Rollup of 7 pull requests

compiler/rustc_feature/src/builtin_attrs.rs

@@ -643,8 +643,8 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         through unstable paths"
     ),
     rustc_attr!(
-        rustc_deprecated_safe_2024, Normal, template!(Word), WarnFollowing,
-        EncodeCrossCrate::Yes,
+        rustc_deprecated_safe_2024, Normal, template!(List: r#"audit_that = "...""#),
+        ErrorFollowing, EncodeCrossCrate::Yes,
         "rustc_deprecated_safe_2024 is supposed to be used in libstd only",
     ),
 

compiler/rustc_mir_build/messages.ftl

@@ -30,7 +30,7 @@ mir_build_call_to_deprecated_safe_fn_requires_unsafe =
     call to deprecated safe function `{$function}` is unsafe and requires unsafe block
     .note = consult the function's documentation for information on how to avoid undefined behavior
     .label = call to unsafe function
-    .suggestion = you can wrap the call in an `unsafe` block if you can guarantee the code is only ever called from single-threaded code
+    .suggestion = you can wrap the call in an `unsafe` block if you can guarantee {$guarantee}
 
 mir_build_call_to_fn_with_requires_unsafe =
     call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -96,18 +96,42 @@ impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
             // from an edition before 2024.
             &UnsafeOpKind::CallToUnsafeFunction(Some(id))
                 if !span.at_least_rust_2024()
-                    && self.tcx.has_attr(id, sym::rustc_deprecated_safe_2024) =>
+                    && let Some(attr) = self.tcx.get_attr(id, sym::rustc_deprecated_safe_2024) =>
             {
+                let suggestion = attr
+                    .meta_item_list()
+                    .unwrap_or_default()
+                    .into_iter()
+                    .find(|item| item.has_name(sym::audit_that))
+                    .map(|item| {
+                        item.value_str().expect(
+                            "`#[rustc_deprecated_safe_2024(audit_that)]` must have a string value",
+                        )
+                    });
+
                 let sm = self.tcx.sess.source_map();
+                let guarantee = suggestion
+                    .as_ref()
+                    .map(|suggestion| format!("that {}", suggestion))
+                    .unwrap_or_else(|| String::from("its unsafe preconditions"));
+                let suggestion = suggestion
+                    .and_then(|suggestion| {
+                        sm.indentation_before(span).map(|indent| {
+                            format!("{}// TODO: Audit that {}.\n", indent, suggestion) // ignore-tidy-todo
+                        })
+                    })
+                    .unwrap_or_default();
+
                 self.tcx.emit_node_span_lint(
                     DEPRECATED_SAFE_2024,
                     self.hir_context,
                     span,
                     CallToDeprecatedSafeFnRequiresUnsafe {
                         span,
                         function: with_no_trimmed_paths!(self.tcx.def_path_str(id)),
+                        guarantee,
                         sub: CallToDeprecatedSafeFnRequiresUnsafeSub {
-                            indent: sm.indentation_before(span).unwrap_or_default(),
+                            start_of_line_suggestion: suggestion,
                             start_of_line: sm.span_extend_to_line(span).shrink_to_lo(),
                             left: span.shrink_to_lo(),
                             right: span.shrink_to_hi(),

compiler/rustc_mir_build/src/errors.rs

@@ -28,17 +28,16 @@ pub(crate) struct CallToDeprecatedSafeFnRequiresUnsafe {
     #[label]
     pub(crate) span: Span,
     pub(crate) function: String,
+    pub(crate) guarantee: String,
     #[subdiagnostic]
     pub(crate) sub: CallToDeprecatedSafeFnRequiresUnsafeSub,
 }
 
 #[derive(Subdiagnostic)]
 #[multipart_suggestion(mir_build_suggestion, applicability = "machine-applicable")]
 pub(crate) struct CallToDeprecatedSafeFnRequiresUnsafeSub {
-    pub(crate) indent: String,
-    #[suggestion_part(
-        code = "{indent}// TODO: Audit that the environment access only happens in single-threaded code.\n" // ignore-tidy-todo
-    )]
+    pub(crate) start_of_line_suggestion: String,
+    #[suggestion_part(code = "{start_of_line_suggestion}")]
     pub(crate) start_of_line: Span,
     #[suggestion_part(code = "unsafe {{ ")]
     pub(crate) left: Span,

compiler/rustc_span/src/symbol.rs

@@ -472,6 +472,7 @@ symbols! {
         attr,
         attr_literals,
         attributes,
+        audit_that,
         augmented_assignments,
         auto_traits,
         automatically_derived,

library/core/src/lib.rs

@@ -170,6 +170,7 @@
 #![feature(internal_impls_macro)]
 #![feature(ip)]
 #![feature(is_ascii_octdigit)]
+#![feature(is_val_statically_known)]
 #![feature(isqrt)]
 #![feature(link_cfg)]
 #![feature(offset_of_enum)]

library/core/src/num/int_macros.rs

@@ -1496,18 +1496,17 @@ macro_rules! int_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     acc = try_opt!(acc.checked_mul(base));
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        return Some(acc);
+                    }
                 }
                 exp /= 2;
                 base = try_opt!(base.checked_mul(base));
             }
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.checked_mul(base)
         }
 
