From 480531461c0ea0eb04cb66d83696323a25d0925a Mon Sep 17 00:00:00 2001
From: Jack Mott <jack.mott@gmail.com>
Date: Sat, 14 Jul 2018 05:35:07 -0500
Subject: [PATCH 1/7] fdimf

---
 library/compiler-builtins/libm/src/lib.rs         |  7 +++++++
 library/compiler-builtins/libm/src/math/fdimf.rs  | 15 +++++++++++++++
 library/compiler-builtins/libm/src/math/mod.rs    | 10 ++++++----
 .../libm/test-generator/src/main.rs               |  2 +-
 4 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/fdimf.rs

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,

From 643287e1f15268cfa481e0cbd56e57b3f6772117 Mon Sep 17 00:00:00 2001
From: Jack Mott <jack.mott@gmail.com>
Date: Sat, 14 Jul 2018 06:20:13 -0500
Subject: [PATCH 2/7] fdim

---
 library/compiler-builtins/libm/src/lib.rs         |  6 ++++++
 library/compiler-builtins/libm/src/math/fdim.rs   | 15 +++++++++++++++
 library/compiler-builtins/libm/src/math/fdimf.rs  |  6 +++---
 library/compiler-builtins/libm/src/math/fmodf.rs  |  5 ++---
 library/compiler-builtins/libm/src/math/mod.rs    | 15 ++++++---------
 .../libm/test-generator/src/main.rs               |  2 +-
 6 files changed, 33 insertions(+), 16 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/fdim.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 7d8ae903a12f..df96aadc725b 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -363,6 +363,8 @@ pub trait F64Ext: private::Sealed {
 
     fn trunc(self) -> Self;
 
+    fn fdim(self, rhs: Self) -> Self;
+
     #[cfg(todo)]
     fn fract(self) -> Self;
 
@@ -480,6 +482,10 @@ impl F64Ext for f64 {
         trunc(self)
     }
 
+    #[inline]
+    fn fdim(self, rhs: Self) -> Self {
+        fdim(self, rhs)
+    }
     #[cfg(todo)]
     #[inline]
     fn fract(self) -> Self {
diff --git a/library/compiler-builtins/libm/src/math/fdim.rs b/library/compiler-builtins/libm/src/math/fdim.rs
new file mode 100644
index 000000000000..2b277eab03e1
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/fdim.rs
@@ -0,0 +1,15 @@
+use core::f64;
+
+pub fn fdim(x: f64, y: f64) -> f64 {
+    if x.is_nan() {
+        x
+    } else if y.is_nan() {
+        y
+    } else {
+        if x > y {
+            x - y
+        } else {
+            0.0
+        }
+    }
+}
diff --git a/library/compiler-builtins/libm/src/math/fdimf.rs b/library/compiler-builtins/libm/src/math/fdimf.rs
index 3cf65d9beeef..44bf2d6806ef 100644
--- a/library/compiler-builtins/libm/src/math/fdimf.rs
+++ b/library/compiler-builtins/libm/src/math/fdimf.rs
@@ -1,9 +1,9 @@
-use super::isnanf;
+use core::f32;
 
 pub fn fdimf(x: f32, y: f32) -> f32 {
-    if isnanf(x) {
+    if x.is_nan() {
         x
-    } else if isnanf(y) {
+    } else if y.is_nan() {
         y
     } else {
         if x > y {
diff --git a/library/compiler-builtins/libm/src/math/fmodf.rs b/library/compiler-builtins/libm/src/math/fmodf.rs
index 909775249085..d84cfeb01b83 100644
--- a/library/compiler-builtins/libm/src/math/fmodf.rs
+++ b/library/compiler-builtins/libm/src/math/fmodf.rs
@@ -1,7 +1,6 @@
+use core::f32;
 use core::u32;
 
-use super::isnanf;
-
 #[inline]
 pub fn fmodf(x: f32, y: f32) -> f32 {
     let mut uxi = x.to_bits();
@@ -11,7 +10,7 @@ pub fn fmodf(x: f32, y: f32) -> f32 {
     let sx = uxi & 0x80000000;
     let mut i;
 
-    if uyi << 1 == 0 || isnanf(y) || ex == 0xff {
+    if uyi << 1 == 0 || y.is_nan() || ex == 0xff {
         return (x * y) / (x * y);
     }
 
