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Remove the `AllocId` from `ByRef` values

`ByRef` const values have no identity beyond their value, we should not treat them as having identity. The `AllocId` often differed between equal constants, because of the way that the miri-engine evaluates constants.
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oli-obk committed Jun 19, 2019
1 parent e951d8e commit 23a1ebb3fca8dc77340dd94400255722260991e9
@@ -43,14 +43,13 @@ pub enum ConstValue<'tcx> {
end: usize,
},

/// An allocation together with a pointer into the allocation.
/// Invariant: the pointer's `AllocId` resolves to the allocation.
/// An allocation together with an offset into the allocation.
/// The alignment exists to allow `const_field` to have `ByRef` access to nonprimitive fields
/// of `repr(packed)` structs. The alignment may be lower than the type of this constant.
/// This permits reads with lower alignment than what the type would normally require.
/// FIXME(RalfJ,oli-obk): The alignment checks are part of miri, but const eval doesn't really
/// need them. Disabling them may be too hard though.
ByRef(Pointer, Align, &'tcx Allocation),
ByRef(Size, Align, &'tcx Allocation),

/// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
/// variants when the code is monomorphic enough for that.
@@ -1335,7 +1335,7 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
impl<'tcx> TypeFoldable<'tcx> for ConstValue<'tcx> {
fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
match *self {
ConstValue::ByRef(ptr, align, alloc) => ConstValue::ByRef(ptr, align, alloc),
ConstValue::ByRef(offset, align, alloc) => ConstValue::ByRef(offset, align, alloc),
ConstValue::Infer(ic) => ConstValue::Infer(ic.fold_with(folder)),
ConstValue::Param(p) => ConstValue::Param(p.fold_with(folder)),
ConstValue::Placeholder(p) => ConstValue::Placeholder(p),
@@ -71,7 +71,7 @@ pub fn codegen_static_initializer(
let static_ = cx.tcx.const_eval(param_env.and(cid))?;

let alloc = match static_.val {
ConstValue::ByRef(ptr, align, alloc) if ptr.offset.bytes() == 0 && align == alloc.align => {
ConstValue::ByRef(offset, align, alloc) if offset.bytes() == 0 && align == alloc.align => {
alloc
},
_ => bug!("static const eval returned {:#?}", static_),
@@ -109,8 +109,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
let b_llval = bx.const_usize((end - start) as u64);
OperandValue::Pair(a_llval, b_llval)
},
ConstValue::ByRef(ptr, align, alloc) => {
return bx.load_operand(bx.from_const_alloc(layout, align, alloc, ptr.offset));
ConstValue::ByRef(offset, align, alloc) => {
return bx.load_operand(bx.from_const_alloc(layout, align, alloc, offset));
},
};

@@ -424,8 +424,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let layout = cx.layout_of(self.monomorphize(&ty));
match bx.tcx().const_eval(param_env.and(cid)) {
Ok(val) => match val.val {
mir::interpret::ConstValue::ByRef(ptr, align, alloc) => {
bx.cx().from_const_alloc(layout, align, alloc, ptr.offset)
mir::interpret::ConstValue::ByRef(offset, align, alloc) => {
bx.cx().from_const_alloc(layout, align, alloc, offset)
}
_ => bug!("promoteds should have an allocation: {:?}", val),
},
@@ -99,7 +99,7 @@ fn op_to_const<'tcx>(
Ok(mplace) => {
let ptr = mplace.ptr.to_ptr().unwrap();
let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
ConstValue::ByRef(ptr, mplace.align, alloc)
ConstValue::ByRef(ptr.offset, mplace.align, alloc)
},
// see comment on `let try_as_immediate` above
Err(ImmTy { imm: Immediate::Scalar(x), .. }) => match x {
@@ -113,7 +113,7 @@ fn op_to_const<'tcx>(
let mplace = op.to_mem_place();
let ptr = mplace.ptr.to_ptr().unwrap();
let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
ConstValue::ByRef(ptr, mplace.align, alloc)
ConstValue::ByRef(ptr.offset, mplace.align, alloc)
},
},
Err(ImmTy { imm: Immediate::ScalarPair(a, b), .. }) => {
@@ -542,7 +542,7 @@ fn validate_and_turn_into_const<'tcx>(
let ptr = mplace.ptr.to_ptr()?;
Ok(tcx.mk_const(ty::Const {
val: ConstValue::ByRef(
ptr,
ptr.offset,
mplace.align,
ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id),
),
@@ -218,7 +218,7 @@ impl LiteralExpander<'tcx> {
(ConstValue::Scalar(Scalar::Ptr(p)), x, y) if x == y => {
let alloc = self.tcx.alloc_map.lock().unwrap_memory(p.alloc_id);
ConstValue::ByRef(
p,
p.offset,
// FIXME(oli-obk): this should be the type's layout
alloc.align,
alloc,
@@ -1436,9 +1436,10 @@ fn slice_pat_covered_by_const<'tcx>(
suffix: &[Pattern<'tcx>],
) -> Result<bool, ErrorReported> {
let data: &[u8] = match (const_val.val, &const_val.ty.sty) {
(ConstValue::ByRef(ptr, _, alloc), ty::Array(t, n)) => {
(ConstValue::ByRef(offset, _, alloc), ty::Array(t, n)) => {
assert_eq!(*t, tcx.types.u8);
let n = n.assert_usize(tcx).unwrap();
let ptr = Pointer::new(AllocId(0), offset);
alloc.get_bytes(&tcx, ptr, Size::from_bytes(n)).unwrap()
},
(ConstValue::Slice { data, start, end }, ty::Slice(t)) => {
@@ -1758,9 +1759,9 @@ fn specialize<'p, 'a: 'p, 'tcx>(
let (alloc, offset, n, ty) = match value.ty.sty {
ty::Array(t, n) => {
match value.val {
ConstValue::ByRef(ptr, _, alloc) => (
ConstValue::ByRef(offset, _, alloc) => (
alloc,
ptr.offset,
offset,
n.unwrap_usize(cx.tcx),
t,
),
@@ -538,10 +538,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpretCx<'mir, 'tcx, M> {
self.layout_of(self.monomorphize(val.ty)?)
})?;
let op = match val.val {
ConstValue::ByRef(ptr, align, _alloc) => {
ConstValue::ByRef(offset, align, alloc) => {
let id = self.tcx.alloc_map.lock().create_memory_alloc(alloc);
// We rely on mutability being set correctly in that allocation to prevent writes
// where none should happen.
let ptr = self.tag_static_base_pointer(ptr);
let ptr = self.tag_static_base_pointer(Pointer::new(id, offset));
Operand::Indirect(MemPlace::from_ptr(ptr, align))
},
ConstValue::Scalar(x) =>
@@ -0,0 +1,17 @@
#![feature(repr_simd, platform_intrinsics)]

// revisions:rpass1 rpass2

#[repr(simd)]
struct I32x2(i32, i32);

extern "platform-intrinsic" {
fn simd_shuffle2<T, U>(x: T, y: T, idx: [u32; 2]) -> U;
}

fn main() {
unsafe {
let _: I32x2 = simd_shuffle2(I32x2(1, 2), I32x2(3, 4), [0, 0]);
let _: I32x2 = simd_shuffle2(I32x2(1, 2), I32x2(3, 4), [0, 0]);
}
}

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