Make some float methods unstable const fn

Some float methods are now `const fn` under the `const_float_methods` feature gate. In order to support `min`, `max`, `abs` and `copysign`, the implementation of some intrinsics had to be moved from Miri to rustc_const_eval.
qinheping · Oct 15, 2024 · 1897d05 · 1897d05
1 parent 4f124de
commit 1897d05
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Showing 11 changed files with 371 additions and 204 deletions.
diff --git a/core/src/intrinsics.rs b/core/src/intrinsics.rs
diff --git a/core/src/lib.rs b/core/src/lib.rs
@@ -120,6 +120,7 @@
 #![feature(const_char_encode_utf16)]
 #![feature(const_eval_select)]
 #![feature(const_exact_div)]
+#![feature(const_float_methods)]
 #![feature(const_fmt_arguments_new)]
 #![feature(const_hash)]
 #![feature(const_heap)]

diff --git a/core/src/num/f128.rs b/core/src/num/f128.rs
@@ -471,7 +471,7 @@ impl f128 {
     #[inline]
     #[must_use]
     #[unstable(feature = "f128", issue = "116909")]
-    pub fn is_sign_positive(self) -> bool {
+    pub const fn is_sign_positive(self) -> bool {
         !self.is_sign_negative()
     }
 
@@ -497,7 +497,7 @@ impl f128 {
     #[inline]
     #[must_use]
     #[unstable(feature = "f128", issue = "116909")]
-    pub fn is_sign_negative(self) -> bool {
+    pub const fn is_sign_negative(self) -> bool {
         // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
         // applies to zeros and NaNs as well.
         // SAFETY: This is just transmuting to get the sign bit, it's fine.
@@ -538,7 +538,7 @@ impl f128 {
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
     // #[unstable(feature = "float_next_up_down", issue = "91399")]
-    pub fn next_up(self) -> Self {
+    pub const fn next_up(self) -> Self {
         // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
         // denormals to zero. This is in general unsound and unsupported, but here
         // we do our best to still produce the correct result on such targets.
@@ -592,7 +592,7 @@ impl f128 {
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
     // #[unstable(feature = "float_next_up_down", issue = "91399")]
-    pub fn next_down(self) -> Self {
+    pub const fn next_down(self) -> Self {
         // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
         // denormals to zero. This is in general unsound and unsupported, but here
         // we do our best to still produce the correct result on such targets.
@@ -627,8 +627,9 @@ impl f128 {
     /// ```
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the operation, without modifying the original"]
-    pub fn recip(self) -> Self {
+    pub const fn recip(self) -> Self {
         1.0 / self
     }
 
@@ -647,8 +648,9 @@ impl f128 {
     /// ```
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the operation, without modifying the original"]
-    pub fn to_degrees(self) -> Self {
+    pub const fn to_degrees(self) -> Self {
         // Use a literal for better precision.
         const PIS_IN_180: f128 = 57.2957795130823208767981548141051703324054724665643215491602_f128;
         self * PIS_IN_180
@@ -670,8 +672,9 @@ impl f128 {
     /// ```
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the operation, without modifying the original"]
-    pub fn to_radians(self) -> f128 {
+    pub const fn to_radians(self) -> f128 {
         // Use a literal for better precision.
         const RADS_PER_DEG: f128 =
             0.0174532925199432957692369076848861271344287188854172545609719_f128;
@@ -698,8 +701,9 @@ impl f128 {
     /// ```
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn max(self, other: f128) -> f128 {
+    pub const fn max(self, other: f128) -> f128 {
         intrinsics::maxnumf128(self, other)
     }
 
@@ -723,8 +727,9 @@ impl f128 {
     /// ```
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn min(self, other: f128) -> f128 {
+    pub const fn min(self, other: f128) -> f128 {
         intrinsics::minnumf128(self, other)
     }
 
