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Pass alloc-variant-zeroed to LLVM #144086

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10 changes: 10 additions & 0 deletions compiler/rustc_codegen_llvm/src/attributes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -436,6 +436,16 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
|| codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR_ZEROED)
{
to_add.push(create_alloc_family_attr(cx.llcx));
if let Some(zv) =
cx.tcx.get_attr(instance.def_id(), rustc_span::sym::rustc_allocator_zeroed_variant)
&& let Some(name) = zv.value_str()
{
to_add.push(llvm::CreateAttrStringValue(
cx.llcx,
"alloc-variant-zeroed",
name.as_str(),
));
}
// apply to argument place instead of function
let alloc_align = AttributeKind::AllocAlign.create_attr(cx.llcx);
attributes::apply_to_llfn(llfn, AttributePlace::Argument(1), &[alloc_align]);
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4 changes: 4 additions & 0 deletions compiler/rustc_feature/src/builtin_attrs.rs
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Expand Up @@ -772,6 +772,10 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
rustc_allocator_zeroed, Normal, template!(Word), WarnFollowing,
EncodeCrossCrate::No,
),
rustc_attr!(
rustc_allocator_zeroed_variant, Normal, template!(NameValueStr: "function"), ErrorPreceding,
EncodeCrossCrate::Yes,
),
gated!(
default_lib_allocator, Normal, template!(Word), WarnFollowing,
EncodeCrossCrate::No, allocator_internals, experimental!(default_lib_allocator),
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1 change: 1 addition & 0 deletions compiler/rustc_span/src/symbol.rs
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Expand Up @@ -1810,6 +1810,7 @@ symbols! {
rustc_abi,
rustc_allocator,
rustc_allocator_zeroed,
rustc_allocator_zeroed_variant,
rustc_allow_const_fn_unstable,
rustc_allow_incoherent_impl,
rustc_allowed_through_unstable_modules,
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1 change: 1 addition & 0 deletions library/alloc/src/alloc.rs
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Expand Up @@ -17,6 +17,7 @@ unsafe extern "Rust" {
#[rustc_allocator]
#[rustc_nounwind]
#[rustc_std_internal_symbol]
#[rustc_allocator_zeroed_variant = "__rust_alloc_zeroed"]
fn __rust_alloc(size: usize, align: usize) -> *mut u8;
#[rustc_deallocator]
#[rustc_nounwind]
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17 changes: 17 additions & 0 deletions tests/codegen/vec-calloc.rs
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Expand Up @@ -176,6 +176,23 @@ pub fn vec_option_i32(n: usize) -> Vec<Option<i32>> {
vec![None; n]
}

// CHECK-LABEL: @vec_array
#[no_mangle]
pub fn vec_array(n: usize) -> Vec<[u32; 1_000_000]> {
// CHECK-NOT: call {{.*}}alloc::vec::from_elem
// CHECK-NOT: call {{.*}}reserve
// CHECK-NOT: call {{.*}}__rust_alloc(

// CHECK: call {{.*}}__rust_alloc_zeroed(

// CHECK-NOT: call {{.*}}alloc::vec::from_elem
// CHECK-NOT: call {{.*}}reserve
// CHECK-NOT: call {{.*}}__rust_alloc(

// CHECK: ret void
vec![[0; 1_000_000]; 3]
}

// Ensure that __rust_alloc_zeroed gets the right attributes for LLVM to optimize it away.
// CHECK: declare noalias noundef ptr @{{.*}}__rust_alloc_zeroed(i64 noundef, i64 allocalign noundef) unnamed_addr [[RUST_ALLOC_ZEROED_ATTRS:#[0-9]+]]

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