Step/main/branch

emulate.c

@@ -308,6 +308,89 @@ void dataProcessingInstr(struct ProcessorState *processor, int address)
   }
 }
 
+void branchInstr(struct ProcessorState *processor, uint32_t address) 
+{
+  // Check if address is valid
+  verifyAddress(address);
+  uint32_t instr = processor->memory[address];
+
+  //  Check if the instruction should be executed according to its condition codes
+  if(!validCond(getBits(instr, 28, 31), processor)){
+    return;
+  }
+
+  // Get offset and sign
+  int32_t offset = getBits(instr, 0, 23);
+  int sign = getBits(offset, 23, 23);
+
+  // New address calculated with left shift and sign extension (and offset of 8)
+  uint32_t branchAddr = processor->registers[14] + ((offset * 4) | ((sign) ? 0xFC000000 : 0)) + 8;
+
+  // New address verified
+  verifyAddress(branchAddr);
+
+  // New address loaded to PC
+  processor->registers[14] = branchAddr;
+
+  return;
+}
+
+// Steps through pipeline calling appropriate instruction method.
+// Sets teminate if instruction is all-0.
+void step(struct ProcessorState *processor, bool *terminate)
+{
+  // Fetches next instruction location (including offset)
+  uint32_t nextAddr = processor->registers[14] + 8;
+
+  // Fetches next instruction to be executed
+  uint32_t nextInstr = processor->memory[nextAddr];
+
+  // Checks for all-0 
+  if (nextInstr == 0) 
+  {
+    *terminate = 1;
+    return;
+  }
+
+  // Check instruction type and call appropriate method
+  switch (getBits(nextInstr, 26, 27))
+  {
+  case 0:
+    if ((getBits(nextInstr, 25, 25) == 0) && (getBits(nextInstr, 4, 8) == 9)) {
+      multiplyInstr(processor, nextAddr);
+    } else {
+      dataProcessingInstr(processor, nextAddr);
+    }
+  case 1: 
+    dataTransferInstr(processor, nextAddr);
+  case 2: 
+    branchInstr(processor, nextAddr);
+  }
+  return;
+} 
+
+int main(int argc, char *argv[])
+{
+  struct ProcessorState *processor;
+
+  // Load file into processor state
+  if (argc == 2) {
+    processor = loadBinary(argv[1]);
+  } else if (argc > 2) {
+    printf("Too many arguments");
+    return 0;
+  } else {
+    printf("No file given");
+    return 0;
+  }
+
+  bool terminate = 0;
+
+  // Loop through instructions until all-0 met
+  while (!terminate) {
+    step(processor, &terminate);
+  }
+} 
 
 //*** TESTING FUNCTIONS ***//
 
@@ -389,10 +472,12 @@ struct ProcessorState *makeProcessor(void)
   return processor;
 }
 
+/*
 int main(void)
 {
   testBitGetters();
   printf("\n");
   testBarrelShifter();
   return 0;
-}
\ No newline at end of file
+}
+*/
\ No newline at end of file