From 1b5f02ef7a3e398c9ab5a822b9fa978a4e32d6bd Mon Sep 17 00:00:00 2001
From: Matthew Laux <matthew.laux@gmail.com>
Date: Mon, 18 Jul 2022 23:35:51 -0500
Subject: [PATCH] a few more instructions for today. abstract out conditional
 jump

---
 src/cpu.c   | 43 +++++++++++++++++++++++++++++++------------
 src/types.h |  2 ++
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/src/cpu.c b/src/cpu.c
index e7d77df..0814bac 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -372,6 +372,16 @@ static void extended_insn(struct cpu *cpu, u8 insn)
     }
 }
 
+static void conditional_jump(struct cpu *cpu, u8 opc, u8 neg_op, int flag) {
+    s8 target = (s8) read8(cpu, cpu->pc);
+    if ((opc == neg_op) ^ flag_isset(cpu, flag)) {
+        cpu->pc += target + 1;
+        cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
+    } else {
+        cpu->pc++;
+    }
+}
+
 void cpu_step(struct cpu *cpu)
 {
     u8 temp;
@@ -400,6 +410,9 @@ void cpu_step(struct cpu *cpu)
             write16(cpu, read16(cpu, cpu->pc), cpu->sp);
             cpu->pc += 2;
             break;
+        case 0x09: // ADD HL,BC
+            add16(cpu, read_bc(cpu));
+            break;
         case 0x19: // ADD HL,DE
             add16(cpu, read_de(cpu));
             break;
@@ -545,17 +558,15 @@ void cpu_step(struct cpu *cpu)
             break;
         case 0x18: // JR r8
             temp = read8(cpu, cpu->pc);
-            cpu->pc += *((signed char *) &temp) + 1;
+            cpu->pc += (s8) temp + 1;
             break;
         case 0x20: // JR NZ,r8
         case 0x28: // JR Z,r8
-            temp = read8(cpu, cpu->pc);
-            if ((opc == 0x20) ^ flag_isset(cpu, FLAG_ZERO)) {
-                cpu->pc += *((signed char *) &temp) + 1;
-                cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
-            } else {
-                cpu->pc++;
-            }
+            conditional_jump(cpu, opc, 0x20, FLAG_ZERO);
+            break;
+        case 0x30: // JR NC, i8
+        case 0x38: // JR C, i8
+            conditional_jump(cpu, opc, 0x30, FLAG_CARRY);
             break;
         case 0x21: // LD HL, d16
             write_hl(cpu, read16(cpu, cpu->pc));
@@ -621,6 +632,15 @@ void cpu_step(struct cpu *cpu)
         case 0x8e: add(cpu, read8(cpu, read_hl(cpu)), 1); break;
         case 0x8f: add(cpu, cpu->a, 1); break;
 
+        case 0xc6: // ADD A, u8
+            add(cpu, read8(cpu, cpu->pc), 0);
+            cpu->pc++;
+            break;
+        case 0xce: // ADC A, u8
+            add(cpu, read8(cpu, cpu->pc), 1);
+            cpu->pc++;
+            break;
+
         case 0x90: subtract(cpu, cpu->b, 0, 0); break;
         case 0x91: subtract(cpu, cpu->c, 0, 0); break;
         case 0x92: subtract(cpu, cpu->d, 0, 0); break;
@@ -691,6 +711,9 @@ void cpu_step(struct cpu *cpu)
         case 0xf7: push(cpu, cpu->pc); cpu->pc = 0x30; break;
         case 0xff: push(cpu, cpu->pc); cpu->pc = 0x38; break;
 
+        case 0x76: // HALT
+            break;
+
         case 0xc1: // POP BC
             write_bc(cpu, pop(cpu));
             break;
@@ -713,10 +736,6 @@ void cpu_step(struct cpu *cpu)
             extended_insn(cpu, read8(cpu, cpu->pc));
             cpu->pc++;
             break;
-        case 0xce:
-            add(cpu, read8(cpu, cpu->pc), 1);
-            cpu->pc++;
-            break;
         case 0xd1: // POP DE
             write_de(cpu, pop(cpu));
             break;
diff --git a/src/types.h b/src/types.h
index e10b2d8..f89918d 100644
--- a/src/types.h
+++ b/src/types.h
@@ -6,4 +6,6 @@ typedef unsigned short u16;
 typedef unsigned long u32;
 typedef unsigned long long u64;
 
+typedef signed char s8;
+
 #endif