Replace `COA.call` with `COA.callWithSigAndArgs` for reduced computation cost by m-Peter · Pull Request #207 · onflow/flow-evm-bridge

m-Peter · 2026-03-18T10:06:43Z

Related: onflow/flow-go#8401
Closes: #206

Description

Previously, to perform contract calls using a COA, it was necessary to produce the callData on Cadence side:

let calldata = EVM.encodeABIWithSignature(signature, args)

To be able to ABI-decode the returned data from the COA call, another step was needed:

let decoded = EVM.decodeABI(types: [Type<[UInt256]>()], data: res.data)
let amountsOut = decoded[0] as! [UInt256]

After doing some profiling on Cadence transactions, the computation cost of ABI encoding/decoding, amounted to about 15%-20% of the total computation, which is not trivial.

To optimize this case, we have a new wrapper function, callWithSigAndArgs, which does all this more efficiently:

coa.callWithSigAndArgs(
    to: to,
    signature: "approve(address,uint256)",
    args: [self.routerAddress, evmAmountIn],
    gasLimit: gasLimit,
    value: valueBalance.attoflow,
    resultTypes: [Type<[UInt256]>()]
)

We do the same for dryCall, by replacing it with dryCallWithSigAndArgs .

NOTE: CI is failing because we still need to deploy the EVM system contract on testnet/mainnet, for these new functions to be available.

For contributor use:

Targeted PR against main branch
Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
Code follows the standards mentioned here.
Updated relevant documentation
Re-reviewed Files changed in the Github PR explorer
Added appropriate labels

…cost

turbolent · 2026-03-23T16:23:38Z

Nice! Thank you for optimizing this 👍

It looks like some of the function signatures changed. We should probably make sure this doesn't break existing contracts and transactions. From what I could see doing a quick search for protectedTransferCall: (xsv search 'protectedTransferCall:' contracts.csv | xsv select location), only the EVM bridge contracts themselves need to be adjusted and no other contracts use it. Not sure about transactions

m-Peter · 2026-03-24T11:45:37Z

Nice! Thank you for optimizing this 👍

It looks like some of the function signatures changed. We should probably make sure this doesn't break existing contracts and transactions. From what I could see doing a quick search for protectedTransferCall: (xsv search 'protectedTransferCall:' contracts.csv | xsv select location), only the EVM bridge contracts themselves need to be adjusted and no other contracts use it. Not sure about transactions

@turbolent I have already checked that the function signature changes affect only "internal" functions. Their access modifiers are either access(self) or access(account). I have also updated all the call-sites of these functions, so I believe we're not introducing any breaking changes to existing contracts / transactions.

joshuahannan

Looks good!

joshuahannan · 2026-03-24T14:28:31Z

-        let decodedSymbolData = EVM.decodeABI(types: [Type<String>()], data: symbolRes.data)
-        assert(decodedNameData.length == 1, message: "Unexpected name() return length of ".concat(decodedNameData.length.toString()))
-        assert(decodedSymbolData.length == 1, message: "Unexpected symbol() return length of ".concat(decodedSymbolData.length.toString()))
+        assert(nameRes.results.length == 1, message: "Unexpected name() return length of ".concat(nameRes.results.length.toString()))


Can you use string interpolation everywhere instead of concat?

Suggested change

assert(nameRes.results.length == 1, message: "Unexpected name() return length of ".concat(nameRes.results.length.toString()))

assert(nameRes.results.length == 1, message: "Unexpected name() return length of \(nameRes.results.length.toString()))

Updated all such occurrences in f931ba9 .

fxamacker

Nice! 👍 Thanks @m-Peter for updating this repo to use optimized EVM functions.

My only suggestion is for code that wasn't modified by this PR.

Maybe we can special case value 0.0 to avoid creating EVM.Balance in several places.

fxamacker · 2026-03-31T20:54:06Z

        let valueBalance = EVM.Balance(attoflow: 0)
        valueBalance.setFLOW(flow: value)


These lines are not modified by PR.

Maybe we can special case value 0.0 to avoid creating EVM.Balance.

Updated in e9246a2 .

fxamacker · 2026-03-31T20:58:46Z

        let valueBalance = EVM.Balance(attoflow: 0)
        valueBalance.setFLOW(flow: value)


Same as above. Maybe we can special case value 0.0 to avoid creating EVM.Balance.

Updated in e9246a2 .

fxamacker · 2026-03-31T21:03:14Z

        let valueBalance = EVM.Balance(attoflow: 0)
        valueBalance.setFLOW(flow: value)


Same as above. Maybe we can special case value 0.0 to avoid creating EVM.Balance.

