diff --git a/src/tools/miri/tests/fail/intrinsics/ctlz_nonzero.rs b/src/tools/miri/tests/fail/intrinsics/ctlz_nonzero.rs
index f73c1b6acb70..3da54b918826 100644
--- a/src/tools/miri/tests/fail/intrinsics/ctlz_nonzero.rs
+++ b/src/tools/miri/tests/fail/intrinsics/ctlz_nonzero.rs
@@ -1,13 +1,8 @@
-#![feature(intrinsics)]
-
-mod rusti {
-    #[rustc_intrinsic]
-    pub unsafe fn ctlz_nonzero<T>(x: T) -> u32;
-}
+#![feature(core_intrinsics)]
 
 pub fn main() {
     unsafe {
-        use crate::rusti::*;
+        use std::intrinsics::*;
 
         ctlz_nonzero(0u8); //~ ERROR: `ctlz_nonzero` called on 0
     }
diff --git a/src/tools/miri/tests/fail/intrinsics/cttz_nonzero.rs b/src/tools/miri/tests/fail/intrinsics/cttz_nonzero.rs
index a41cb8b15536..2b68f6713d80 100644
--- a/src/tools/miri/tests/fail/intrinsics/cttz_nonzero.rs
+++ b/src/tools/miri/tests/fail/intrinsics/cttz_nonzero.rs
@@ -1,13 +1,8 @@
-#![feature(intrinsics)]
-
-mod rusti {
-    #[rustc_intrinsic]
-    pub unsafe fn cttz_nonzero<T>(x: T) -> u32;
-}
+#![feature(core_intrinsics)]
 
 pub fn main() {
     unsafe {
-        use crate::rusti::*;
+        use std::intrinsics::*;
 
         cttz_nonzero(0u8); //~ ERROR: `cttz_nonzero` called on 0
     }
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_inf1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_inf1.rs
index 7ee0117ffb33..831a65966ce2 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_inf1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_inf1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_infneg1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_infneg1.rs
index 22bf881cef0a..a7032e97430e 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_infneg1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_infneg1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nan.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nan.rs
index 571121f4019f..e8c987619568 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nan.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nan.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nanneg.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nanneg.rs
index 12600ef61255..c8b29cbcfe99 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nanneg.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_nanneg.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_neg.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_neg.rs
index f848a137c279..0996d0244e88 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_neg.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_neg.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big1.rs
index 43ef4a95738f..f28227134d86 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big2.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big2.rs
index 83432c2b77c0..9e400b4ad406 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big2.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_big2.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_small1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_small1.rs
index 609443e6d4ef..9aca349b918c 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_small1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_32_too_small1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_inf1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_inf1.rs
index fb3eb11c0bb5..54361f6c32c4 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_inf1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_inf1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg1.rs
index b46c4777ba71..75f522963673 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg2.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg2.rs
index 8a3b9dbdc710..20d8fa1ae801 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg2.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_infneg2.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_nan.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_nan.rs
index e0c826cb0463..611a0ade0a56 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_nan.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_nan.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_neg.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_neg.rs
index c7c5bf402264..8ff8c3bee00b 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_neg.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_neg.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big1.rs
index fb3d7bda4e47..1f662e6c32a4 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big2.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big2.rs
index 2cf27b33553c..fad172801eaa 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big2.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big2.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big3.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big3.rs
index 22dca505e64b..7eb3559527aa 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big3.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big3.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big4.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big4.rs
index b59c8fa8e0c2..351fc6c6f1cb 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big4.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big4.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big5.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big5.rs
index 4ad0cd343a40..a6f73c797107 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big5.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big5.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big6.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big6.rs
index fd47dfc03d7a..b01ff3aafc03 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big6.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big6.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big7.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big7.rs
index 680ebda1c96b..a573e4e852c8 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big7.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_big7.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small1.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small1.rs
index e4cb36c5d2eb..4fb38c9bc2e7 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small1.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small1.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small2.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small2.rs
index fe4bac92bd3e..c4c0d3c17f03 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small2.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small2.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {
diff --git a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small3.rs b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small3.rs
index 219efd803162..de7d2215fd62 100644
--- a/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small3.rs
+++ b/src/tools/miri/tests/fail/intrinsics/float_to_int_64_too_small3.rs
@@ -1,8 +1,6 @@
-#![feature(intrinsics)]
-
+#![feature(core_intrinsics)]
 // Directly call intrinsic to avoid debug assertions in libstd
-#[rustc_intrinsic]
-unsafe fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+use std::intrinsics::float_to_int_unchecked;
 
 fn main() {
     unsafe {