Struct rustc_mir::transform::const_prop::ConstPropMachine

struct ConstPropMachine<'mir, 'tcx> {
    stack: Vec<Frame<'mir, 'tcx, (), ()>>,
    written_only_inside_own_block_locals: FxHashSet<Local>,
    only_propagate_inside_block_locals: BitSet<Local>,
    can_const_prop: IndexVec<Local, ConstPropMode>,
}

Fields

stack: Vec<Frame<'mir, 'tcx, (), ()>>

The virtual call stack.

written_only_inside_own_block_locals: FxHashSet<Local>

OnlyInsideOwnBlock locals that were written in the current block get erased at the end.

only_propagate_inside_block_locals: BitSet<Local>

Locals that need to be cleared after every block terminates.

can_const_prop: IndexVec<Local, ConstPropMode>

Implementations

impl<'mir, 'tcx> ConstPropMachine<'mir, 'tcx>

fn new(
    only_propagate_inside_block_locals: BitSet<Local>,
    can_const_prop: IndexVec<Local, ConstPropMode>
) -> Self

Trait Implementations

impl<'mir, 'tcx> Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>

type PointerTag = ()

Tag tracked alongside every pointer. This is used to implement “Stacked Borrows” https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html. The default() is used for pointers to consts, statics, vtables and functions. The Debug formatting is used for displaying pointers; we cannot use Display as () does not implement that, but it should be “nice” output.

type ExtraFnVal = !

Machines can define extra (non-instance) things that represent values of function pointers. For example, Miri uses this to return a function pointer from dlsym that can later be called to execute the right thing.

type MemoryMap = FxHashMap<AllocId, (MemoryKind<Self::MemoryKind>, Allocation)>

Memory’s allocation map

const GLOBAL_KIND: Option<Self::MemoryKind>

The memory kind to use for copied global memory (held in tcx) – or None if such memory should not be mutated and thus any such attempt will cause a ModifiedStatic error to be raised. Statics are copied under two circumstances: When they are mutated, and when tag_allocation (see below) returns an owned allocation that is added to the memory so that the work is not done twice.

type AllocExtra = ()

Extra data stored in every allocation.

type FrameExtra = ()

Extra data stored in every call frame.

fn enforce_alignment(_memory_extra: &Self::MemoryExtra) -> bool

Whether memory accesses should be alignment-checked.

fn force_int_for_alignment_check(_memory_extra: &Self::MemoryExtra) -> bool

Whether, when checking alignment, we should force_int and thus support custom alignment logic based on whatever the integer address happens to be.

fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool

Whether to enforce the validity invariant

fn call_extra_fn(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    fn_val: !,
    _abi: Abi,
    _args: &[OpTy<'tcx>],
    _ret: Option<(&PlaceTy<'tcx>, BasicBlock)>,
    _unwind: Option<BasicBlock>
) -> InterpResult<'tcx>

Execute fn_val. It is the hook’s responsibility to advance the instruction pointer as appropriate.

fn init_allocation_extra<'b>(
    _memory_extra: &Self::MemoryExtra,
    _id: AllocId,
    alloc: Cow<'b, Allocation>,
    _kind: Option<MemoryKind<Self::MemoryKind>>
) -> (Cow<'b, Allocation<Self::PointerTag>>, Self::PointerTag)

Called to initialize the “extra” state of an allocation and make the pointers it contains (in relocations) tagged. The way we construct allocations is to always first construct it without extra and then add the extra. This keeps uniform code paths for handling both allocations created by CTFE for globals, and allocations created by Miri during evaluation.

fn tag_global_base_pointer(
    _memory_extra: &Self::MemoryExtra,
    _id: AllocId
) -> Self::PointerTag

Return the “base” tag for the given global allocation: the one that is used for direct accesses to this static/const/fn allocation. If id is not a global allocation, this will return an unusable tag (i.e., accesses will be UB)!

type MemoryKind = !

Additional memory kinds a machine wishes to distinguish from the builtin ones

type MemoryExtra = ()

Extra data stored in memory. A reference to this is available when AllocExtra gets initialized, so you can e.g., have an Rc here if there is global state you need access to in the AllocExtra hooks.

fn load_mir(
    _ecx: &InterpCx<'mir, 'tcx, Self>,
    _instance: InstanceDef<'tcx>
) -> InterpResult<'tcx, &'tcx Body<'tcx>>

Entry point for obtaining the MIR of anything that should get evaluated. So not just functions and shims, but also const/static initializers, anonymous constants, …

fn find_mir_or_eval_fn(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _instance: Instance<'tcx>,
    _abi: Abi,
    _args: &[OpTy<'tcx>],
    _ret: Option<(&PlaceTy<'tcx>, BasicBlock)>,
    _unwind: Option<BasicBlock>
) -> InterpResult<'tcx, Option<&'mir Body<'tcx>>>

