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Miri: ptr_offset_from: support offset_from with twice the same non-null integer

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This commit is contained in:
Ralf Jung 2019-11-04 13:24:27 +01:00
parent da0c7c664b
commit 047e702c66
1 changed files with 20 additions and 3 deletions
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23
src/librustc_mir/interpret/intrinsics.rs
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@ -251,8 +251,26 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
"ptr_offset_from" => {
let a = self.force_ptr(self.read_immediate(args[0])?.to_scalar()?)?;
let b = self.force_ptr(self.read_immediate(args[1])?.to_scalar()?)?;
let isize_layout = self.layout_of(self.tcx.types.isize)?;
let a = self.read_immediate(args[0])?.to_scalar()?;
let b = self.read_immediate(args[1])?.to_scalar()?;
// Special case: if both scalars are *equal integers*
// and not NULL, their offset is 0.
// This is the dual to the special exception for offset-by-0
// in the inbounds pointer offset operation.
if a.is_bits() && b.is_bits() {
let a = a.to_usize(self)?;
let b = b.to_usize(self)?;
if a == b && a != 0 {
self.write_scalar(Scalar::from_int(0, isize_layout.size), dest)?;
return Ok(true);
}
}
// General case: we need two pointers.
let a = self.force_ptr(a)?;
let b = self.force_ptr(b)?;
if a.alloc_id != b.alloc_id {
throw_ub_format!(
"ptr_offset_from cannot compute offset of pointers into different \
@ -266,7 +284,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
BinOp::Sub, a_offset, b_offset,
)?;
let pointee_layout = self.layout_of(substs.type_at(0))?;
let isize_layout = self.layout_of(self.tcx.types.isize)?;
let val = ImmTy::from_scalar(val, isize_layout);
let size = ImmTy::from_int(pointee_layout.size.bytes(), isize_layout);
self.exact_div(val, size, dest)?;