From 3e8676c327086e4761674060793dcfd2f03d0c48 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Mon, 18 Sep 2023 18:34:44 +0200
Subject: [PATCH 01/10] isqrt: initial implementation

---
 library/core/src/num/int_macros.rs  | 80 +++++++++++++++++++++++++++++
 library/core/src/num/uint_macros.rs | 35 +++++++++++++
 2 files changed, 115 insertions(+)

diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 1f43520e1b3..66bd8001353 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -898,6 +898,45 @@ pub const fn checked_pow(self, mut exp: u32) -> Option<Self> {
             acc.checked_mul(base)
         }
 
+        /// Returns the square root of the number, rounded down.
+        ///
+        /// Returns `None` if `self` is negative.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        /// ```
+        #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".checked_isqrt(), Some(3));")]
+        /// ```
+        #[stable(feature = "isqrt", since = "1.73.0")]
+        #[rustc_const_stable(feature = "isqrt", since = "1.73.0")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline]
+        pub const fn checked_isqrt(self) -> Option<Self> {
+            if self < 0 {
+                return None;
+            } else if self < 2 {
+                return Some(self);
+            }
+
+            let mut x: Self = self;
+            let mut c: Self = 0;
+            let mut d: Self = 1 << (self.ilog2() & !1);
+
+            while (d != 0) {
+                if x >= c + d {
+                    x -= c + d;
+                    c = (c >> 1) + d;
+                } else {
+                    c >>= 1;
+                }
+                d >>= 2;
+            }
+
+            return Some(c);
+        }
+
         /// Saturating integer addition. Computes `self + rhs`, saturating at the numeric
         /// bounds instead of overflowing.
         ///
@@ -2061,6 +2100,47 @@ pub const fn pow(self, mut exp: u32) -> Self {
             acc * base
         }
 
+        /// Returns the square root of the number, rounded down.
+        ///
+        /// # Panics
+        ///
+        /// This function will panic if `self` is negative.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        /// ```
+        #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".isqrt(), 3);")]
+        /// ```
+        #[stable(feature = "isqrt", since = "1.73.0")]
+        #[rustc_const_stable(feature = "isqrt", since = "1.73.0")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline]
+        pub const fn isqrt(self) -> Self {
+            if self < 0 {
+                panic!("argument of integer square root must be non-negative")
+            } else if self < 2 {
+                return self;
+            }
+
+            let mut x: Self = self;
+            let mut c: Self = 0;
+            let mut d: Self = 1 << (self.ilog2() & !1);
+
+            while (d != 0) {
+                if x >= c + d {
+                    x -= c + d;
+                    c = (c >> 1) + d;
+                } else {
+                    c >>= 1;
+                }
+                d >>= 2;
+            }
+
+            return c;
+        }
+
         /// Calculates the quotient of Euclidean division of `self` by `rhs`.
         ///
         /// This computes the integer `q` such that `self = q * rhs + r`, with
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 23ca37817d4..4c093ab8220 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -1979,6 +1979,41 @@ pub const fn pow(self, mut exp: u32) -> Self {
             acc * base
         }
 
+        /// Returns the square root of the number, rounded down.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        /// ```
+        #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".isqrt(), 3);")]
+        /// ```
+        #[stable(feature = "isqrt", since = "1.73.0")]
+        #[rustc_const_stable(feature = "isqrt", since = "1.73.0")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline]
+        pub const fn isqrt(self) -> Self {
+            if self < 2 {
+                return self;
+            }
+
+            let mut x: Self = self;
+            let mut c: Self = 0;
+            let mut d: Self = 1 << (self.ilog2() & !1);
+
+            while (d != 0) {
+                if x >= c + d {
+                    x -= c + d;
+                    c = (c >> 1) + d;
+                } else {
+                    c >>= 1;
+                }
+                d >>= 2;
+            }
+
+            return c;
+        }
+
         /// Performs Euclidean division.
         ///
         /// Since, for the positive integers, all common

From 1b34f1c6b2b407c286f0e0bac084114c7475c61e Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Mon, 18 Sep 2023 19:27:26 +0200
Subject: [PATCH 02/10] isqrt: add tests

