#[rustc_allocator] documentation disagrees with implementation

[gparker42]

The documentation of #[rustc_allocator] seems to disagree with its implementation.

The documentation says it applies a returns-nonnull hint. The implementation instead only applies a returns-noalias hint.

    // compiler/rustc_middle/src/middle/codegen_fn_attrs.rs:49
    /// `#[rustc_allocator]`: a hint to LLVM that the pointer returned from this
    /// function is never null.
    const ALLOCATOR                 = 1 << 1;

    // compiler/rustc_codegen_llvm/src/attributes.rs:304
    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR) {
        Attribute::NoAlias.apply_llfn(llvm::AttributePlace::ReturnValue, llfn);
    }

[hkBst]

Middle part still the same:

rust/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs

Lines 96 to 98 in a6434ef

	/// `#[rustc_allocator]`: a hint to LLVM that the pointer returned from this
	/// function is never null and the function has no side effects other than allocating.
	const ALLOCATOR = 1 << 1;

Codegen part seems pretty different, but does still include the NoAlias at the bottom of:

rust/compiler/rustc_codegen_llvm/src/attributes.rs

Lines 437 to 456 in a6434ef

	if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR)
	|| codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR_ZEROED)
	{
	to_add.push(create_alloc_family_attr(cx.llcx));
	// 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]);
	to_add.push(llvm::CreateAllocSizeAttr(cx.llcx, 0));
	let mut flags = AllocKindFlags::Alloc | AllocKindFlags::Aligned;
	if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR) {
	flags |= AllocKindFlags::Uninitialized;
	} else {
	flags |= AllocKindFlags::Zeroed;
	}
	to_add.push(llvm::CreateAllocKindAttr(cx.llcx, flags));
	// apply to return place instead of function (unlike all other attributes applied in this
	// function)
	let no_alias = AttributeKind::NoAlias.create_attr(cx.llcx);
	attributes::apply_to_llfn(llfn, AttributePlace::ReturnValue, &[no_alias]);
	}

although there is also to_add.push(llvm::CreateAllocKindAttr(cx.llcx, flags));

I cannot tell if this is still an issue...