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 1666c6153608..949f21a57ff3 100644
--- a/library/compiler-builtins/libm/src/math/support/hex_float.rs
+++ b/library/compiler-builtins/libm/src/math/support/hex_float.rs
@@ -4,6 +4,12 @@
 
 use super::{f32_from_bits, f64_from_bits};
 
+/// Construct a 16-bit float from hex float representation (C-style)
+#[cfg(f16_enabled)]
+pub const fn hf16(s: &str) -> f16 {
+    f16::from_bits(parse_any(s, 16, 10) as u16)
+}
+
 /// Construct a 32-bit float from hex float representation (C-style)
 pub const fn hf32(s: &str) -> f32 {
     f32_from_bits(parse_any(s, 32, 23) as u32)
@@ -14,6 +20,12 @@ pub const fn hf64(s: &str) -> f64 {
     f64_from_bits(parse_any(s, 64, 52) as u64)
 }
 
+/// Construct a 128-bit float from hex float representation (C-style)
+#[cfg(f128_enabled)]
+pub const fn hf128(s: &str) -> f128 {
+    f128::from_bits(parse_any(s, 128, 112))
+}
+
 const fn parse_any(s: &str, bits: u32, sig_bits: u32) -> u128 {
     let exp_bits: u32 = bits - sig_bits - 1;
     let max_msb: i32 = (1 << (exp_bits - 1)) - 1;
@@ -230,6 +242,57 @@ mod tests {
         }
     }
 
+    // HACK(msrv): 1.63 rejects unknown width float literals at an AST level, so use a macro to
+    // hide them from the AST.
+    #[cfg(f16_enabled)]
+    macro_rules! f16_tests {
+        () => {
+            #[test]
+            fn test_f16() {
+                let checks = [
+                    ("0x.1234p+16", (0x1234 as f16).to_bits()),
+                    ("0x1.234p+12", (0x1234 as f16).to_bits()),
+                    ("0x12.34p+8", (0x1234 as f16).to_bits()),
+                    ("0x123.4p+4", (0x1234 as f16).to_bits()),
+                    ("0x1234p+0", (0x1234 as f16).to_bits()),
+                    ("0x1234.p+0", (0x1234 as f16).to_bits()),
+                    ("0x1234.0p+0", (0x1234 as f16).to_bits()),
+                    ("0x1.ffcp+15", f16::MAX.to_bits()),
+                    ("0x1.0p+1", 2.0f16.to_bits()),
+                    ("0x1.0p+0", 1.0f16.to_bits()),
+                    ("0x1.ffp+8", 0x5ffc),
+                    ("+0x1.ffp+8", 0x5ffc),
+                    ("0x1p+0", 0x3c00),
+                    ("0x1.998p-4", 0x2e66),
+                    ("0x1.9p+6", 0x5640),
+                    ("0x0.0p0", 0.0f16.to_bits()),
+                    ("-0x0.0p0", (-0.0f16).to_bits()),
+                    ("0x1.0p0", 1.0f16.to_bits()),
+                    ("0x1.998p-4", (0.1f16).to_bits()),
+                    ("-0x1.998p-4", (-0.1f16).to_bits()),
+                    ("0x0.123p-12", 0x0123),
+                    ("0x1p-24", 0x0001),
+                ];
+                for (s, exp) in checks {
+                    println!("parsing {s}");
+                    let act = hf16(s).to_bits();
+                    assert_eq!(
+                        act, exp,
+                        "parsing {s}: {act:#06x} != {exp:#06x}\nact: {act:#018b}\nexp: {exp:#018b}"
+                    );
+                }
+            }
+
+            #[test]
+            fn test_macros_f16() {
+                assert_eq!(hf16!("0x1.ffp+8").to_bits(), 0x5ffc_u16);
+            }
+        };
+    }
+
+    #[cfg(f16_enabled)]
+    f16_tests!();
+
     #[test]
     fn test_f32() {
         let checks = [
@@ -308,16 +371,67 @@ mod tests {
         }
     }
 