---
 library/core/tests/num/int_macros.rs  | 11 +++++++++++
 library/core/tests/num/uint_macros.rs | 10 ++++++++++
 2 files changed, 21 insertions(+)

diff --git a/library/core/tests/num/int_macros.rs b/library/core/tests/num/int_macros.rs
index 439bbe66997..a9ce8433864 100644
--- a/library/core/tests/num/int_macros.rs
+++ b/library/core/tests/num/int_macros.rs
@@ -290,6 +290,17 @@ fn test_pow() {
                 assert_eq!(r.saturating_pow(0), 1 as $T);
             }
 
+            #[test]
+            fn test_isqrt() {
+                assert_eq!($T::MIN.checked_isqrt(), None);
+                assert_eq!((-1 as $T).checked_isqrt(), None);
+                assert_eq!((0 as $T).isqrt(), 0 as $T);
+                assert_eq!((1 as $T).isqrt(), 1 as $T);
+                assert_eq!((2 as $T).isqrt(), 1 as $T);
+                assert_eq!((99 as $T).isqrt(), 9 as $T);
+                assert_eq!((100 as $T).isqrt(), 10 as $T);
+            }
+
             #[test]
             fn test_div_floor() {
                 let a: $T = 8;
diff --git a/library/core/tests/num/uint_macros.rs b/library/core/tests/num/uint_macros.rs
index 7d6203db0b9..9a8421c7b95 100644
--- a/library/core/tests/num/uint_macros.rs
+++ b/library/core/tests/num/uint_macros.rs
@@ -206,6 +206,16 @@ fn test_pow() {
                 assert_eq!(r.saturating_pow(2), MAX);
             }
 
+            #[test]
+            fn test_isqrt() {
+                assert_eq!((0 as $T).isqrt(), 0 as $T);
+                assert_eq!((1 as $T).isqrt(), 1 as $T);
+                assert_eq!((2 as $T).isqrt(), 1 as $T);
+                assert_eq!((99 as $T).isqrt(), 9 as $T);
+                assert_eq!((100 as $T).isqrt(), 10 as $T);
+                assert_eq!($T::MAX.isqrt(), (1 << ($T::BITS / 2)) - 1);
+            }
+
             #[test]
             fn test_div_floor() {
                 assert_eq!((8 as $T).div_floor(3), 2);

From 68f0b475c76de88fb5cb37c8cd0163703354415a Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Tue, 26 Sep 2023 15:44:28 +0200
Subject: [PATCH 03/10] isqrt: remove duplication by delegating to unsigned
 integers

---
 library/core/src/num/int_macros.rs  | 50 +++++++----------------------
 library/core/src/num/uint_macros.rs |  2 +-
 2 files changed, 12 insertions(+), 40 deletions(-)

diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 66bd8001353..8bc82b5fc88 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -915,26 +915,10 @@ pub const fn checked_pow(self, mut exp: u32) -> Option<Self> {
         #[inline]
         pub const fn checked_isqrt(self) -> Option<Self> {
             if self < 0 {
-                return None;
-            } else if self < 2 {
-                return Some(self);
+                None
+            } else {
+                Some((self as $UnsignedT).isqrt() as Self)
             }
-
-            let mut x: Self = self;
-            let mut c: Self = 0;
-            let mut d: Self = 1 << (self.ilog2() & !1);
-
-            while (d != 0) {
-                if x >= c + d {
-                    x -= c + d;
-                    c = (c >> 1) + d;
-                } else {
-                    c >>= 1;
-                }
-                d >>= 2;
-            }
-
-            return Some(c);
         }
 
         /// Saturating integer addition. Computes `self + rhs`, saturating at the numeric
@@ -2118,27 +2102,15 @@ pub const fn pow(self, mut exp: u32) -> Self {
                       without modifying the original"]
         #[inline]
         pub const fn isqrt(self) -> Self {
-            if self < 0 {
-                panic!("argument of integer square root must be non-negative")
-            } else if self < 2 {
-                return self;
+            // I would like to implement it as
+            // ```
+            // self.checked_isqrt().expect("argument of integer square root must be non-negative")
+            // ```
+            // but `expect` is not yet stable as a `const fn`.
+            match self.checked_isqrt() {
+                Some(sqrt) => sqrt,
+                None => panic!("argument of integer square root must be non-negative"),
             }
-
-            let mut x: Self = self;
-            let mut c: Self = 0;
-            let mut d: Self = 1 << (self.ilog2() & !1);
-
-            while (d != 0) {
-                if x >= c + d {
-                    x -= c + d;
-                    c = (c >> 1) + d;
-                } else {
-                    c >>= 1;
-                }
-                d >>= 2;
-            }
-
-            return c;
         }
 
         /// Calculates the quotient of Euclidean division of `self` by `rhs`.
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 4c093ab8220..f8005694ceb 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -2011,7 +2011,7 @@ pub const fn isqrt(self) -> Self {
                 d >>= 2;
             }
 
-            return c;
+            c
         }
 
         /// Performs Euclidean division.

