From 6653bb38d5bb95bda0937e876094ef3b8bfca92c Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-no-reply-9879165716479413131@oli-obk.de>
Date: Mon, 7 May 2018 18:02:57 +0200
Subject: [PATCH] Implement missing intrinsic

---
 miri/intrinsic.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/miri/intrinsic.rs b/miri/intrinsic.rs
index 9f4950e8c9f..453e834566a 100644
--- a/miri/intrinsic.rs
+++ b/miri/intrinsic.rs
@@ -315,6 +315,20 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for EvalContext<'a, 'mir, 'tcx, super:
                 self.write_primval(dest, result.0, dest_layout.ty)?;
             }
 
+            "exact_div" => {
+                // Performs an exact division, resulting in undefined behavior where
+                // `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`
+                let ty = substs.type_at(0);
+                let a = self.value_to_primval(args[0])?;
+                let b = self.value_to_primval(args[1])?;
+                // check x % y != 0
+                if self.binary_op(mir::BinOp::Rem, a, ty, b, ty)?.0 != PrimVal::Bytes(0) {
+                    return err!(ValidationFailure(format!("exact_div: {:?} cannot be divided by {:?}", a, b)));
+                }
+                let result = self.binary_op(mir::BinOp::Div, a, ty, b, ty)?;
+                self.write_primval(dest, result.0, dest_layout.ty)?;
+            },
+
             "likely" | "unlikely" | "forget" => {}
 
             "init" => {