fix: get beeg.gba working again

src/cpu/arm/data_processing.zig

@@ -13,6 +13,7 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime instrKind: u4
             const old_carry = @boolToInt(cpu.cpsr.c.read());
 
             // If certain conditions are met, PC is 12 ahead instead of 8
+            // TODO: What are these conditions? I can't remember
             if (!I and opcode >> 4 & 1 == 1) cpu.r[15] += 4;
 
             const op1 = if (rn == 0xF) cpu.fakePC() else cpu.r[rn];
@@ -127,6 +128,8 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime instrKind: u4
                     setArmLogicOpFlags(S, cpu, rd, result);
                 },
             }
+
+            if (rd == 0xF) cpu.pipe.flush();
         }
     }.inner;
 }