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index a9ba87aa2ce4..e526314a6673 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 fdim;
 mod fdimf;
 mod floor;
 mod floorf;
@@ -37,13 +38,9 @@ mod truncf;
 //mod service;
 
 pub use self::{
-    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,
+    ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, fdim::fdim, 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 {
-    x.to_bits() & 0x7fffffff > 0x7f800000
-}
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 29529356247c..bf679ca64191 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -724,7 +724,7 @@ f64_f64! {
 // With signature `fn(f64, f64) -> f64`
 f64f64_f64! {
     // atan2,
-    // fdim,
+    fdim,
     // fmod,
     hypot,
     // pow,

From 5c2409fcca9e91f862b7f061e253e72270d8505c Mon Sep 17 00:00:00 2001
From: Lucas Marques <lucas.smarques@outlook.com>
Date: Sat, 14 Jul 2018 00:23:58 -0300
Subject: [PATCH 3/7] implement ceil

---
 library/compiler-builtins/libm/src/lib.rs     |  2 -
 .../compiler-builtins/libm/src/math/ceil.rs   | 39 +++++++++++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    | 10 +++--
 3 files changed, 45 insertions(+), 6 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/ceil.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 30f879769d0b..5af219fccf92 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -349,7 +349,6 @@ impl F32Ext for f32 {
 pub trait F64Ext: private::Sealed {
     fn floor(self) -> Self;
 
-    #[cfg(todo)]
     fn ceil(self) -> Self;
 
     fn round(self) -> Self;
@@ -457,7 +456,6 @@ impl F64Ext for f64 {
         floor(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn ceil(self) -> Self {
         ceil(self)
diff --git a/library/compiler-builtins/libm/src/math/ceil.rs b/library/compiler-builtins/libm/src/math/ceil.rs
new file mode 100644
index 000000000000..4db2ca840368
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/ceil.rs
@@ -0,0 +1,39 @@
+use core::f64;
+
+const TOINT: f64 = 1. / f64::EPSILON;
+
+#[inline]
+pub fn ceil(x: f64) -> f64 {
+    let u: u64 = x.to_bits();
+    let e: i64 = (u >> 52 & 0x7ff) as i64;
+    let y: f64;
+
+    if e >= 0x3ff + 52 || x == 0. {
+        return x;
+    }
+    // y = int(x) - x, where int(x) is an integer neighbor of x
+    y = if (u >> 63) != 0 {
+        x - TOINT + TOINT - x
+    } else {
+        x + TOINT - TOINT - x
+    };
+    // special case because of non-nearest rounding modes
+    if e <= 0x3ff - 1 {
+        force_eval!(y);
+        return if (u >> 63) != 0 { -0. } else { 1. };
+    }
+    if y < 0. {
+        x + y + 1.
+    } else {
+        x + y
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn sanity_check() {
+        assert_eq!(super::ceil(1.1), 2.0);
+        assert_eq!(super::ceil(2.9), 3.0);
+    }
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index fb5e3df90901..7c676095dc9f 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -6,6 +6,7 @@ macro_rules! force_eval {
     };
 }
 
+mod ceil;
 mod ceilf;
 mod expf;
 mod fabs;
@@ -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,
+    ceil::ceil, 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,
 };
 
 fn isnanf(x: f32) -> bool {

From 42e52da01052183a7c8f09e13e7d209bdd7e09c9 Mon Sep 17 00:00:00 2001
From: Lucas Marques <lucas.smarques@outlook.com>
Date: Sat, 14 Jul 2018 00:41:03 -0300
Subject: [PATCH 4/7] enable test generation for ceil

---
 library/compiler-builtins/libm/test-generator/src/main.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index be5ed0784f8b..d386da9f650f 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -700,7 +700,7 @@ f64_f64! {
     // asin,
     // atan,
     // cbrt,
-    // ceil,
+    ceil,
     // cos,
     // cosh,
     // exp,

From 6d5a9699c2c069d324072c90c8b7aa4ccb62ff24 Mon Sep 17 00:00:00 2001
From: Jack Mott <jack.mott@gmail.com>
Date: Sat, 14 Jul 2018 11:51:46 -0500
Subject: [PATCH 5/7] fix rebase merge

---
 library/compiler-builtins/libm/src/math/mod.rs | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index 21bd7a480b5f..324220a35984 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -42,6 +42,8 @@ pub use self::cosf::cosf;
 pub use self::expf::expf;
 pub use self::fabs::fabs;
 pub use self::fabsf::fabsf;
+pub use self::fdim::fdim;
+pub use self::fdimf::fdimf;
 pub use self::floor::floor;
 pub use self::floorf::floorf;
 pub use self::fmodf::fmodf;
@@ -65,20 +67,9 @@ pub use self::sqrtf::sqrtf;
 pub use self::trunc::trunc;
 pub use self::truncf::truncf;
 
