src/core/cpu.zig

@@ -323,21 +323,8 @@ pub const Arm7tdmi = struct {
         return self.bus.io.haltcnt == .Halt;
     }
 
-    pub fn setCpsrNoFlush(self: *Self, value: u32) void {
-        if (value & 0x1F != self.cpsr.raw & 0x1F) self.changeModeFromIdx(@truncate(u5, value & 0x1F));
-        self.cpsr.raw = value;
-    }
-
     pub fn setCpsr(self: *Self, value: u32) void {
         if (value & 0x1F != self.cpsr.raw & 0x1F) self.changeModeFromIdx(@truncate(u5, value & 0x1F));
-
-        const new: PSR = .{ .raw = value };
-        if (self.cpsr.t.read() != new.t.read()) {
-            // If THUMB to ARM or ARM to THUMB, flush pipeline
-            self.r[15] &= if (new.t.read()) ~@as(u32, 1) else ~@as(u32, 3);
-            if (new.t.read()) self.pipe.reload(u16, self) else self.pipe.reload(u32, self);
-        }
-
         self.cpsr.raw = value;
     }
 
@@ -500,7 +487,8 @@ pub const Arm7tdmi = struct {
         // log.debug("Handling Interrupt!", .{});
         self.bus.io.haltcnt = .Execute;
 
-        const ret_addr = self.r[15] - if (self.cpsr.t.read()) 2 else @as(u32, 4);
+        // FIXME: This seems weird, but retAddr.gba suggests I need to make these changes
+        const ret_addr = self.r[15] - if (self.cpsr.t.read()) 0 else @as(u32, 4);
         const new_spsr = self.cpsr.raw;
 
         self.changeMode(.Irq);
@@ -510,7 +498,7 @@ pub const Arm7tdmi = struct {
         self.r[14] = ret_addr;
         self.spsr.raw = new_spsr;
         self.r[15] = 0x0000_0018;
-        self.pipe.reload(u32, self);
+        self.pipe.reload(self);
     }
 
     inline fn fetch(self: *Self, comptime T: type) T {
@@ -692,18 +680,17 @@ const Pipline = struct {
         return opcode;
     }
 
-    pub fn reload(self: *Self, comptime T: type, cpu: *Arm7tdmi) void {
-        comptime std.debug.assert(T == u32 or T == u16);
+    pub fn reload(self: *Self, cpu: *Arm7tdmi) void {
+        if (cpu.cpsr.t.read()) {
+            self.stage[0] = cpu.bus.read(u16, cpu.r[15]);
+            self.stage[1] = cpu.bus.read(u16, cpu.r[15] + 2);
+            cpu.r[15] += 4;
+        } else {
+            self.stage[0] = cpu.bus.read(u32, cpu.r[15]);
+            self.stage[1] = cpu.bus.read(u32, cpu.r[15] + 4);
+            cpu.r[15] += 8;
+        }
 
-        // Sometimes, the pipeline can be reloaded twice in the same instruction
-        // This can happen if:
-        // 1. R15 is written to
-        // 2. The CPSR is written to (and T changes), so R15 is written to again
-
-        self.stage[0] = cpu.bus.read(T, cpu.r[15]);
-        self.stage[1] = cpu.bus.read(T, cpu.r[15] + if (T == u32) 4 else @as(u32, 2));
-
-        cpu.r[15] += if (T == u32) 8 else @as(u32, 4);
         self.flushed = true;
     }
 };

src/core/cpu/arm/block_data_transfer.zig

@@ -55,7 +55,7 @@ pub fn blockDataTransfer(comptime P: bool, comptime U: bool, comptime S: bool, c
 
                 if (L) {
                     cpu.r[15] = bus.read(u32, und_addr);
-                    cpu.pipe.reload(u32, cpu);
+                    cpu.pipe.reload(cpu);
                 } else {
                     // FIXME: Should r15 on write be +12 ahead?
                     bus.write(u32, und_addr, cpu.r[15] + 4);
@@ -92,7 +92,7 @@ pub fn blockDataTransfer(comptime P: bool, comptime U: bool, comptime S: bool, c
                     cpu.r[i] = value;
                     if (i == 0xF) {
                         cpu.r[i] &= ~@as(u32, 3); // Align r15
-                        cpu.pipe.reload(u32, cpu);
+                        cpu.pipe.reload(cpu);
 
                         if (S) cpu.setCpsr(cpu.spsr.raw);
                     }

src/core/cpu/arm/branch.zig

@@ -12,7 +12,7 @@ pub fn branch(comptime L: bool) InstrFn {
             if (L) cpu.r[14] = cpu.r[15] - 4;
 
             cpu.r[15] +%= sext(u32, u24, opcode) << 2;
-            cpu.pipe.reload(u32, cpu);
+            cpu.pipe.reload(cpu);
         }
     }.inner;
 }
@@ -24,5 +24,5 @@ pub fn branchAndExchange(cpu: *Arm7tdmi, _: *Bus, opcode: u32) void {
     cpu.r[15] = cpu.r[rn] & if (thumb) ~@as(u32, 1) else ~@as(u32, 3);
 
     cpu.cpsr.t.write(thumb);
-    if (thumb) cpu.pipe.reload(u16, cpu) else cpu.pipe.reload(u32, cpu);
+    cpu.pipe.reload(cpu);
 }

