diff --git a/library/compiler-builtins/libm/crates/compiler-builtins-smoke-test/src/lib.rs b/library/compiler-builtins/libm/crates/compiler-builtins-smoke-test/src/lib.rs
index 3416a2229598..b9521eb07152 100644
--- a/library/compiler-builtins/libm/crates/compiler-builtins-smoke-test/src/lib.rs
+++ b/library/compiler-builtins/libm/crates/compiler-builtins-smoke-test/src/lib.rs
@@ -93,6 +93,8 @@ no_mangle! {
     fabsf16(x: f16) -> f16;
     fdim(x: f64, y: f64) -> f64;
     fdimf(x: f32, y: f32) -> f32;
+    fdimf128(x: f128, y: f128) -> f128;
+    fdimf16(x: f16, y: f16) -> f16;
     floor(x: f64) -> f64;
     floorf(x: f32) -> f32;
     fma(x: f64, y: f64, z: f64) -> f64;
diff --git a/library/compiler-builtins/libm/crates/libm-macros/src/shared.rs b/library/compiler-builtins/libm/crates/libm-macros/src/shared.rs
index 24fccd6f2489..60838196236f 100644
--- a/library/compiler-builtins/libm/crates/libm-macros/src/shared.rs
+++ b/library/compiler-builtins/libm/crates/libm-macros/src/shared.rs
@@ -47,7 +47,7 @@ const ALL_OPERATIONS_NESTED: &[(FloatTy, Signature, Option<Signature>, &[&str])]
         FloatTy::F16,
         Signature { args: &[Ty::F16, Ty::F16], returns: &[Ty::F16] },
         None,
-        &["copysignf16"],
+        &["copysignf16", "fdimf16"],
     ),
     (
         // `(f32, f32) -> f32`
@@ -90,7 +90,7 @@ const ALL_OPERATIONS_NESTED: &[(FloatTy, Signature, Option<Signature>, &[&str])]
         FloatTy::F128,
         Signature { args: &[Ty::F128, Ty::F128], returns: &[Ty::F128] },
         None,
-        &["copysignf128"],
+        &["copysignf128", "fdimf128"],
     ),
     (
         // `(f32, f32, f32) -> f32`
diff --git a/library/compiler-builtins/libm/crates/libm-test/benches/random.rs b/library/compiler-builtins/libm/crates/libm-test/benches/random.rs
index 8c6afff25981..e790022779f5 100644
--- a/library/compiler-builtins/libm/crates/libm-test/benches/random.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/benches/random.rs
@@ -117,7 +117,14 @@ libm_macros::for_each_function! {
         exp10 | exp10f | exp2 | exp2f => (true, Some(musl_math_sys::MACRO_FN_NAME)),
 
         // Musl does not provide `f16` and `f128` functions
-        copysignf16 | copysignf128 | fabsf16 | fabsf128 | truncf16 | truncf128  => (false, None),
+        copysignf128
+        | copysignf16
+        | fabsf128
+        | fabsf16
+        | fdimf128
+        | fdimf16
+        | truncf128
+        | truncf16 => (false, None),
 
         // By default we never skip (false) and always have a musl function available
         _ => (false, Some(musl_math_sys::MACRO_FN_NAME))
diff --git a/library/compiler-builtins/libm/crates/libm-test/src/domain.rs b/library/compiler-builtins/libm/crates/libm-test/src/domain.rs
index adafb9faa351..68b91bf02e8c 100644
--- a/library/compiler-builtins/libm/crates/libm-test/src/domain.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/src/domain.rs
@@ -200,6 +200,16 @@ impl HasDomain<f128> for crate::op::fabsf128::Routine {
     const DOMAIN: Domain<f128> = Domain::<f128>::UNBOUNDED;
 }
 
