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feat(op-acceptance-tests): add EIP-7939 CLZ opcode acceptance test #20073

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joshklop merged 1 commit into from
Apr 15, 2026
+43 −0
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feat(op-acceptance-tests): add EIP-7939 CLZ opcode acceptance test #20073

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43 changes: 43 additions & 0 deletions op-acceptance-tests/tests/osaka_on_l2_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import (
"github.com/ethereum-optimism/optimism/op-devstack/sysgo"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/rpc"
)

Expand Down Expand Up @@ -72,3 +73,45 @@ func TestEIP7823UpperBoundModExp(gt *testing.T) {
t.Require().NoError(err)
t.Require().Equal([]byte{3}, result, "2^3 mod 5 should equal 3")
}

func TestEIP7939CLZ(gt *testing.T) {
t := devtest.ParallelT(gt)
sysgo.SkipOnOpGeth(t, "osaka is not supported in op-geth")

karstOffset := uint64(3)
sys := presets.NewMinimal(t, presets.WithDeployerOptions(sysgo.WithKarstAtOffset(&karstOffset)))

activationBlock := sys.L2Chain.AwaitActivation(t, forks.Karst)
t.Require().Greater(activationBlock.Number, uint64(0), "karst must not activate at genesis")
preForkBlockNum := activationBlock.Number - 1
postForkBlockNum := activationBlock.Number + 1
sys.L2EL.WaitForBlockNumber(postForkBlockNum)

l2Client := sys.L2EL.EthClient()

// EVM init code that computes CLZ(1) and returns the 32-byte result.
// CLZ(1) = 255 because 1 has 255 leading zero bits in a uint256.
clzCode := []byte{
byte(vm.PUSH1), 1, // stack: [1]
byte(vm.CLZ), // stack: [255] (1 has 255 leading zeros)
byte(vm.PUSH1), 0, // stack: [0, 255]
byte(vm.MSTORE), // mem[0:32] = 255
byte(vm.PUSH1), 32, // stack: [32]
byte(vm.PUSH1), 0, // stack: [0, 32]
byte(vm.RETURN), // return mem[0:32]
}

// Pre-fork: CLZ opcode (0x1e) is not yet valid, so execution should fail.
_, err := l2Client.Call(t.Ctx(), ethereum.CallMsg{
Data: clzCode,
}, rpc.BlockNumber(preForkBlockNum))
t.Require().Error(err, "pre-fork: CLZ opcode should not be available")

// Post-fork: CLZ opcode is valid, execution should succeed.
result, err := l2Client.Call(t.Ctx(), ethereum.CallMsg{
Data: clzCode,
}, rpc.BlockNumber(postForkBlockNum))
t.Require().NoError(err, "post-fork: CLZ opcode should be available")
expected := common.LeftPadBytes([]byte{0xff}, 32) // 255 as uint256
t.Require().Equal(expected, result, "CLZ(1) should equal 255")
}
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