65 lines
2.1 KiB
Rust
65 lines
2.1 KiB
Rust
use error::EvalResult;
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use memory::{Memory, Pointer};
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use primval::PrimVal;
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/// A `Value` represents a single self-contained Rust value.
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///
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/// A `Value` can either refer to a block of memory inside an allocation (`ByRef`) or to a primitve
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/// value held directly, outside of any allocation (`ByVal`).
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///
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/// For optimization of a few very common cases, there is also a representation for a pair of
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/// primitive values (`ByValPair`). It allows Miri to avoid making allocations for checked binary
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/// operations and fat pointers. This idea was taken from rustc's trans.
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#[derive(Clone, Copy, Debug)]
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pub enum Value {
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ByRef(Pointer),
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ByVal(PrimVal),
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ByValPair(PrimVal, PrimVal),
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}
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impl<'a, 'tcx: 'a> Value {
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pub(super) fn read_ptr(&self, mem: &Memory<'a, 'tcx>) -> EvalResult<'tcx, Pointer> {
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use self::Value::*;
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match *self {
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ByRef(ptr) => mem.read_ptr(ptr),
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ByVal(ptr) | ByValPair(ptr, _) => {
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Ok(ptr.try_as_ptr().expect("unimplemented: `read_ptr` on non-ptr primval"))
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}
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}
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}
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pub(super) fn expect_ptr_vtable_pair(
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&self,
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mem: &Memory<'a, 'tcx>
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) -> EvalResult<'tcx, (Pointer, Pointer)> {
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use self::Value::*;
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match *self {
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ByRef(ptr) => {
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let ptr = mem.read_ptr(ptr)?;
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let vtable = mem.read_ptr(ptr.offset(mem.pointer_size() as isize))?;
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Ok((ptr, vtable))
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}
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ByValPair(ptr, vtable)
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if ptr.try_as_ptr().is_some() && vtable.try_as_ptr().is_some()
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=> {
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let ptr = ptr.try_as_ptr().unwrap();
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let vtable = vtable.try_as_ptr().unwrap();
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Ok((ptr, vtable))
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}
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_ => bug!("expected ptr and vtable, got {:?}", self),
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}
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}
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pub(super) fn expect_slice_len(&self, mem: &Memory<'a, 'tcx>) -> EvalResult<'tcx, u64> {
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use self::Value::*;
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match *self {
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ByRef(ptr) => mem.read_usize(ptr.offset(mem.pointer_size() as isize)),
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ByValPair(_, val) if val.kind.is_int() => Ok(val.bits),
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_ => unimplemented!(),
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}
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}
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}
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