@@ -757,7 +762,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     // #[unstable(feature = "float_minimum_maximum", issue = "91079")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn maximum(self, other: f128) -> f128 {
+    pub const fn maximum(self, other: f128) -> f128 {
         if self > other {
             self
         } else if other > self {
@@ -798,7 +803,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     // #[unstable(feature = "float_minimum_maximum", issue = "91079")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn minimum(self, other: f128) -> f128 {
+    pub const fn minimum(self, other: f128) -> f128 {
         if self < other {
             self
         } else if other < self {
@@ -1269,9 +1274,20 @@ impl f128 {
     /// ```
     #[inline]
     #[unstable(feature = "f128", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "method returns a new number and does not mutate the original value"]
-    pub fn clamp(mut self, min: f128, max: f128) -> f128 {
-        assert!(min <= max, "min > max, or either was NaN. min = {min:?}, max = {max:?}");
+    pub const fn clamp(mut self, min: f128, max: f128) -> f128 {
+        #[inline] // inline to avoid LLVM crash
+        const fn assert_at_const(min: f128, max: f128) {
+            // Note that we cannot format in constant expressions.
+            assert!(min <= max, "min > max, or either was NaN");
+        }
+        #[inline] // inline to avoid codegen regression
+        fn assert_at_rt(min: f128, max: f128) {
+            assert!(min <= max, "min > max, or either was NaN. min = {min:?}, max = {max:?}");
+        }
+        // FIXME(const-hack): We would prefer to have streamlined panics when formatters become const-friendly.
+        intrinsics::const_eval_select((min, max), assert_at_const, assert_at_rt);
         if self < min {
             self = min;
         }

diff --git a/core/src/num/f16.rs b/core/src/num/f16.rs
@@ -459,7 +459,7 @@ impl f16 {
     #[inline]
     #[must_use]
     #[unstable(feature = "f16", issue = "116909")]
-    pub fn is_sign_positive(self) -> bool {
+    pub const fn is_sign_positive(self) -> bool {
         !self.is_sign_negative()
     }
 
@@ -488,7 +488,7 @@ impl f16 {
     #[inline]
     #[must_use]
     #[unstable(feature = "f16", issue = "116909")]
-    pub fn is_sign_negative(self) -> bool {
+    pub const fn is_sign_negative(self) -> bool {
         // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
         // applies to zeros and NaNs as well.
         // SAFETY: This is just transmuting to get the sign bit, it's fine.
@@ -529,7 +529,7 @@ impl f16 {
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
     // #[unstable(feature = "float_next_up_down", issue = "91399")]
-    pub fn next_up(self) -> Self {
+    pub const fn next_up(self) -> Self {
         // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
         // denormals to zero. This is in general unsound and unsupported, but here
         // we do our best to still produce the correct result on such targets.
@@ -583,7 +583,7 @@ impl f16 {
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
     // #[unstable(feature = "float_next_up_down", issue = "91399")]
-    pub fn next_down(self) -> Self {
+    pub const fn next_down(self) -> Self {
         // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
         // denormals to zero. This is in general unsound and unsupported, but here
         // we do our best to still produce the correct result on such targets.
@@ -618,8 +618,9 @@ impl f16 {
     /// ```
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the operation, without modifying the original"]
-    pub fn recip(self) -> Self {
+    pub const fn recip(self) -> Self {
         1.0 / self
     }
 
@@ -638,8 +639,9 @@ impl f16 {
     /// ```
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the operation, without modifying the original"]
-    pub fn to_degrees(self) -> Self {
+    pub const fn to_degrees(self) -> Self {
         // Use a literal for better precision.
         const PIS_IN_180: f16 = 57.2957795130823208767981548141051703_f16;
         self * PIS_IN_180
@@ -661,8 +663,9 @@ impl f16 {
     /// ```
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the operation, without modifying the original"]
-    pub fn to_radians(self) -> f16 {
+    pub const fn to_radians(self) -> f16 {
         // Use a literal for better precision.
         const RADS_PER_DEG: f16 = 0.017453292519943295769236907684886_f16;
         self * RADS_PER_DEG
@@ -687,8 +690,9 @@ impl f16 {
     /// ```
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn max(self, other: f16) -> f16 {
+    pub const fn max(self, other: f16) -> f16 {
         intrinsics::maxnumf16(self, other)
     }
 
@@ -711,8 +715,9 @@ impl f16 {
     /// ```
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn min(self, other: f16) -> f16 {
+    pub const fn min(self, other: f16) -> f16 {
         intrinsics::minnumf16(self, other)
     }
 
