MTCannon: improve consistency & add EmptyThreadStack test (#12389)

* Add EmptyThreadStacks test

* add go evm check

* improve consistency and update test

* delete emptyThreadedProofGenerator

* forge lint update

* fix solidity versioning and hash & add proof variations in test

cannon/mipsevm/tests/evm_multithreaded_test.go

@@ -1193,6 +1193,39 @@ func TestEVM_UnsupportedSyscall(t *testing.T) {
 	}
 }
 
+func TestEVM_EmptyThreadStacks(t *testing.T) {
+	t.Parallel()
+	var tracer *tracing.Hooks
+
+	cases := []struct {
+		name           string
+		otherStackSize int
+		traverseRight  bool
+	}{
+		{name: "Traverse right with empty stacks", otherStackSize: 0, traverseRight: true},
+		{name: "Traverse left with empty stacks", otherStackSize: 0, traverseRight: false},
+		{name: "Traverse right with one non-empty stack on the other side", otherStackSize: 1, traverseRight: true},
+		{name: "Traverse left with one non-empty stack on the other side", otherStackSize: 1, traverseRight: false},
+	}
+	// Generate proof variations
+	proofVariations := GenerateEmptyThreadProofVariations(t)
+
+	for i, c := range cases {
+		for _, proofCase := range proofVariations {
+			testName := fmt.Sprintf("%v (proofCase=%v)", c.name, proofCase.Name)
+			t.Run(testName, func(t *testing.T) {
+				goVm, state, contracts := setup(t, i*123, nil)
+				mttestutil.SetupThreads(int64(i*123), state, c.traverseRight, 0, c.otherStackSize)
+
+				require.PanicsWithValue(t, "Active thread stack is empty", func() { _, _ = goVm.Step(false) })
+
+				errorMessage := "MIPS2: active thread stack is empty"
+				testutil.AssertEVMReverts(t, state, contracts, tracer, proofCase.Proof, errorMessage)
+			})
+		}
+	}
+}
+
 func TestEVM_NormalTraversalStep_HandleWaitingThread(t *testing.T) {
 	var tracer *tracing.Hooks
 	cases := []struct {

cannon/mipsevm/tests/helpers.go

@@ -129,3 +129,20 @@ func GetMipsVersionTestCases(t require.TestingT) []VersionedVMTestCase {
 		}
 	}
 }
+
+type threadProofTestcase struct {
+	Name  string
+	Proof []byte
+}
+
+func GenerateEmptyThreadProofVariations(t require.TestingT) []threadProofTestcase {
+	defaultThreadProof := multiThreadedProofGenerator(t, multithreaded.CreateEmptyState())
+	zeroBytesThreadProof := make([]byte, multithreaded.THREAD_WITNESS_SIZE)
+	copy(zeroBytesThreadProof[multithreaded.SERIALIZED_THREAD_SIZE:], defaultThreadProof[multithreaded.SERIALIZED_THREAD_SIZE:])
+	nilBytesThreadProof := defaultThreadProof[multithreaded.SERIALIZED_THREAD_SIZE:]
+	return []threadProofTestcase{
+		{Name: "default thread proof", Proof: defaultThreadProof},
+		{Name: "zeroed thread bytes proof", Proof: zeroBytesThreadProof},
+		{Name: "nil thread bytes proof", Proof: nilBytesThreadProof},
+	}
+}

packages/contracts-bedrock/semver-lock.json

@@ -136,8 +136,8 @@
     "sourceCodeHash": "0xaf7416f27db1b393092f51d290a29293184105bc5f0d89cd6048f687cebc7d69"
   },
   "src/cannon/MIPS2.sol": {
-    "initCodeHash": "0xbb203b0d83efddfa0f664dbc63ec55844318b48fe8133758307f64e87c892a47",
-    "sourceCodeHash": "0x16614cc0e6abf7e81e1e5dc2c0773ee7101cb38af40e0907a8800ca7eddd3b5a"
+    "initCodeHash": "0x9ba94a69090a8c89786cdb2a5980deba4b5b16bbf5909f8275e090dbcd65e5c3",
+    "sourceCodeHash": "0x3859b4bf63f485800b0eb6ffb83a79c8d134f7e4cbbe93fbc72cc2ccd4f91b82"
   },
   "src/cannon/PreimageOracle.sol": {
     "initCodeHash": "0x64ea814bf9769257c91da57928675d3f8462374b0c23bdf860ccfc79f41f7801",

packages/contracts-bedrock/src/cannon/MIPS2.sol

@@ -57,8 +57,8 @@ contract MIPS2 is ISemver {
     }
 
     /// @notice The semantic version of the MIPS2 contract.
-    /// @custom:semver 1.0.0-beta.14
-    string public constant version = "1.0.0-beta.14";
+    /// @custom:semver 1.0.0-beta.15
+    string public constant version = "1.0.0-beta.15";
 
     /// @notice The preimage oracle contract.
     IPreimageOracle internal immutable ORACLE;
@@ -162,8 +162,11 @@ contract MIPS2 is ISemver {
                 return outputState();
             }
 
-            if (state.leftThreadStack == EMPTY_THREAD_ROOT && state.rightThreadStack == EMPTY_THREAD_ROOT) {
-                revert("MIPS2: illegal vm state");
+            if (
+                (state.leftThreadStack == EMPTY_THREAD_ROOT && !state.traverseRight)
+                    || (state.rightThreadStack == EMPTY_THREAD_ROOT && state.traverseRight)
+            ) {
+                revert("MIPS2: active thread stack is empty");
             }
 
             state.step += 1;