ea901653da
The # is a more conventional prefix for hexadecimal, and when ISA information is not available, there may be a decimal number in front which would be confusing. So prefer [1#10c] for the ISA-less encoding format. Here '1' is decimal and '#10c' is hexadecimal.
79 lines
2.1 KiB
Rust
79 lines
2.1 KiB
Rust
//! The `Encoding` struct.
|
|
|
|
use std::fmt;
|
|
|
|
/// Bits needed to encode an instruction as binary machine code.
|
|
///
|
|
/// The encoding consists of two parts, both specific to the target ISA: An encoding *recipe*, and
|
|
/// encoding *bits*. The recipe determines the native instruction format and the mapping of
|
|
/// operands to encoded bits. The encoding bits provide additional information to the recipe,
|
|
/// typically parts of the opcode.
|
|
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
|
|
pub struct Encoding {
|
|
recipe: u16,
|
|
bits: u16,
|
|
}
|
|
|
|
impl Encoding {
|
|
/// Create a new `Encoding` containing `(recipe, bits)`.
|
|
pub fn new(recipe: u16, bits: u16) -> Encoding {
|
|
Encoding {
|
|
recipe: recipe,
|
|
bits: bits,
|
|
}
|
|
}
|
|
|
|
/// Get the recipe number in this encoding.
|
|
pub fn recipe(self) -> usize {
|
|
self.recipe as usize
|
|
}
|
|
|
|
/// Get the recipe-specific encoding bits.
|
|
pub fn bits(self) -> u16 {
|
|
self.bits
|
|
}
|
|
|
|
/// Is this a legal encoding, or the default placeholder?
|
|
pub fn is_legal(self) -> bool {
|
|
self != Self::default()
|
|
}
|
|
}
|
|
|
|
/// The default encoding is the illegal one.
|
|
impl Default for Encoding {
|
|
fn default() -> Self {
|
|
Self::new(0xffff, 0xffff)
|
|
}
|
|
}
|
|
|
|
/// ISA-independent display of an encoding.
|
|
impl fmt::Display for Encoding {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
if self.is_legal() {
|
|
write!(f, "{}#{:02x}", self.recipe, self.bits)
|
|
} else {
|
|
write!(f, "-")
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Temporary object that holds enough context to properly display an encoding.
|
|
/// This is meant to be created by `TargetIsa::display_enc()`.
|
|
pub struct DisplayEncoding {
|
|
pub encoding: Encoding,
|
|
pub recipe_names: &'static [&'static str],
|
|
}
|
|
|
|
impl fmt::Display for DisplayEncoding {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
if self.encoding.is_legal() {
|
|
write!(f,
|
|
"{}#{:02x}",
|
|
self.recipe_names[self.encoding.recipe()],
|
|
self.encoding.bits)
|
|
} else {
|
|
write!(f, "-")
|
|
}
|
|
}
|
|
}
|