diff --git a/README.md b/README.md
index ffef4e52..07b78ca4 100644
--- a/README.md
+++ b/README.md
@@ -213,16 +213,22 @@ These builtins are needed to support 128-bit integers, which are in the process
 - [x] udivti3.c
 - [x] umodti3.c
 
+These builtins are needed to support 128-bit floating point numbers, which are
+in the process of being added to Rust.
+
+- [x] addtf3.c
+- [x] comparetf2.c
+- [x] divtf3.c
+- [x] multf3.c
+- [x] subtf3.c
+
 ## Unimplemented functions
 
-These builtins involve floating-point types ("`f128`", "`f80`" and complex numbers) that are not supported by Rust.
+These builtins involve floating-point types ("`f80`" and complex numbers) that are not supported by Rust.
 
-- ~~addtf3.c~~
-- ~~comparetf2.c~~
 - ~~divdc3.c~~
 - ~~divsc3.c~~
 - ~~divtc3.c~~
-- ~~divtf3.c~~
 - ~~divxc3.c~~
 - ~~extenddftf2.c~~
 - ~~extendsftf2.c~~
@@ -250,7 +256,6 @@ These builtins involve floating-point types ("`f128`", "`f80`" and complex numbe
 - ~~muldc3.c~~
 - ~~mulsc3.c~~
 - ~~multc3.c~~
-- ~~multf3.c~~
 - ~~mulxc3.c~~
 - ~~powitf2.c~~
 - ~~powixf2.c~~
@@ -264,7 +269,6 @@ These builtins involve floating-point types ("`f128`", "`f80`" and complex numbe
 - ~~ppc/gcc_qmul.c~~
 - ~~ppc/gcc_qsub.c~~
 - ~~ppc/multc3.c~~
-- ~~subtf3.c~~
 - ~~trunctfdf2.c~~
 - ~~trunctfsf2.c~~
 - ~~x86_64/floatdixf.c~~
diff --git a/src/float/add.rs b/src/float/add.rs
index 804f4b51..d4f7fd3a 100644
--- a/src/float/add.rs
+++ b/src/float/add.rs
@@ -201,6 +201,10 @@ intrinsics! {
         add(a, b)
     }
 
+    pub extern "C" fn __addtf3(a: f128, b: f128) -> f128 {
+        add(a, b)
+    }
+
     #[cfg(target_arch = "arm")]
     pub extern "C" fn __addsf3vfp(a: f32, b: f32) -> f32 {
         a + b
diff --git a/src/float/cmp.rs b/src/float/cmp.rs
index 1c8917af..46e903dc 100644
--- a/src/float/cmp.rs
+++ b/src/float/cmp.rs
@@ -170,6 +170,41 @@ intrinsics! {
     pub extern "C" fn __gtdf2(a: f64, b: f64) -> i32 {
         cmp(a, b).to_ge_abi()
     }
+
+    #[avr_skip]
+    pub extern "C" fn __letf2(a: f128, b: f128) -> i32 {
+        cmp(a, b).to_le_abi()
+    }
+
+    #[avr_skip]
+    pub extern "C" fn __getf2(a: f128, b: f128) -> i32 {
+        cmp(a, b).to_ge_abi()
+    }
+
+    #[avr_skip]
+    pub extern "C" fn __unordtf2(a: f128, b: f128) -> i32 {
+        unord(a, b) as i32
+    }
+
+    #[avr_skip]
+    pub extern "C" fn __eqtf2(a: f128, b: f128) -> i32 {
+        cmp(a, b).to_le_abi()
+    }
+
+    #[avr_skip]
+    pub extern "C" fn __lttf2(a: f128, b: f128) -> i32 {
+        cmp(a, b).to_le_abi()
+    }
+
+    #[avr_skip]
+    pub extern "C" fn __netf2(a: f128, b: f128) -> i32 {
+        cmp(a, b).to_le_abi()
+    }
+
+    #[avr_skip]
+    pub extern "C" fn __gttf2(a: f128, b: f128) -> i32 {
+        cmp(a, b).to_ge_abi()
+    }
 }
 
