From 4db0a8163e6641923466da99ff84d34dfdca44fa Mon Sep 17 00:00:00 2001
From: vin <git@vineetk.net>
Date: Sun, 9 Jun 2024 16:02:04 +0530
Subject: [PATCH] implement some more instructions and branching?

---
 cpu.c | 89 ++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 64 insertions(+), 25 deletions(-)

diff --git a/cpu.c b/cpu.c
index 3bbfc42..c5b35f6 100644
--- a/cpu.c
+++ b/cpu.c
@@ -76,6 +76,7 @@ opcode_arg(enum addressing_mode mode)
 
 	switch (mode) {
 	case AM_IMM:
+	case AM_REL:
 		val = arg;
 		break;
 	case AM_ZP:
@@ -128,13 +129,23 @@ adc(uint8_t arg)
 static void
 and(uint8_t arg)
 {
-/* TODO: complete this */
+	regs.a &= arg;
+
+	STATUS_UPDATE_ZERO(regs.a);
+	STATUS_UPDATE_NEGATIVE(regs.a);
 }
 
 static void
 asl(uint8_t arg)
 {
-/* TODO: complete this */
+	uint16_t tmp;
+
+	tmp = regs.a << 1;
+	regs.a = tmp & 0xFF;
+
+	regs.status.carry = tmp > 0xFF;
+	STATUS_UPDATE_ZERO(regs.a);
+	STATUS_UPDATE_NEGATIVE(regs.a);
 }
 
 static void
@@ -152,43 +163,51 @@ bbs(uint8_t arg)
 static void
 bcc(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.carry == 0)
+		regs.pc += arg;
 }
 
 static void
 bcs(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.carry == 1)
+		regs.pc += arg;
 }
 
 static void
 beq(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.zero == 1)
+		regs.pc += arg;
 }
 
 static void
 bit(uint8_t arg)
 {
-/* TODO: complete this */
+	regs.status.zero = (regs.a & arg) == 0;
+	regs.status.overflow = (arg & (1 << 6)) > 0;
+	regs.status.negative = (arg & (1 << 7)) > 0;
 }
 
 static void
 bmi(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.negative == 1)
+		regs.pc += arg;
 }
 
 static void
 bne(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.zero == 0)
+		regs.pc += arg;
 }
 
 static void
 bpl(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.negative == 0)
+		regs.pc += arg;
 }
 
 static void
@@ -198,7 +217,7 @@ bra(uint8_t arg)
 }
 
 static void
-brk()
+brk(void)
 {
 	/* TODO: push regs.pc and regs.status to stack and load IRQ vector */
 	regs.status.brk = 1;
@@ -208,55 +227,75 @@ brk()
 static void
 bvc(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.overflow == 0)
+		regs.pc += arg;
 }
 
 static void
 bvs(uint8_t arg)
 {
-/* TODO: complete this */
+	if (regs.status.overflow == 1)
+		regs.pc += arg;
 }
 
 static void
-clc(uint8_t arg)
+clc(void)
 {
-/* TODO: complete this */
+	regs.status.carry = 0;
 }
 
 static void
-cld(uint8_t arg)
+cld(void)
 {
-/* TODO: complete this */
+	regs.status.decimal_mode = 0;
 }
 
 static void
-cli(uint8_t arg)
+cli(void)
 {
-/* TODO: complete this */
+	regs.status.interrupt_disable = 0;
 }
 
 static void
-clv(uint8_t arg)
+clv(void)
 {
-/* TODO: complete this */
+	regs.status.overflow = 0;
 }
 
 static void
 cmp(uint8_t arg)
 {
-/* TODO: complete this */
+	uint8_t tmp;
+
+	tmp = regs.a - arg;
+
+	regs.status.carry = regs.a >= arg;
+	regs.status.zero = regs.a == arg;
+	regs.status.negative = (tmp & (1 << 7)) > 0;
 }
 
 static void
 cpx(uint8_t arg)
 {
-/* TODO: complete this */
+	uint8_t tmp;
+
+	tmp = regs.x - arg;
+
+	regs.status.carry = regs.x >= arg;
+	regs.status.zero = regs.x == arg;
+	regs.status.negative = (tmp & (1 << 7)) > 0;
 }
 
 static void
 cpy(uint8_t arg)
 {
-/* TODO: complete this */
+	uint8_t tmp;
+
+	tmp = regs.y - arg;
+
+	regs.status.carry = regs.y >= arg;
+	regs.status.zero = regs.y == arg;
+	regs.status.negative = (tmp & (1 << 7)) > 0;
 }
 
 static void
@@ -290,7 +329,7 @@ inc(uint8_t arg)
 }
 
 static void
-inx()
+inx(void)
 {
 	regs.x++;
 
@@ -496,7 +535,7 @@ stz(uint8_t arg)
 }
 
 static void
-tax()
+tax(void)
 {
 	regs.x = regs.a;