[WIP] Drop trait demo

.gitignore

@@ -39,6 +39,7 @@ cscope.out
 .local.vimrc
 .lvimrc
 .vscode
+.zed
 
 .clang-format
 .clang-tidy

gcc/rust/Make-lang.in

@@ -224,6 +224,8 @@ GRS_OBJS = \
     rust/rust-compile-base.o \
     rust/rust-tree.o \
     rust/rust-compile-context.o \
+    rust/rust-compile-datum.o \
+    rust/rust-compile-drop.o \
     rust/rust-export-metadata.o \
     rust/rust-imports.o \
     rust/rust-import-archive.o \

gcc/rust/backend/rust-compile-context.h

@@ -19,6 +19,9 @@
 #ifndef RUST_COMPILE_CONTEXT
 #define RUST_COMPILE_CONTEXT
 
+#include "rust-compile-drop.h"
+#include "rust-compile-datum.h"
+#include "rust-location.h"
 #include "rust-system.h"
 #include "rust-hir-map.h"
 #include "rust-name-resolver.h"
@@ -28,6 +31,9 @@
 #include "rust-mangle.h"
 #include "rust-tree.h"
 #include "rust-immutable-name-resolution-context.h"
+#include "rust-tyty.h"
+#include <algorithm>
+#include <tuple>
 
 namespace Rust {
 namespace Compile {
@@ -101,6 +107,7 @@ class Context
   {
     scope_stack.push_back (scope);
     statements.push_back ({});
+    cleanups.push_back ({});
   }
 
   tree pop_block ()
@@ -110,9 +117,17 @@ class Context
 
     auto stmts = statements.back ();
     statements.pop_back ();
-
-    Backend::block_add_statements (block, stmts);
-
+    auto cls = cleanups.back ();
+    cleanups.pop_back ();
+    std::reverse (cls.begin (), cls.end ());
+    if (cls.empty ())
+      {
+	Backend::block_add_statements (block, stmts);
+      }
+    else
+      {
+	Backend::block_add_statements_with_cleanups (block, stmts, cls);
+      }
     return block;
   }
 
@@ -130,6 +145,7 @@ class Context
   }
 
   void add_statement (tree stmt) { statements.back ().push_back (stmt); }
+  void add_cleanup (tree stmt) { cleanups.back ().push_back (stmt); }
 
   void insert_var_decl (HirId id, ::Bvariable *decl)
   {
@@ -146,6 +162,20 @@ class Context
     return true;
   }
 
+  void insert_var_drop_place (HirId id, DropPlace *dp)
+  {
+    var_drop_places[id] = dp;
+  }
+
+  bool lookup_var_drop_place (HirId id, DropPlace **dp)
+  {
+    auto it = var_drop_places.find (id);
+    if (it == var_drop_places.end ())
+      return false;
+    *dp = it->second;
+    return true;
+  }
+
   void insert_function_decl (const TyTy::FnType *ref, tree fn)
   {
     auto id = ref->get_ty_ref ();
@@ -417,7 +447,9 @@ class Context
   std::map<HirId, tree> compiled_fn_map;
   std::map<HirId, tree> compiled_consts;
   std::map<HirId, tree> compiled_labels;
+  std::map<HirId, DropPlace *> var_drop_places;
   std::vector<::std::vector<tree>> statements;
+  std::vector<::std::vector<tree>> cleanups;
   std::vector<tree> scope_stack;
   std::vector<::Bvariable *> loop_value_stack;
   std::vector<tree> loop_begin_labels;