From d49da0fe54251fbee190dc2adcdbffe787aecae7 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Tue, 26 Sep 2023 16:05:51 +0200
Subject: [PATCH 04/10] isqrt: add more tests

---
 library/core/tests/num/int_macros.rs  | 17 +++++++++++++++++
 library/core/tests/num/uint_macros.rs | 15 +++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/library/core/tests/num/int_macros.rs b/library/core/tests/num/int_macros.rs
index a9ce8433864..dd0ea5e9238 100644
--- a/library/core/tests/num/int_macros.rs
+++ b/library/core/tests/num/int_macros.rs
@@ -299,6 +299,23 @@ fn test_isqrt() {
                 assert_eq!((2 as $T).isqrt(), 1 as $T);
                 assert_eq!((99 as $T).isqrt(), 9 as $T);
                 assert_eq!((100 as $T).isqrt(), 10 as $T);
+
+                let n_max: $T = (1024 * 1024).min($T::MAX as u128) as $T;
+                for n in 0..=n_max {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    let (square, overflow) = (isqrt + 1).overflowing_pow(2);
+                    assert!(overflow || square > n);
+                }
+
+                for n in ($T::MAX - 127)..=$T::MAX {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    let (square, overflow) = (isqrt + 1).overflowing_pow(2);
+                    assert!(overflow || square > n);
+                }
             }
 
             #[test]
diff --git a/library/core/tests/num/uint_macros.rs b/library/core/tests/num/uint_macros.rs
index 9a8421c7b95..1ae7d048757 100644
--- a/library/core/tests/num/uint_macros.rs
+++ b/library/core/tests/num/uint_macros.rs
@@ -214,6 +214,21 @@ fn test_isqrt() {
                 assert_eq!((99 as $T).isqrt(), 9 as $T);
                 assert_eq!((100 as $T).isqrt(), 10 as $T);
                 assert_eq!($T::MAX.isqrt(), (1 << ($T::BITS / 2)) - 1);
+
+                let n_max: $T = (1024 * 1024).min($T::MAX as u128) as $T;
+                for n in 0..=n_max {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    assert!(isqrt + 1 == (1 as $T) << ($T::BITS / 2) || (isqrt + 1).pow(2) > n);
+                }
+
+                for n in ($T::MAX - 255)..=$T::MAX {
+                    let isqrt: $T = n.isqrt();
+
+                    assert!(isqrt.pow(2) <= n);
+                    assert!(isqrt + 1 == (1 as $T) << ($T::BITS / 2) || (isqrt + 1).pow(2) > n);
+                }
             }
 
             #[test]

From 17dfb18bd1ad15ce4437bb44ba30b0c82aad3e07 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Thu, 28 Sep 2023 10:43:41 +0200
Subject: [PATCH 05/10] fixup! isqrt: initial implementation

Fix C-ism and type inference.
---
 library/core/src/num/uint_macros.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index f8005694ceb..b232d5d50cb 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -1997,11 +1997,11 @@ pub const fn isqrt(self) -> Self {
                 return self;
             }
 
-            let mut x: Self = self;
-            let mut c: Self = 0;
-            let mut d: Self = 1 << (self.ilog2() & !1);
+            let mut x = self;
+            let mut c = 0;
+            let mut d = 1 << (self.ilog2() & !1);
 
-            while (d != 0) {
+            while d != 0 {
                 if x >= c + d {
                     x -= c + d;
                     c = (c >> 1) + d;

From c97ab231415aa46cd1d35e8d00d601dec0d23e86 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Thu, 28 Sep 2023 11:15:43 +0200
Subject: [PATCH 06/10] isqrt: fix stability

