37 lines
1.4 KiB
Zig
37 lines
1.4 KiB
Zig
const Bus = @import("../../Bus.zig");
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const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
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const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
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const cmp = @import("../arm/data_processing.zig").cmp;
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const add = @import("../arm/data_processing.zig").add;
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pub fn format5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
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return struct {
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fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
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const src_idx = @as(u4, h2) << 3 | (opcode >> 3 & 0x7);
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const dst_idx = @as(u4, h1) << 3 | (opcode & 0x7);
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const src = if (src_idx == 0xF) (cpu.r[src_idx] + 2) & 0xFFFF_FFFE else cpu.r[src_idx];
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const dst = if (dst_idx == 0xF) (cpu.r[dst_idx] + 2) & 0xFFFF_FFFE else cpu.r[dst_idx];
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switch (op) {
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0b00 => {
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// ADD
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const sum = add(false, cpu, dst, src);
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cpu.r[dst_idx] = if (dst_idx == 0xF) sum & 0xFFFF_FFFE else sum;
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},
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0b01 => cmp(cpu, dst, src), // CMP
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0b10 => {
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// MOV
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cpu.r[dst_idx] = if (dst_idx == 0xF) src & 0xFFFF_FFFE else src;
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},
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0b11 => {
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// BX
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cpu.cpsr.t.write(src & 1 == 1);
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cpu.r[15] = src & 0xFFFF_FFFE;
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},
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}
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}
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}.inner;
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}
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