-    #[test]
-    fn test_f32_almost_extra_precision() {
-        // Exact maximum precision allowed
-        hf32("0x1.abcdeep+0");
+    // HACK(msrv): 1.63 rejects unknown width float literals at an AST level, so use a macro to
+    // hide them from the AST.
+    #[cfg(f128_enabled)]
+    macro_rules! f128_tests {
+        () => {
+            #[test]
+            fn test_f128() {
+                let checks = [
+                    ("0x.1234p+16", (0x1234 as f128).to_bits()),
+                    ("0x1.234p+12", (0x1234 as f128).to_bits()),
+                    ("0x12.34p+8", (0x1234 as f128).to_bits()),
+                    ("0x123.4p+4", (0x1234 as f128).to_bits()),
+                    ("0x1234p+0", (0x1234 as f128).to_bits()),
+                    ("0x1234.p+0", (0x1234 as f128).to_bits()),
+                    ("0x1234.0p+0", (0x1234 as f128).to_bits()),
+                    ("0x1.ffffffffffffffffffffffffffffp+16383", f128::MAX.to_bits()),
+                    ("0x1.0p+1", 2.0f128.to_bits()),
+                    ("0x1.0p+0", 1.0f128.to_bits()),
+                    ("0x1.ffep+8", 0x4007ffe0000000000000000000000000),
+                    ("+0x1.ffep+8", 0x4007ffe0000000000000000000000000),
+                    ("0x1p+0", 0x3fff0000000000000000000000000000),
+                    ("0x1.999999999999999999999999999ap-4", 0x3ffb999999999999999999999999999a),
+                    ("0x1.9p+6", 0x40059000000000000000000000000000),
+                    ("0x0.0p0", 0.0f128.to_bits()),
+                    ("-0x0.0p0", (-0.0f128).to_bits()),
+                    ("0x1.0p0", 1.0f128.to_bits()),
+                    ("0x1.999999999999999999999999999ap-4", (0.1f128).to_bits()),
+                    ("-0x1.999999999999999999999999999ap-4", (-0.1f128).to_bits()),
+                    ("0x0.abcdef0123456789abcdef012345p-16382", 0x0000abcdef0123456789abcdef012345),
+                    ("0x1p-16494", 0x00000000000000000000000000000001),
+                ];
+                for (s, exp) in checks {
+                    println!("parsing {s}");
+                    let act = hf128(s).to_bits();
+                    assert_eq!(
+                        act, exp,
+                        "parsing {s}: {act:#034x} != {exp:#034x}\nact: {act:#0130b}\nexp: {exp:#0130b}"
+                    );
+                }
+            }
+
+            #[test]
+            fn test_macros_f128() {
+                assert_eq!(hf128!("0x1.ffep+8").to_bits(), 0x4007ffe0000000000000000000000000_u128);
+            }
+        }
     }
 
+    #[cfg(f128_enabled)]
+    f128_tests!();
+
     #[test]
     fn test_macros() {
-        assert_eq!(hf32!("0x1.ffep+8").to_bits(), 0x43fff000u32);
-        assert_eq!(hf64!("0x1.ffep+8").to_bits(), 0x407ffe0000000000u64);
+        // FIXME(msrv): enable once parsing works
+        // #[cfg(f16_enabled)]
+        // assert_eq!(hf16!("0x1.ffp+8").to_bits(), 0x5ffc_u16);
+        assert_eq!(hf32!("0x1.ffep+8").to_bits(), 0x43fff000_u32);
+        assert_eq!(hf64!("0x1.ffep+8").to_bits(), 0x407ffe0000000000_u64);
+        // FIXME(msrv): enable once parsing works
+        // #[cfg(f128_enabled)]
+        // assert_eq!(hf128!("0x1.ffep+8").to_bits(), 0x4007ffe0000000000000000000000000_u128);
     }
 }
 
@@ -328,6 +442,69 @@ mod tests_panicking {
     extern crate std;
     use super::*;
 
