diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index ac390313a6797..aacbbd5058e05 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -1246,18 +1246,15 @@ macro_rules! iterator {
             {
                 // The addition might panic on overflow
                 // Use the len of the slice to hint optimizer to remove result index bounds check.
-                let _n = make_slice!(self.ptr, self.end).len();
+                let n = make_slice!(self.ptr, self.end).len();
                 self.try_fold(0, move |i, x| {
                     if predicate(x) { Err(i) }
                     else { Ok(i + 1) }
                 }).err()
-                    // // FIXME(#48116/#45964):
-                    // // This assume() causes misoptimization on LLVM 6.
-                    // // Commented out until it is fixed again.
-                    // .map(|i| {
-                    //     unsafe { assume(i < n) };
-                    //     i
-                    // })
+                    .map(|i| {
+                        unsafe { assume(i < n) };
+                        i
+                    })
             }
 
             #[inline]
@@ -1274,13 +1271,10 @@ macro_rules! iterator {
                     if predicate(x) { Err(i) }
                     else { Ok(i) }
                 }).err()
-                    // // FIXME(#48116/#45964):
-                    // // This assume() causes misoptimization on LLVM 6.
-                    // // Commented out until it is fixed again.
-                    // .map(|i| {
-                    //     unsafe { assume(i < n) };
-                    //     i
-                    // })
+                    .map(|i| {
+                        unsafe { assume(i < n) };
+                        i
+                    })
             }
         }
 
diff --git a/src/llvm b/src/llvm
index 9f81beaf32608..ba2edd794c7de 160000
--- a/src/llvm
+++ b/src/llvm
@@ -1 +1 @@
-Subproject commit 9f81beaf32608fbe1fe0f2a82f974e800e9d8c62
+Subproject commit ba2edd794c7def715007931fcd1b4ce62aa711c8