From ff2001040f06bda894fb512684e34ea12deade6e Mon Sep 17 00:00:00 2001
From: Christian Poveda <christianpoveda@protonmail.com>
Date: Fri, 2 Aug 2019 13:42:10 -0500
Subject: [PATCH] Add shim for ldexp

---
 src/shims/foreign_items.rs        | 12 ++++++++++--
 tests/run-pass/intrinsics-math.rs |  4 ++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/shims/foreign_items.rs b/src/shims/foreign_items.rs
index bcfcda2fd01c..332132947823 100644
--- a/src/shims/foreign_items.rs
+++ b/src/shims/foreign_items.rs
@@ -603,7 +603,15 @@ fn emulate_foreign_item(
                 };
                 this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
             }
-
+            // underscore case for windows
+            "_ldexp" | "ldexp" => {
+                // FIXME: Using host floats.
+                let x = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
+                let exp = this.read_scalar(args[1])?.to_i32()?;
+                // FIXME: We should use cmath if there are any imprecisions.
+                let n = x * 2.0f64.powi(exp);
+                this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
+            }
             // Some things needed for `sys::thread` initialization to go through.
             "signal" | "sigaction" | "sigaltstack" => {
                 this.write_scalar(Scalar::from_int(0, dest.layout.size), dest)?;
@@ -973,4 +981,4 @@ fn eval_path_scalar(&mut self, path: &[&str]) -> InterpResult<'tcx, Option<Scala
         }
         return Ok(None);
     }
-}
\ No newline at end of file
+}
diff --git a/tests/run-pass/intrinsics-math.rs b/tests/run-pass/intrinsics-math.rs
index 20c0f6749488..9a7a70bd0092 100644
--- a/tests/run-pass/intrinsics-math.rs
+++ b/tests/run-pass/intrinsics-math.rs
@@ -85,4 +85,8 @@ pub fn main() {
     assert_approx_eq!(1.0f32.tan(), 1.557408f32);
     assert_approx_eq!(1.0f64.tan(), 1.557408f64);
 
+    extern {
+        fn ldexp(x: f64, n: i32) -> f64;
+    }
+    unsafe { assert_approx_eq!(ldexp(0.65f64, 3i32), 5.2f64); }
 }