+    // HACK(msrv): 1.63 rejects unknown width float literals at an AST level, so use a macro to
+    // hide them from the AST.
+    #[cfg(f16_enabled)]
+    macro_rules! f16_tests {
+        () => {
+            #[test]
+            fn test_f16_almost_extra_precision() {
+                // Exact maximum precision allowed
+                hf16("0x1.ffcp+0");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too precise")]
+            fn test_f16_extra_precision() {
+                // One bit more than the above.
+                hf16("0x1.ffdp+0");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too huge")]
+            fn test_f16_overflow() {
+                // One bit more than the above.
+                hf16("0x1p+16");
+            }
+
+            #[test]
+            fn test_f16_tiniest() {
+                let x = hf16("0x1.p-24");
+                let y = hf16("0x0.001p-12");
+                let z = hf16("0x0.8p-23");
+                assert_eq!(x, y);
+                assert_eq!(x, z);
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too tiny")]
+            fn test_f16_too_tiny() {
+                hf16("0x1.p-25");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too tiny")]
+            fn test_f16_also_too_tiny() {
+                hf16("0x0.8p-24");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too tiny")]
+            fn test_f16_again_too_tiny() {
+                hf16("0x0.001p-13");
+            }
+        };
+    }
+
+    #[cfg(f16_enabled)]
+    f16_tests!();
+
+    #[test]
+    fn test_f32_almost_extra_precision() {
+        // Exact maximum precision allowed
+        hf32("0x1.abcdeep+0");
+    }
+
     #[test]
     #[should_panic]
     fn test_f32_extra_precision2() {
@@ -388,4 +565,61 @@ mod tests_panicking {
         // One bit more than the above.
         hf64("0x1.abcdabcdabcdf8p+0");
     }
+
+    // HACK(msrv): 1.63 rejects unknown width float literals at an AST level, so use a macro to
+    // hide them from the AST.
+    #[cfg(f128_enabled)]
+    macro_rules! f128_tests {
+        () => {
+            #[test]
+            fn test_f128_almost_extra_precision() {
+                // Exact maximum precision allowed
+                hf128("0x1.ffffffffffffffffffffffffffffp+16383");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too precise")]
+            fn test_f128_extra_precision() {
+                // One bit more than the above.
+                hf128("0x1.ffffffffffffffffffffffffffff8p+16383");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too huge")]
+            fn test_f128_overflow() {
+                // One bit more than the above.
+                hf128("0x1p+16384");
+            }
+
+            #[test]
+            fn test_f128_tiniest() {
+                let x = hf128("0x1.p-16494");
+                let y = hf128("0x0.0000000000000001p-16430");
+                let z = hf128("0x0.8p-16493");
+                assert_eq!(x, y);
+                assert_eq!(x, z);
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too tiny")]
+            fn test_f128_too_tiny() {
+                hf128("0x1.p-16495");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too tiny")]
+            fn test_f128_again_too_tiny() {
+                hf128("0x0.0000000000000001p-16431");
+            }
+
+            #[test]
+            #[should_panic(expected = "the value is too tiny")]
+            fn test_f128_also_too_tiny() {
+                hf128("0x0.8p-16494");
+            }
+        };
+    }
+
+    #[cfg(f128_enabled)]
+    f128_tests!();
 }
diff --git a/library/compiler-builtins/libm/src/math/support/macros.rs b/library/compiler-builtins/libm/src/math/support/macros.rs
index c9a36c0db1a7..d8ba04cffe7f 100644
--- a/library/compiler-builtins/libm/src/math/support/macros.rs
+++ b/library/compiler-builtins/libm/src/math/support/macros.rs
@@ -87,6 +87,17 @@ macro_rules! select_implementation {
     (@cfg $provided:meta; $ex:expr) => { #[cfg($provided)] $ex };
 }
 
+/// Construct a 16-bit float from hex float representation (C-style), guaranteed to
+/// evaluate at compile time.
+#[cfg(f16_enabled)]
+#[allow(unused_macros)]
+macro_rules! hf16 {
+    ($s:literal) => {{
+        const X: f16 = $crate::math::support::hf16($s);
+        X
+    }};
+}
+
 /// Construct a 32-bit float from hex float representation (C-style), guaranteed to
 /// evaluate at compile time.
 #[allow(unused_macros)]
@@ -107,6 +118,17 @@ macro_rules! hf64 {
     }};
 }
 
+/// Construct a 128-bit float from hex float representation (C-style), guaranteed to
+/// evaluate at compile time.
+#[cfg(f128_enabled)]
+#[allow(unused_macros)]
+macro_rules! hf128 {
+    ($s:literal) => {{
+        const X: f128 = $crate::math::support::hf128($s);
+        X
+    }};
+}
+
 /// Assert `F::biteq` with better messages.
 #[cfg(test)]
 macro_rules! assert_biteq {
diff --git a/library/compiler-builtins/libm/src/math/support/mod.rs b/library/compiler-builtins/libm/src/math/support/mod.rs
index ddfc2e3e0717..da9e2c9ed62c 100644
--- a/library/compiler-builtins/libm/src/math/support/mod.rs
+++ b/library/compiler-builtins/libm/src/math/support/mod.rs
@@ -8,6 +8,10 @@ mod int_traits;
 #[allow(unused_imports)]
 pub use float_traits::{Float, IntTy};
 pub(crate) use float_traits::{f32_from_bits, f64_from_bits};
+#[cfg(f16_enabled)]
+pub use hex_float::hf16;
+#[cfg(f128_enabled)]
+pub use hex_float::hf128;
 #[allow(unused_imports)]
 pub use hex_float::{hf32, hf64};
 pub use int_traits::{CastFrom, CastInto, DInt, HInt, Int, MinInt};