+#[cfg(f16_enabled)]
+impl HasDomain<f16> for crate::op::fdimf16::Routine {
+    const DOMAIN: Domain<f16> = Domain::<f16>::UNBOUNDED;
+}
+
+#[cfg(f128_enabled)]
+impl HasDomain<f128> for crate::op::fdimf128::Routine {
+    const DOMAIN: Domain<f128> = Domain::<f128>::UNBOUNDED;
+}
+
 #[cfg(f16_enabled)]
 impl HasDomain<f16> for crate::op::truncf16::Routine {
     const DOMAIN: Domain<f16> = Domain::<f16>::UNBOUNDED;
diff --git a/library/compiler-builtins/libm/crates/libm-test/src/mpfloat.rs b/library/compiler-builtins/libm/crates/libm-test/src/mpfloat.rs
index a4aad81f7092..9d95356d39b3 100644
--- a/library/compiler-builtins/libm/crates/libm-test/src/mpfloat.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/src/mpfloat.rs
@@ -181,7 +181,7 @@ libm_macros::for_each_function! {
         // Remap function names that are different between mpfr and libm
         expm1 | expm1f => exp_m1,
         fabs | fabsf => abs,
-        fdim | fdimf => positive_diff,
+        fdim | fdimf | fdimf16 | fdimf128  => positive_diff,
         fma | fmaf => mul_add,
         fmax | fmaxf => max,
         fmin | fminf => min,
diff --git a/library/compiler-builtins/libm/crates/libm-test/tests/compare_built_musl.rs b/library/compiler-builtins/libm/crates/libm-test/tests/compare_built_musl.rs
index a395c6c5d38d..836c425a5896 100644
--- a/library/compiler-builtins/libm/crates/libm-test/tests/compare_built_musl.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/tests/compare_built_musl.rs
@@ -48,7 +48,16 @@ where
 libm_macros::for_each_function! {
     callback: musl_rand_tests,
     // Musl does not support `f16` and `f128` on all platforms.
-    skip: [copysignf16, copysignf128, fabsf16, fabsf128, truncf16, truncf128],
+    skip: [
+        copysignf128,
+        copysignf16,
+        fabsf128,
+        fabsf16,
+        fdimf128,
+        fdimf16,
+        truncf128,
+        truncf16,
+    ],
     attributes: [
         #[cfg_attr(x86_no_sse, ignore)] // FIXME(correctness): wrong result on i586
         [exp10, exp10f, exp2, exp2f, rint]
@@ -144,9 +153,11 @@ libm_macros::for_each_function! {
         ynf,
 
         // Not provided by musl
-        fabsf16,
         fabsf128,
-        truncf16,
+        fabsf16,
+        fdimf128,
+        fdimf16,
         truncf128,
+        truncf16,
     ],
 }
diff --git a/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs b/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs
index 2d8856e166e4..123abfdaf8b1 100644
--- a/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs
@@ -120,6 +120,8 @@ libm_macros::for_each_function! {
         copysignf128,
         fdim,
         fdimf,
+        fdimf16,
+        fdimf128,
         fma,
         fmaf,
         fmax,
diff --git a/library/compiler-builtins/libm/crates/util/src/main.rs b/library/compiler-builtins/libm/crates/util/src/main.rs
index c8a03068a319..b979c60ad3c0 100644
--- a/library/compiler-builtins/libm/crates/util/src/main.rs
+++ b/library/compiler-builtins/libm/crates/util/src/main.rs
@@ -84,7 +84,14 @@ fn do_eval(basis: &str, op: &str, inputs: &[&str]) {
         emit_types: [CFn, RustFn, RustArgs],
         extra: (basis, op, inputs),
         fn_extra: match MACRO_FN_NAME {
-            copysignf16 | copysignf128 | fabsf16 | fabsf128 | truncf16 | truncf128  => None,
+            copysignf128
+            | copysignf16
+            | fabsf128
+            | fabsf16
+            | fdimf128
+            | fdimf16
+            | truncf128
+            | truncf16  => None,
             _ => Some(musl_math_sys::MACRO_FN_NAME)
         }
     }
diff --git a/library/compiler-builtins/libm/etc/function-definitions.json b/library/compiler-builtins/libm/etc/function-definitions.json
index 1e6d260feea2..dbaac931c769 100644
--- a/library/compiler-builtins/libm/etc/function-definitions.json
+++ b/library/compiler-builtins/libm/etc/function-definitions.json
@@ -301,6 +301,20 @@
         ],
         "type": "f32"
     },
+    "fdimf128": {
+        "sources": [
+            "src/math/fdimf128.rs",
+            "src/math/generic/fdim.rs"
+        ],
+        "type": "f128"
+    },
+    "fdimf16": {
+        "sources": [
+            "src/math/fdimf16.rs",
+            "src/math/generic/fdim.rs"
+        ],
+        "type": "f16"
+    },
     "floor": {
         "sources": [
             "src/libm_helper.rs",
diff --git a/library/compiler-builtins/libm/etc/function-list.txt b/library/compiler-builtins/libm/etc/function-list.txt
index 8aa901762abb..7f96a436227e 100644
--- a/library/compiler-builtins/libm/etc/function-list.txt
+++ b/library/compiler-builtins/libm/etc/function-list.txt
@@ -43,6 +43,8 @@ fabsf128
 fabsf16
 fdim
 fdimf
+fdimf128
+fdimf16
 floor
 floorf
 fma
diff --git a/library/compiler-builtins/libm/src/libm_helper.rs b/library/compiler-builtins/libm/src/libm_helper.rs
index f087267e46c7..73bae456761b 100644
--- a/library/compiler-builtins/libm/src/libm_helper.rs
+++ b/library/compiler-builtins/libm/src/libm_helper.rs
@@ -176,6 +176,7 @@ libm_helper! {
     funcs: {
         (fn copysign(x: f16, y: f16) -> (f16);      => copysignf16);
         (fn fabs(x: f16) -> (f16);                  => fabsf16);
+        (fn fdim(x: f16, y: f16) -> (f16);          => fdimf16);
     }
 }
 
