Fix offset bug when loading `exited` and `exitCode`

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

@@ -103,9 +103,9 @@ contract MIPS {
             from, to := copyMem(from, to, 4) // lo
             from, to := copyMem(from, to, 4) // hi
             from, to := copyMem(from, to, 4) // heap
-            let exitCode := shr(248, mload(from))
+            let exitCode := mload(from)
             from, to := copyMem(from, to, 1) // exitCode
-            let exited := shr(248, mload(from))
+            let exited := mload(from)
             from, to := copyMem(from, to, 1) // exited
             from, to := copyMem(from, to, 8) // step
             from := add(from, 32) // offset to registers
@@ -137,7 +137,7 @@ contract MIPS {
 
             // Compute the hash of the resulting MIPS state
             out_ := keccak256(start, sub(to, start))
-            out_ := or(shl(248, status), and(not(shl(248, 0xff)), out_))
+            out_ := or(and(not(shl(248, 0xFF)), out_), shl(248, status))
         }
     }
 

packages/contracts-bedrock/test/MIPS.t.sol

@@ -1558,7 +1558,7 @@ contract MIPS_Test is CommonTest {
     ///      1. Exited with success (Invalid)
     ///      2. Exited with failure (Panic)
     ///      3. Unfinished
-    function vmStatus(MIPS.State memory state) internal pure returns (uint8 out_) {
+    function vmStatus(MIPS.State memory state) internal pure returns (uint256 out_) {
         if (state.exited) {
             if (state.exitCode == 0) {
                 return 0;
@@ -1574,7 +1574,7 @@ contract MIPS_Test is CommonTest {
 
     function outputState(MIPS.State memory state) internal pure returns (bytes32 out_) {
         bytes memory enc = encodeState(state);
-        uint8 status = vmStatus(state);
+        uint256 status = vmStatus(state);
         assembly {
             out_ := keccak256(add(enc, 0x20), 226)
             out_ := or(and(not(shl(248, 0xFF)), out_), shl(248, status))