diff --git a/library/compiler-builtins/examples/intrinsics.rs b/library/compiler-builtins/examples/intrinsics.rs
index 519cea2ae0ee..ddbb976a252f 100644
--- a/library/compiler-builtins/examples/intrinsics.rs
+++ b/library/compiler-builtins/examples/intrinsics.rs
@@ -6,7 +6,7 @@
 #![allow(unused_features)]
 #![cfg_attr(thumb, no_main)]
 #![deny(dead_code)]
-#![feature(llvm_asm)]
+#![feature(test)]
 #![feature(lang_items)]
 #![feature(start)]
 #![feature(allocator_api)]
@@ -276,14 +276,9 @@ mod intrinsics {
 }
 
 fn run() {
+    use core::hint::black_box as bb;
     use intrinsics::*;
 
-    // A copy of "test::black_box". Used to prevent LLVM from optimizing away the intrinsics during LTO
-    fn bb<T>(dummy: T) -> T {
-        unsafe { llvm_asm!("" : : "r"(&dummy)) }
-        dummy
-    }
-
     bb(aeabi_d2f(bb(2.)));
     bb(aeabi_d2i(bb(2.)));
     bb(aeabi_d2l(bb(2.)));
diff --git a/library/compiler-builtins/src/arm.rs b/library/compiler-builtins/src/arm.rs
index 2b17b4f9613e..545d6a17a45c 100644
--- a/library/compiler-builtins/src/arm.rs
+++ b/library/compiler-builtins/src/arm.rs
@@ -9,135 +9,135 @@ use core::intrinsics;
 #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_uidivmod() {
-    llvm_asm!("
-        push {lr}
-        sub sp, sp, #4
-        mov r2, sp
-        bl __udivmodsi4
-        ldr r1, [sp]
-        add sp, sp, #4
-        pop {pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_uidivmod() {
+    asm!(
+        "push {{lr}}",
+        "sub sp, sp, #4",
+        "mov r2, sp",
+        "bl __udivmodsi4",
+        "ldr r1, [sp]",
+        "add sp, sp, #4",
+        "pop {{pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(target_os = "ios")]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_uidivmod() {
-    llvm_asm!("
-        push {lr}
-        sub sp, sp, #4
-        mov r2, sp
-        bl ___udivmodsi4
-        ldr r1, [sp]
-        add sp, sp, #4
-        pop {pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_uidivmod() {
+    asm!(
+        "push {{lr}}",
+        "sub sp, sp, #4",
+        "mov r2, sp",
+        "bl ___udivmodsi4",
+        "ldr r1, [sp]",
+        "add sp, sp, #4",
+        "pop {{pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(not(target_os = "ios"))]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_uldivmod() {
-    llvm_asm!("
-        push {r4, lr}
-        sub sp, sp, #16
-        add r4, sp, #8
-        str r4, [sp]
-        bl __udivmoddi4
-        ldr r2, [sp, #8]
-        ldr r3, [sp, #12]
-        add sp, sp, #16
-        pop {r4, pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_uldivmod() {
+    asm!(
+        "push {{r4, lr}}",
+        "sub sp, sp, #16",
+        "add r4, sp, #8",
+        "str r4, [sp]",
+        "bl __udivmoddi4",
+        "ldr r2, [sp, #8]",
+        "ldr r3, [sp, #12]",
+        "add sp, sp, #16",
+        "pop {{r4, pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(target_os = "ios")]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_uldivmod() {
-    llvm_asm!("
-        push {r4, lr}
-        sub sp, sp, #16
-        add r4, sp, #8
-        str r4, [sp]
-        bl ___udivmoddi4
-        ldr r2, [sp, #8]
-        ldr r3, [sp, #12]
-        add sp, sp, #16
-        pop {r4, pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_uldivmod() {
+    asm!(
+        "push {{r4, lr}}",
+        "sub sp, sp, #16",
+        "add r4, sp, #8",
+        "str r4, [sp]",
+        "bl ___udivmoddi4",
+        "ldr r2, [sp, #8]",
+        "ldr r3, [sp, #12]",
+        "add sp, sp, #16",
+        "pop {{r4, pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(not(target_os = "ios"))]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_idivmod() {
-    llvm_asm!("
-        push {r0, r1, r4, lr}
-        bl __aeabi_idiv
-        pop {r1, r2}
-        muls r2, r2, r0
-        subs r1, r1, r2
-        pop {r4, pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_idivmod() {
+    asm!(
+        "push {{r0, r1, r4, lr}}",
+        "bl __aeabi_idiv",
+        "pop {{r1, r2}}",
+        "muls r2, r2, r0",
+        "subs r1, r1, r2",
+        "pop {{r4, pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(target_os = "ios")]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_idivmod() {
-    llvm_asm!("
-        push {r0, r1, r4, lr}
-        bl ___aeabi_idiv
-        pop {r1, r2}
-        muls r2, r2, r0
-        subs r1, r1, r2
-        pop {r4, pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_idivmod() {
+    asm!(
+        "push {{r0, r1, r4, lr}}",
+        "bl ___aeabi_idiv",
+        "pop {{r1, r2}}",
+        "muls r2, r2, r0",
+        "subs r1, r1, r2",
+        "pop {{r4, pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(not(target_os = "ios"))]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_ldivmod() {
-    llvm_asm!("
-        push {r4, lr}
-        sub sp, sp, #16
-        add r4, sp, #8
-        str r4, [sp]
-        bl __divmoddi4
-        ldr r2, [sp, #8]
-        ldr r3, [sp, #12]
-        add sp, sp, #16
-        pop {r4, pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_ldivmod() {
+    asm!(
+        "push {{r4, lr}}",
+        "sub sp, sp, #16",
+        "add r4, sp, #8",
+        "str r4, [sp]",
+        "bl __divmoddi4",
+        "ldr r2, [sp, #8]",
+        "ldr r3, [sp, #12]",
+        "add sp, sp, #16",
+        "pop {{r4, pc}}",
+        options(noreturn)
+    );
 }
 
