Update Wasm benchmarks

substrate/frame/contracts/src/benchmarking/code.rs

@@ -31,8 +31,8 @@ use sp_std::{borrow::ToOwned, prelude::*};
 use wasm_instrument::parity_wasm::{
 	builder,
 	elements::{
-		self, BlockType, CustomSection, External, FuncBody, Instruction, Instructions, Module,
-		Section, ValueType,
+		self, BlockType, CustomSection, External, FuncBody, Instruction, Instructions, Local,
+		Module, Section, ValueType,
 	},
 };
 
@@ -281,17 +281,21 @@ impl<T: Config> WasmModule<T> {
 	/// instrumentation runtime by nesting blocks as deeply as possible given the byte budget.
 	/// `code_location`: Whether to place the code into `deploy` or `call`.
 	pub fn sized(target_bytes: u32, code_location: Location) -> Self {
-		use self::elements::Instruction::{End, I32Const, If, Return};
+		use self::elements::Instruction::{End, GetLocal, If, Return};
 		// Base size of a contract is 63 bytes and each expansion adds 6 bytes.
 		// We do one expansion less to account for the code section and function body
 		// size fields inside the binary wasm module representation which are leb128 encoded
 		// and therefore grow in size when the contract grows. We are not allowed to overshoot
 		// because of the maximum code size that is enforced by `instantiate_with_code`.
 		let expansions = (target_bytes.saturating_sub(63) / 6).saturating_sub(1);
-		const EXPANSION: [Instruction; 4] = [I32Const(0), If(BlockType::NoResult), Return, End];
+		const EXPANSION: [Instruction; 4] = [GetLocal(0), If(BlockType::NoResult), Return, End];
 		let mut module =
 			ModuleDefinition { memory: Some(ImportedMemory::max::<T>()), ..Default::default() };
-		let body = Some(body::repeated(expansions, &EXPANSION));
+		let body = Some(body::repeated_with_locals(
+			&[Local::new(1, ValueType::I32)],
+			expansions,
+			&EXPANSION,
+		));
 		match code_location {
 			Location::Call => module.call_body = body,
 			Location::Deploy => module.deploy_body = body,
@@ -373,15 +377,21 @@ pub mod body {
 		/// Insert a I32Const with incrementing value for each insertion.
 		/// (start_at, increment_by)
 		Counter(u32, u32),
-		/// Insert the specified amount of I64Const with a random value.
-		RandomI64Repeated(usize),
 	}
 
 	pub fn plain(instructions: Vec<Instruction>) -> FuncBody {
 		FuncBody::new(Vec::new(), Instructions::new(instructions))
 	}
 
 	pub fn repeated(repetitions: u32, instructions: &[Instruction]) -> FuncBody {
+		repeated_with_locals(&[], repetitions, instructions)
+	}
+
+	pub fn repeated_with_locals(
+		locals: &[Local],
+		repetitions: u32,
+		instructions: &[Instruction],
+	) -> FuncBody {
 		let instructions = Instructions::new(
 			instructions
 				.iter()
@@ -391,15 +401,10 @@ pub mod body {
 				.chain(sp_std::iter::once(Instruction::End))
 				.collect(),
 		);
-		FuncBody::new(Vec::new(), instructions)
+		FuncBody::new(locals.to_vec(), instructions)
 	}
 
 	pub fn repeated_dyn(repetitions: u32, mut instructions: Vec<DynInstr>) -> FuncBody {
-		use rand::{distributions::Standard, prelude::*};
-
-		// We do not need to be secure here.
-		let mut rng = rand_pcg::Pcg32::seed_from_u64(8446744073709551615);
-
 		// We need to iterate over indices because we cannot cycle over mutable references
 		let body = (0..instructions.len())
 			.cycle()
@@ -411,8 +416,6 @@ pub mod body {
 					*offset += *increment_by;
 					vec![Instruction::I32Const(current as i32)]
 				},
-				DynInstr::RandomI64Repeated(num) =>
-					(&mut rng).sample_iter(Standard).take(*num).map(Instruction::I64Const).collect(),
 			})
 			.chain(sp_std::iter::once(Instruction::End))
 			.collect();

substrate/frame/contracts/src/benchmarking/mod.rs

@@ -48,7 +48,7 @@ use pallet_balances;
 use pallet_contracts_uapi::CallFlags;
 use sp_runtime::traits::{Bounded, Hash};
 use sp_std::prelude::*;
-use wasm_instrument::parity_wasm::elements::{BlockType, Instruction, ValueType};
+use wasm_instrument::parity_wasm::elements::{BlockType, Instruction, Local, ValueType};
 
 /// How many runs we do per API benchmark.
 ///
@@ -2582,19 +2582,22 @@ benchmarks! {
 		let origin = RawOrigin::Signed(instance.caller.clone());
 	}: call(origin, instance.addr, 0u32.into(), Weight::MAX, None, vec![])
 
-	// We make the assumption that pushing a constant and dropping a value takes roughly
-	// the same amount of time. We call this weight `w_base`.
-	// The weight that would result from the respective benchmark we call: `w_bench`.
-	//
-	// w_base = w_i{32,64}const = w_drop = w_bench / 2
+	// We add two `i64` integers from local variables and store the result into yet another
+	// local variable. The combination of this computation is our weight base `w_base`.
 	#[pov_mode = Ignored]
-	instr_i64const {
+	instr_i64add {
 		let r in 0 .. INSTR_BENCHMARK_RUNS;
 		let mut sbox = Sandbox::from(&WasmModule::<T>::from(ModuleDefinition {
-			call_body: Some(body::repeated_dyn(r, vec![
-				RandomI64Repeated(1),
-				Regular(Instruction::Drop),
-			])),
+			call_body: Some(body::repeated_with_locals(
+				&[Local::new(3, ValueType::I64)],
+				r,
+				&[
+					Instruction::GetLocal(0),
+					Instruction::GetLocal(1),
+					Instruction::I64Add,
+					Instruction::SetLocal(2),
+				],
+			)),
 			.. Default::default()
 		}));
 	}: {

substrate/frame/contracts/src/schedule.rs

@@ -396,10 +396,12 @@ impl Default for Limits {
 }
 
 impl<T: Config> Default for InstructionWeights<T> {
-	/// We price both `i64.const` and `drop` as `instr_i64const / 2`. The reason
-	/// for that is that we cannot benchmark either of them on its own.
+	/// We price all of `i64.add`, `local.get` and `local.set` as `instr_i64add / 2`. The reason
+	/// for that is that we cannot benchmark either of them on their own and division by 2 makes
+	/// for a decent compromise between the optimization capabilities of Wasmi (stack) and
+	/// Wasmi (register).
 	fn default() -> Self {
-		Self { base: cost_instr!(instr_i64const, 1), _phantom: PhantomData }
+		Self { base: cost_instr!(instr_i64add, 1), _phantom: PhantomData }
 	}
 }