Some cleanup

[rust.git] / src / librustc_mir / interpret / eval_context.rs

diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index 5be8135fee9241f8d657087479e03d5527fcc9d3..6598b0f99f2a99e4e73606ed637672c7fa39ad74 100644 (file)
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -21,7 +21,7 @@
 
 use super::{
     Immediate, Operand, MemPlace, MPlaceTy, Place, PlaceTy, ScalarMaybeUndef,
-    Memory, Machine, PointerArithmetic, FnVal, StackPopInfo
+    Memory, Machine, StackPopInfo
 };
 
 pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
@@ -86,7 +86,7 @@ pub struct Frame<'mir, 'tcx, Tag=(), Extra=()> {
     /// The block that is currently executed (or will be executed after the above call stacks
     /// return).
     /// If this is `None`, we are unwinding and this function doesn't need any clean-up.
-    /// Just continue the same as with
+    /// Just continue the same as with `Resume`.
     pub block: Option<mir::BasicBlock>,
 
     /// The index of the currently evaluated statement.
@@ -551,6 +551,19 @@ pub fn push_stack_frame(
         }
     }
 
+    /// Pops the current frame from the stack, deallocating the
+    /// memory for allocated locals.
+    ///
+    /// If `unwinding` is `false`, then we are performing a normal return
+    /// from a function. In this case, we jump back into the frame of the caller,
+    /// and continue execution as normal.
+    ///
+    /// If `unwinding` is `true`, then we are in the middle of a panic,
+    /// and need to unwind this frame. In this case, we jump to the
+    /// `cleanup` block for the function, which is responsible for running
+    /// `Drop` impls for any locals that have been initialized at this point.
+    /// The cleanup block ends with a special `Resume` terminator, which will
+    /// cause us to continue unwinding.
     pub(super) fn pop_stack_frame(
         &mut self,
         unwinding: bool
@@ -817,25 +830,4 @@ pub fn generate_stacktrace(&self, explicit_span: Option<Span>) -> Vec<FrameInfo<
         trace!("generate stacktrace: {:#?}, {:?}", frames, explicit_span);
         frames
     }
-
-    /// Resolve the function at the specified slot in the provided
-    /// vtable. An index of '0' corresponds to the first method
-    /// declared in the trait of the provided vtable
-    pub fn get_vtable_slot(
-        &self,
-        vtable: Scalar<M::PointerTag>,
-        idx: usize
-    ) -> InterpResult<'tcx, FnVal<'tcx, M::ExtraFnVal>> {
-        let ptr_size = self.pointer_size();
-        // Skip over the 'drop_ptr', 'size', and 'align' fields
-        let vtable_slot = vtable.ptr_offset(ptr_size * (idx as u64 + 3), self)?;
-        let vtable_slot = self.memory.check_ptr_access(
-            vtable_slot,
-            ptr_size,
-            self.tcx.data_layout.pointer_align.abi,
-        )?.expect("cannot be a ZST");
-        let fn_ptr = self.memory.get(vtable_slot.alloc_id)?
-            .read_ptr_sized(self, vtable_slot)?.not_undef()?;
-        Ok(self.memory.get_fn(fn_ptr)?)
-    }
 }