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Auto merge of #50744 - nikic:mutable-noalias, r=alexcrichton

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Emit noalias on &mut parameters by default

This used to be disabled due to LLVM bugs in the handling of
noalias information in conjunction with unwinding. However,
according to #31681 all known LLVM bugs have been fixed by
LLVM 6.0, so it's probably time to reenable this optimization.

-Z no-mutable-noalias is left as an escape-hatch to debug problems
suspected to stem from this change.
This commit is contained in:
bors 2018-05-19 07:42:03 +00:00
commit bdace29de0
3 changed files with 14 additions and 10 deletions
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10
src/test/codegen/function-arguments.rs
View file

@ -10,6 +10,7 @@
// compile-flags: -C no-prepopulate-passes
// ignore-tidy-linelength
// min-llvm-version 6.0
#![crate_type = "lib"]
#![feature(custom_attribute)]
@ -52,16 +53,14 @@ pub fn named_borrow<'r>(_: &'r i32) {
pub fn unsafe_borrow(_: &UnsafeInner) {
}
// CHECK: @mutable_unsafe_borrow(i16* dereferenceable(2) %arg0)
// CHECK: @mutable_unsafe_borrow(i16* noalias dereferenceable(2) %arg0)
// ... 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) %arg0)
// CHECK: @mutable_borrow(i32* noalias dereferenceable(4) %arg0)
// 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) {
}
@ -103,9 +102,8 @@ pub fn helper(_: usize) {
pub fn slice(_: &[u8]) {
}
// CHECK: @mutable_slice([0 x i8]* nonnull %arg0.0, [[USIZE]] %arg0.1)
// CHECK: @mutable_slice([0 x i8]* noalias nonnull %arg0.0, [[USIZE]] %arg0.1)
// 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_slice(_: &mut [u8]) {
}