 #[cfg(target_arch = "arm")]
diff --git a/src/float/div.rs b/src/float/div.rs
index d587fe4f..9038f6b9 100644
--- a/src/float/div.rs
+++ b/src/float/div.rs
@@ -914,6 +914,15 @@ intrinsics! {
         div64(a, b)
     }
 
+    // TODO: how should `HInt` be handled?
+    pub extern "C" fn __divtf3(a: f128, b: f128) -> f128 {
+        if cfg!(target_pointer_width = "64") {
+            div32(a, b)
+        } else {
+            div64(a, b)
+        }
+    }
+
     #[cfg(target_arch = "arm")]
     pub extern "C" fn __divsf3vfp(a: f32, b: f32) -> f32 {
         a / b
diff --git a/src/float/mod.rs b/src/float/mod.rs
index fdbe9dde..3917a24c 100644
--- a/src/float/mod.rs
+++ b/src/float/mod.rs
@@ -59,7 +59,7 @@ pub(crate) trait Float:
     /// A mask for the significand
     const SIGNIFICAND_MASK: Self::Int;
 
-    // The implicit bit of the float format
+    /// The implicit bit of the float format
     const IMPLICIT_BIT: Self::Int;
 
     /// A mask for the exponent
@@ -171,5 +171,8 @@ macro_rules! float_impl {
     };
 }
 
+// FIXME: there aren't any intrinsics for f16 that I know of, do we need this?
+float_impl!(f16, u16, i16, i16, 16, 10);
 float_impl!(f32, u32, i32, i16, 32, 23);
 float_impl!(f64, u64, i64, i16, 64, 52);
+float_impl!(f128, u128, i128, i16, 128, 112);
diff --git a/src/float/mul.rs b/src/float/mul.rs
index 378fa970..eed29527 100644
--- a/src/float/mul.rs
+++ b/src/float/mul.rs
@@ -199,6 +199,10 @@ intrinsics! {
         mul(a, b)
     }
 
+    pub extern "C" fn __multf3(a: f128, b: f128) -> f128 {
+        mul(a, b)
+    }
+
     #[cfg(target_arch = "arm")]
     pub extern "C" fn __mulsf3vfp(a: f32, b: f32) -> f32 {
         a * b
diff --git a/src/float/sub.rs b/src/float/sub.rs
index 64653ee2..6bb3271a 100644
--- a/src/float/sub.rs
+++ b/src/float/sub.rs
@@ -1,5 +1,6 @@
 use crate::float::add::__adddf3;
 use crate::float::add::__addsf3;
+use crate::float::add::__addtf3;
 use crate::float::Float;
 
 intrinsics! {
@@ -15,6 +16,10 @@ intrinsics! {
         __adddf3(a, f64::from_repr(b.repr() ^ f64::SIGN_MASK))
     }
 
+    pub extern "C" fn __subtf3(a: f128, b: f128) -> f128 {
+        __addtf3(a, f128::from_repr(b.repr() ^ f128::SIGN_MASK))
+    }
+
     #[cfg(target_arch = "arm")]
     pub extern "C" fn __subsf3vfp(a: f32, b: f32) -> f32 {
         a - b
diff --git a/src/lib.rs b/src/lib.rs
index a414efde..62bd69ff 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,17 +2,19 @@
 #![cfg_attr(not(feature = "no-asm"), feature(asm))]
 #![feature(abi_unadjusted)]
 #![feature(asm_experimental_arch)]
+#![feature(c_unwind)]
 #![cfg_attr(not(feature = "no-asm"), feature(global_asm))]
 #![feature(cfg_target_has_atomic)]
 #![feature(compiler_builtins)]
 #![feature(core_ffi_c)]
 #![feature(core_intrinsics)]
+#![feature(f128)]
+#![feature(f16)]
 #![feature(inline_const)]
 #![feature(lang_items)]
 #![feature(linkage)]
 #![feature(naked_functions)]
 #![feature(repr_simd)]
-#![feature(c_unwind)]
 #![no_builtins]
 #![no_std]
 #![allow(unused_features)]