diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index b18687c1e333..571cf365c8c8 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -34,10 +34,8 @@ pub fn _eq(a: u64, b: u64) -> bool {
 ///
 /// This trait is sealed and cannot be implemented outside of `libm`.
 pub trait F32Ext: private::Sealed {
-    #[cfg(todo)]
     fn floor(self) -> Self;
 
-    #[cfg(todo)]
     fn ceil(self) -> Self;
 
     fn round(self) -> Self;
@@ -141,13 +139,11 @@ pub trait F32Ext: private::Sealed {
 }
 
 impl F32Ext for f32 {
-    #[cfg(todo)]
     #[inline]
     fn floor(self) -> Self {
         floorf(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn ceil(self) -> Self {
         ceilf(self)
diff --git a/library/compiler-builtins/libm/src/math/ceilf.rs b/library/compiler-builtins/libm/src/math/ceilf.rs
new file mode 100644
index 000000000000..b4f58bfb86f3
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/ceilf.rs
@@ -0,0 +1,29 @@
+use core::f32;
+
+pub fn ceilf(x: f32) -> f32 {
+    let mut ui = x.to_bits();
+    let e = (((ui >> 23) & 0xff) - 0x7f) as i32;
+
+    if e >= 23 {
+        return x;
+    }
+    if e >= 0 {
+        let m = 0x007fffff >> e;
+        if (ui & m) == 0 {
+            return x;
+        }
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 == 0 {
+            ui += m;
+        }
+        ui &= !m;
+    } else {
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 != 0 {
+            return -0.0;
+        } else if ui << 1 != 0 {
+            return 1.0;
+        }
+    }
+    return f32::from_bits(ui);
+}
diff --git a/library/compiler-builtins/libm/src/math/floorf.rs b/library/compiler-builtins/libm/src/math/floorf.rs
new file mode 100644
index 000000000000..9c263b51828b
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/floorf.rs
@@ -0,0 +1,30 @@
+use core::f32;
+
+#[inline]
+pub fn floorf(x: f32) -> f32 {
+    let mut ui = x.to_bits();
+    let e = (((ui >> 23) & 0xff) - 0x7f) as i32;
+
+    if e >= 23 {
+        return x;
+    }
+    if e >= 0 {
+        let m: u32 = 0x007fffff >> e;
+        if (ui & m) == 0 {
+            return x;
+        }
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 != 0 {
+            ui += m;
+        }
+        ui &= !m;
+    } else {
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 == 0 {
+            ui = 0;
+        } else if ui << 1 != 0 {
+            return -1.0;
+        }
+    }
+    return f32::from_bits(ui);
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index 93a067102119..d0121048d96b 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -6,8 +6,10 @@ macro_rules! force_eval {
     };
 }
 
+mod ceilf;
 mod fabs;
 mod fabsf;
+mod floorf;
 mod fmodf;
 mod powf;
 mod round;
@@ -27,8 +29,10 @@ mod hypotf;
 //mod service;
 
 pub use self::{
+    ceilf::ceilf,
     fabs::fabs,
     fabsf::fabsf,
+    floorf::floorf,
     fmodf::fmodf,
     powf::powf,
     round::round,
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 6474ab6f475c..257232ca694a 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -652,12 +652,12 @@ fn main() -> Result<(), Box<Error>> {
 // With signature `fn(f32) -> f32`
 f32_f32! {
     // acosf,
-    // floorf,
+    floorf,
     truncf,
     // asinf,
     // atanf,
     // cbrtf,
-    // ceilf,
+    ceilf,
     // cosf,
     // coshf,
     // exp2f,