Auto merge of #46739 - arielb1:simple-loops, r=nikomatsakis

[needs perf run] Try to improve LLVM pass ordering

Fixes #45466

src/rustllvm/llvm-rebuild-trigger

@@ -1,4 +1,4 @@
 # If this file is modified, then llvm will be (optionally) cleaned and then rebuilt.
 # The actual contents of this file do not matter, but to trigger a change on the
 # build bots then the contents should be changed so git updates the mtime.
-2017-11-07
+2017-11-08

src/test/codegen/issue-45466.rs

@@ -0,0 +1,25 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// min-llvm-version 4.0
+// compile-flags: -O
+
+#![crate_type="rlib"]
+
+// CHECK-LABEL: @memzero
+// CHECK-NOT: store
+// CHECK: call void @llvm.memset
+// CHECK-NOT: store
+#[no_mangle]
+pub fn memzero(data: &mut [u8]) {
+    for i in 0..data.len() {
+        data[i] = 0;
+    }
+}