diff --git a/library/compiler-builtins/libm/src/math/generic/sqrt.rs b/library/compiler-builtins/libm/src/math/generic/sqrt.rs
index 9481c4cdb7bb..e97a43d34956 100644
--- a/library/compiler-builtins/libm/src/math/generic/sqrt.rs
+++ b/library/compiler-builtins/libm/src/math/generic/sqrt.rs
@@ -419,9 +419,7 @@ mod tests {
     fn conformance_tests_f16() {
         let cases = [
             (f16::PI, 0x3f17_u16),
-            // 10_000.0, using a hex literal for MSRV hack (Rust < 1.67 checks literal widths as
-            // part of the AST, so the `cfg` is irrelevant here).
-            (f16::from_bits(0x70e2), 0x5640_u16),
+            (10000.0_f16, 0x5640_u16),
             (f16::from_bits(0x0000000f), 0x13bf_u16),
             (f16::INFINITY, f16::INFINITY.to_bits()),
         ];
diff --git a/library/compiler-builtins/libm/src/math/support/float_traits.rs b/library/compiler-builtins/libm/src/math/support/float_traits.rs
index 4e5011f62e0f..60c8bfca5165 100644
--- a/library/compiler-builtins/libm/src/math/support/float_traits.rs
+++ b/library/compiler-builtins/libm/src/math/support/float_traits.rs
@@ -1,5 +1,3 @@
-#![allow(unknown_lints)] // FIXME(msrv) we shouldn't need this
-
 use core::{fmt, mem, ops};
 
 use super::int_traits::{CastFrom, Int, MinInt};
@@ -289,10 +287,7 @@ macro_rules! float_impl {
                 cfg_if! {
                     // fma is not yet available in `core`
                     if #[cfg(intrinsics_enabled)] {
-                        // FIXME(msrv,bench): once our benchmark rustc version is above the
-                        // 2022-09-23 nightly, this can be removed.
-                        #[allow(unused_unsafe)]
-                        unsafe { core::intrinsics::$fma_intrinsic(self, y, z) }
+                        core::intrinsics::$fma_intrinsic(self, y, z)
                     } else {
                         super::super::$fma_fn(self, y, z)
                     }
diff --git a/library/compiler-builtins/libm/src/math/support/hex_float.rs b/library/compiler-builtins/libm/src/math/support/hex_float.rs
index c8558b90053d..2f9369e50441 100644
--- a/library/compiler-builtins/libm/src/math/support/hex_float.rs
+++ b/library/compiler-builtins/libm/src/math/support/hex_float.rs
@@ -121,7 +121,7 @@ const fn parse_finite(
         Ok(Parsed { sig, exp }) => (sig, exp),
     };
 
-    let mut round_bits = u128_ilog2(sig) as i32 - sig_bits as i32;
+    let mut round_bits = sig.ilog2() as i32 - sig_bits as i32;
 
     // Round at least up to min_lsb
     if exp < min_lsb - round_bits {
@@ -299,29 +299,11 @@ const fn parse_hex(mut b: &[u8]) -> Result<Parsed, HexFloatParseError> {
         ));
     };
 
-    {
-        let e;
-        if negate_exp {
-            e = (exp as i64) - (pexp as i64);
-        } else {
-            e = (exp as i64) + (pexp as i64);
-        };
-
-        exp = if e < i32::MIN as i64 {
-            i32::MIN
-        } else if e > i32::MAX as i64 {
-            i32::MAX
-        } else {
-            e as i32
-        };
-    }
-    /* FIXME(msrv): once MSRV >= 1.66, replace the above workaround block with:
     if negate_exp {
         exp = exp.saturating_sub_unsigned(pexp);
     } else {
         exp = exp.saturating_add_unsigned(pexp);
     };
-    */
 
     Ok(Parsed { sig, exp })
 }
@@ -342,14 +324,6 @@ const fn hex_digit(c: u8) -> Option<u8> {
     }
 }
 
-/* FIXME(msrv): vendor some things that are not const stable at our MSRV */
-
-/// `u128::ilog2`
-const fn u128_ilog2(v: u128) -> u32 {
-    assert!(v != 0);
-    u128::BITS - 1 - v.leading_zeros()
-}
-
 #[cfg(any(test, feature = "unstable-public-internals"))]
 mod hex_fmt {
     use core::fmt;