chore: dedup code in THUMB instructions

src/cpu/arm/data_processing.zig

@@ -263,7 +263,7 @@ fn setArmLogicOpFlags(comptime S: bool, cpu: *Arm7tdmi, rd: u4, result: u32) voi
     }
 }
 
-fn setLogicOpFlags(comptime S: bool, cpu: *Arm7tdmi, result: u32) void {
+pub fn setLogicOpFlags(comptime S: bool, cpu: *Arm7tdmi, result: u32) void {
     if (S) {
         cpu.cpsr.n.write(result >> 31 & 1 == 1);
         cpu.cpsr.z.write(result == 0);

src/cpu/thumb/format1.zig

@@ -5,6 +5,8 @@ const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
 const shifter = @import("../barrel_shifter.zig");
 
+const setLogicOpFlags = @import("../arm/data_processing.zig").setLogicOpFlags;
+
 pub fn format1(comptime op: u2, comptime offset: u5) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
@@ -12,17 +14,15 @@ pub fn format1(comptime op: u2, comptime offset: u5) InstrFn {
             const rd = opcode & 0x7;
 
             const result = switch (op) {
-                0b00 => shifter.logicalLeft(true, &cpu.cpsr, cpu.r[rs], offset),
+                0b00 => shifter.logicalLeft(true, &cpu.cpsr, cpu.r[rs], offset), // LSL
-                0b01 => shifter.logicalRight(true, &cpu.cpsr, cpu.r[rs], offset),
+                0b01 => shifter.logicalRight(true, &cpu.cpsr, cpu.r[rs], offset), // LSR
-                0b10 => shifter.arithmeticRight(true, &cpu.cpsr, cpu.r[rs], offset),
+                0b10 => shifter.arithmeticRight(true, &cpu.cpsr, cpu.r[rs], offset), // ASR
                 else => std.debug.panic("[CPU|THUMB|Fmt1] {} is an invalid op", .{op}),
             };
 
+            // Equivalent to an ARM MOVS
             cpu.r[rd] = result;
-
+            setLogicOpFlags(true, cpu, result);
-            // Instructions of this type are equivalent to a MOVS
-            cpu.cpsr.n.write(result >> 31 & 1 == 1);
-            cpu.cpsr.z.write(result == 0);
         }
     }.inner;
 }

src/cpu/thumb/format12.zig

@@ -7,8 +7,9 @@ const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
 pub fn format12(comptime isSP: bool, comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
-            const left = if (isSP) cpu.r[13] else cpu.r[15] + 2 & 0xFFFF_FFFD; // fetch (+2)
+            // ADD
-            const right = @truncate(u10, opcode & 0xFF) << 2;
+            const left = if (isSP) cpu.r[13] else cpu.fakePC() & 0xFFFF_FFFC;
+            const right = (opcode & 0xFF) << 2;
             const result = left + right; // TODO: What about overflows?
             cpu.r[rd] = result;
         }

src/cpu/thumb/format16.zig

@@ -3,20 +3,24 @@ const std = @import("std");
 const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
+
 const checkCond = @import("../../cpu.zig").checkCond;
 const u32SignExtend = @import("../../util.zig").u32SignExtend;
 
 pub fn format16(comptime cond: u4) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
-            const offset = (opcode & 0xFF) << 1;
+            // B
+            const offset = u32SignExtend(8, opcode & 0xFF) << 1;
 
-            const do_execute = switch (cond) {
+            const should_execute = switch (cond) {
                 0xE, 0xF => std.debug.panic("[CPU/THUMB] Undefined conditional branch with condition {}", .{cond}),
                 else => checkCond(cpu.cpsr, cond),
             };
 
