[gccrs COMMIT] lang: Register lang items for alloc crate

From: Enes Cevik <[email protected]>

This patch registers several lang items as stubs to progress towards
compiling the 'alloc' crate.

- 'oom', 'alloc_layout': Require no specific handling; symbol generation
  is sufficient.
- 'box_free': Full implementation requires a mature drop infrastructure.
  Registered as a stub for now.
- 'drop_in_place': Full implementation requires a mature drop
  infrastructure. Registered as a stub for now.
- 'maybe_uninit': Requires layout engine maturity and niche-filling
  mechanisms. Registered as a stub.
- 'future_trait', 'poll', 'Ready', 'Pending': Registered as stubs due
  to lack of async support.
- 'generator', 'generator_state': Registered as stubs due to lack of
  generator support.

The 'Ready' and 'Pending' lang items are excluded from the new test
cases because lang item attributes on enum variants are not currently
handled (see Rust-GCC/gccrs#4703).

gcc/rust/ChangeLog:

	* hir/rust-ast-lower-base.cc (warn_if_stub_lang_item): New
	function.
	(ASTLoweringBase::handle_lang_item_attribute): Emit a warning
	if lang item is stub.
	* util/rust-lang-item.cc (Rust::LangItem::lang_items): Add new
	lang items to the BiMap.
	* util/rust-lang-item.h (class LangItem): Add new lang items
	to Kind enum.

gcc/testsuite/ChangeLog:

	* rust/compile/lang-items-stub.rs: New test.
	* rust/compile/lang-items-symbol.rs: New test.

Signed-off-by: Enes Cevik <[email protected]>
---
This change was merged into the gccrs repository and is posted here for
upstream visibility and potential drive-by review, as requested by GCC
release managers.
Each commit email contains a link to its details on github from where you can
find the Pull-Request and associated discussions.


Commit on github: https://github.com/Rust-GCC/gccrs/commit/d02b5ac3d9f99823fee00e0180e830b366ce8ad1

The commit has been mentioned in the following issue(s):
 - Rust-GCC/gccrs#4703: https://github.com/Rust-GCC/gccrs/issues/4703

The commit has been mentioned in the following pull-request(s):
 - https://github.com/Rust-GCC/gccrs/pull/4721

 gcc/rust/hir/rust-ast-lower-base.cc           | 29 +++++++++++++--
 gcc/rust/util/rust-lang-item.cc               | 12 +++++++
 gcc/rust/util/rust-lang-item.h                | 12 +++++++
 gcc/testsuite/rust/compile/lang-items-stub.rs | 36 +++++++++++++++++++
 .../rust/compile/lang-items-symbol.rs         |  8 +++++
 5 files changed, 95 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/rust/compile/lang-items-stub.rs
 create mode 100644 gcc/testsuite/rust/compile/lang-items-symbol.rs

diff --git a/gcc/rust/hir/rust-ast-lower-base.cc b/gcc/rust/hir/rust-ast-lower-base.cc
index ffa7a0f39..7cbe52af6 100644
--- a/gcc/rust/hir/rust-ast-lower-base.cc
+++ b/gcc/rust/hir/rust-ast-lower-base.cc
@@ -853,6 +853,28 @@ ASTLoweringBase::handle_doc_item_attribute (const ItemWrapper &,
   rust_assert (meta_item);
 }
 
+static void
+warn_if_stub_lang_item (location_t locus, LangItem::Kind kind)
+{
+  switch (kind)
+    {
+    case LangItem::Kind::FUTURE_TRAIT:
+    case LangItem::Kind::POLL:
+    case LangItem::Kind::READY:
+    case LangItem::Kind::PENDING:
+    case LangItem::Kind::GENERATOR:
+    case LangItem::Kind::GENERATOR_STATE:
+    case LangItem::Kind::MAYBE_UNINIT:
+    case LangItem::Kind::BOX_FREE:
+    case LangItem::Kind::DROP_IN_PLACE:
+      rust_warning_at (locus, 0, "%qs is not implemented and has no effect",
+		       LangItem::PrettyString (kind).c_str ());
+      break;
+    default:
+      break;
+    }
+}
+
 void
 ASTLoweringBase::handle_lang_item_attribute (const ItemWrapper &item,
 					     const AST::Attribute &attr)
@@ -863,8 +885,11 @@ ASTLoweringBase::handle_lang_item_attribute (const ItemWrapper &item,
   auto lang_item_type = LangItem::Parse (*lang_item_type_str);
 