-pub use self::{
-    ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, fdim::fdim, 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,
-};
 mod k_cosf;
 mod k_sinf;
 mod rem_pio2_large;
 mod rem_pio2f;
 
 use self::{k_cosf::k_cosf, k_sinf::k_sinf, rem_pio2_large::rem_pio2_large, rem_pio2f::rem_pio2f};
-
-fn isnanf(x: f32) -> bool {
-    x.to_bits() & 0x7fffffff > 0x7f800000
-}

From 722e2e32cce55d857432e823a62fb46652f01b4c Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Sat, 14 Jul 2018 12:20:10 -0500
Subject: [PATCH 6/7] ci: don't test the master master

---
 library/compiler-builtins/libm/.travis.yml | 1 -
 1 file changed, 1 deletion(-)

diff --git a/library/compiler-builtins/libm/.travis.yml b/library/compiler-builtins/libm/.travis.yml
index 2bbb60fc64d1..223b586ea6da 100644
--- a/library/compiler-builtins/libm/.travis.yml
+++ b/library/compiler-builtins/libm/.travis.yml
@@ -35,6 +35,5 @@ before_cache:
 
 branches:
   only:
-    - master
     - staging
     - trying

From 08dabf5dca8a182de50c74f39a237b05d8b4a4f7 Mon Sep 17 00:00:00 2001
From: Erik <erikdesjardins@users.noreply.github.com>
Date: Sat, 14 Jul 2018 02:50:23 -0400
Subject: [PATCH 7/7] implement exp

---
 library/compiler-builtins/libm/src/lib.rs     |   2 -
 .../compiler-builtins/libm/src/math/exp.rs    | 150 ++++++++++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    |   2 +
 .../libm/test-generator/src/main.rs           |   2 +-
 4 files changed, 153 insertions(+), 3 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/exp.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 9095fd892a62..f112aaaca6b1 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -378,7 +378,6 @@ pub trait F64Ext: private::Sealed {
 
     fn sqrt(self) -> Self;
 
-    #[cfg(todo)]
     fn exp(self) -> Self;
 