         /// Strict exponentiation. Computes `self.pow(exp)`, panicking if
@@ -1547,18 +1546,17 @@ macro_rules! int_impl {
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     acc = acc.strict_mul(base);
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        return acc;
+                    }
                 }
                 exp /= 2;
                 base = base.strict_mul(base);
             }
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.strict_mul(base)
         }
 
         /// Returns the square root of the number, rounded down.
@@ -2175,26 +2173,44 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
+        #[rustc_allow_const_fn_unstable(is_val_statically_known)]
         pub const fn wrapping_pow(self, mut exp: u32) -> Self {
             if exp == 0 {
                 return 1;
             }
             let mut base = self;
             let mut acc: Self = 1;
 
-            while exp > 1 {
-                if (exp & 1) == 1 {
-                    acc = acc.wrapping_mul(base);
+            if intrinsics::is_val_statically_known(exp) {
+                while exp > 1 {
+                    if (exp & 1) == 1 {
+                        acc = acc.wrapping_mul(base);
+                    }
+                    exp /= 2;
+                    base = base.wrapping_mul(base);
                 }
-                exp /= 2;
-                base = base.wrapping_mul(base);
-            }
 
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc.wrapping_mul(base)
+                // since exp!=0, finally the exp must be 1.
+                // Deal with the final bit of the exponent separately, since
+                // squaring the base afterwards is not necessary.
+                acc.wrapping_mul(base)
+            } else {
+                // This is faster than the above when the exponent is not known
+                // at compile time. We can't use the same code for the constant
+                // exponent case because LLVM is currently unable to unroll
+                // this loop.
+                loop {
+                    if (exp & 1) == 1 {
+                        acc = acc.wrapping_mul(base);
+                        // since exp!=0, finally the exp must be 1.
+                        if exp == 1 {
+                            return acc;
+                        }
+                    }
+                    exp /= 2;
+                    base = base.wrapping_mul(base);
+                }
+            }
         }
 
         /// Calculates `self` + `rhs`.
@@ -2690,9 +2706,14 @@ macro_rules! int_impl {
             // Scratch space for storing results of overflowing_mul.
             let mut r;
 
-            while exp > 1 {
+            loop {
                 if (exp & 1) == 1 {
                     r = acc.overflowing_mul(base);
+                    // since exp!=0, finally the exp must be 1.
+                    if exp == 1 {
+                        r.1 |= overflown;
+                        return r;
+                    }
                     acc = r.0;
                     overflown |= r.1;
                 }
@@ -2701,14 +2722,6 @@ macro_rules! int_impl {
                 base = r.0;
                 overflown |= r.1;
             }
-
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            r = acc.overflowing_mul(base);
-            r.1 |= overflown;
-            r
         }
 
         /// Raises self to the power of `exp`, using exponentiation by squaring.
@@ -2728,26 +2741,45 @@ macro_rules! int_impl {
                       without modifying the original"]
         #[inline]
         #[rustc_inherit_overflow_checks]
+        #[rustc_allow_const_fn_unstable(is_val_statically_known)]
         pub const fn pow(self, mut exp: u32) -> Self {
             if exp == 0 {
                 return 1;
             }
             let mut base = self;
             let mut acc = 1;
 
-            while exp > 1 {
-                if (exp & 1) == 1 {
-                    acc = acc * base;
+            if intrinsics::is_val_statically_known(exp) {
+                while exp > 1 {
+                    if (exp & 1) == 1 {
+                        acc = acc * base;
+                    }
+                    exp /= 2;
+                    base = base * base;
                 }
-                exp /= 2;
-                base = base * base;
-            }
 
-            // since exp!=0, finally the exp must be 1.
-            // Deal with the final bit of the exponent separately, since
-            // squaring the base afterwards is not necessary and may cause a
-            // needless overflow.
-            acc * base
+                // since exp!=0, finally the exp must be 1.
+                // Deal with the final bit of the exponent separately, since
+                // squaring the base afterwards is not necessary and may cause a
+                // needless overflow.
+                acc * base
+            } else {
+                // This is faster than the above when the exponent is not known
+                // at compile time. We can't use the same code for the constant
+                // exponent case because LLVM is currently unable to unroll
+                // this loop.
+                loop {
+                    if (exp & 1) == 1 {
+                        acc = acc * base;
+                        // since exp!=0, finally the exp must be 1.
+                        if exp == 1 {
+                            return acc;
+                        }
+                    }
+                    exp /= 2;
+                    base = base * base;
+                }
+            }
         }
 
         /// Returns the square root of the number, rounded down.