---
 library/core/src/lib.rs             |  1 +
 library/core/src/num/int_macros.rs  | 10 ++++++----
 library/core/src/num/uint_macros.rs |  5 +++--
 library/core/tests/lib.rs           |  1 +
 4 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 8b04bafcda5..be734a9ba52 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -178,6 +178,7 @@
 #![feature(ip)]
 #![feature(ip_bits)]
 #![feature(is_ascii_octdigit)]
+#![feature(isqrt)]
 #![feature(maybe_uninit_uninit_array)]
 #![feature(ptr_alignment_type)]
 #![feature(ptr_metadata)]
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 8bc82b5fc88..d1fe8b55cc1 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -906,10 +906,11 @@ pub const fn checked_pow(self, mut exp: u32) -> Option<Self> {
         ///
         /// Basic usage:
         /// ```
+        /// #![feature(isqrt)]
         #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".checked_isqrt(), Some(3));")]
         /// ```
-        #[stable(feature = "isqrt", since = "1.73.0")]
-        #[rustc_const_stable(feature = "isqrt", since = "1.73.0")]
+        #[unstable(feature = "isqrt", issue = "none")]
+        #[rustc_const_unstable(feature = "isqrt", issue = "none")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
@@ -2094,10 +2095,11 @@ pub const fn pow(self, mut exp: u32) -> Self {
         ///
         /// Basic usage:
         /// ```
+        /// #![feature(isqrt)]
         #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".isqrt(), 3);")]
         /// ```
-        #[stable(feature = "isqrt", since = "1.73.0")]
-        #[rustc_const_stable(feature = "isqrt", since = "1.73.0")]
+        #[unstable(feature = "isqrt", issue = "none")]
+        #[rustc_const_unstable(feature = "isqrt", issue = "none")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index b232d5d50cb..5de672d5d7e 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -1985,10 +1985,11 @@ pub const fn pow(self, mut exp: u32) -> Self {
         ///
         /// Basic usage:
         /// ```
+        /// #![feature(isqrt)]
         #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".isqrt(), 3);")]
         /// ```
-        #[stable(feature = "isqrt", since = "1.73.0")]
-        #[rustc_const_stable(feature = "isqrt", since = "1.73.0")]
+        #[unstable(feature = "isqrt", issue = "none")]
+        #[rustc_const_unstable(feature = "isqrt", issue = "none")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs
index 17011b845cf..4d67f6f1511 100644
--- a/library/core/tests/lib.rs
+++ b/library/core/tests/lib.rs
@@ -56,6 +56,7 @@
 #![feature(min_specialization)]
 #![feature(numfmt)]
 #![feature(num_midpoint)]
+#![feature(isqrt)]
 #![feature(step_trait)]
 #![feature(str_internals)]
 #![feature(std_internals)]

From 51463175a46599eb69375861bfe3626f68d643a4 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Thu, 28 Sep 2023 12:12:18 +0200
Subject: [PATCH 07/10] isqrt: cite source and rename variables to match
 original C code

---
 library/core/src/num/uint_macros.rs | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 5de672d5d7e..371d6e180c2 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -1998,21 +1998,26 @@ pub const fn isqrt(self) -> Self {
                 return self;
             }
 
-            let mut x = self;
-            let mut c = 0;
-            let mut d = 1 << (self.ilog2() & !1);
+            // The algorithm is based on the one presented in
+            // <https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_(base_2)>
+            // which cites as source the following C code:
+            // <https://web.archive.org/web/20120306040058/http://medialab.freaknet.org/martin/src/sqrt/sqrt.c>.
 
-            while d != 0 {
-                if x >= c + d {
-                    x -= c + d;
-                    c = (c >> 1) + d;
+            let mut op = self;
+            let mut res = 0;
+            let mut one = 1 << (self.ilog2() & !1);
+
+            while one != 0 {
+                if op >= res + one {
+                    op -= res + one;
+                    res = (res >> 1) + one;
                 } else {
-                    c >>= 1;
+                    res >>= 1;
                 }
-                d >>= 2;
+                one >>= 2;
             }
 
-            c
+            res
         }
 
         /// Performs Euclidean division.

