Add IS_HOTSHOT_ALIVE opcode

src/osp/OneStepProofEntry.sol

@@ -177,7 +177,7 @@ contract OneStepProofEntry is IOneStepProofEntry {
                 opcode <= Instructions.SET_GLOBAL_STATE_U64) ||
             (opcode >= Instructions.READ_PRE_IMAGE && opcode <= Instructions.UNLINK_MODULE) ||
             (opcode >= Instructions.NEW_COTHREAD && opcode <= Instructions.SWITCH_COTHREAD) ||
-            (opcode == Instructions.READ_HOTSHOT_COMMITMENT)
+            (opcode == Instructions.READ_HOTSHOT_COMMITMENT || opcode == Instructions.IS_HOTSHOT_ALIVE)
         ) {
             prover = proverHostIo;
         } else {

src/osp/OneStepProverHostIo.sol

@@ -16,6 +16,7 @@ import "../bridge/IBridge.sol";
 
 interface IHotShot {
     function commitments(uint256) external view returns (uint256);
+    function availabilities(uint256) external view returns (bool);
 }
 
 contract OneStepProverHostIo is IOneStepProver {
@@ -314,6 +315,28 @@ contract OneStepProverHostIo is IOneStepProver {
         return true;
     }
 
+    function executeIsHotShotAlive(
+        ExecutionContext calldata execCtx,
+        Machine memory mach,
+        Module memory,
+        Instruction calldata,
+        bytes calldata proof
+    ) internal view {
+        uint256 height = mach.valueStack.pop().assumeI64();
+        uint8 liveness = uint8(proof[0]);
+        validateHotShotLiveness(execCtx, height, liveness > 0);
+
+    }
+
+    function validateHotShotLiveness(
+        ExecutionContext calldata,
+        uint256 height,
+        bool result
+    ) internal view returns (bool) {
+        bool expected = hotshot.availabilities(height);
+        return result == expected;
+    }
+
     function executeReadHotShotCommitment(
         ExecutionContext calldata execCtx,
         Machine memory mach,
@@ -717,7 +740,10 @@ contract OneStepProverHostIo is IOneStepProver {
             impl = executeSwitchCoThread;
         } else if (opcode == Instructions.READ_HOTSHOT_COMMITMENT) {
             impl = executeReadHotShotCommitment;
-        } else {
+        } else if (opcode == Instructions.IS_HOTSHOT_ALIVE) {
+            impl = executeIsHotShotAlive;
+        }
+        else {
             revert("INVALID_MEMORY_OPCODE");
         }
 

src/state/Instructions.sol

@@ -153,6 +153,7 @@ library Instructions {
     uint16 internal constant SWITCH_COTHREAD = 0x8032;
 
     uint16 internal constant READ_HOTSHOT_COMMITMENT = 0x9001;
+    uint16 internal constant IS_HOTSHOT_ALIVE = 0x9002;
 
     uint256 internal constant INBOX_INDEX_SEQUENCER = 0;
     uint256 internal constant INBOX_INDEX_DELAYED = 1;

src/test-helpers/HotShot.sol

@@ -3,8 +3,13 @@ pragma solidity ^0.8.0;
 
 contract MockHotShot {
     mapping(uint256 => uint256) public commitments;
+    mapping(uint256 => bool) public availabilities;
 
     function setCommitment(uint256 height, uint256 commitment) external {
         commitments[height] = commitment;
     }
+
+    function setAvailability(uint256 l1Height, bool isAlive) external {
+        availabilities[l1Height] = isAlive;
+    }
 }