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Fundamentally, we have *three* disjoint categories of functions: 1. const-stable functions 2. private/unstable functions that are meant to be callable from const-stable functions 3. functions that can make use of unstable const features This PR implements the following system: - `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions. - `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category. - `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls. Also, several holes in recursive const stability checking are being closed. There's still one potential hole that is hard to avoid, which is when MIR building automatically inserts calls to a particular function in stable functions -- which happens in the panic machinery. Those need to *not* be `rustc_const_unstable` (or manually get a `rustc_const_stable_indirect`) to be sure they follow recursive const stability. But that's a fairly rare and special case so IMO it's fine. The net effect of this is that a `#[unstable]` or unmarked function can be constified simply by marking it as `const fn`, and it will then be const-callable from stable `const fn` and subject to recursive const stability requirements. If it is publicly reachable (which implies it cannot be unmarked), it will be const-unstable under the same feature gate. Only if the function ever becomes `#[stable]` does it need a `#[rustc_const_unstable]` or `#[rustc_const_stable]` marker to decide if this should also imply const-stability. Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to use unstable const lang features (including intrinsics), or (b) `#[stable]` functions that are not yet intended to be const-stable. Adding `#[rustc_const_stable]` is only needed for functions that are actually meant to be directly callable from stable const code. `#[rustc_const_stable_indirect]` is used to mark intrinsics as const-callable and for `#[rustc_const_unstable]` functions that are actually called from other, exposed-on-stable `const fn`. No other attributes are required.
90 lines
3.7 KiB
Diff
90 lines
3.7 KiB
Diff
From ad7ffe71baba46865f2e65266ab025920dfdc20b Mon Sep 17 00:00:00 2001
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From: bjorn3 <bjorn3@users.noreply.github.com>
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Date: Thu, 18 Feb 2021 18:45:28 +0100
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Subject: [PATCH] Disable 128bit atomic operations
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Cranelift doesn't support them yet
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---
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library/core/src/panic/unwind_safe.rs | 6 -----
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library/core/src/sync/atomic.rs | 38 ---------------------------
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library/core/tests/atomic.rs | 4 ---
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4 files changed, 4 insertions(+), 50 deletions(-)
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diff --git a/library/core/src/panic/unwind_safe.rs b/library/core/src/panic/unwind_safe.rs
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index 092b7cf..158cf71 100644
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--- a/library/core/src/panic/unwind_safe.rs
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+++ b/library/core/src/panic/unwind_safe.rs
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@@ -216,9 +216,6 @@ impl RefUnwindSafe for crate::sync::atomic::AtomicI32 {}
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#[cfg(target_has_atomic_load_store = "64")]
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#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
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impl RefUnwindSafe for crate::sync::atomic::AtomicI64 {}
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-#[cfg(target_has_atomic_load_store = "128")]
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-#[unstable(feature = "integer_atomics", issue = "99069")]
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-impl RefUnwindSafe for crate::sync::atomic::AtomicI128 {}
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#[cfg(target_has_atomic_load_store = "ptr")]
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#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
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@@ -235,9 +232,6 @@ impl RefUnwindSafe for crate::sync::atomic::AtomicU32 {}
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#[cfg(target_has_atomic_load_store = "64")]
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#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
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impl RefUnwindSafe for crate::sync::atomic::AtomicU64 {}
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-#[cfg(target_has_atomic_load_store = "128")]
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-#[unstable(feature = "integer_atomics", issue = "99069")]
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-impl RefUnwindSafe for crate::sync::atomic::AtomicU128 {}
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#[cfg(target_has_atomic_load_store = "8")]
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#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
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diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs
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index d9de37e..8293fce 100644
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--- a/library/core/src/sync/atomic.rs
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+++ b/library/core/src/sync/atomic.rs
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@@ -2996,44 +2996,6 @@ atomic_int! {
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8,
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u64 AtomicU64
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}
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-#[cfg(target_has_atomic_load_store = "128")]
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-atomic_int! {
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- cfg(target_has_atomic = "128"),
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- cfg(target_has_atomic_equal_alignment = "128"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- rustc_const_unstable(feature = "integer_atomics", issue = "99069"),
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- rustc_const_unstable(feature = "integer_atomics", issue = "99069"),
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- cfg_attr(not(test), rustc_diagnostic_item = "AtomicI128"),
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- "i128",
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- "#![feature(integer_atomics)]\n\n",
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- atomic_min, atomic_max,
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- 16,
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- i128 AtomicI128
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-}
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-#[cfg(target_has_atomic_load_store = "128")]
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-atomic_int! {
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- cfg(target_has_atomic = "128"),
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- cfg(target_has_atomic_equal_alignment = "128"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- unstable(feature = "integer_atomics", issue = "99069"),
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- rustc_const_unstable(feature = "integer_atomics", issue = "99069"),
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- rustc_const_unstable(feature = "integer_atomics", issue = "99069"),
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- cfg_attr(not(test), rustc_diagnostic_item = "AtomicU128"),
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- "u128",
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- "#![feature(integer_atomics)]\n\n",
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- atomic_umin, atomic_umax,
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- 16,
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- u128 AtomicU128
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-}
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#[cfg(target_has_atomic_load_store = "ptr")]
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macro_rules! atomic_int_ptr_sized {
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( $($target_pointer_width:literal $align:literal)* ) => { $(
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--
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2.26.2.7.g19db9cfb68
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