55 lines
1.6 KiB
Zig
55 lines
1.6 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").thumb.InstrFn;
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const checkCond = @import("../../cpu.zig").checkCond;
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const sext = @import("zba-util").sext;
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pub fn fmt16(comptime cond: u4) InstrFn {
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return struct {
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fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
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// B
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if (cond == 0xE or cond == 0xF)
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cpu.panic("[CPU/THUMB.16] Undefined conditional branch with condition {}", .{cond});
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if (!checkCond(cpu.cpsr, cond)) return;
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cpu.r[15] +%= sext(u32, u8, opcode & 0xFF) << 1;
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cpu.pipe.reload(cpu);
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}
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}.inner;
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}
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pub fn fmt18() InstrFn {
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return struct {
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// B but conditional
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fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
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cpu.r[15] +%= sext(u32, u11, opcode & 0x7FF) << 1;
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cpu.pipe.reload(cpu);
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}
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}.inner;
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}
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pub fn fmt19(comptime is_low: bool) InstrFn {
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return struct {
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fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
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// BL
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const offset = opcode & 0x7FF;
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if (is_low) {
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// Instruction 2
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const next_opcode = cpu.r[15] - 2;
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cpu.r[15] = cpu.r[14] +% (offset << 1);
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cpu.r[14] = next_opcode | 1;
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cpu.pipe.reload(cpu);
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} else {
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// Instruction 1
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const lr_offset = sext(u32, u11, offset) << 12;
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cpu.r[14] = (cpu.r[15] +% lr_offset) & ~@as(u32, 1);
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}
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}
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}.inner;
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}
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