rust/src/test/codegen/function-arguments.rs
Björn Steinbrink a17fb64fce Workaround LLVM optimizer bug by not marking &mut pointers as noalias
LLVM's memory dependence analysis doesn't properly account for calls
that could unwind and thus effectively act as a branching point. This
can lead to stores that are only visible when the call unwinds being
removed, possibly leading to calls to drop() functions with b0rked
memory contents.

As there is no fix for this in LLVM yet and we want to keep
compatibility to current LLVM versions anyways, we have to workaround
this bug by omitting the noalias attribute on &mut function arguments.
Benchmarks suggest that the performance loss by this change is very
small.

Thanks to @RalfJung for pushing me towards not removing too many
noalias annotations and @alexcrichton for helping out with the test for
this bug.

Fixes #29485
2016-02-10 23:09:47 +01:00

147 lines
3.8 KiB
Rust

// Copyright 2015 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.
// compile-flags: -C no-prepopulate-passes
#![crate_type = "lib"]
#![feature(allocator)]
pub struct S {
_field: [i64; 4],
}
pub struct UnsafeInner {
_field: std::cell::UnsafeCell<i16>,
}
// CHECK: zeroext i1 @boolean(i1 zeroext)
#[no_mangle]
pub fn boolean(x: bool) -> bool {
x
}
// CHECK: @readonly_borrow(i32* noalias readonly dereferenceable(4))
// FIXME #25759 This should also have `nocapture`
#[no_mangle]
pub fn readonly_borrow(_: &i32) {
}
// CHECK: @static_borrow(i32* noalias readonly dereferenceable(4))
// static borrow may be captured
#[no_mangle]
pub fn static_borrow(_: &'static i32) {
}
// CHECK: @named_borrow(i32* noalias readonly dereferenceable(4))
// borrow with named lifetime may be captured
#[no_mangle]
pub fn named_borrow<'r>(_: &'r i32) {
}
// CHECK: @unsafe_borrow(%UnsafeInner* dereferenceable(2))
// unsafe interior means this isn't actually readonly and there may be aliases ...
#[no_mangle]
pub fn unsafe_borrow(_: &UnsafeInner) {
}
// CHECK: @mutable_unsafe_borrow(%UnsafeInner* dereferenceable(2))
// ... unless this is a mutable borrow, those never alias
// ... except that there's this LLVM bug that forces us to not use noalias, see #29485
#[no_mangle]
pub fn mutable_unsafe_borrow(_: &mut UnsafeInner) {
}
// CHECK: @mutable_borrow(i32* dereferenceable(4))
// FIXME #25759 This should also have `nocapture`
// ... there's this LLVM bug that forces us to not use noalias, see #29485
#[no_mangle]
pub fn mutable_borrow(_: &mut i32) {
}
// CHECK: @indirect_struct(%S* noalias nocapture dereferenceable(32))
#[no_mangle]
pub fn indirect_struct(_: S) {
}
// CHECK: @borrowed_struct(%S* noalias readonly dereferenceable(32))
// FIXME #25759 This should also have `nocapture`
#[no_mangle]
pub fn borrowed_struct(_: &S) {
}
// CHECK: noalias dereferenceable(4) i32* @_box(i32* noalias dereferenceable(4))
#[no_mangle]
pub fn _box(x: Box<i32>) -> Box<i32> {
x
}
// CHECK: @struct_return(%S* noalias nocapture sret dereferenceable(32))
#[no_mangle]
pub fn struct_return() -> S {
S {
_field: [0, 0, 0, 0]
}
}
// Hack to get the correct size for the length part in slices
// CHECK: @helper([[USIZE:i[0-9]+]])
#[no_mangle]
fn helper(_: usize) {
}
// CHECK: @slice(i8* noalias nonnull readonly, [[USIZE]])
// FIXME #25759 This should also have `nocapture`
#[no_mangle]
fn slice(_: &[u8]) {
}
// CHECK: @mutable_slice(i8* nonnull, [[USIZE]])
// FIXME #25759 This should also have `nocapture`
// ... there's this LLVM bug that forces us to not use noalias, see #29485
#[no_mangle]
fn mutable_slice(_: &mut [u8]) {
}
// CHECK: @unsafe_slice(%UnsafeInner* nonnull, [[USIZE]])
// unsafe interior means this isn't actually readonly and there may be aliases ...
#[no_mangle]
pub fn unsafe_slice(_: &[UnsafeInner]) {
}
// CHECK: @str(i8* noalias nonnull readonly, [[USIZE]])
// FIXME #25759 This should also have `nocapture`
#[no_mangle]
fn str(_: &[u8]) {
}
// CHECK: @trait_borrow(i8* nonnull, void (i8*)** nonnull)
// FIXME #25759 This should also have `nocapture`
#[no_mangle]
fn trait_borrow(_: &Drop) {
}
// CHECK: @trait_box(i8* noalias nonnull, void (i8*)** nonnull)
#[no_mangle]
fn trait_box(_: Box<Drop>) {
}
// CHECK: { i16*, [[USIZE]] } @return_slice(i16* noalias nonnull readonly, [[USIZE]])
#[no_mangle]
fn return_slice(x: &[u16]) -> &[u16] {
x
}
// CHECK: noalias i8* @allocator()
#[no_mangle]
#[allocator]
pub fn allocator() -> *const i8 {
std::ptr::null()
}