Auto merge of #42750 - arielb1:unwind-stack, r=eddyb

Update LLVM to pick StackColoring improvement

Fixes #40883.

r? @eddyb

Author: bors

src/llvm

@@ -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.
-2017-06-18
+2017-06-19

src/rustllvm/llvm-rebuild-trigger

@@ -0,0 +1,102 @@
+// 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.
+
+// check that we don't have linear stack usage with multiple calls to `push`
+// min-llvm-version 4.0
+
+#![feature(test)]
+
+extern crate test;
+use std::mem;
+
+fn meal() -> Big {
+    if test::black_box(false) {
+        panic!()
+    }
+    Big { drop_me: [
+        None, None, None, None, None, None, None, None,
+        None, None, None, None, None, None, None, None,
+        None, None, None, None, None, None, None, None,
+        None, None, None, None, None, None, None, None,
+        None, None, None, None, None, None, None, None,
+        None, None, None, None, None, None, None, None,
+    ]}
+}
+
+pub struct Big {
+    drop_me: [Option<Box<u8>>; 48],
+}
+
+#[inline]
+fn push(out: &mut Vec<Big>) {
+    out.push(meal());
+}
+
+#[inline(never)]
+pub fn supersize_me(out: &mut Vec<Big>) {
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out); // 16 calls to `push`
+
+    verify_stack_usage(out);
+
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out);
+    push(out); // 16 calls to `push`
+}
+
+#[inline(never)]
+fn verify_stack_usage(before_ptr: *mut Vec<Big>) {
+    // to check stack usage, create locals before and after
+    // and check the difference in addresses between them.
+    let mut stack_var: Vec<Big> = vec![];
+    test::black_box(&mut stack_var);
+    let stack_usage = isize::abs(
+        (&mut stack_var as *mut _ as isize) -
+            (before_ptr as isize)) as usize;
+    // give space for 2 copies of `Big` + 128 "misc" bytes.
+    if stack_usage > mem::size_of::<Big>() * 2 + 128 {
+        panic!("used {} bytes of stack, but `struct Big` is only {} bytes",
+               stack_usage, mem::size_of::<Big>());
+    }
+
+}
+
+pub fn main() {
+    let mut v = vec![];
+    test::black_box(&mut v);
+    supersize_me(&mut v);
+}