@@ -185,5 +186,6 @@ libm_helper! {
     funcs: {
         (fn copysign(x: f128, y: f128) -> (f128);   => copysignf128);
         (fn fabs(x: f128) -> (f128);                => fabsf128);
+        (fn fdim(x: f128, y: f128) -> (f128);       => fdimf128);
     }
 }
diff --git a/library/compiler-builtins/libm/src/math/fdimf128.rs b/library/compiler-builtins/libm/src/math/fdimf128.rs
new file mode 100644
index 000000000000..6f3d1d0ff1d5
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/fdimf128.rs
@@ -0,0 +1,12 @@
+/// Positive difference (f128)
+///
+/// Determines the positive difference between arguments, returning:
+/// * x - y if x > y, or
+/// * +0    if x <= y, or
+/// * NAN   if either argument is NAN.
+///
+/// A range error may occur.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn fdimf128(x: f128, y: f128) -> f128 {
+    super::generic::fdim(x, y)
+}
diff --git a/library/compiler-builtins/libm/src/math/fdimf16.rs b/library/compiler-builtins/libm/src/math/fdimf16.rs
new file mode 100644
index 000000000000..37bd68858179
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/fdimf16.rs
@@ -0,0 +1,12 @@
+/// Positive difference (f16)
+///
+/// Determines the positive difference between arguments, returning:
+/// * x - y if x > y, or
+/// * +0    if x <= y, or
+/// * NAN   if either argument is NAN.
+///
+/// A range error may occur.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn fdimf16(x: f16, y: f16) -> f16 {
+    super::generic::fdim(x, y)
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index 723be0e1dfd3..03adb6be1934 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -343,10 +343,12 @@ cfg_if! {
     if #[cfg(f16_enabled)] {
         mod copysignf16;
         mod fabsf16;
+        mod fdimf16;
         mod truncf16;
 
         pub use self::copysignf16::copysignf16;
         pub use self::fabsf16::fabsf16;
+        pub use self::fdimf16::fdimf16;
         pub use self::truncf16::truncf16;
     }
 }
@@ -355,10 +357,12 @@ cfg_if! {
     if #[cfg(f128_enabled)] {
         mod copysignf128;
         mod fabsf128;
+        mod fdimf128;
         mod truncf128;
 
         pub use self::copysignf128::copysignf128;
         pub use self::fabsf128::fabsf128;
+        pub use self::fdimf128::fdimf128;
         pub use self::truncf128::truncf128;
     }
 }