Updated in e9246a2 .

fxamacker · 2026-03-31T21:06:26Z

+        resultTypes: [Type]?
+    ): EVM.ResultDecoded {
        let valueBalance = EVM.Balance(attoflow: 0)
        valueBalance.setFLOW(flow: value)


Same as above. Maybe we can special case value 0.0 to avoid creating EVM.Balance.

Updated in e9246a2 .

joshuahannan · 2026-04-08T16:02:53Z

@m-Peter I'd like to start upgrading these contracts on testnet soon. Are the tests not passing because this function is not available in the emulator yet?

m-Peter · 2026-04-08T16:05:32Z

@joshuahannan The tests are not passing, because the EVM contract has not been updated on mainnet. The CI is built by fetching dependencies from mainnet, and the current EVM contract on mainnet doesn't have the desired methods.

joshuahannan · 2026-04-08T16:13:28Z

good to know! I'll schedule a multisig to upgrade the EVM contract on mainnet

m-Peter · 2026-04-09T10:52:30Z

good to know! I'll schedule a multisig to upgrade the EVM contract on mainnet

@joshuahannan It would be good to first upgrade the EVM contract on testnet, and see that everything's working well.

joshuahannan · 2026-04-09T14:58:55Z

Yes, that was the plan, just trying to get this update to the EVM contract merged first: onflow/flow-go#8529

Switches the EVM contract dependency from mainnet://e467b9dd11fa00df.EVM to testnet://8c5303eaa26202d6.EVM and updates the hash and block height to match the testnet version. All tests pass.

joshuahannan · 2026-04-09T17:28:35Z

@m-Peter I just updated the dependency to use testnet instead of mainnet for EVM so we could make sure these tests pass and merge it. Is that okay?

m-Peter · 2026-04-09T17:36:28Z

@m-Peter I just updated the dependency to use testnet instead of mainnet for EVM so we could make sure these tests pass and merge it. Is that okay?

@joshuahannan That's awesome 🎉 I wasn't sure if that was possible, I thought it had to be from mainnet only. CI now seems to be ✔️

m-Peter self-assigned this Mar 18, 2026

github-project-automation Bot added this to FlowEVM Bridge and 🌊 Flow 4D Mar 18, 2026

github-project-automation Bot moved this to 👀 In Review in 🌊 Flow 4D Mar 18, 2026

m-Peter force-pushed the mpeter/optimize-evm-call-usage branch 2 times, most recently from 0480739 to c058e91 Compare March 19, 2026 07:57

m-Peter mentioned this pull request Mar 19, 2026

[Flow EVM] Optimize EVM and Cross-VM Bridge onflow/flow-go#8401

Closed

12 tasks

m-Peter force-pushed the mpeter/optimize-evm-call-usage branch 4 times, most recently from 0b195c1 to 6dc3a89 Compare March 19, 2026 14:14

m-Peter requested review from joshuahannan and turbolent March 19, 2026 14:16

m-Peter marked this pull request as ready for review March 19, 2026 17:04

m-Peter requested a review from a team as a code owner March 19, 2026 17:04

Replace COA.call with COA.callWithSigAndArgs for reduced computation …

ae1fbc4

…cost

m-Peter force-pushed the mpeter/optimize-evm-call-usage branch from 6dc3a89 to ae1fbc4 Compare March 23, 2026 10:05

joshuahannan approved these changes Mar 24, 2026

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github-project-automation Bot moved this to Done in FlowEVM Bridge Mar 24, 2026

fxamacker approved these changes Mar 31, 2026

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m-Peter added 2 commits April 3, 2026 15:42

Avoid creating EVM.Balance structs for value of 0

e9246a2

Use the Cadence String interpolation feature instead of concat()

f931ba9

Update EVM dependency source from mainnet to testnet

f8c0d1b

Switches the EVM contract dependency from mainnet://e467b9dd11fa00df.EVM to testnet://8c5303eaa26202d6.EVM and updates the hash and block height to match the testnet version. All tests pass.

joshuahannan merged commit fe30b25 into main Apr 9, 2026
2 checks passed

joshuahannan deleted the mpeter/optimize-evm-call-usage branch April 9, 2026 18:06

github-project-automation Bot moved this from 👀 In Review to ✅ Done in 🌊 Flow 4D Apr 9, 2026

m-Peter mentioned this pull request May 7, 2026

Update EVM dependency source from testnet to mainnet #212

Merged

6 tasks

	assert(nameRes.results.length == 1, message: "Unexpected name() return length of ".concat(nameRes.results.length.toString()))
	assert(nameRes.results.length == 1, message: "Unexpected name() return length of \(nameRes.results.length.toString()))

		let valueBalance = EVM.Balance(attoflow: 0)
		valueBalance.setFLOW(flow: value)

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m-Peter commented Mar 18, 2026 •

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