diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 30f879769d0b..7d8ae903a12f 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -42,6 +42,8 @@ pub trait F32Ext: private::Sealed {
 
     fn trunc(self) -> Self;
 
+    fn fdim(self, rhs: Self) -> Self;
+
     #[cfg(todo)]
     fn fract(self) -> Self;
 
@@ -156,6 +158,11 @@ impl F32Ext for f32 {
         truncf(self)
     }
 
+    #[inline]
+    fn fdim(self, rhs: Self) -> Self {
+        fdimf(self, rhs)
+    }
+
     #[cfg(todo)]
     #[inline]
     fn fract(self) -> Self {
diff --git a/library/compiler-builtins/libm/src/math/fdimf.rs b/library/compiler-builtins/libm/src/math/fdimf.rs
new file mode 100644
index 000000000000..3cf65d9beeef
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/fdimf.rs
@@ -0,0 +1,15 @@
+use super::isnanf;
+
+pub fn fdimf(x: f32, y: f32) -> f32 {
+    if isnanf(x) {
+        x
+    } else if isnanf(y) {
+        y
+    } else {
+        if x > y {
+            x - y
+        } else {
+            0.0
+        }
+    }
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index fb5e3df90901..a9ba87aa2ce4 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -10,6 +10,7 @@ mod ceilf;
 mod expf;
 mod fabs;
 mod fabsf;
+mod fdimf;
 mod floor;
 mod floorf;
 mod fmodf;
@@ -36,10 +37,11 @@ mod truncf;
 //mod service;
 
 pub use self::{
-    ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, floor::floor, floorf::floorf, fmodf::fmodf,
-    hypot::hypot, hypotf::hypotf, log::log, log10::log10, log10f::log10f, log1p::log1p,
-    log1pf::log1pf, log2::log2, log2f::log2f, logf::logf, powf::powf, round::round, roundf::roundf,
-    scalbn::scalbn, scalbnf::scalbnf, sqrt::sqrt, sqrtf::sqrtf, trunc::trunc, truncf::truncf,
+    ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, fdimf::fdimf, floor::floor, floorf::floorf,
+    fmodf::fmodf, hypot::hypot, hypotf::hypotf, log::log, log10::log10, log10f::log10f,
+    log1p::log1p, log1pf::log1pf, log2::log2, log2f::log2f, logf::logf, powf::powf, round::round,
+    roundf::roundf, scalbn::scalbn, scalbnf::scalbnf, sqrt::sqrt, sqrtf::sqrtf, trunc::trunc,
+    truncf::truncf,
 };
 
 fn isnanf(x: f32) -> bool {
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index be5ed0784f8b..29529356247c 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -662,7 +662,6 @@ f32_f32! {
     // coshf,
     // exp2f,
     expf,
-    // fdimf,
     log10f,
     log1pf,
     log2f,
@@ -679,6 +678,7 @@ f32_f32! {
 // With signature `fn(f32, f32) -> f32`
 f32f32_f32! {
     // atan2f,
+    fdimf,
     hypotf,
     fmodf,
     powf,