130a1df71e
This obviates the patch that teaches LLVM internals about
_rust_{re,de}alloc functions by putting annotations directly in the IR
for the optimizer.
The sole test change is required to anchor FileCheck to the body of the
`box_uninitialized` method, so it doesn't see the `allocalign` on
`__rust_alloc` and get mad about the string `alloca` showing up. Since I
was there anyway, I added some checks on the attributes to prove the
right attributes got set.
While we're here, we also emit allocator attributes on
__rust_alloc_zeroed. This should allow LLVM to perform more
optimizations for zeroed blocks, and probably fixes #90032. [This
comment](https://github.com/rust-lang/rust/issues/24194#issuecomment-308791157)
mentions "weird UB-like behaviour with bitvec iterators in
rustc_data_structures" so we may need to back this change out if things
go wrong.
The new test cases require LLVM 15, so we copy them into LLVM
14-supporting versions, which we can delete when we drop LLVM 14.
25 lines
956 B
Rust
25 lines
956 B
Rust
// compile-flags: -O
|
|
// min-llvm-version: 15.0
|
|
#![crate_type="lib"]
|
|
|
|
use std::mem::MaybeUninit;
|
|
|
|
// Boxing a `MaybeUninit` value should not copy junk from the stack
|
|
#[no_mangle]
|
|
pub fn box_uninitialized() -> Box<MaybeUninit<usize>> {
|
|
// CHECK-LABEL: @box_uninitialized
|
|
// CHECK-NOT: store
|
|
// CHECK-NOT: alloca
|
|
// CHECK-NOT: memcpy
|
|
// CHECK-NOT: memset
|
|
Box::new(MaybeUninit::uninit())
|
|
}
|
|
|
|
// FIXME: add a test for a bigger box. Currently broken, see
|
|
// https://github.com/rust-lang/rust/issues/58201.
|
|
|
|
// Hide the `allocalign` attribute in the declaration of __rust_alloc
|
|
// from the CHECK-NOT above, and also verify the attributes got set reasonably.
|
|
// CHECK: declare noalias ptr @__rust_alloc(i{{[0-9]+}}, i{{[0-9]+}} allocalign) unnamed_addr [[RUST_ALLOC_ATTRS:#[0-9]+]]
|
|
|
|
// CHECK-DAG: attributes [[RUST_ALLOC_ATTRS]] = { {{.*}} allockind("alloc,uninitialized,aligned") allocsize(0) uwtable "alloc-family"="__rust_alloc" {{.*}} }
|