 #[cfg(target_os = "ios")]
 #[naked]
 #[cfg_attr(not(feature = "mangled-names"), no_mangle)]
-pub unsafe fn __aeabi_ldivmod() {
-    llvm_asm!("
-        push {r4, lr}
-        sub sp, sp, #16
-        add r4, sp, #8
-        str r4, [sp]
-        bl ___divmoddi4
-        ldr r2, [sp, #8]
-        ldr r3, [sp, #12]
-        add sp, sp, #16
-        pop {r4, pc}
-    " ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __aeabi_ldivmod() {
+    asm!(
+        "push {{r4, lr}}",
+        "sub sp, sp, #16",
+        "add r4, sp, #8",
+        "str r4, [sp]",
+        "bl ___divmoddi4",
+        "ldr r2, [sp, #8]",
+        "ldr r3, [sp, #12]",
+        "add sp, sp, #16",
+        "pop {{r4, pc}}",
+        options(noreturn)
+    );
 }
 
 // The following functions use weak linkage to allow users to override
diff --git a/library/compiler-builtins/src/lib.rs b/library/compiler-builtins/src/lib.rs
index 4a7c746a2ff5..1f93042e4619 100644
--- a/library/compiler-builtins/src/lib.rs
+++ b/library/compiler-builtins/src/lib.rs
@@ -1,7 +1,6 @@
 #![cfg_attr(feature = "compiler-builtins", compiler_builtins)]
 #![cfg_attr(not(feature = "no-asm"), feature(asm))]
 #![feature(abi_unadjusted)]
-#![cfg_attr(not(feature = "no-asm"), feature(llvm_asm))]
 #![cfg_attr(not(feature = "no-asm"), feature(global_asm))]
 #![feature(cfg_target_has_atomic)]
 #![feature(compiler_builtins)]
diff --git a/library/compiler-builtins/src/x86.rs b/library/compiler-builtins/src/x86.rs
index e038231bb0e9..4992de9da04b 100644
--- a/library/compiler-builtins/src/x86.rs
+++ b/library/compiler-builtins/src/x86.rs
@@ -16,26 +16,27 @@ use core::intrinsics;
 ))]
 #[naked]
 #[no_mangle]
-pub unsafe fn ___chkstk_ms() {
-    llvm_asm!("
-        push   %ecx
-        push   %eax
-        cmp    $$0x1000,%eax
-        lea    12(%esp),%ecx
-        jb     1f
-    2:
-        sub    $$0x1000,%ecx
-        test   %ecx,(%ecx)
-        sub    $$0x1000,%eax
-        cmp    $$0x1000,%eax
-        ja     2b
-    1:
-        sub    %eax,%ecx
-        test   %ecx,(%ecx)
-        pop    %eax
-        pop    %ecx
-        ret" ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn ___chkstk_ms() {
+    asm!(
+        "push   %ecx",
+        "push   %eax",
+        "cmp    $0x1000,%eax",
+        "lea    12(%esp),%ecx",
+        "jb     1f",
+        "2:",
+        "sub    $0x1000,%ecx",
+        "test   %ecx,(%ecx)",
+        "sub    $0x1000,%eax",
+        "cmp    $0x1000,%eax",
+        "ja     2b",
+        "1:",
+        "sub    %eax,%ecx",
+        "test   %ecx,(%ecx)",
+        "pop    %eax",
+        "pop    %ecx",
+        "ret",
+        options(noreturn, att_syntax)
+    );
 }
 
