Struct FrameLayout 

pub struct FrameLayout { /* private fields */ }

A laid-out frame: slot offsets and the prologue and epilogue.

Offsets are from the stack pointer after the prologue; they are negative for locals kept in the red zone.

Examples

use backend_lang::mir::{Function, SlotKind};
use backend_lang::x86_64::SYSV;

let mut f = Function::new("leaf", &SYSV);
let a = f.stack_slot(SlotKind::Local { size: 8, align: 8 })?;
let frame = f.frame_layout().unwrap();
// A leaf with 8 bytes of locals uses the red zone: nothing is allocated.
assert!(frame.uses_red_zone());
assert_eq!(frame.alloc(), 0);
assert!(frame.slot_offset(a).unwrap() < 0);

Implementations

impl FrameLayout

pub fn slot_offset(&self, slot: StackSlot) -> Option<i32>

A slot’s offset from the stack pointer after the prologue, or None for a slot the layout does not have.

Examples

use backend_lang::mir::{Function, SlotKind};
use backend_lang::x86_64::SYSV;

let mut f = Function::new("f", &SYSV);
let arg = f.stack_slot(SlotKind::Incoming { offset: 0, size: 8 })?;
let frame = f.frame_layout().unwrap();
// rbp is pushed: [rsp] = saved rbp, [rsp+8] = return address, [rsp+16] = argument.
assert_eq!(frame.slot_offset(arg), Some(16));

pub fn pushed(&self) -> &[PReg]

The general-purpose callee-saved registers pushed after the frame pointer, in push order.

Examples

use backend_lang::mir::Function;
use backend_lang::x86_64::SYSV;

assert!(Function::new("f", &SYSV).frame_layout().unwrap().pushed().is_empty());

pub fn vec_saves(&self) -> &[(PReg, i32)]

Vector callee-saved registers saved into the frame, with their save slots’ offsets.

Examples

use backend_lang::mir::Function;
use backend_lang::x86_64::SYSV;

assert!(Function::new("f", &SYSV).frame_layout().unwrap().vec_saves().is_empty());

pub fn prologue(&self) -> &[FrameStep]

The prologue, in execution order.

Examples

use backend_lang::mir::Function;
use backend_lang::target::frame::FrameStep;
use backend_lang::x86_64::{SYSV, RBP};

let frame = Function::new("f", &SYSV).frame_layout().unwrap();
assert_eq!(frame.prologue(), [FrameStep::Push(RBP), FrameStep::SetFramePointer]);

pub fn epilogue(&self) -> &[FrameStep]

The epilogue, in execution order (the return itself is not part of it).

Examples

use backend_lang::mir::Function;
use backend_lang::target::frame::FrameStep;
use backend_lang::x86_64::{SYSV, RBP};

let frame = Function::new("f", &SYSV).frame_layout().unwrap();
assert_eq!(frame.epilogue(), [FrameStep::Pop(RBP)]);

pub const fn alloc(&self) -> u32

Bytes the prologue subtracts from the stack pointer after its pushes.

Examples

use backend_lang::mir::Function;
use backend_lang::x86_64::SYSV;

assert_eq!(Function::new("f", &SYSV).frame_layout().unwrap().alloc(), 0);

pub const fn cfa_offset(&self) -> u32

The canonical frame address (the stack pointer before the call) minus the stack pointer after the prologue: return address, pushes, and allocation.

Examples

use backend_lang::mir::Function;
use backend_lang::x86_64::SYSV;

// Return address plus the saved rbp.
assert_eq!(Function::new("f", &SYSV).frame_layout().unwrap().cfa_offset(), 16);

pub const fn frame_pointer(&self) -> bool

Whether the frame keeps a frame pointer.

Examples

use backend_lang::mir::Function;
use backend_lang::x86_64::SYSV;

assert!(Function::new("f", &SYSV).frame_layout().unwrap().frame_pointer());

pub const fn uses_red_zone(&self) -> bool

Whether the locals live in the red zone below the stack pointer.

Examples

use backend_lang::mir::Function;
use backend_lang::x86_64::SYSV;

assert!(!Function::new("f", &SYSV).frame_layout().unwrap().uses_red_zone());

Trait Implementations

impl Clone for FrameLayout

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 FrameLayout

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

Formats the value using the given formatter.

impl Eq for FrameLayout

impl PartialEq for FrameLayout

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for FrameLayout