85k ops/sec

contracts/MIPS.sol

@@ -66,13 +66,6 @@ contract MIPS {
     uint256 signed = ((1 << (32-idx)) - 1) << idx;
     uint256 mask = (1 << idx) - 1;
     return uint32(dat&mask | (isSigned ? signed : 0));
-
-    /*if (idx == 16) {
-      return dat&0xFFFF | (dat&0x8000 != 0 ? 0xFFFF0000 : 0);
-    } else if (idx == 8) {
-      return dat&0xFF | (dat&0x80 != 0 ? 0xFFFFFF00 : 0);
-    }
-    return dat;*/
   }
 
   // will revert if any required input state is missing
@@ -209,21 +202,21 @@ contract MIPS {
     // jumps (with branch delay slot)
     // nothing is written to the state by this time
 
-
-    if (opcode == 0 && (func == 8 || func == 9)) {
+    if (opcode == 0) {
+      if (func == 8 || func == 9) {
         // jr/jalr (val is already right)
         return stepNextPC(stateHash, uint32(nextPC), val | (func == 9 ? STORE_LINK : 0));
       }
 
       // syscall (can read and write)
-    if (opcode == 0 && func == 0xC) {
+      if (func == 0xC) {
         //revert("unhandled syscall");
         stateHash = handleSyscall(stateHash);
       }
 
       // lo and hi registers
       // can write back
-    if (opcode == 0) {
+      if (func >= 0x10 && func < 0x1c) {
         if (func == 0x10) val = ReadMemory(stateHash, REG_HI); // mfhi
         else if (func == 0x11) storeAddr = REG_HI; // mthi
         else if (func == 0x12) val = ReadMemory(stateHash, REG_LO); // mflo
@@ -253,6 +246,7 @@ contract MIPS {
           storeAddr = REG_LO;
         }
       }
+    }
 
     // stupid sc, write a 1 to rt
     if (opcode == 0x38) {
@@ -280,6 +274,7 @@ contract MIPS {
 
     // transform ArithLogI
     // TODO: replace with table
+    if (opcode >= 8 && opcode < 0xF) {
       if (opcode == 8) { opcode = 0; func = 0x20; }        // addi
       else if (opcode == 9) { opcode = 0; func = 0x21; }   // addiu
       else if (opcode == 0xa) { opcode = 0; func = 0x2a; } // slti
@@ -287,6 +282,7 @@ contract MIPS {
       else if (opcode == 0xc) { opcode = 0; func = 0x24; } // andi
       else if (opcode == 0xd) { opcode = 0; func = 0x25; } // ori
       else if (opcode == 0xe) { opcode = 0; func = 0x26; } // xori
+    }
 
     // 0 is opcode SPECIAL
     if (opcode == 0) {