 // FIXME: __alloca should be an alias to __chkstk
@@ -47,10 +48,11 @@ pub unsafe fn ___chkstk_ms() {
 ))]
 #[naked]
 #[no_mangle]
-pub unsafe fn __alloca() {
-    llvm_asm!("jmp ___chkstk   // Jump to ___chkstk since fallthrough may be unreliable"
-         ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn __alloca() {
+    asm!(
+        "jmp ___chkstk", // Jump to ___chkstk since fallthrough may be unreliable"
+        options(noreturn, att_syntax)
+    );
 }
 
 #[cfg(all(
@@ -61,27 +63,27 @@ pub unsafe fn __alloca() {
 ))]
 #[naked]
 #[no_mangle]
-pub unsafe fn ___chkstk() {
-    llvm_asm!("
-        push   %ecx
-        cmp    $$0x1000,%eax
-        lea    8(%esp),%ecx     // esp before calling this routine -> ecx
-        jb     1f
-    2:
-        sub    $$0x1000,%ecx
-        test   %ecx,(%ecx)
-        sub    $$0x1000,%eax
-        cmp    $$0x1000,%eax
-        ja     2b
-    1:
-        sub    %eax,%ecx
-        test   %ecx,(%ecx)
-
-        lea    4(%esp),%eax     // load pointer to the return address into eax
-        mov    %ecx,%esp        // install the new top of stack pointer into esp
-        mov    -4(%eax),%ecx    // restore ecx
-        push   (%eax)           // push return address onto the stack
-        sub    %esp,%eax        // restore the original value in eax
-        ret" ::: "memory" : "volatile");
-    intrinsics::unreachable();
+pub unsafe extern "C" fn ___chkstk() {
+    asm!(
+        "push   %ecx",
+        "cmp    $0x1000,%eax",
+        "lea    8(%esp),%ecx", // esp before calling this routine -> ecx
+        "jb     1f",
+        "2:",
+        "sub    $0x1000,%ecx",
+        "test   %ecx,(%ecx)",
+        "sub    $0x1000,%eax",
+        "cmp    $0x1000,%eax",
+        "ja     2b",
+        "1:",
+        "sub    %eax,%ecx",
+        "test   %ecx,(%ecx)",
+        "lea    4(%esp),%eax",  // load pointer to the return address into eax
+        "mov    %ecx,%esp",     // install the new top of stack pointer into esp
+        "mov    -4(%eax),%ecx", // restore ecx
+        "push   (%eax)",        // push return address onto the stack
+        "sub    %esp,%eax",     // restore the original value in eax
+        "ret",
+        options(noreturn, att_syntax)
+    );
 }
diff --git a/library/compiler-builtins/src/x86_64.rs b/library/compiler-builtins/src/x86_64.rs
index 91c0f24fca6d..b382b886c553 100644
--- a/library/compiler-builtins/src/x86_64.rs
+++ b/library/compiler-builtins/src/x86_64.rs
@@ -16,77 +16,76 @@ use core::intrinsics;
 ))]
 #[naked]
 #[no_mangle]
-pub unsafe fn ___chkstk_ms() {
-    llvm_asm!("
-        push   %rcx
-        push   %rax
-        cmp    $$0x1000,%rax
-        lea    24(%rsp),%rcx
-        jb     1f
-    2:
-        sub    $$0x1000,%rcx
-        test   %rcx,(%rcx)
-        sub    $$0x1000,%rax
-        cmp    $$0x1000,%rax
-        ja     2b
-    1:
-        sub    %rax,%rcx
-        test   %rcx,(%rcx)
-        pop    %rax
-        pop    %rcx
-        ret" ::: "memory" : "volatile");
-    intrinsics::unreachable();
-}
-
-#[cfg(all(
-    windows,
-    target_env = "gnu",
-    not(feature = "no-asm"),
-    not(feature = "mangled-names")
-))]
-#[naked]
-#[no_mangle]
-pub unsafe fn __alloca() {
