simon987/Much-Assembly-Required
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Merge pull request #83 from Francessco121/feature/pushf-popf

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Add PUSHF and POPF instructions
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Simon Fortier 2018-01-01 10:20:27 -05:00 committed by GitHub
commit 93786d92cb
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4 changed files with 106 additions and 0 deletions
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2
Server/src/main/java/net/simon987/server/assembly/CPU.java
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@ -97,6 +97,8 @@ public class CPU implements JSONSerialisable {
instructionSet.add(new JncInstruction(this));
instructionSet.add(new JnoInstruction(this));
instructionSet.add(new JoInstruction(this));
instructionSet.add(new PushfInstruction(this));
instructionSet.add(new PopfInstruction(this));
status = new Status();
memory = new Memory(config.getInt("memory_size"));

16
Server/src/main/java/net/simon987/server/assembly/Status.java
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@ -132,4 +132,20 @@ public class Status {
public void setErrorFlag(boolean errorFlag) {
this.errorFlag = errorFlag;
}
public char toByte() {
char stat = 0;
stat = (char) (stat | ((signFlag ? 1 : 0) << 3));
stat = (char) (stat | ((zeroFlag ? 1 : 0) << 2));
stat = (char) (stat | ((carryFlag ? 1 : 0) << 1));
stat = (char) (stat | (overflowFlag ? 1 : 0));
return stat;
}
public void fromByte(char stat) {
setSignFlag((stat & (1 << 3)) != 0);
setZeroFlag((stat & (1 << 2)) != 0);
setCarryFlag((stat & (1 << 1)) != 0);
setOverflowFlag((stat & 1) != 0);
}
}

46
Server/src/main/java/net/simon987/server/assembly/instruction/PopfInstruction.java Normal file
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@ -0,0 +1,46 @@
package net.simon987.server.assembly.instruction;
import net.simon987.server.assembly.CPU;
import net.simon987.server.assembly.Instruction;
import net.simon987.server.assembly.Register;
import net.simon987.server.assembly.Status;
/**
* Pops a single word off the top of the stack and sets the CPU flags to it.
*/
public class PopfInstruction extends Instruction {
/**
* Opcode of the instruction
*/
public static final int OPCODE = 44;
private CPU cpu;
public PopfInstruction(CPU cpu) {
super("popf", OPCODE);
this.cpu = cpu;
}
@Override
public Status execute(Status status) {
Register sp = cpu.getRegisterSet().getRegister("SP");
// Get the word on the top of the stack
char flags = (char) cpu.getMemory().get(sp.getValue());
// Overwrite the CPU flags
status.fromByte(flags);
// Increment SP
sp.setValue(sp.getValue() + 1);
return status;
}
public boolean noOperandsValid() {
return true;
}
}

42
Server/src/main/java/net/simon987/server/assembly/instruction/PushfInstruction.java Normal file
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@ -0,0 +1,42 @@
package net.simon987.server.assembly.instruction;
import net.simon987.server.assembly.CPU;
import net.simon987.server.assembly.Instruction;
import net.simon987.server.assembly.Register;
import net.simon987.server.assembly.Status;
/**
* Pushes the current CPU flags onto the stack.
*/
public class PushfInstruction extends Instruction {
/**
* Opcode of the instruction
*/
public static final int OPCODE = 43;
private CPU cpu;
public PushfInstruction(CPU cpu) {
super("pushf", OPCODE);
this.cpu = cpu;
}
@Override
public Status execute(Status status) {
// Decrement SP
Register sp = cpu.getRegisterSet().getRegister("SP");
sp.setValue(sp.getValue() - 1);
// Push the current flags
cpu.getMemory().set(sp.getValue(), status.toByte());
return status;
}
public boolean noOperandsValid() {
return true;
}
}