Handle additional jumps for listing 50

asm_files/list-0050.asm

@@ -0,0 +1,38 @@
+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 50
+; ========================================================================
+
+bits 16
+
+mov ax, 10
+mov bx, 10
+mov cx, 10
+
+label_0:
+cmp bx, cx
+je label_1
+
+add ax, 1
+jp label_2
+
+label_1:
+sub bx, 5
+jb label_3
+
+label_2:
+sub cx, 2
+
+label_3:
+loopnz label_0

asm_files/list-0050.txt

@@ -0,0 +1,37 @@
+--- test\listing_0050_challenge_jumps execution ---
+mov ax, 10 ; ax:0x0->0xa ip:0x0->0x3 
+mov bx, 10 ; bx:0x0->0xa ip:0x3->0x6 
+mov cx, 10 ; cx:0x0->0xa ip:0x6->0x9 
+cmp bx, cx ; ip:0x9->0xb flags:->PZ 
+je $+7 ; ip:0xb->0x12 
+sub bx, 5 ; bx:0xa->0x5 ip:0x12->0x15 flags:PZ->P 
+jb $+5 ; ip:0x15->0x17 
+sub cx, 2 ; cx:0xa->0x8 ip:0x17->0x1a flags:P-> 
+loopnz $-17 ; cx:0x8->0x7 ip:0x1a->0x9 
+cmp bx, cx ; ip:0x9->0xb flags:->CAS 
+je $+7 ; ip:0xb->0xd 
+add ax, 1 ; ax:0xa->0xb ip:0xd->0x10 flags:CAS-> 
+jp $+7 ; ip:0x10->0x12 
+sub bx, 5 ; bx:0x5->0x0 ip:0x12->0x15 flags:->PZ 
+jb $+5 ; ip:0x15->0x17 
+sub cx, 2 ; cx:0x7->0x5 ip:0x17->0x1a flags:PZ->P 
+loopnz $-17 ; cx:0x5->0x4 ip:0x1a->0x9 
+cmp bx, cx ; ip:0x9->0xb flags:P->CPAS 
+je $+7 ; ip:0xb->0xd 
+add ax, 1 ; ax:0xb->0xc ip:0xd->0x10 flags:CPAS->P 
+jp $+7 ; ip:0x10->0x17 
+sub cx, 2 ; cx:0x4->0x2 ip:0x17->0x1a flags:P-> 
+loopnz $-17 ; cx:0x2->0x1 ip:0x1a->0x9 
+cmp bx, cx ; ip:0x9->0xb flags:->CPAS 
+je $+7 ; ip:0xb->0xd 
+add ax, 1 ; ax:0xc->0xd ip:0xd->0x10 flags:CPAS-> 
+jp $+7 ; ip:0x10->0x12 
+sub bx, 5 ; bx:0x0->0xfffb ip:0x12->0x15 flags:->CAS 
+jb $+5 ; ip:0x15->0x1a 
+loopnz $-17 ; cx:0x1->0x0 ip:0x1a->0x1c 
+
+Final registers:
+      ax: 0x000d (13)
+      bx: 0xfffb (65531)
+      ip: 0x001c (28)
+   flags: CAS

execution.odin

@@ -108,25 +108,33 @@ execute_instruction :: proc(cpu: ^Cpu, inst: Instruction) {
             check_carry_flag(cpu, dst_val, src_val, false)
         }
     } else if jmp_offset,ok := inst.src.(Jump); ok {
+        jump: bool
         #partial switch inst.opname {
-        case .JNZ, .JNE:
-            if !cpu.flags[.ZF] {
+        case .JNZ, .JNE: jump = !cpu.flags[.ZF]
+        case .JE, .JZ:   jump =  cpu.flags[.ZF]
+        case .JP, .JPE:  jump =  cpu.flags[.PF]
+        case .JB, .JNAE: jump =  cpu.flags[.CF]
+
+        case .LOOPNZ, .LOOPNE:
+            cpu.registers[.cx].full -= 1
+            // According to this resource, the loopnz inst does not change any flags
+            // https://yassinebridi.github.io/asm-docs/8086_instruction_set.html#LOOPNZ
+            // check_zero_flag(cpu, cpu.registers[.cx].full)
+            jump = cpu.registers[.cx].full != 0 && !cpu.flags[.ZF]
+        }
+        if jump {
             cpu.registers[.ip].full += i16(jmp_offset)
-                if jmp_offset < 0 {
             cpu.registers[.ip].full -= i16(inst.bytes_read)
         }
     }
 }
-    }
-}
 
 execute_instructions :: proc(cpu: ^Cpu, instructions: DecodedInstructions) {
     halt := false
-    fmt.println(instructions.total_bytes_decoded)
     for !halt && get_ip(cpu) < instructions.total_bytes_decoded {
         inst,ok := instructions.inst_map[get_ip(cpu)]
         if !ok {
-            // Something went wrong with a jump, most likely
+            panic("Something went wrong with a jump, most likely")
         }
         cpu.registers[.ip].full += i16(inst.bytes_read)
         execute_instruction(cpu, inst)

instructions.odin

@@ -106,6 +106,7 @@ Op :: enum {
     LOOP,
     LOOPZ,
     LOOPNZ,
+    LOOPNE,
     JCXZ,
 }
 

sim8086.odin

@@ -44,7 +44,7 @@ main :: proc() {
     }
 
     cpu := Cpu {
-        memory = make([dynamic]u8, 65536),
+        memory = make([dynamic]u8, 1_048_576), // Exact num per the manual
     }
 
     execute_instructions(&cpu, decoded_insts)