-    llvm_asm!("mov    %rcx,%rax  // x64 _alloca is a normal function with parameter in rcx
-          jmp    ___chkstk  // Jump to ___chkstk since fallthrough may be unreliable"
-         ::: "memory" : "volatile");
-    intrinsics::unreachable();
-}
-
-#[cfg(all(
-    windows,
-    target_env = "gnu",
-    not(feature = "no-asm"),
-    not(feature = "mangled-names")
-))]
-#[naked]
-#[no_mangle]
-pub unsafe fn ___chkstk() {
-    llvm_asm!(
-        "
-        push   %rcx
-        cmp    $$0x1000,%rax
-        lea    16(%rsp),%rcx  // rsp before calling this routine -> rcx
-        jb     1f
-    2:
-        sub    $$0x1000,%rcx
-        test   %rcx,(%rcx)
-        sub    $$0x1000,%rax
-        cmp    $$0x1000,%rax
-        ja     2b
-    1:
-        sub    %rax,%rcx
-        test   %rcx,(%rcx)
-
-        lea    8(%rsp),%rax   // load pointer to the return address into rax
-        mov    %rcx,%rsp      // install the new top of stack pointer into rsp
-        mov    -8(%rax),%rcx  // restore rcx
-        push   (%rax)         // push return address onto the stack
-        sub    %rsp,%rax      // restore the original value in rax
-        ret"
-        ::: "memory" : "volatile"
+pub unsafe extern "C" fn ___chkstk_ms() {
+    asm!(
+        "push   %rcx",
+        "push   %rax",
+        "cmp    $0x1000,%rax",
+        "lea    24(%rsp),%rcx",
+        "jb     1f",
+        "2:",
+        "sub    $0x1000,%rcx",
+        "test   %rcx,(%rcx)",
+        "sub    $0x1000,%rax",
+        "cmp    $0x1000,%rax",
+        "ja     2b",
+        "1:",
+        "sub    %rax,%rcx",
+        "test   %rcx,(%rcx)",
+        "pop    %rax",
+        "pop    %rcx",
+        "ret",
+        options(noreturn, att_syntax)
+    );
+}
+
+#[cfg(all(
+    windows,
+    target_env = "gnu",
+    not(feature = "no-asm"),
+    not(feature = "mangled-names")
+))]
+#[naked]
+#[no_mangle]
+pub unsafe extern "C" fn __alloca() {
+    asm!(
+        "mov    %rcx,%rax", // x64 _alloca is a normal function with parameter in rcx
+        "jmp    ___chkstk", // Jump to ___chkstk since fallthrough may be unreliable"
+        options(noreturn, att_syntax)
+    );
+}
+
+#[cfg(all(
+    windows,
+    target_env = "gnu",
+    not(feature = "no-asm"),
+    not(feature = "mangled-names")
+))]
+#[naked]
+#[no_mangle]
+pub unsafe extern "C" fn ___chkstk() {
+    asm!(
+        "push   %rcx",
+        "cmp    $0x1000,%rax",
+        "lea    16(%rsp),%rcx", // rsp before calling this routine -> rcx
+        "jb     1f",
+        "2:",
+        "sub    $0x1000,%rcx",
+        "test   %rcx,(%rcx)",
+        "sub    $0x1000,%rax",
+        "cmp    $0x1000,%rax",
+        "ja     2b",
+        "1:",
+        "sub    %rax,%rcx",
+        "test   %rcx,(%rcx)",
+        "lea    8(%rsp),%rax",  // load pointer to the return address into rax
+        "mov    %rcx,%rsp",     // install the new top of stack pointer into rsp
+        "mov    -8(%rax),%rcx", // restore rcx
+        "push   (%rax)",        // push return address onto the stack
+        "sub    %rsp,%rax",     // restore the original value in rax
+        "ret",
+        options(noreturn, att_syntax)
     );
-    intrinsics::unreachable();
 }
 
 // HACK(https://github.com/rust-lang/rust/issues/62785): x86_64-unknown-uefi needs special LLVM