[pallet-revive] change some getter APIs to return value in register (#…

…6920)

Call data, return data and code sizes can never exceed `u32::MAX`; they
are also not generic. Hence we know that they are guaranteed to always
fit into a 64bit register and `revive` can just zero extend them into a
256bit integer value. Which is slightly more efficient than passing them
on the stack.

---------

Signed-off-by: Cyrill Leutwiler <[email protected]>
Signed-off-by: xermicus <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: Alexander Theißen <[email protected]>

prdoc/pr_6920.prdoc

@@ -0,0 +1,14 @@
+title: '[pallet-revive] change some getter APIs to return value in register'
+doc:
+- audience: Runtime Dev
+  description: Call data, return data and code sizes can never exceed `u32::MAX`;
+    they are also not generic. Hence we know that they are guaranteed to always fit
+    into a 64bit register and `revive` can just zero extend them into a 256bit integer
+    value. Which is slightly more efficient than passing them on the stack.
+crates:
+- name: pallet-revive-fixtures
+  bump: major
+- name: pallet-revive
+  bump: major
+- name: pallet-revive-uapi
+  bump: major

substrate/frame/revive/fixtures/contracts/call_data_size.rs

@@ -30,8 +30,5 @@ pub extern "C" fn deploy() {}
 #[no_mangle]
 #[polkavm_derive::polkavm_export]
 pub extern "C" fn call() {
-	let mut buf = [0; 32];
-	api::call_data_size(&mut buf);
-
-	api::return_value(ReturnFlags::empty(), &buf);
+	api::return_value(ReturnFlags::empty(), &api::call_data_size().to_le_bytes());
 }

substrate/frame/revive/fixtures/contracts/common/src/lib.rs

@@ -121,7 +121,7 @@ macro_rules! input {
 	// e.g input!(buffer, 512, var1: u32, var2: [u8], );
 	($buffer:ident, $size:expr, $($rest:tt)*) => {
 		let mut $buffer = [0u8; $size];
-		let input_size = $crate::u64_output!($crate::api::call_data_size,);
+		let input_size = $crate::api::call_data_size();
 		let $buffer = &mut &mut $buffer[..$size.min(input_size as usize)];
 		$crate::api::call_data_copy($buffer, 0);
 		input!(@inner $buffer, 0, $($rest)*);

substrate/frame/revive/fixtures/contracts/extcodesize.rs

@@ -18,7 +18,7 @@
 #![no_std]
 #![no_main]
 
-use common::{input, u64_output};
+use common::input;
 use uapi::{HostFn, HostFnImpl as api};
 
 #[no_mangle]
@@ -30,7 +30,7 @@ pub extern "C" fn deploy() {}
 pub extern "C" fn call() {
 	input!(address: &[u8; 20], expected: u64,);
 
-	let received = u64_output!(api::code_size, address);
+	let received = api::code_size(address);
 
 	assert_eq!(expected, received);
 }

substrate/frame/revive/fixtures/contracts/return_data_api.rs

@@ -75,9 +75,7 @@ fn recursion_guard() -> [u8; 20] {
 
 /// Assert [api::return_data_size] to match the `expected` value.
 fn assert_return_data_size_of(expected: u64) {
-	let mut return_data_size = [0xff; 32];
-	api::return_data_size(&mut return_data_size);
-	assert_eq!(return_data_size, u256_bytes(expected));
+	assert_eq!(api::return_data_size(), expected);
 }
 
 /// Assert the return data to be reset after a balance transfer.

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

@@ -596,19 +596,15 @@ mod benchmarks {
 	#[benchmark(pov_mode = Measured)]
 	fn seal_code_size() {
 		let contract = Contract::<T>::with_index(1, WasmModule::dummy(), vec![]).unwrap();
-		build_runtime!(runtime, memory: [contract.address.encode(), vec![0u8; 32], ]);
+		build_runtime!(runtime, memory: [contract.address.encode(),]);
 
 		let result;
 		#[block]
 		{
-			result = runtime.bench_code_size(memory.as_mut_slice(), 0, 20);
+			result = runtime.bench_code_size(memory.as_mut_slice(), 0);
 		}
 
