Struct Allocation

Source

pub struct Allocation { /* private fields */ }

Expand description

What the allocator did.

§Examples

use backend_lang::mir::{Effects, Function, Operand};
use backend_lang::regalloc;
use backend_lang::x86_64::{op, GPR, SYSV, RAX};

let mut f = Function::new("f", &SYSV);
let b = f.block()?;
let v = f.vreg(GPR)?;
f.push(b, op::MOV64RI, &[v.into(), Operand::Imm(7)])?;
f.push(b, op::COPY, &[RAX.into(), v.into()])?;
f.push_with(b, op::RET, &[], Effects::new().uses(&[RAX]))?;
let a = regalloc::allocate(&mut f)?;
assert_eq!(a.spilled(), 0);
// The value was given rax, the register it is copied to: no move left.
assert_eq!(backend_lang::emit(&f)?, [0x55, 0x48, 0x89, 0xE5, 0xB8, 7, 0, 0, 0, 0x5D, 0xC3]);

Implementations§

Source §

impl Allocation

Source

pub fn rounds(&self) -> u32

The coloring rounds run (1 when nothing spilled).

§Examples

See Allocation.

Source

pub fn spilled(&self) -> u32

The values spilled to stack slots.

§Examples

See Allocation.

Source

pub fn rematerialized(&self) -> u32

The spilled values rematerialized at their uses instead of stored.

§Examples

See Allocation.

Source

pub fn max_pressure(&self) -> u32

The most values of one class live at once, before any spilling: the register pressure the function itself demands.

§Examples

See Allocation.

Source

pub fn assignment(&self) -> Option<(&Function, &[Location])>

With Options::keep_assignment: the virtual function the final round colored (after spill code was inserted), and each of its virtual registers’ locations, indexed by VReg::index.

§Examples

use backend_lang::mir::{Function, Operand};
use backend_lang::regalloc::{self, Location, Options};
use backend_lang::x86_64::{op, GPR, SYSV};

let mut f = Function::new("f", &SYSV);
let b = f.block()?;
let v = f.vreg(GPR)?;
f.push(b, op::MOV64RI, &[v.into(), Operand::Imm(7)])?;
f.push(b, op::CMP64, &[v.into(), Operand::Imm(1)])?;
f.push(b, op::RET, &[])?;
let a = regalloc::allocate_with(&mut f, &Options::new().keep_assignment(true))?;
let (virt, locs) = a.assignment().unwrap();
assert_eq!(virt.vreg_count(), locs.len());
assert!(matches!(locs[0], Location::Reg(_)));