Cargo.toml

@@ -32,6 +32,7 @@ shared_memory = { version = "0.10.0", optional = true }
 
 [features]
 default = ["std"]
+wasmtime = [ "sc-executor/wasmtime" ]
 wasm-api = []
 std = [
 	"parity-scale-codec/std",

polkadot/parachain/src/wasm_executor/mod.rs

@@ -198,6 +198,9 @@ pub fn validate_candidate_internal(
 	spawner: impl SpawnNamed + 'static,
 ) -> Result<ValidationResult, ValidationError> {
 	let executor = sc_executor::WasmExecutor::new(
+		#[cfg(all(feature = "wasmtime", not(any(target_os = "android", target_os = "unknown"))))]
+		sc_executor::WasmExecutionMethod::Compiled,
+		#[cfg(any(not(feature = "wasmtime"), target_os = "android", target_os = "unknown"))]
 		sc_executor::WasmExecutionMethod::Interpreted,
 		// TODO: Make sure we don't use more than 1GB: https://github.com/paritytech/polkadot/issues/699
 		Some(1024),

polkadot/parachain/test-parachains/halt/src/lib.rs

@@ -50,6 +50,6 @@ pub fn oom(_: core::alloc::Layout) -> ! {
 
 #[cfg(not(feature = "std"))]
 #[no_mangle]
-pub extern fn validate_block(params: *const u8, len: usize) -> usize {
+pub extern fn validate_block(params: *const u8, len: usize) -> u64 {
 	loop {}
 }