src/core/cpu/arm/data_processing.zig

@@ -76,9 +76,8 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime kind: u4) Ins
                 else => {
                     cpu.r[rd] = result;
                     if (rd == 0xF) {
-                        if (S) cpu.setCpsrNoFlush(cpu.spsr.raw);
-
-                        cpu.pipe.reload(u32, cpu);
+                        if (S) cpu.setCpsr(cpu.spsr.raw);
+                        cpu.pipe.reload(cpu);
                     }
                 },
             }
@@ -180,5 +179,5 @@ pub fn adc(overflow: *bool, left: u32, right: u32, old_carry: u1) u32 {
 
 fn undefinedTestBehaviour(cpu: *Arm7tdmi) void {
     @setCold(true);
-    cpu.setCpsrNoFlush(cpu.spsr.raw);
+    cpu.setCpsr(cpu.spsr.raw);
 }

src/core/cpu/arm/single_data_transfer.zig

@@ -47,13 +47,13 @@ pub fn singleDataTransfer(comptime I: bool, comptime P: bool, comptime U: bool,
             address = modified_base;
             if (W and P or !P) {
                 cpu.r[rn] = address;
-                if (rn == 0xF) cpu.pipe.reload(u32, cpu);
+                if (rn == 0xF) cpu.pipe.reload(cpu);
             }
 
             if (L) {
                 // This emulates the LDR rd == rn behaviour
                 cpu.r[rd] = result;
-                if (rd == 0xF) cpu.pipe.reload(u32, cpu);
+                if (rd == 0xF) cpu.pipe.reload(cpu);
             }
         }
     }.inner;

src/core/cpu/arm/software_interrupt.zig

@@ -17,7 +17,7 @@ pub fn armSoftwareInterrupt() InstrFn {
             cpu.r[14] = ret_addr; // Resume Execution
             cpu.spsr.raw = cpsr; // Previous mode CPSR
             cpu.r[15] = 0x0000_0008;
-            cpu.pipe.reload(u32, cpu);
+            cpu.pipe.reload(cpu);
         }
     }.inner;
 }

src/core/cpu/thumb/block_data_transfer.zig

@@ -34,7 +34,7 @@ pub fn fmt14(comptime L: bool, comptime R: bool) InstrFn {
                 if (L) {
                     const value = bus.read(u32, address);
                     cpu.r[15] = value & ~@as(u32, 1);
-                    cpu.pipe.reload(u16, cpu);
+                    cpu.pipe.reload(cpu);
                 } else {
                     bus.write(u32, address, cpu.r[14]);
                 }
@@ -55,7 +55,7 @@ pub fn fmt15(comptime L: bool, comptime rb: u3) InstrFn {
             if (opcode & 0xFF == 0) {
                 if (L) {
                     cpu.r[15] = bus.read(u32, address);
-                    cpu.pipe.reload(u16, cpu);
+                    cpu.pipe.reload(cpu);
                 } else {
                     bus.write(u32, address, cpu.r[15] + 2);
                 }

src/core/cpu/thumb/branch.zig

@@ -15,7 +15,7 @@ pub fn fmt16(comptime cond: u4) InstrFn {
             if (!checkCond(cpu.cpsr, cond)) return;
 
             cpu.r[15] +%= sext(u32, u8, opcode & 0xFF) << 1;
-            cpu.pipe.reload(u16, cpu);
+            cpu.pipe.reload(cpu);
         }
     }.inner;
 }
@@ -25,7 +25,7 @@ pub fn fmt18() InstrFn {
         // B but conditional
         fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
             cpu.r[15] +%= sext(u32, u11, opcode & 0x7FF) << 1;
-            cpu.pipe.reload(u16, cpu);
+            cpu.pipe.reload(cpu);
         }
     }.inner;
 }
@@ -43,7 +43,7 @@ pub fn fmt19(comptime is_low: bool) InstrFn {
                 cpu.r[15] = cpu.r[14] +% (offset << 1);
                 cpu.r[14] = next_opcode | 1;
 
-                cpu.pipe.reload(u16, cpu);
+                cpu.pipe.reload(cpu);
             } else {
                 // Instruction 1
                 const lr_offset = sext(u32, u11, offset) << 12;

src/core/cpu/thumb/data_processing.zig

@@ -83,13 +83,13 @@ pub fn fmt5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
                     cpu.r[15] = op2 & ~@as(u32, 1);
 
                     cpu.cpsr.t.write(is_thumb);
-                    if (is_thumb) cpu.pipe.reload(u16, cpu) else cpu.pipe.reload(u32, cpu);
+                    cpu.pipe.reload(cpu);
                 },
                 else => {
                     cpu.r[rd] = result;
                     if (rd == 0xF) {
                         cpu.r[15] &= ~@as(u32, 1);
-                        cpu.pipe.reload(u16, cpu);
+                        cpu.pipe.reload(cpu);
                     }
                 },
             }

src/core/cpu/thumb/software_interrupt.zig

@@ -17,7 +17,7 @@ pub fn fmt17() InstrFn {
             cpu.r[14] = ret_addr; // Resume Execution
             cpu.spsr.raw = cpsr; // Previous mode CPSR
             cpu.r[15] = 0x0000_0008;
-            cpu.pipe.reload(u32, cpu);
+            cpu.pipe.reload(cpu);
         }
     }.inner;
 }