106 lines
3.3 KiB
Rust
106 lines
3.3 KiB
Rust
#![no_std]
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extern crate alloc;
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mod macros;
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use {alloc::vec::Vec, hashbrown::HashSet};
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/// Assembler
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///
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/// - Opcode-generic, instruction-type-specific methods are named `i_param_<type>`
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/// - You likely won't need to use them, but they are here, just in case :)
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/// - Instruction-specific methods are named `i_<instruction>`
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#[derive(Default)]
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pub struct Assembler {
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pub buf: Vec<u8>,
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pub sub: HashSet<usize>,
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}
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// Implement both assembler and generate module for text-code-based one
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macros::impl_both!(
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bbbb(p0: R, p1: R, p2: R, p3: R)
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=> [DIR, DIRF, FMAF],
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bbb(p0: R, p1: R, p2: R)
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=> [ADD, SUB, MUL, AND, OR, XOR, SL, SR, SRS, CMP, CMPU, /*BRC,*/ ADDF, SUBF, MULF],
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bbdh(p0: R, p1: R, p2: I, p3: u16)
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=> [LD, ST],
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bbd(p0: R, p1: R, p2: I)
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=> [ADDI, MULI, ANDI, ORI, XORI, SLI, SRI, SRSI, CMPI, CMPUI,
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BMC, JAL, JEQ, JNE, JLT, JGT, JLTU, JGTU, ADDFI, MULFI],
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bb(p0: R, p1: R)
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=> [NEG, NOT, CP, SWA, NEGF, ITF, FTI],
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bd(p0: R, p1: I)
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=> [LI],
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n()
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=> [UN, NOP, ECALL],
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);
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impl Assembler {
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// Special-cased for text-assembler
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//
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// `p2` is not a register, but the instruction is still BBB
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#[inline(always)]
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pub fn i_brc(&mut self, p0: u8, p1: u8, p2: u8) {
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self.i_param_bbb(hbbytecode::opcode::BRC, p0, p1, p2)
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}
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/// Append 12 zeroes (UN) at the end
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///
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/// # HoleyBytes lore
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///
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/// In reference HBVM implementation checks are done in
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/// a separate phase before execution.
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///
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/// This way execution will be much faster as they have to
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/// be done only once.
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///
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/// There was an issue. You cannot statically check register values and
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/// `JAL` instruction could hop at the end of program to some byte, which
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/// will be interpreted as some valid opcode and VM in attempt to decode
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/// the instruction performed out-of-bounds read which leads to undefined behaviour.
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///
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/// Several options were considered to overcome this, but inserting some data at
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/// program's end which when executed would lead to undesired behaviour, though
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/// not undefined behaviour.
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///
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/// Newly created `UN` (as UNreachable) was chosen as
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/// - It was a good idea to add some equivalent to `ud2` anyways
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/// - It was chosen to be zero
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/// - What if you somehow reached that code, it will appropriately bail :)
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/// - (yes, originally `NOP` was considered)
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///
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/// Why 12 bytes? That's the size of largest instruction parameter part.
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pub fn finalise(&mut self) {
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self.buf.extend([0; 12]);
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}
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}
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/// Immediate value
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///
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/// # Implementor notice
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/// It should insert exactly 8 bytes, otherwise output will be malformed.
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/// This is not checked in any way
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pub trait Imm {
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/// Insert immediate value
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fn insert(&self, asm: &mut Assembler);
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}
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/// Implement immediate values
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macro_rules! impl_imm_le_bytes {
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($($ty:ty),* $(,)?) => {
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$(
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impl Imm for $ty {
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#[inline(always)]
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fn insert(&self, asm: &mut Assembler) {
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// Convert to little-endian bytes, insert.
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asm.buf.extend(self.to_le_bytes());
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}
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}
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)*
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};
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}
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impl_imm_le_bytes!(u64, i64, f64);
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