From 42e0c8c0a1cabb24b48f56470aea1656a47f9cc7 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Wed, 10 Jul 2019 12:59:36 +0200
Subject: [PATCH 1/2] Add FMA tests that cause it to segfault

---
 .../compiler-builtins/libm/src/math/fma.rs    | 19 +++++++++++++++++++
 library/compiler-builtins/libm/tests/unit.rs  | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 library/compiler-builtins/libm/tests/unit.rs

diff --git a/library/compiler-builtins/libm/src/math/fma.rs b/library/compiler-builtins/libm/src/math/fma.rs
index 07d90f8b727d..6d4471a9a04f 100644
--- a/library/compiler-builtins/libm/src/math/fma.rs
+++ b/library/compiler-builtins/libm/src/math/fma.rs
@@ -205,3 +205,22 @@ pub fn fma(x: f64, y: f64, z: f64) -> f64 {
     }
     scalbn(r, e)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn fma_segfault() {
+        // These two inputs cause fma to segfault on release due to overflow:
+        assert_eq!(
+            fma(
+                -0.0000000000000002220446049250313,
+                -0.0000000000000002220446049250313,
+                -0.0000000000000002220446049250313
+            ),
+            -0.00000000000000022204460492503126,
+        );
+
+        assert_eq!(fma(-0.992, -0.992, -0.992), -0.00793599999988632,);
+    }
+}
diff --git a/library/compiler-builtins/libm/tests/unit.rs b/library/compiler-builtins/libm/tests/unit.rs
new file mode 100644
index 000000000000..4e7002817a64
--- /dev/null
+++ b/library/compiler-builtins/libm/tests/unit.rs
@@ -0,0 +1,19 @@
+use libm::*;
+
+#[test]
+fn fma_segfault() {
+    // These two inputs cause fma to segfault on release due to overflow:
+    assert_eq!(
+        fma(
+            -0.0000000000000002220446049250313,
+            -0.0000000000000002220446049250313,
+            -0.0000000000000002220446049250313
+        ),
+        -0.00000000000000022204460492503126,
+    );
+
+    assert_eq!(
+        fma(-0.992, -0.992, -0.992),
+        -0.00793599999988632,
+    );
+}

From c2b0bbb814544d8c8ccc662b6294948629f0ceb6 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Wed, 10 Jul 2019 13:01:02 +0200
Subject: [PATCH 2/2] Fix overflow bug in fma

---
 .../compiler-builtins/libm/src/math/fma.rs    |  4 ++--
 library/compiler-builtins/libm/tests/unit.rs  | 19 -------------------
 2 files changed, 2 insertions(+), 21 deletions(-)
 delete mode 100644 library/compiler-builtins/libm/tests/unit.rs

diff --git a/library/compiler-builtins/libm/src/math/fma.rs b/library/compiler-builtins/libm/src/math/fma.rs
index 6d4471a9a04f..99f77bc7967a 100644
--- a/library/compiler-builtins/libm/src/math/fma.rs
+++ b/library/compiler-builtins/libm/src/math/fma.rs
@@ -126,8 +126,8 @@ pub fn fma(x: f64, y: f64, z: f64) -> f64 {
     } else {
         /* r -= z */
         let t = rlo;
-        rlo -= zlo;
-        rhi = rhi - zhi - (t < rlo) as u64;
+        rlo = rlo.wrapping_sub(zlo);
+        rhi = rhi.wrapping_sub(zhi.wrapping_sub((t < rlo) as u64));
         if (rhi >> 63) != 0 {
             rlo = (-(rlo as i64)) as u64;
             rhi = (-(rhi as i64)) as u64 - (rlo != 0) as u64;
diff --git a/library/compiler-builtins/libm/tests/unit.rs b/library/compiler-builtins/libm/tests/unit.rs
deleted file mode 100644
index 4e7002817a64..000000000000
--- a/library/compiler-builtins/libm/tests/unit.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-use libm::*;
-
-#[test]
-fn fma_segfault() {
-    // These two inputs cause fma to segfault on release due to overflow:
-    assert_eq!(
-        fma(
-            -0.0000000000000002220446049250313,
-            -0.0000000000000002220446049250313,
-            -0.0000000000000002220446049250313
-        ),
-        -0.00000000000000022204460492503126,
-    );
-
-    assert_eq!(
-        fma(-0.992, -0.992, -0.992),
-        -0.00793599999988632,
-    );
-}