-		assert_ok!(result);
-		assert_eq!(
-			U256::from_little_endian(&memory[20..]),
-			U256::from(WasmModule::dummy().code.len())
-		);
+		assert_eq!(result.unwrap(), WasmModule::dummy().code.len() as u64);
 	}
 
 	#[benchmark(pov_mode = Measured)]
@@ -783,19 +779,34 @@ mod benchmarks {
 		assert_eq!(U256::from_little_endian(&memory[..]), runtime.ext().minimum_balance());
 	}
 
+	#[benchmark(pov_mode = Measured)]
+	fn seal_return_data_size() {
+		let mut setup = CallSetup::<T>::default();
+		let (mut ext, _) = setup.ext();
+		let mut runtime = crate::wasm::Runtime::new(&mut ext, vec![]);
+		let mut memory = memory!(vec![],);
+		*runtime.ext().last_frame_output_mut() =
+			ExecReturnValue { data: vec![42; 256], ..Default::default() };
+		let result;
+		#[block]
+		{
+			result = runtime.bench_return_data_size(memory.as_mut_slice());
+		}
+		assert_eq!(result.unwrap(), 256);
+	}
+
 	#[benchmark(pov_mode = Measured)]
 	fn seal_call_data_size() {
 		let mut setup = CallSetup::<T>::default();
 		let (mut ext, _) = setup.ext();
 		let mut runtime = crate::wasm::Runtime::new(&mut ext, vec![42u8; 128 as usize]);
-		let mut memory = memory!(vec![0u8; 32 as usize],);
+		let mut memory = memory!(vec![0u8; 4],);
 		let result;
 		#[block]
 		{
-			result = runtime.bench_call_data_size(memory.as_mut_slice(), 0);
+			result = runtime.bench_call_data_size(memory.as_mut_slice());
 		}
-		assert_ok!(result);
-		assert_eq!(U256::from_little_endian(&memory[..]), U256::from(128));
+		assert_eq!(result.unwrap(), 128);
 	}
 
 	#[benchmark(pov_mode = Measured)]

substrate/frame/revive/src/exec.rs

@@ -298,7 +298,7 @@ pub trait Ext: sealing::Sealed {
 	fn code_hash(&self, address: &H160) -> H256;
 
 	/// Returns the code size of the contract at the given `address` or zero.
-	fn code_size(&self, address: &H160) -> U256;
+	fn code_size(&self, address: &H160) -> u64;
 
 	/// Returns the code hash of the contract being executed.
 	fn own_code_hash(&mut self) -> &H256;
@@ -1663,7 +1663,7 @@ where
 			})
 	}
 
-	fn code_size(&self, address: &H160) -> U256 {
+	fn code_size(&self, address: &H160) -> u64 {
 		<ContractInfoOf<T>>::get(&address)
 			.and_then(|contract| CodeInfoOf::<T>::get(contract.code_hash))
 			.map(|info| info.code_len())

substrate/frame/revive/src/tests.rs

@@ -4377,11 +4377,11 @@ fn call_data_size_api_works() {
 		// Call the contract: It echoes back the value returned by the call data size API.
 		let received = builder::bare_call(addr).build_and_unwrap_result();
 		assert_eq!(received.flags, ReturnFlags::empty());
-		assert_eq!(U256::from_little_endian(&received.data), U256::zero());
+		assert_eq!(u64::from_le_bytes(received.data.try_into().unwrap()), 0);
 
 		let received = builder::bare_call(addr).data(vec![1; 256]).build_and_unwrap_result();
 		assert_eq!(received.flags, ReturnFlags::empty());
-		assert_eq!(U256::from_little_endian(&received.data), U256::from(256));
+		assert_eq!(u64::from_le_bytes(received.data.try_into().unwrap()), 256);
 	});
 }
 

substrate/frame/revive/src/wasm/mod.rs

@@ -242,7 +242,7 @@ impl<T: Config> CodeInfo<T> {
 	}
 
 	/// Returns the code length.
-	pub fn code_len(&self) -> U256 {
+	pub fn code_len(&self) -> u64 {
 		self.code_len.into()
 	}
 }