     #[cfg(todo)]
@@ -518,7 +517,6 @@ impl F64Ext for f64 {
         sqrt(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn exp(self) -> Self {
         exp(self)
diff --git a/library/compiler-builtins/libm/src/math/exp.rs b/library/compiler-builtins/libm/src/math/exp.rs
new file mode 100644
index 000000000000..cd63b8fb3f15
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/exp.rs
@@ -0,0 +1,150 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_exp.c */
+/*
+ * ====================================================
+ * Copyright (C) 2004 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/* exp(x)
+ * Returns the exponential of x.
+ *
+ * Method
+ *   1. Argument reduction:
+ *      Reduce x to an r so that |r| <= 0.5*ln2 ~ 0.34658.
+ *      Given x, find r and integer k such that
+ *
+ *               x = k*ln2 + r,  |r| <= 0.5*ln2.
+ *
+ *      Here r will be represented as r = hi-lo for better
+ *      accuracy.
+ *
+ *   2. Approximation of exp(r) by a special rational function on
+ *      the interval [0,0.34658]:
+ *      Write
+ *          R(r**2) = r*(exp(r)+1)/(exp(r)-1) = 2 + r*r/6 - r**4/360 + ...
+ *      We use a special Remez algorithm on [0,0.34658] to generate
+ *      a polynomial of degree 5 to approximate R. The maximum error
+ *      of this polynomial approximation is bounded by 2**-59. In
+ *      other words,
+ *          R(z) ~ 2.0 + P1*z + P2*z**2 + P3*z**3 + P4*z**4 + P5*z**5
+ *      (where z=r*r, and the values of P1 to P5 are listed below)
+ *      and
+ *          |                  5          |     -59
+ *          | 2.0+P1*z+...+P5*z   -  R(z) | <= 2
+ *          |                             |
+ *      The computation of exp(r) thus becomes
+ *                              2*r
+ *              exp(r) = 1 + ----------
+ *                            R(r) - r
+ *                                 r*c(r)
+ *                     = 1 + r + ----------- (for better accuracy)
+ *                                2 - c(r)
+ *      where
+ *                              2       4             10
+ *              c(r) = r - (P1*r  + P2*r  + ... + P5*r   ).
+ *
+ *   3. Scale back to obtain exp(x):
+ *      From step 1, we have
+ *         exp(x) = 2^k * exp(r)
+ *
+ * Special cases:
+ *      exp(INF) is INF, exp(NaN) is NaN;
+ *      exp(-INF) is 0, and
+ *      for finite argument, only exp(0)=1 is exact.
+ *
+ * Accuracy:
+ *      according to an error analysis, the error is always less than
+ *      1 ulp (unit in the last place).
+ *
+ * Misc. info.
+ *      For IEEE double
+ *          if x >  709.782712893383973096 then exp(x) overflows
+ *          if x < -745.133219101941108420 then exp(x) underflows
+ */
+
+use super::scalbn;
+
+const HALF: [f64; 2] = [0.5, -0.5];
+const LN2HI: f64 = 6.93147180369123816490e-01; /* 0x3fe62e42, 0xfee00000 */
+const LN2LO: f64 = 1.90821492927058770002e-10; /* 0x3dea39ef, 0x35793c76 */
+const INVLN2: f64 = 1.44269504088896338700e+00; /* 0x3ff71547, 0x652b82fe */
+const P1: f64 = 1.66666666666666019037e-01; /* 0x3FC55555, 0x5555553E */
+const P2: f64 = -2.77777777770155933842e-03; /* 0xBF66C16C, 0x16BEBD93 */
+const P3: f64 = 6.61375632143793436117e-05; /* 0x3F11566A, 0xAF25DE2C */
+const P4: f64 = -1.65339022054652515390e-06; /* 0xBEBBBD41, 0xC5D26BF1 */
+const P5: f64 = 4.13813679705723846039e-08; /* 0x3E663769, 0x72BEA4D0 */
+
+#[inline]
+pub fn exp(mut x: f64) -> f64 {
+    let x1p1023 = f64::from_bits(0x7fe0000000000000); // 0x1p1023 === 2 ^ 1023
+    let x1p_149 = f64::from_bits(0x36a0000000000000); // 0x1p-149 === 2 ^ -149
+
+    let hi: f64;
+    let lo: f64;
+    let c: f64;
+    let xx: f64;
+    let y: f64;
+    let k: i32;
+    let sign: i32;
+    let mut hx: u32;
+
+    hx = (x.to_bits() >> 32) as u32;
+    sign = (hx >> 31) as i32;
+    hx &= 0x7fffffff; /* high word of |x| */
+
+    /* special cases */
+    if hx >= 0x4086232b {
+        /* if |x| >= 708.39... */
+        if x.is_nan() {
+            return x;
+        }
+        if x > 709.782712893383973096 {
+            /* overflow if x!=inf */
+            x *= x1p1023;
+            return x;
+        }
+        if x < -708.39641853226410622 {
+            /* underflow if x!=-inf */
+            force_eval!((-x1p_149 / x) as f32);
+            if x < -745.13321910194110842 {
+                return 0.;
+            }
+        }
+    }
+
+    /* argument reduction */
+    if hx > 0x3fd62e42 {
+        /* if |x| > 0.5 ln2 */
+        if hx >= 0x3ff0a2b2 {
+            /* if |x| >= 1.5 ln2 */
+            k = (INVLN2 * x + HALF[sign as usize]) as i32;
+        } else {
+            k = 1 - sign - sign;
+        }
+        hi = x - k as f64 * LN2HI; /* k*ln2hi is exact here */
+        lo = k as f64 * LN2LO;
+        x = hi - lo;
+    } else if hx > 0x3e300000 {
+        /* if |x| > 2**-28 */
+        k = 0;
+        hi = x;
+        lo = 0.;
+    } else {
+        /* inexact if x!=0 */
+        force_eval!(x1p1023 + x);
+        return 1. + x;
+    }
+
+    /* x is now in primary range */
+    xx = x * x;
+    c = x - xx * (P1 + xx * (P2 + xx * (P3 + xx * (P4 + xx * P5))));
+    y = 1. + (x * c / (2. - c) - lo + hi);
+    if k == 0 {
+        y
+    } else {
+        scalbn(y, k)
+    }
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index ee846ebb9ccc..2a84b463d9fd 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -9,6 +9,7 @@ macro_rules! force_eval {
 mod ceil;
 mod ceilf;
 mod cosf;
+mod exp;
 mod expf;
 mod fabs;
 mod fabsf;
@@ -39,6 +40,7 @@ mod truncf;
 pub use self::ceil::ceil;
 pub use self::ceilf::ceilf;
 pub use self::cosf::cosf;
+pub use self::exp::exp;
 pub use self::expf::expf;
 pub use self::fabs::fabs;
 pub use self::fabsf::fabsf;
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 291c30f6394f..a54d8b2710f5 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -703,7 +703,7 @@ f64_f64! {
     ceil,
     // cos,
     // cosh,
-    // exp,
+    exp,
     // exp2,
     // expm1,
     floor,