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pub fn writeSetSub6(comptime op: enum { set, sub }, code: *[1]u8, addend: anytype) void {
const mask: u8 = 0b11_000000;
const actual: i8 = @truncate(addend);
var value: u8 = mem.readInt(u8, code, .little);
switch (op) {
.set => value = (value & mask) | @as(u8, @bitCast(actual & ~mask)),
.sub => value = (value & mask) | (@as(u8, @bitCast(@as(i8, @bitCast(value)) -| actual)) & ~mask),
}
mem.writeInt(u8, code, value, .little);
}
pub fn writeAddend(
comptime Int: type,
comptime op: enum { add, sub },
code: *[@typeInfo(Int).Int.bits / 8]u8,
value: anytype,
) void {
var V: Int = mem.readInt(Int, code, .little);
const addend: Int = @truncate(value);
switch (op) {
.add => V +|= addend, // TODO: I think saturating arithmetic is correct here
.sub => V -|= addend,
}
mem.writeInt(Int, code, V, .little);
}
pub fn writeInstU(code: *[4]u8, value: u32) void {
var inst = Instruction{
.U = mem.bytesToValue(std.meta.TagPayload(
Instruction,
Instruction.U,
), code),
};
const compensated: u32 = @bitCast(@as(i32, @bitCast(value)) + 0x800);
inst.U.imm12_31 = bitSlice(compensated, 31, 12);
mem.writeInt(u32, code, inst.toU32(), .little);
}
pub fn writeInstI(code: *[4]u8, value: u32) void {
var inst = Instruction{
.I = mem.bytesToValue(std.meta.TagPayload(
Instruction,
Instruction.I,
), code),
};
inst.I.imm0_11 = bitSlice(value, 11, 0);
mem.writeInt(u32, code, inst.toU32(), .little);
}
pub fn writeInstS(code: *[4]u8, value: u32) void {
var inst = Instruction{
.S = mem.bytesToValue(std.meta.TagPayload(
Instruction,
Instruction.S,
), code),
};
inst.S.imm0_4 = bitSlice(value, 4, 0);
inst.S.imm5_11 = bitSlice(value, 11, 5);
mem.writeInt(u32, code, inst.toU32(), .little);
}
fn bitSlice(
value: anytype,
comptime high: comptime_int,
comptime low: comptime_int,
) std.math.IntFittingRange(0, 1 << high - low) {
return @truncate((value >> low) & (1 << (high - low + 1)) - 1);
}
const bits = @import("../arch/riscv64/bits.zig");
const mem = std.mem;
const std = @import("std");
pub const Instruction = bits.Instruction;
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