paoda
/
arm32
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

feat(v5te): stub LDRD / STRD

This commit is contained in:
Rekai Nyangadzayi Musuka 2023-09-06 22:01:04 -05:00
parent 67bae5dcb4
commit ea3db88bec
1 changed files with 40 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
src/arm/cpu/arm/half_signed_data_transfer.zig
View File

@ -17,9 +17,11 @@ pub fn halfAndSignedDataTransfer(comptime InstrFn: type, comptime P: bool, compt
const modified_base = if (U) base +% offset else base -% offset;
var address = if (P) modified_base else base;
const op: u2 = @truncate(opcode >> 5);
var result: u32 = undefined;
if (L) {
switch (@as(u2, @truncate(opcode >> 5))) {
switch (op) {
0b01 => {
// LDRH
const value = cpu.read(u16, address);
@ -36,15 +38,46 @@ pub fn halfAndSignedDataTransfer(comptime InstrFn: type, comptime P: bool, compt
// FIXME: I shouldn't have to use @as(u8, ...) here
result = if (address & 1 == 1) sext(u32, u8, @as(u8, @truncate(value >> 8))) else sext(u32, u16, value);
},
0b00 => unreachable, // SWP
0b00 => unreachable, // SWP / SWPB dealt with in single_data_swap.zig
}
} else {
if (opcode >> 5 & 0x01 == 0x01) {
switch (op) {
0b01 => {
// STRH
// FIXME: I shouldn't have to use @as(u8, ...) here
// FIXME: I shouldn't have to use @as(u16, ...) here
cpu.write(u16, address, @as(u16, @truncate(cpu.r[rd])));
} else unreachable; // SWP
},
0b10 => {
// LDRD
if (Arm32.arch != .v5te) cpu.panic("LDRD: unsupported on arm{s}", .{@tagName(Arm32.arch)});
if (rd & 0 != 0) cpu.panic("LDRD: UNDEFINED behaviour when Rd is not even", .{});
if (rd == 0xE) cpu.panic("LDRD: UNPREDICTABLE behaviour when rd == 14", .{});
if (address & 0x7 != 0b000) cpu.panic("LDRD: UNPREDICTABLE when address (0x{X:0>8} is not double (64-bit) aligned", .{address});
// Why do we not make use of result here?
//
// It's because L is not set so there's no chance of writing an undefined
// value to the register
//
// despite this reason, this is bad design imo
// TODO: Refactor this handler
cpu.r[rd] = cpu.read(u32, address);
cpu.r[rd + 1] = cpu.read(u32, address + 4);
},
0b11 => {
// STRD
if (Arm32.arch != .v5te) cpu.panic("STRD: unsupported on arm{s}", .{@tagName(Arm32.arch)});
if (rd & 0 != 0) cpu.panic("STRD: UNDEFINED behaviour when Rd is not even", .{});
if (rd == 0xE) cpu.panic("STRD: UNPREDICTABLE behaviour when rd == 14", .{});
if (address & 0x7 != 0b000) cpu.panic("STRD: UNPREDICTABLE when address (0x{X:0>8} is not double (64-bit) aligned", .{address});
cpu.write(u32, address, cpu.r[rd]);
cpu.write(u32, address + 4, cpu.r[rd + 1]);
},
else => unreachable,
}
}
address = modified_base;