substrate/frame/revive/src/wasm/runtime.rs

@@ -290,6 +290,8 @@ pub enum RuntimeCosts {
 	Caller,
 	/// Weight of calling `seal_call_data_size`.
 	CallDataSize,
+	/// Weight of calling `seal_return_data_size`.
+	ReturnDataSize,
 	/// Weight of calling `seal_origin`.
 	Origin,
 	/// Weight of calling `seal_is_contract`.
@@ -453,6 +455,7 @@ impl<T: Config> Token<T> for RuntimeCosts {
 			CopyToContract(len) => T::WeightInfo::seal_copy_to_contract(len),
 			CopyFromContract(len) => T::WeightInfo::seal_return(len),
 			CallDataSize => T::WeightInfo::seal_call_data_size(),
+			ReturnDataSize => T::WeightInfo::seal_return_data_size(),
 			CallDataLoad => T::WeightInfo::seal_call_data_load(),
 			CallDataCopy(len) => T::WeightInfo::seal_call_data_copy(len),
 			Caller => T::WeightInfo::seal_caller(),
@@ -1283,17 +1286,13 @@ pub mod env {
 	/// Returns the total size of the contract call input data.
 	/// See [`pallet_revive_uapi::HostFn::call_data_size `].
 	#[stable]
-	fn call_data_size(&mut self, memory: &mut M, out_ptr: u32) -> Result<(), TrapReason> {
+	fn call_data_size(&mut self, memory: &mut M) -> Result<u64, TrapReason> {
 		self.charge_gas(RuntimeCosts::CallDataSize)?;
-		let value =
-			U256::from(self.input_data.as_ref().map(|input| input.len()).unwrap_or_default());
-		Ok(self.write_fixed_sandbox_output(
-			memory,
-			out_ptr,
-			&value.to_little_endian(),
-			false,
-			already_charged,
-		)?)
+		Ok(self
+			.input_data
+			.as_ref()
+			.map(|input| input.len().try_into().expect("usize fits into u64; qed"))
+			.unwrap_or_default())
 	}
 
 	/// Stores the input passed by the caller into the supplied buffer.
@@ -1420,16 +1419,10 @@ pub mod env {
 	/// Retrieve the code size for a given contract address.
 	/// See [`pallet_revive_uapi::HostFn::code_size`].
 	#[stable]
-	fn code_size(&mut self, memory: &mut M, addr_ptr: u32, out_ptr: u32) -> Result<(), TrapReason> {
+	fn code_size(&mut self, memory: &mut M, addr_ptr: u32) -> Result<u64, TrapReason> {
 		self.charge_gas(RuntimeCosts::CodeSize)?;
 		let address = memory.read_h160(addr_ptr)?;
-		Ok(self.write_fixed_sandbox_output(
-			memory,
-			out_ptr,
-			&self.ext.code_size(&address).to_little_endian(),
-			false,
-			already_charged,
-		)?)
+		Ok(self.ext.code_size(&address))
 	}
 
 	/// Stores the address of the current contract into the supplied buffer.
@@ -1667,14 +1660,15 @@ pub mod env {
 	/// Stores the length of the data returned by the last call into the supplied buffer.
 	/// See [`pallet_revive_uapi::HostFn::return_data_size`].
 	#[stable]
-	fn return_data_size(&mut self, memory: &mut M, out_ptr: u32) -> Result<(), TrapReason> {
-		Ok(self.write_fixed_sandbox_output(
-			memory,
-			out_ptr,
-			&U256::from(self.ext.last_frame_output().data.len()).to_little_endian(),
-			false,
-			|len| Some(RuntimeCosts::CopyToContract(len)),
-		)?)
+	fn return_data_size(&mut self, memory: &mut M) -> Result<u64, TrapReason> {
+		self.charge_gas(RuntimeCosts::ReturnDataSize)?;
+		Ok(self
+			.ext
+			.last_frame_output()
+			.data
+			.len()
+			.try_into()
+			.expect("usize fits into u64; qed"))
 	}
 
 	/// Stores data returned by the last call, starting from `offset`, into the supplied buffer.