From 77f9eae9956f6c7c23bdf81c2efdd47625382ea2 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Thu, 28 Sep 2023 12:32:58 +0200
Subject: [PATCH 08/10] fixup! isqrt: fix stability

---
 library/core/src/num/int_macros.rs  | 8 ++++----
 library/core/src/num/uint_macros.rs | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index d1fe8b55cc1..3cbb55af3bc 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -909,8 +909,8 @@ pub const fn checked_pow(self, mut exp: u32) -> Option<Self> {
         /// #![feature(isqrt)]
         #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".checked_isqrt(), Some(3));")]
         /// ```
-        #[unstable(feature = "isqrt", issue = "none")]
-        #[rustc_const_unstable(feature = "isqrt", issue = "none")]
+        #[unstable(feature = "isqrt", issue = "116226")]
+        #[rustc_const_unstable(feature = "isqrt", issue = "116226")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
@@ -2098,8 +2098,8 @@ pub const fn pow(self, mut exp: u32) -> Self {
         /// #![feature(isqrt)]
         #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".isqrt(), 3);")]
         /// ```
-        #[unstable(feature = "isqrt", issue = "none")]
-        #[rustc_const_unstable(feature = "isqrt", issue = "none")]
+        #[unstable(feature = "isqrt", issue = "116226")]
+        #[rustc_const_unstable(feature = "isqrt", issue = "116226")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 371d6e180c2..565fc1930ea 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -1988,8 +1988,8 @@ pub const fn pow(self, mut exp: u32) -> Self {
         /// #![feature(isqrt)]
         #[doc = concat!("assert_eq!(10", stringify!($SelfT), ".isqrt(), 3);")]
         /// ```
-        #[unstable(feature = "isqrt", issue = "none")]
-        #[rustc_const_unstable(feature = "isqrt", issue = "none")]
+        #[unstable(feature = "isqrt", issue = "116226")]
+        #[rustc_const_unstable(feature = "isqrt", issue = "116226")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]

From fcdfd5b0b9efcf7797b0f1bf7e7ed47ff99de198 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Thu, 28 Sep 2023 13:59:19 +0200
Subject: [PATCH 09/10] isqrt: `assume` that `isqrt` takes half as many bits

https://github.com/rust-lang/rust/issues/89273#issuecomment-970581089
---
 library/core/src/num/uint_macros.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 565fc1930ea..f2190efa4d3 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -2017,6 +2017,13 @@ pub const fn isqrt(self) -> Self {
                 one >>= 2;
             }
 
+            // SAFETY: the result is positive and fits in an integer with half as many bits.
+            // Inform the optimizer about it.
+            unsafe {
+                intrinsics::assume(0 < res);
+                intrinsics::assume(res < 1 << (Self::BITS / 2));
+            }
+
             res
         }
 

From 25648de28f10799fa6274f64fa12475292231c72 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Thu, 28 Sep 2023 17:43:01 +0200
Subject: [PATCH 10/10] isqrt: disable long running tests in Miri

---
 library/core/tests/num/int_macros.rs  | 4 ++++
 library/core/tests/num/uint_macros.rs | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/library/core/tests/num/int_macros.rs b/library/core/tests/num/int_macros.rs
index dd0ea5e9238..165d9a29617 100644
--- a/library/core/tests/num/int_macros.rs
+++ b/library/core/tests/num/int_macros.rs
@@ -299,7 +299,11 @@ fn test_isqrt() {
                 assert_eq!((2 as $T).isqrt(), 1 as $T);
                 assert_eq!((99 as $T).isqrt(), 9 as $T);
                 assert_eq!((100 as $T).isqrt(), 10 as $T);
+            }
 
+            #[cfg(not(miri))] // Miri is too slow
+            #[test]
+            fn test_lots_of_isqrt() {
                 let n_max: $T = (1024 * 1024).min($T::MAX as u128) as $T;
                 for n in 0..=n_max {
                     let isqrt: $T = n.isqrt();
diff --git a/library/core/tests/num/uint_macros.rs b/library/core/tests/num/uint_macros.rs
index 1ae7d048757..955440647eb 100644
--- a/library/core/tests/num/uint_macros.rs
+++ b/library/core/tests/num/uint_macros.rs
@@ -214,7 +214,11 @@ fn test_isqrt() {
                 assert_eq!((99 as $T).isqrt(), 9 as $T);
                 assert_eq!((100 as $T).isqrt(), 10 as $T);
                 assert_eq!($T::MAX.isqrt(), (1 << ($T::BITS / 2)) - 1);
+            }
 
+            #[cfg(not(miri))] // Miri is too slow
+            #[test]
+            fn test_lots_of_isqrt() {
                 let n_max: $T = (1024 * 1024).min($T::MAX as u128) as $T;
                 for n in 0..=n_max {
                     let isqrt: $T = n.isqrt();