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interpret: simplify pointer arithmetic logic

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This commit is contained in:
Ralf Jung 2024-08-01 10:19:13 +02:00
parent de78cb56b2
commit 5d5c97aad7
27 changed files with 73 additions and 187 deletions
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98
compiler/rustc_middle/src/mir/interpret/pointer.rs
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@ -5,7 +5,7 @@ use rustc_data_structures::static_assert_size;
use rustc_macros::{HashStable, TyDecodable, TyEncodable};
use rustc_target::abi::{HasDataLayout, Size};
use super::{AllocId, InterpResult};
use super::AllocId;
////////////////////////////////////////////////////////////////////////////////
// Pointer arithmetic
@ -40,62 +40,13 @@ pub trait PointerArithmetic: HasDataLayout {
}
#[inline]
fn target_usize_to_isize(&self, val: u64) -> i64 {
let val = val as i64;
// Now wrap-around into the machine_isize range.
if val > self.target_isize_max() {
// This can only happen if the ptr size is < 64, so we know max_usize_plus_1 fits into
// i64.
debug_assert!(self.pointer_size().bits() < 64);
let max_usize_plus_1 = 1u128 << self.pointer_size().bits();
val - i64::try_from(max_usize_plus_1).unwrap()
} else {
val
}
}
/// Helper function: truncate given value-"overflowed flag" pair to pointer size and
/// update "overflowed flag" if there was an overflow.
/// This should be called by all the other methods before returning!
#[inline]
fn truncate_to_ptr(&self, (val, over): (u64, bool)) -> (u64, bool) {
let val = u128::from(val);
let max_ptr_plus_1 = 1u128 << self.pointer_size().bits();
(u64::try_from(val % max_ptr_plus_1).unwrap(), over || val >= max_ptr_plus_1)
fn truncate_to_target_usize(&self, val: u64) -> u64 {
self.pointer_size().truncate(val.into()).try_into().unwrap()
}
#[inline]
fn overflowing_offset(&self, val: u64, i: u64) -> (u64, bool) {
// We do not need to check if i fits in a machine usize. If it doesn't,
// either the wrapping_add will wrap or res will not fit in a pointer.
let res = val.overflowing_add(i);
self.truncate_to_ptr(res)
}
#[inline]
fn overflowing_signed_offset(&self, val: u64, i: i64) -> (u64, bool) {
// We need to make sure that i fits in a machine isize.
let n = i.unsigned_abs();
if i >= 0 {
let (val, over) = self.overflowing_offset(val, n);
(val, over || i > self.target_isize_max())
} else {
let res = val.overflowing_sub(n);
let (val, over) = self.truncate_to_ptr(res);
(val, over || i < self.target_isize_min())
}
}
#[inline]
fn offset<'tcx>(&self, val: u64, i: u64) -> InterpResult<'tcx, u64> {
let (res, over) = self.overflowing_offset(val, i);
if over { throw_ub!(PointerArithOverflow) } else { Ok(res) }
}
#[inline]
fn signed_offset<'tcx>(&self, val: u64, i: i64) -> InterpResult<'tcx, u64> {
let (res, over) = self.overflowing_signed_offset(val, i);
if over { throw_ub!(PointerArithOverflow) } else { Ok(res) }
fn sign_extend_to_target_isize(&self, val: u64) -> i64 {
self.pointer_size().sign_extend(val.into()).try_into().unwrap()
}
}
@ -331,7 +282,7 @@ impl<Prov> Pointer<Option<Prov>> {
}
}
impl<'tcx, Prov> Pointer<Prov> {
impl<Prov> Pointer<Prov> {
#[inline(always)]
pub fn new(provenance: Prov, offset: Size) -> Self {
Pointer { provenance, offset }
@ -349,43 +300,16 @@ impl<'tcx, Prov> Pointer<Prov> {
Pointer { provenance: f(self.provenance), ..self }
}
#[inline]
pub fn offset(self, i: Size, cx: &impl HasDataLayout) -> InterpResult<'tcx, Self> {
Ok(Pointer {
offset: Size::from_bytes(cx.data_layout().offset(self.offset.bytes(), i.bytes())?),
..self
})
}
#[inline]
pub fn overflowing_offset(self, i: Size, cx: &impl HasDataLayout) -> (Self, bool) {
let (res, over) = cx.data_layout().overflowing_offset(self.offset.bytes(), i.bytes());
let ptr = Pointer { offset: Size::from_bytes(res), ..self };
(ptr, over)
}
#[inline(always)]
pub fn wrapping_offset(self, i: Size, cx: &impl HasDataLayout) -> Self {
self.overflowing_offset(i, cx).0
}
#[inline]
pub fn signed_offset(self, i: i64, cx: &impl HasDataLayout) -> InterpResult<'tcx, Self> {
Ok(Pointer {
offset: Size::from_bytes(cx.data_layout().signed_offset(self.offset.bytes(), i)?),
..self
})
}
#[inline]
pub fn overflowing_signed_offset(self, i: i64, cx: &impl HasDataLayout) -> (Self, bool) {
let (res, over) = cx.data_layout().overflowing_signed_offset(self.offset.bytes(), i);
let ptr = Pointer { offset: Size::from_bytes(res), ..self };
(ptr, over)
let res =
cx.data_layout().truncate_to_target_usize(self.offset.bytes().wrapping_add(i.bytes()));
Pointer { offset: Size::from_bytes(res), ..self }
}
#[inline(always)]
pub fn wrapping_signed_offset(self, i: i64, cx: &impl HasDataLayout) -> Self {
self.overflowing_signed_offset(i, cx).0
// It's wrapping anyway, so we can just cast to `u64`.
self.wrapping_offset(Size::from_bytes(i as u64), cx)
}
}