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feat: implement S (when rd != 15) for several data processing instructions

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-05 15:45:52 -05:00
parent 28a70d0112
commit 5037b8f0cc
3 changed files with 52 additions and 42 deletions
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12
src/cpu/barrel_shifter.zig
View File

@ -4,7 +4,7 @@ const arm = @import("../cpu.zig");
const Arm7tdmi = arm.Arm7tdmi;
const CPSR = arm.CPSR;
pub inline fn exec(cpu: *Arm7tdmi, opcode: u32) u32 {
pub inline fn exec(comptime S: bool, cpu: *Arm7tdmi, opcode: u32) u32 {
var shift_amt: u8 = undefined;
if (opcode >> 4 & 1 == 1) {
shift_amt = @truncate(u8, cpu.r[opcode >> 8 & 0xF]);
@ -14,12 +14,22 @@ pub inline fn exec(cpu: *Arm7tdmi, opcode: u32) u32 {
const rm = cpu.r[opcode & 0xF];
if (S) {
return switch (@truncate(u2, opcode >> 5)) {
0b00 => logical_left(&cpu.cpsr, rm, shift_amt),
0b01 => logical_right(&cpu.cpsr, rm, shift_amt),
0b10 => arithmetic_right(&cpu.cpsr, rm, shift_amt),
0b11 => rotate_right(&cpu.cpsr, rm, shift_amt),
};
} else {
var dummy = CPSR{ .raw = 0x0000_0000 };
return switch (@truncate(u2, opcode >> 5)) {
0b00 => logical_left(&dummy, rm, shift_amt),
0b01 => logical_right(&dummy, rm, shift_amt),
0b10 => arithmetic_right(&dummy, rm, shift_amt),
0b11 => rotate_right(&dummy, rm, shift_amt),
};
}
}
pub inline fn logical_left(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {

59
src/cpu/data_processing.zig
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@ -16,60 +16,57 @@ pub fn comptimeDataProcessing(comptime I: bool, comptime S: bool, comptime instr
if (I) {
op2 = std.math.rotr(u32, opcode & 0xFF, (opcode >> 8 & 0xF) << 1);
} else {
op2 = BarrelShifter.exec(cpu, opcode);
if (S and rd == 0xF) {
std.debug.panic("[CPU] Data Processing Instruction w/ S set and Rd == 15", .{});
} else {
op2 = BarrelShifter.exec(S, cpu, opcode);
}
}
switch (instrKind) {
0x4 => {
// ADD
cpu.r[rd] = cpu.r[op1] + op2;
var result: u32 = undefined;
const didOverflow = @addWithOverflow(u32, cpu.r[op1], op2, &result);
cpu.r[rd] = result;
if (S) std.debug.panic("[CPU] TODO: implement ADD condition codes", .{});
if (S and rd != 0xF) {
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
cpu.cpsr.c.write(didOverflow);
cpu.cpsr.v.write(((op1 ^ result) & (op2 ^ result)) >> 31 & 1 == 1);
}
},
0x8 => {
// TST
std.debug.panic("[CPU] TODO: implement TST, also figure out barrel shifter flags\n", .{});
const result = cpu.r[op1] & op2;
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
// Barrel Shifter should always calc CPSR C in TST
if (!S) _ = BarrelShifter.exec(true, cpu, opcode);
},
0xD => {
// MOV
cpu.r[rd] = op2;
if (S) std.debug.panic("[CPU] implement MOV condition codes", .{});
if (S and rd != 0xF) {
cpu.cpsr.n.write(op2 >> 31 & 1 == 1);
cpu.cpsr.z.write(op2 == 0);
// C set by Barr0x15el Shifter, V is unnafected
}
},
0xA => {
// CMP
const op1_val = cpu.r[op1];
const v_ctx = (op1_val >> 31 == 1) or (op2 >> 31 == 1);
const result = op1_val -% op2;
const result = cpu.r[op1] -% op2;
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
cpu.cpsr.c.write(op2 <= op1_val);
cpu.cpsr.v.write(v_ctx and (result >> 31 & 1 == 1));
cpu.cpsr.c.write(op2 <= cpu.r[op1]);
cpu.cpsr.v.write(((op1 ^ result) & (~op2 ^ result)) >> 31 & 1 == 1);
},
else => std.debug.panic("[CPU] TODO: implement data processing type {}", .{instrKind}),
}
}
}.dataProcessing;
}
// fn registerOp2(cpu: *const Arm7tdmi, opcode: u32) u32 {
// var amount: u32 = undefined;
// if (opcode >> 4 & 0x01 == 0x01) {
// amount = cpu.r[opcode >> 8 & 0xF] & 0xFF;
// } else {
// amount = opcode >> 7 & 0x1F;
// }
// const rm = opcode & 0xF;
// const r_val = cpu.r[rm];
// return switch (opcode >> 5 & 0x03) {
// 0b00 => r_val << @truncate(u5, amount),
// 0b01 => r_val >> @truncate(u5, amount),
// 0b10 => @bitCast(u32, @bitCast(i32, r_val) >> @truncate(u5, amount)),
// 0b11 => std.math.rotr(u32, r_val, amount),
// else => unreachable,
// };
// }

11
src/cpu/single_data_transfer.zig
View File

@ -6,6 +6,7 @@ const BarrelShifter = @import("barrel_shifter.zig");
const Bus = @import("../bus.zig").Bus;
const Arm7tdmi = arm.Arm7tdmi;
const InstrFn = arm.InstrFn;
const CPSR = arm.CPSR;
pub fn comptimeSingleDataTransfer(comptime I: bool, comptime P: bool, comptime U: bool, comptime B: bool, comptime W: bool, comptime L: bool) InstrFn {
return struct {
@ -53,10 +54,12 @@ fn registerOffset(cpu: *Arm7tdmi, opcode: u32) u32 {
const rm = cpu.r[opcode & 0xF];
var dummy = CPSR{ .raw = 0x0000_0000 };
return switch (@truncate(u2, opcode >> 5)) {
0b00 => BarrelShifter.logical_left(&cpu.cpsr, rm, shift_byte),
0b01 => BarrelShifter.logical_right(&cpu.cpsr, rm, shift_byte),
0b10 => BarrelShifter.arithmetic_right(&cpu.cpsr, rm, shift_byte),
0b11 => BarrelShifter.rotate_right(&cpu.cpsr, rm, shift_byte),
0b00 => BarrelShifter.logical_left(&dummy, rm, shift_byte),
0b01 => BarrelShifter.logical_right(&dummy, rm, shift_byte),
0b10 => BarrelShifter.arithmetic_right(&dummy, rm, shift_byte),
0b11 => BarrelShifter.rotate_right(&dummy, rm, shift_byte),
};
}