Struct Reads 

pub struct Reads { /* private fields */ }

How many times each register is read, kept across the commits of one pass.

A removal has to know whether anything still reads what the instruction wrote, and asking the function that question once per commit is the length of the function once per commit. So it is asked once and the answer is carried, which each commit brings up to date with what it did.

A virtual register is counted by its number in a list rather than in a map, since the numbers run from nought with no gaps and this is asked about every operand of every function. The few physical registers an instruction names before allocation are counted the same way by their number, which is one byte. They used to go in a map, and hashing one was most of what counting it cost.

Implementations

impl Reads

pub fn of(func: &Func) -> Self

Every read in the function, counting the arguments an edge carries as reads, which they are.

pub fn count(&self, reg: Reg) -> usize

How many reads of that register there are.

Trait Implementations

impl Clone for Reads

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Reads

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Reads

fn default() -> Self

Returns the “default value” for a type.