   if (lang_item_type)
-    mappings.insert_lang_item (*lang_item_type,
-			       item.get_mappings ().get_defid ());
+    {
+      mappings.insert_lang_item (*lang_item_type,
+				 item.get_mappings ().get_defid ());
+      warn_if_stub_lang_item (attr.get_locus (), *lang_item_type);
+    }
   else
     rust_error_at (attr.get_locus (), "unknown lang item");
 }
diff --git a/gcc/rust/util/rust-lang-item.cc b/gcc/rust/util/rust-lang-item.cc
index 731fd23f3..c58ab401f 100644
--- a/gcc/rust/util/rust-lang-item.cc
+++ b/gcc/rust/util/rust-lang-item.cc
@@ -124,9 +124,21 @@ const BiMap<std::string, LangItem::Kind> Rust::LangItem::lang_items = {{
   {"discriminant_kind", Kind::DISCRIMINANT_KIND},
   {"discriminant_type", Kind::DISCRIMINANT_TYPE},
   {"manually_drop", Kind::MANUALLY_DROP},
+  {"drop_in_place", Kind::DROP_IN_PLACE},
 
   {"exchange_malloc", Kind::EXCHANGE_MALLOC},
   {"owned_box", Kind::OWNED_BOX},
+  {"oom", Kind::OOM},
+  {"alloc_layout", Kind::ALLOC_LAYOUT},
+  {"box_free", Kind::BOX_FREE},
+  {"maybe_uninit", Kind::MAYBE_UNINIT},
+
+  {"future_trait", Kind::FUTURE_TRAIT},
+  {"poll", Kind::POLL},
+  {"Ready", Kind::READY},
+  {"Pending", Kind::PENDING},
+  {"generator", Kind::GENERATOR},
+  {"generator_state", Kind::GENERATOR_STATE},
 }};
 
 tl::optional<LangItem::Kind>
diff --git a/gcc/rust/util/rust-lang-item.h b/gcc/rust/util/rust-lang-item.h
index 9684148f7..d6bea1a8e 100644
--- a/gcc/rust/util/rust-lang-item.h
+++ b/gcc/rust/util/rust-lang-item.h
@@ -160,9 +160,21 @@ public:
     DISCRIMINANT_KIND,
 
     MANUALLY_DROP,
+    DROP_IN_PLACE,
 
     EXCHANGE_MALLOC,
     OWNED_BOX,
+    OOM,
+    ALLOC_LAYOUT,
+    BOX_FREE,
+    MAYBE_UNINIT,
+
+    FUTURE_TRAIT,
+    POLL,
+    READY,
+    PENDING,
+    GENERATOR,
+    GENERATOR_STATE,
   };
 
   static const BiMap<std::string, Kind> lang_items;
diff --git a/gcc/testsuite/rust/compile/lang-items-stub.rs b/gcc/testsuite/rust/compile/lang-items-stub.rs
new file mode 100644
index 000000000..09dd06e0e
--- /dev/null
+++ b/gcc/testsuite/rust/compile/lang-items-stub.rs
@@ -0,0 +1,36 @@
+#![feature(no_core, lang_items)]
+#![no_core]
+
+
+#[lang = "sized"]
+pub trait Sized {}
+
+#[lang = "future_trait"] // { dg-warning "...lang = .future_trait... is not implemented and has no effect" }
+pub trait Future {
+    #[lang = "poll"] // { dg-warning "...lang = .poll... is not implemented and has no effect" }
+    fn poll() {}
+}
+
+#[lang = "generator"] // { dg-warning "...lang = .generator... is not implemented and has no effect" }
+pub trait Generator {}
+
+#[lang = "generator_state"] // { dg-warning "...lang = .generator_state... is not implemented and has no effect" }
+pub enum GeneratorState {}
+
+#[lang = "box_free"] // { dg-warning "...lang = .box_free... is not implemented and has no effect" }
+pub fn _box_free() {}
+
+#[repr(transparent)]
+pub struct ManuallyDrop<T: ?Sized> {
+    _value: T,
+}
+
+#[lang = "maybe_uninit"] // { dg-warning "...lang = .maybe_uninit... is not implemented and has no effect" }
+#[repr(transparent)]
+pub union MaybeUninit<T> {
+    uninit: (),
+    value: ManuallyDrop<T>,
+}
+
+#[lang = "drop_in_place"] // { dg-warning "...lang = .drop_in_place... is not implemented and has no effect" }
+pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {}
diff --git a/gcc/testsuite/rust/compile/lang-items-symbol.rs b/gcc/testsuite/rust/compile/lang-items-symbol.rs
new file mode 100644
index 000000000..bc113d52b
--- /dev/null
+++ b/gcc/testsuite/rust/compile/lang-items-symbol.rs
@@ -0,0 +1,8 @@
+#![feature(no_core, lang_items)]
+#![no_core]
+
+#[lang = "alloc_layout"]
+pub struct Layout;
+
+#[lang = "oom"]
+pub fn _oom() {}

base-commit: a7cc9cf930c956a736e83bb236f0bcea3270d93a
-- 
2.54.0