@@ -744,7 +749,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     // #[unstable(feature = "float_minimum_maximum", issue = "91079")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn maximum(self, other: f16) -> f16 {
+    pub const fn maximum(self, other: f16) -> f16 {
         if self > other {
             self
         } else if other > self {
@@ -784,7 +789,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     // #[unstable(feature = "float_minimum_maximum", issue = "91079")]
     #[must_use = "this returns the result of the comparison, without modifying either input"]
-    pub fn minimum(self, other: f16) -> f16 {
+    pub const fn minimum(self, other: f16) -> f16 {
         if self < other {
             self
         } else if other < self {
@@ -1244,9 +1249,20 @@ impl f16 {
     /// ```
     #[inline]
     #[unstable(feature = "f16", issue = "116909")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[must_use = "method returns a new number and does not mutate the original value"]
-    pub fn clamp(mut self, min: f16, max: f16) -> f16 {
-        assert!(min <= max, "min > max, or either was NaN. min = {min:?}, max = {max:?}");
+    pub const fn clamp(mut self, min: f16, max: f16) -> f16 {
+        #[inline] // inline to avoid LLVM crash
+        const fn assert_at_const(min: f16, max: f16) {
+            // Note that we cannot format in constant expressions.
+            assert!(min <= max, "min > max, or either was NaN");
+        }
+        #[inline] // inline to avoid codegen regression
+        fn assert_at_rt(min: f16, max: f16) {
+            assert!(min <= max, "min > max, or either was NaN. min = {min:?}, max = {max:?}");
+        }
+        // FIXME(const-hack): We would prefer to have streamlined panics when formatters become const-friendly.
+        intrinsics::const_eval_select((min, max), assert_at_const, assert_at_rt);
         if self < min {
             self = min;
         }

diff --git a/core/src/num/f32.rs b/core/src/num/f32.rs
@@ -828,8 +828,9 @@ impl f32 {
     /// ```
     #[must_use = "this returns the result of the operation, without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[inline]
-    pub fn recip(self) -> f32 {
+    pub const fn recip(self) -> f32 {
         1.0 / self
     }
 
@@ -845,8 +846,9 @@ impl f32 {
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[inline]
-    pub fn to_degrees(self) -> f32 {
+    pub const fn to_degrees(self) -> f32 {
         // Use a constant for better precision.
         const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
         self * PIS_IN_180
@@ -864,8 +866,9 @@ impl f32 {
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[inline]
-    pub fn to_radians(self) -> f32 {
+    pub const fn to_radians(self) -> f32 {
         const RADS_PER_DEG: f32 = consts::PI / 180.0;
         self * RADS_PER_DEG
     }
@@ -885,8 +888,9 @@ impl f32 {
     /// ```
     #[must_use = "this returns the result of the comparison, without modifying either input"]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[inline]
-    pub fn max(self, other: f32) -> f32 {
+    pub const fn max(self, other: f32) -> f32 {
         intrinsics::maxnumf32(self, other)
     }
 
@@ -905,8 +909,9 @@ impl f32 {
     /// ```
     #[must_use = "this returns the result of the comparison, without modifying either input"]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[inline]
-    pub fn min(self, other: f32) -> f32 {
+    pub const fn min(self, other: f32) -> f32 {
         intrinsics::minnumf32(self, other)
     }
 
@@ -933,7 +938,7 @@ impl f32 {
     #[must_use = "this returns the result of the comparison, without modifying either input"]
     #[unstable(feature = "float_minimum_maximum", issue = "91079")]
     #[inline]
-    pub fn maximum(self, other: f32) -> f32 {
+    pub const fn maximum(self, other: f32) -> f32 {
         if self > other {
             self
         } else if other > self {
@@ -968,7 +973,7 @@ impl f32 {
     #[must_use = "this returns the result of the comparison, without modifying either input"]
     #[unstable(feature = "float_minimum_maximum", issue = "91079")]
     #[inline]
-    pub fn minimum(self, other: f32) -> f32 {
+    pub const fn minimum(self, other: f32) -> f32 {
         if self < other {
             self
         } else if other < self {
@@ -1401,9 +1406,19 @@ impl f32 {
     /// ```
     #[must_use = "method returns a new number and does not mutate the original value"]
     #[stable(feature = "clamp", since = "1.50.0")]
+    #[rustc_const_unstable(feature = "const_float_methods", issue = "130843")]
     #[inline]
-    pub fn clamp(mut self, min: f32, max: f32) -> f32 {
-        assert!(min <= max, "min > max, or either was NaN. min = {min:?}, max = {max:?}");
+    pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
+        const fn assert_at_const(min: f32, max: f32) {
+            // Note that we cannot format in constant expressions.
+            assert!(min <= max, "min > max, or either was NaN");
+        }
+        #[inline] // inline to avoid codegen regression
+        fn assert_at_rt(min: f32, max: f32) {
+            assert!(min <= max, "min > max, or either was NaN. min = {min:?}, max = {max:?}");
+        }
+        // FIXME(const-hack): We would prefer to have streamlined panics when formatters become const-friendly.
+        intrinsics::const_eval_select((min, max), assert_at_const, assert_at_rt);
         if self < min {
             self = min;
         }