Minor changes

2 files changed, 17 insertions, 24 deletions

diff --git a/src/main.c b/src/main.c
index 00d6be2..40bb871 100644
--- a/src/main.c
+++ b/src/main.c
@@ -13,7 +13,7 @@ int main(int argc, char *argv[])
 
   // Initialize
   MemInit();
-  MemLoadROM("../roms/chip8-test-suite/3-corax+.ch8");
+  MemLoadROM("../roms/chip8-test-suite/4-flags.ch8");
 
   ScreenInit(800,400);
   VCPUInit();
diff --git a/src/vcpu.c b/src/vcpu.c
index 08f4e06..d3eeb11 100644
--- a/src/vcpu.c
+++ b/src/vcpu.c
@@ -122,43 +122,36 @@ void VCPUExecute(){
       break;
       
     case 0x4: // VX = VX + VY
-      if((State.V[State.X] + State.V[State.Y]) > 255)
-        State.V[REG_FLAG]=1;
-      else
-        State.V[REG_FLAG]=0;
-      State.V[State.X]=State.V[State.X] + State.V[State.Y];
+      unsigned char x=State.V[State.X];
+      unsigned char y=State.V[State.Y];
+      State.V[State.X]=x+y;
+      State.V[REG_FLAG]=((x+y) > 255);
       break;
       
     case 0x5: // VX = VX - VY
-      if(State.V[State.X] > State.V[State.Y])
-        State.V[REG_FLAG]=1;
-      else
-        State.V[REG_FLAG]=0;
-      State.V[State.X]=State.V[State.X] - State.V[State.Y];
+      unsigned char x2=State.V[State.X];
+      unsigned char y2=State.V[State.Y];
+      State.V[State.X]=x2-y2;
+      State.V[REG_FLAG]=(x2>=y2);
       break;
       
     case 0x6: // VX = VX SHR 1
-      if(State.V[State.X] & 0x1 == 1)
-        State.V[REG_FLAG]=1;
-      else
-        State.V[REG_FLAG]=0;
+      char flag=State.V[State.X] & 0x1 == 1;
       State.V[State.X]=State.V[State.X] >> 1;
+      State.V[REG_FLAG]=flag;
       break;
       
     case 0x7: // VX = VY - VX
-      if(State.V[State.Y] > State.V[State.X])
-        State.V[REG_FLAG]=1;
-      else
-        State.V[REG_FLAG]=0;
-      State.V[State.X]=State.V[State.Y] - State.V[State.X];
+      unsigned char x3=State.V[State.X];
+      unsigned char y3=State.V[State.Y];
+      State.V[State.X]=y3-x3;
+      State.V[REG_FLAG]=(y3>=x3);
       break;
       
     case 0xE: // VX = VX SHL 1
-      if(State.V[State.X] >> 7 == 1)
-        State.V[REG_FLAG]=1;
-      else
-        State.V[REG_FLAG]=0;
+      char flag2=State.V[State.X] >> 7 == 1;
       State.V[State.X]=State.V[State.X] << 1;
+      State.V[REG_FLAG]=flag2;
       break;
       
     }