don't keep calling m()

contracts/Challenge.sol

@@ -19,6 +19,7 @@ contract Challenge {
 
   // the mips machine state transition function
   IMIPS immutable mips;
+  IMIPSMemory immutable mem;
 
   // the program start state
   bytes32 immutable GlobalStartState;
@@ -35,6 +36,7 @@ contract Challenge {
   constructor(IMIPS imips, bytes32 globalStartState) {
     owner = msg.sender;
     mips = imips;
+    mem = imips.m();
     GlobalStartState = globalStartState;
   }
 
@@ -52,7 +54,7 @@ contract Challenge {
     for (uint32 i = 0; i < 32; i += 4) {
       uint256 tv = uint256(val>>(224-(i*8)));
 
-      stateHash = mips.m().WriteMemory(stateHash, addr+i, uint32(tv));
+      stateHash = mem.WriteMemory(stateHash, addr+i, uint32(tv));
     }
     return stateHash;
   }
@@ -108,8 +110,8 @@ contract Challenge {
     // confirm the finalSystemHash asserts the state you claim (in $t0-$t7) and the machine is stopped
     // you must load these proofs into MIPS before calling this
     // we disagree at the end
-    require(mips.m().ReadBytes32(finalSystemState, 0x30000800) == assertionRoot, "you are claiming a different state root in machine");
-    require(mips.m().ReadMemory(finalSystemState, 0xC0000080) == 0xDEAD0000, "machine is not stopped in final state (PC == 0xDEAD0000)");
+    require(mem.ReadBytes32(finalSystemState, 0x30000800) == assertionRoot, "you are claiming a different state root in machine");
+    require(mem.ReadMemory(finalSystemState, 0xC0000080) == 0xDEAD0000, "machine is not stopped in final state (PC == 0xDEAD0000)");
 
     return newChallengeTrusted(startState, finalSystemState, stepCount);
   }