attr: Handle `rustc_const_{un}stable` properly

Since extern functions cannot be marked as const (they take no
qualifiers) but some intrinsics are const, while still being `extern
"rust-intrinsic", we need to be able to handle the
`#[rustc_const_stable]` and `#[rustc_const_unstable]` attribute.

Technically, this simply indicates that a certain intrinsic is constant
and can be used in const contexts, such as `size_of` or `offset`.

We also need to mark all const intrinsics with `rustc_const_stable` in
the testsuite.
This commit is contained in:
Arthur Cohen 2022-08-08 08:48:26 +02:00
parent 7beea479c5
commit 084f959076
13 changed files with 135 additions and 3 deletions

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@ -235,11 +235,48 @@ ConstChecker::check_function_call (HirId fn_id, Location locus)
return;
auto maybe_fn = mappings.lookup_hir_item (fn_id);
if (!maybe_fn || maybe_fn->get_item_kind () != Item::ItemKind::Function)
if (maybe_fn && maybe_fn->get_item_kind () != Item::ItemKind::Function)
return;
// There are const extern functions (intrinsics)
// TODO: Should we check the ABI is only "rust intrinsics"? Is that handled
// elsewhere?
HirId parent_block;
auto maybe_extern_item
= mappings.lookup_hir_extern_item (fn_id, &parent_block);
if (maybe_extern_item
&& maybe_extern_item->get_extern_kind ()
!= ExternalItem::ExternKind::Function)
return;
auto is_error = false;
if (maybe_fn)
{
auto fn = static_cast<Function *> (maybe_fn);
if (!fn->get_qualifiers ().is_const ())
is_error = true;
}
if (maybe_extern_item)
{
{
auto fn = static_cast<ExternalFunctionItem *> (maybe_extern_item);
auto is_const_extern = std::any_of (
fn->get_outer_attrs ().begin (), fn->get_outer_attrs ().end (),
[] (const AST::Attribute &attr) {
// `starts_with` in C++11...
// FIXME: Is it really how we want to handle `rustc_const_stable`
// and `rustc_const_unstable`?
// TODO: Add these attributes to the attribute check and handle
// `stable` and `unstable` as well
return attr.get_path ().as_string ().rfind ("rustc_const_", 0) == 0;
});
if (!is_const_extern)
is_error = true;
}
}
if (is_error)
rust_error_at (locus, "only functions marked as %<const%> are allowed to "
"be called from constant contexts");
}
@ -522,6 +559,9 @@ ConstChecker::visit (Function &function)
if (const_fn)
const_context.enter (function.get_mappings ().get_hirid ());
for (auto &param : function.get_function_params ())
param.get_type ()->accept_vis (*this);
function.get_definition ()->accept_vis (*this);
if (const_fn)

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@ -0,0 +1,76 @@
// { dg-additional-options "-w" }
mod intrinsics {
extern "rust-intrinsic" {
pub fn wrapping_add<T>(a: T, b: T) -> T;
pub fn rotate_left<T>(a: T, b: T) -> T;
pub fn rotate_right<T>(a: T, b: T) -> T;
pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
}
}
mod mem {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
pub fn transmute<T, U>(_: T) -> U;
pub fn size_of<T>() -> usize;
}
}
macro_rules! impl_uint {
($($ty:ident = $lang:literal),*) => {
$(
impl $ty {
pub fn wrapping_add(self, rhs: Self) -> Self {
// intrinsics::wrapping_add(self, rhs)
self + rhs
}
pub fn rotate_left(self, n: u32) -> Self {
unsafe {
intrinsics::rotate_left(self, n as Self)
}
}
pub fn rotate_right(self, n: u32) -> Self {
unsafe {
intrinsics::rotate_right(self, n as Self)
}
}
pub fn to_le(self) -> Self {
#[cfg(target_endian = "little")]
{
self
}
}
pub const fn from_le_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
// { dg-error "only functions marked as .const. are allowed to be called from constant contexts" "" { target *-*-* } .-1 }
Self::from_le(Self::from_ne_bytes(bytes))
}
pub const fn from_le(x: Self) -> Self {
#[cfg(target_endian = "little")]
{
x
}
}
pub const fn from_ne_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
// { dg-error "only functions marked as .const. are allowed to be called from constant contexts" "" { target *-*-* } .-1 }
unsafe { mem::transmute(bytes) }
}
}
)*
}
}
impl_uint!(
u8 = "u8",
u16 = "u16",
u32 = "u32",
u64 = "u64",
u128 = "u128",
usize = "usize"
);

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@ -1,4 +1,5 @@
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -4,6 +4,7 @@ extern "C" {
mod intrinsics {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}
}

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@ -1,5 +1,6 @@
// { dg-additional-options "-w" }
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -1,16 +1,22 @@
// { dg-additional-options "-w" }
mod intrinsics {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
pub fn wrapping_add<T>(a: T, b: T) -> T;
#[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
pub fn rotate_left<T>(a: T, b: T) -> T;
#[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
pub fn rotate_right<T>(a: T, b: T) -> T;
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
}
}
mod mem {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
fn transmute<T, U>(_: T) -> U;
#[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
fn size_of<T>() -> usize;
}
}

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@ -1,5 +1,6 @@
// { dg-additional-options "-w" }
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -1,5 +1,6 @@
// { dg-additional-options "-w" }
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -1,6 +1,7 @@
// { dg-additional-options "-w" }
// { dg-output "slice_access=3\n" }
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -2,6 +2,7 @@
// { dg-output "" }
mod intrinsics {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
}
}

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@ -1,5 +1,6 @@
// { dg-additional-options "-w" }
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -1,5 +1,6 @@
// { dg-additional-options "-w" }
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
}

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@ -2,6 +2,7 @@
// { dg-output "t1sz=5 t2sz=10" }
mod mem {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
fn transmute<T, U>(_: T) -> U;
}
}