Entry point to all function calls.

fn call_intrinsic(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _instance: Instance<'tcx>,
    _args: &[OpTy<'tcx>],
    _ret: Option<(&PlaceTy<'tcx>, BasicBlock)>,
    _unwind: Option<BasicBlock>
) -> InterpResult<'tcx>

Directly process an intrinsic without pushing a stack frame. It is the hook’s responsibility to advance the instruction pointer as appropriate.

fn assert_panic(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _msg: &AssertMessage<'tcx>,
    _unwind: Option<BasicBlock>
) -> InterpResult<'tcx>

Called to evaluate Assert MIR terminators that trigger a panic.

fn ptr_to_int(
    _mem: &Memory<'mir, 'tcx, Self>,
    _ptr: Pointer
) -> InterpResult<'tcx, u64>

fn binary_ptr_op(
    _ecx: &InterpCx<'mir, 'tcx, Self>,
    _bin_op: BinOp,
    _left: &ImmTy<'tcx>,
    _right: &ImmTy<'tcx>
) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)>

Called for all binary operations where the LHS has pointer type.

fn box_alloc(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _dest: &PlaceTy<'tcx>
) -> InterpResult<'tcx>

Heap allocations via the box keyword.

fn access_local(
    _ecx: &InterpCx<'mir, 'tcx, Self>,
    frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
    local: Local
) -> InterpResult<'tcx, InterpOperand<Self::PointerTag>>

Called to read the specified local from the frame. Since reading a ZST is not actually accessing memory or locals, this is never invoked for ZST reads.

fn access_local_mut<'a>(
    ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
    frame: usize,
    local: Local
) -> InterpResult<'tcx, Result<&'a mut LocalValue<Self::PointerTag>, MemPlace<Self::PointerTag>>>

Called to write the specified local from the frame. Since writing a ZST is not actually accessing memory or locals, this is never invoked for ZST reads.

fn before_access_global(
    _memory_extra: &(),
    _alloc_id: AllocId,
    allocation: &Allocation<Self::PointerTag, Self::AllocExtra>,
    _static_def_id: Option<DefId>,
    is_write: bool
) -> InterpResult<'tcx>

Called before a global allocation is accessed. def_id is Some if this is the “lazy” allocation of a static.

fn init_frame_extra(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    frame: Frame<'mir, 'tcx>
) -> InterpResult<'tcx, Frame<'mir, 'tcx>>

Called immediately before a new stack frame gets pushed.

fn stack<'a>(
    ecx: &'a InterpCx<'mir, 'tcx, Self>
) -> &'a [Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>]

Borrow the current thread’s stack.

fn stack_mut<'a>(
    ecx: &'a mut InterpCx<'mir, 'tcx, Self>
) -> &'a mut Vec<Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>>

Mutably borrow the current thread’s stack.

fn abort(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _msg: String
) -> InterpResult<'tcx, !>

Called to evaluate Abort MIR terminator.

fn before_terminator(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>
) -> InterpResult<'tcx>

Called before a basic block terminator is executed. You can use this to detect endlessly running programs.

fn thread_local_static_alloc_id(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    def_id: DefId
) -> InterpResult<'tcx, AllocId>

Return the AllocId for the given thread-local static in the current thread.

fn extern_static_alloc_id(
    mem: &Memory<'mir, 'tcx, Self>,
    def_id: DefId
) -> InterpResult<'tcx, AllocId>

Return the AllocId backing the given extern static.

fn before_deallocation(
    _memory_extra: &mut Self::MemoryExtra,
    _id: AllocId
) -> InterpResult<'tcx>

Called to notify the machine before a deallocation occurs.

fn after_static_mem_initialized(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _ptr: Pointer<Self::PointerTag>,
    _size: Size
) -> InterpResult<'tcx>

Called after initializing static memory using the interpreter.

fn retag(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _kind: RetagKind,
    _place: &PlaceTy<'tcx, Self::PointerTag>
) -> InterpResult<'tcx>

Executes a retagging operation

fn after_stack_push(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx>

Called immediately after a stack frame got pushed and its locals got initialized.

fn after_stack_pop(
    _ecx: &mut InterpCx<'mir, 'tcx, Self>,
    _frame: Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
    _unwinding: bool
) -> InterpResult<'tcx, StackPopJump>

Called immediately after a stack frame got popped, but before jumping back to the caller.

fn int_to_ptr(
    _mem: &Memory<'mir, 'tcx, Self>,
    int: u64
) -> InterpResult<'tcx, Pointer<Self::PointerTag>>