feat(cpu): implement THUMB format 9 loads / stores

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-29 22:34:24 -04:00
parent b8a9aaee86
commit 0598ba402d
2 changed files with 45 additions and 0 deletions

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@ -25,6 +25,7 @@ const format4 = @import("cpu/thumb/format4.zig").format4;
const format2 = @import("cpu/thumb/format2.zig").format2; const format2 = @import("cpu/thumb/format2.zig").format2;
const format5 = @import("cpu/thumb/format5.zig").format5; const format5 = @import("cpu/thumb/format5.zig").format5;
const format6 = @import("cpu/thumb/format6.zig").format6; const format6 = @import("cpu/thumb/format6.zig").format6;
const format9 = @import("cpu/thumb/format9.zig").format9;
const format12 = @import("cpu/thumb/format12.zig").format12; const format12 = @import("cpu/thumb/format12.zig").format12;
const format15 = @import("cpu/thumb/format15.zig").format15; const format15 = @import("cpu/thumb/format15.zig").format15;
const format16 = @import("cpu/thumb/format16.zig").format16; const format16 = @import("cpu/thumb/format16.zig").format16;
@ -369,6 +370,14 @@ fn thumbPopulate() [0x400]ThumbInstrFn {
lut[i] = format6(rd); lut[i] = format6(rd);
} }
if (i >> 7 & 0x7 == 0b011) {
const B = i >> 6 & 1 == 1;
const L = i >> 5 & 1 == 1;
const offset = i & 0x1F;
lut[i] = format9(B, L, offset);
}
if (i >> 6 & 0xF == 0b1010) { if (i >> 6 & 0xF == 0b1010) {
const isSP = i >> 5 & 1 == 1; const isSP = i >> 5 & 1 == 1;
const rd = i >> 2 & 0x7; const rd = i >> 2 & 0x7;

36
src/cpu/thumb/format9.zig Normal file
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@ -0,0 +1,36 @@
const std = @import("std");
const Bus = @import("../../Bus.zig");
const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
pub fn format9(comptime B: bool, comptime L: bool, comptime offset: u5) InstrFn {
return struct {
fn inner(cpu: *Arm7tdmi, bus: *Bus, opcode: u16) void {
const rb = opcode >> 3 & 0x7;
const rd = opcode & 0x7;
if (L) {
if (B) {
// LDRB
const address = cpu.r[rb] + offset;
cpu.r[rd] = bus.read8(address);
} else {
// LDR
const address = cpu.r[rb] + (@as(u32, offset) << 2);
cpu.r[rd] = bus.read32(address & 0xFFFF_FFFC);
}
} else {
if (B) {
// STRB
const address = cpu.r[rb] + offset;
bus.write8(address, @truncate(u8, cpu.r[rd]));
} else {
// STR
const address = cpu.r[rb] + (@as(u32, offset) << 2);
bus.write32(address & 0xFFFF_FFFC, cpu.r[rd]);
}
}
}
}.inner;
}