-            if (do_execute) cpu.r[15] = (cpu.fakePC() & 0xFFFF_FFFC) +% u32SignExtend(8, offset);
+            if (should_execute) {
+                cpu.r[15] = (cpu.fakePC() & 0xFFFF_FFFC) +% offset;
+            }
         }
     }.inner;
 }

src/cpu/thumb/format19.zig

@@ -8,6 +8,7 @@ const u32SignExtend = @import("../../util.zig").u32SignExtend;
 pub fn format19(comptime is_low: bool) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
+            // BL
             const offset = opcode & 0x3FF;
 
             if (is_low) {

src/cpu/thumb/format3.zig

@@ -4,6 +4,11 @@ const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
 
+const add = @import("../arm/data_processing.zig").add;
+const sub = @import("../arm/data_processing.zig").sub;
+const cmp = @import("../arm/data_processing.zig").cmp;
+const setLogicOpFlags = @import("../arm/data_processing.zig").setLogicOpFlags;
+
 pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
@@ -13,44 +18,11 @@ pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
                 0b00 => {
                     // MOV
                     cpu.r[rd] = offset;
-
+                    setLogicOpFlags(true, cpu, offset);
-                    cpu.cpsr.n.unset();
-                    cpu.cpsr.z.write(offset == 0);
-                },
-                0b01 => {
-                    // CMP
-                    const left = cpu.r[rd];
-                    const result = left -% offset;
-
-                    cpu.cpsr.n.write(result >> 31 & 1 == 1);
-                    cpu.cpsr.z.write(result == 0);
-                    cpu.cpsr.c.write(offset <= left);
-                    cpu.cpsr.v.write(((left ^ result) & (~offset ^ result)) >> 31 & 1 == 1);
-                },
-                0b10 => {
-                    // ADD
-                    const left = cpu.r[rd];
-
-                    var result: u32 = undefined;
-                    const didOverflow = @addWithOverflow(u32, left, offset, &result);
-                    cpu.r[rd] = result;
-
-                    cpu.cpsr.n.write(result >> 31 & 1 == 1);
-                    cpu.cpsr.z.write(result == 0);
-                    cpu.cpsr.c.write(didOverflow);
-                    cpu.cpsr.v.write(((left ^ result) & (offset ^ result)) >> 31 & 1 == 1);
-                },
-                0b11 => {
-                    // SUB
-                    const left = cpu.r[rd];
-                    const result = left -% offset;
-                    cpu.r[rd] = result;
-
-                    cpu.cpsr.n.write(result >> 31 & 1 == 1);
-                    cpu.cpsr.z.write(result == 0);
-                    cpu.cpsr.c.write(offset <= left);
-                    cpu.cpsr.v.write(((left ^ result) & (~offset ^ result)) >> 31 & 1 == 1);
                 },
+                0b01 => cmp(cpu, cpu.r[rd], offset), // CMP
+                0b10 => cpu.r[rd] = add(true, cpu, cpu.r[rd], offset), // ADD
+                0b11 => cpu.r[rd] = sub(true, cpu, cpu.r[rd], offset), // SUB
             }
         }
     }.inner;

src/cpu/thumb/format5.zig

@@ -4,6 +4,8 @@ const Bus = @import("../../Bus.zig");
 const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
 const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
 
+const cmp = @import("../arm/data_processing.zig").cmp;
+
 pub fn format5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
@@ -11,24 +13,14 @@ pub fn format5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
             const dst = @as(u4, h1) << 3 | (opcode & 0x7);
 
             switch (op) {
-                0b01 => {
+                0b01 => cmp(cpu, cpu.r[dst], cpu.r[src]), // CMP
-                    // CMP
-                    const left = cpu.r[dst];
-                    const right = cpu.r[src];
-                    const result = left -% right;
-
-                    cpu.cpsr.n.write(result >> 31 & 1 == 1);
-                    cpu.cpsr.z.write(result == 0);
-                    cpu.cpsr.c.write(right <= left);
-                    cpu.cpsr.v.write(((left ^ result) & (~right ^ result)) >> 31 & 1 == 1);
-                },
                 0b10 => cpu.r[dst] = cpu.r[src], // MOV
                 0b11 => {
                     // BX
                     cpu.cpsr.t.write(cpu.r[src] & 1 == 1);
                     cpu.r[15] = cpu.r[src] & 0xFFFF_FFFE;
                 },
-                else => std.debug.panic("[CPU] Op #{} is invalid for THUMB Format 5", .{op}),
+                else => std.debug.panic("[CPU|THUMB|Fmt5] {} is an invalid op", .{op}),
             }
         }
     }.inner;

src/cpu/thumb/format6.zig

@@ -7,6 +7,7 @@ const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
 pub fn format6(comptime rd: u3) InstrFn {
     return struct {
         fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
+            // LDR
             const offset = (opcode & 0xFF) << 2;
 
             // FIXME: Should this overflow?