diff --git a/src/cpu.zig b/src/cpu.zig index d269aaf..c8de217 100644 --- a/src/cpu.zig +++ b/src/cpu.zig @@ -28,6 +28,7 @@ const format3 = @import("cpu/thumb/format3.zig").format3; const format4 = @import("cpu/thumb/format4.zig").format4; const format5 = @import("cpu/thumb/format5.zig").format5; const format6 = @import("cpu/thumb/format6.zig").format6; +const format78 = @import("cpu/thumb/format78.zig").format78; const format9 = @import("cpu/thumb/format9.zig").format9; const format10 = @import("cpu/thumb/format10.zig").format10; const format12 = @import("cpu/thumb/format12.zig").format12; @@ -450,8 +451,10 @@ fn thumbPopulate() [0x400]ThumbInstrFn { lut[i] = format6(rd); } else if (i >> 6 & 0xF == 0b0101) { - // TODO: Format 7 and Format 8 - lut[i] = thumbUndefined; + const op = i >> 5 & 0x3; + const T = i >> 3 & 1 == 1; + + lut[i] = format78(op, T); } else if (i >> 7 & 0x7 == 0b000) { const op = i >> 5 & 0x3; const offset = i & 0x1F; diff --git a/src/cpu/thumb/format10.zig b/src/cpu/thumb/format10.zig index fef8198..d1093ab 100644 --- a/src/cpu/thumb/format10.zig +++ b/src/cpu/thumb/format10.zig @@ -14,7 +14,8 @@ pub fn format10(comptime L: bool, comptime offset: u5) InstrFn { if (L) { // LDRH - cpu.r[rd] = bus.read16(address & 0xFFFF_FFFE); + const value = bus.read16(address & 0xFFFF_FFFE); + cpu.r[rd] = std.math.rotr(u32, @as(u32, value), 8 * (address & 1)); } else { // STRH bus.write16(address & 0xFFFF_FFFE, @truncate(u16, cpu.r[rd])); diff --git a/src/cpu/thumb/format78.zig b/src/cpu/thumb/format78.zig new file mode 100644 index 0000000..7eae426 --- /dev/null +++ b/src/cpu/thumb/format78.zig @@ -0,0 +1,60 @@ +const std = @import("std"); + +const Bus = @import("../../Bus.zig"); +const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi; +const InstrFn = @import("../../cpu.zig").ThumbInstrFn; +const u32SignExtend = @import("../../util.zig").u32SignExtend; + +pub fn format78(comptime op: u2, comptime T: bool) InstrFn { + return struct { + fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void { + const ro = opcode >> 6 & 0x7; + const rb = opcode >> 3 & 0x7; + const rd = opcode & 0x7; + + const address = cpu.r[rb] + cpu.r[ro]; + + if (T) { + switch (op) { + 0b00 => { + // STRH + bus.write16(address & 0xFFFF_FFFE, @truncate(u16, cpu.r[rd])); + }, + 0b01 => { + // LDRH + const value = bus.read16(address & 0xFFFF_FFFE); + cpu.r[rd] = std.math.rotr(u32, @as(u32, value), 8 * (address & 1)); + }, + 0b10 => { + // LDSB + cpu.r[rd] = u32SignExtend(8, @as(u32, bus.read8(address))); + }, + 0b11 => { + // LDSH + cpu.r[rd] = u32SignExtend(16, @as(u32, bus.read16(address & 0xFFFF_FFFE))); + }, + } + } else { + switch (op) { + 0b00 => { + // STR + bus.write32(address & 0xFFFF_FFFC, cpu.r[rd]); + }, + 0b01 => { + // STRB + bus.write8(address, @truncate(u8, cpu.r[rd])); + }, + 0b10 => { + // LDR + const value = bus.read32(address & 0xFFFF_FFFC); + cpu.r[rd] = std.math.rotr(u32, value, 8 * (address & 0x3)); + }, + 0b11 => { + // LDRB + cpu.r[rd] = bus.read8(address); + }, + } + } + } + }.inner; +} diff --git a/src/cpu/thumb/format9.zig b/src/cpu/thumb/format9.zig index 2d807a7..fb772ad 100644 --- a/src/cpu/thumb/format9.zig +++ b/src/cpu/thumb/format9.zig @@ -18,7 +18,8 @@ pub fn format9(comptime B: bool, comptime L: bool, comptime offset: u5) InstrFn } else { // LDR const address = cpu.r[rb] + (@as(u32, offset) << 2); - cpu.r[rd] = bus.read32(address & 0xFFFF_FFFC); + const value = bus.read32(address & 0xFFFF_FFFC); + cpu.r[rd] = std.math.rotr(u32, value, 8 * (address & 0x3)); } } else { if (B) {