diff --git a/src/cpu/thumb/format12.zig b/src/cpu/thumb/format12.zig index fa026aa..86df0cc 100644 --- a/src/cpu/thumb/format12.zig +++ b/src/cpu/thumb/format12.zig @@ -8,7 +8,7 @@ pub fn format12(comptime isSP: bool, comptime rd: u3) InstrFn { return struct { fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void { // ADD - const left = if (isSP) cpu.r[13] else cpu.fakePC() & 0xFFFF_FFFC; + const left = if (isSP) cpu.r[13] else (cpu.r[15] + 2) & 0xFFFF_FFFD; const right = (opcode & 0xFF) << 2; const result = left + right; // TODO: What about overflows? cpu.r[rd] = result; diff --git a/src/cpu/thumb/format16.zig b/src/cpu/thumb/format16.zig index 8ec032c..e116818 100644 --- a/src/cpu/thumb/format16.zig +++ b/src/cpu/thumb/format16.zig @@ -19,7 +19,7 @@ pub fn format16(comptime cond: u4) InstrFn { }; if (should_execute) { - cpu.r[15] = (cpu.fakePC() & 0xFFFF_FFFC) +% offset; + cpu.r[15] = (cpu.r[15] + 2) +% offset; } } }.inner; diff --git a/src/cpu/thumb/format19.zig b/src/cpu/thumb/format19.zig index 0c5927a..86efb03 100644 --- a/src/cpu/thumb/format19.zig +++ b/src/cpu/thumb/format19.zig @@ -19,7 +19,7 @@ pub fn format19(comptime is_low: bool) InstrFn { cpu.r[14] = old_pc | 1; } else { // Instruction 1 - cpu.r[14] = (cpu.fakePC() & 0xFFFF_FFFC) + (u32SignExtend(11, @as(u32, offset)) << 12); + cpu.r[14] = (cpu.r[15] + 2) + (u32SignExtend(11, @as(u32, offset)) << 12); } } }.inner; diff --git a/src/cpu/thumb/format6.zig b/src/cpu/thumb/format6.zig index 392578c..27e24f2 100644 --- a/src/cpu/thumb/format6.zig +++ b/src/cpu/thumb/format6.zig @@ -11,7 +11,7 @@ pub fn format6(comptime rd: u3) InstrFn { const offset = (opcode & 0xFF) << 2; // FIXME: Should this overflow? - cpu.r[rd] = bus.read32((cpu.fakePC() & 0xFFFF_FFFC) + offset); + cpu.r[rd] = bus.read32((cpu.r[15] + 2 & 0xFFFF_FFFD) + offset); } }.inner; }