gcc/rust/backend/rust-compile-datum.cc

@@ -0,0 +1,156 @@
+// Copyright (C) 2020-2026 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-compile-datum.h"
+#include "rust-backend.h"
+#include "rust-compile-context.h"
+#include "rust-compile-drop.h"
+#include "rust-compile-type.h"
+#include "rust-tyty.h"
+namespace Rust {
+namespace Compile {
+
+Datum
+Datum::to_lvalue (Context *ctx, HirId expr_id)
+{
+  if (kind == DatumKind::Lvalue)
+    return *this;
+  assert (is_valid () && "invalid datum");
+  DropContext *drop_ctx = DropContext::get (ctx);
+  tree compiled_type = TyTyResolveCompile::compile (ctx, ty);
+  assert_node (compiled_type, "something wrong with compiled_type");
+  tree pstatement = NULL_TREE;
+  tree fndecl = ctx->peek_fn ().fndecl;
+  tree bind_tree = ctx->peek_enclosing_scope ();
+  LocalVariable tmp
+    = Backend::temporary_variable (fndecl, bind_tree, compiled_type, val, false,
+				   locus, &pstatement);
+  assert (pstatement != NULL_TREE);
+  ctx->add_statement (pstatement);
+  val = Backend::var_expression (tmp, locus);
+  if (drop_ctx->needs_drop (ty))
+    {
+      DropPath tmp_path;
+      tmp_path.root = expr_id;
+      tmp_path.var_name = "tmp_expr_" + std::to_string (expr_id);
+      DropPlace *place = drop_ctx->make_drop_place (val, tmp_path, ty);
+      assert (place != nullptr);
+      tree drop_expr = drop_ctx->drop (place);
+      assert_node (drop_expr, "drop expr is not valid");
+      ctx->add_cleanup (drop_expr);
+      ctx->add_statement (drop_ctx->init (place));
+      drop_place = place;
+    }
+  kind = DatumKind::Lvalue;
+  return *this;
+}
+
+Datum
+Datum::to_rvalue (Context *ctx)
+{
+  if (kind == DatumKind::Rvalue)
+    return *this;
+  assert (is_valid () && "invalid datum");
+  DropContext *drop_ctx = DropContext::get (ctx);
+  tree compiled_type = TyTyResolveCompile::compile (ctx, ty);
+  assert_node (compiled_type, "something wrong with compiled type");
+  tree pstatement = NULL_TREE;
+  tree fndecl = ctx->peek_fn ().fndecl;
+  tree bind_tree = ctx->peek_enclosing_scope ();
+  LocalVariable scratch
+    = Backend::temporary_variable (fndecl, bind_tree, compiled_type, NULL_TREE,
+				   false, locus, &pstatement);
+  assert (pstatement != NULL_TREE);
+  ctx->add_statement (pstatement);
+  tree scratch_expr = Backend::var_expression (scratch, locus);
+  tree copy = Backend::assignment_statement (scratch_expr, val, locus);
+  ctx->add_statement (copy);
+  if (needs_drop (drop_ctx) && drop_place)
+    ctx->add_statement (drop_ctx->uninit (drop_place));
+  return Datum::new_rvalue (scratch_expr, ty, locus);
+}
+
+void
+Datum::store_to (Context *ctx, tree dest_ptr)
+{
+  tree assignment = Backend::assignment_statement (dest_ptr, val, locus);
+  ctx->add_statement (assignment);
+  post_store (ctx);
+}
+
+void
+Datum::post_store (Context *ctx)
+{
+  if (kind == DatumKind::Lvalue && ty != nullptr && drop_place != nullptr)
+    {
+      DropContext *drop_ctx = DropContext::get (ctx);
+      if (drop_ctx->needs_drop (ty))
+	ctx->add_statement (drop_ctx->uninit (drop_place));
+    }
+}
+
+Datum
+Datum::get_field (Context *ctx, size_t field_index, location_t field_locus)
+{
+  tree field_expr
+    = Backend::struct_field_expression (val, field_index, field_locus);
+  TyTy::BaseType *field_ty = nullptr;
+  assert (is_valid () && "invalid datum in get_field");
+  TyTy::BaseType *resolved = ty->destructure ();
+  switch (resolved->get_kind ())
+    {
+    case TyTy::TypeKind::ADT:
+      {
+	TyTy::ADTType *adt = resolved->as<TyTy::ADTType> ();
+	TyTy::VariantDef *variant = adt->get_variants ().at (0);
+	field_ty = variant->get_field_at_index (field_index)->get_field_type ();
+	break;
+      }
+    case TyTy::TypeKind::TUPLE:
+      {
+	TyTy::TupleType *tuple = resolved->as<TyTy::TupleType> ();
+	field_ty = tuple->get_field (field_index);
+	break;
+      }
+    default:
+      todo_die ("handle all remaining cases explicitly");
+      break;
+    }
+  DropPlace *field_dp = nullptr;
+  if (drop_place != nullptr && !drop_place->is_leaf ())
+    {
+      DropPath child_path = drop_place->path.child (field_index);
+      for (auto *child : drop_place->children)
+	if (child->path == child_path)
+	  field_dp = child;
+    }
+  return Datum::new_lvalue (field_expr, field_ty, field_dp, field_locus);
+}
+
+void
+Datum::add_clean_if_rvalue (Context *ctx, HirId expr_id)
+{
+  if (kind == DatumKind::Lvalue)
+    return;
+  DropContext *drop_ctx = DropContext::get (ctx);
+  if (!needs_drop (drop_ctx))
+    return;
+  to_lvalue (ctx, expr_id);
+}
+} // namespace Compile
+} // namespace Rust

gcc/rust/backend/rust-compile-datum.h

@@ -0,0 +1,97 @@
+// Copyright (C) 2020-2026 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_COMPILE_DATUM_H
+#define RUST_COMPILE_DATUM_H
+
+#include "rust-compile-drop.h"
+#include "rust-location.h"
+#include "rust-tyty.h"
+
+namespace Rust {
+namespace Compile {
+
+class Context;
+enum class DatumKind
+{
+  Lvalue,
+  Rvalue,
+  Invalid,
+};
+
+struct Datum
+{
+  tree val = NULL_TREE;
+  TyTy::BaseType *ty = nullptr;
+  DatumKind kind = DatumKind::Invalid;
+  DropPlace *drop_place = nullptr;
+  location_t locus = UNDEF_LOCATION;
+
+  static Datum new_datum (tree val, TyTy::BaseType *ty, DatumKind kind,
+			  DropPlace *drop_place, location_t locus)
+  {
+    Datum d;
+    d.val = val;
+    d.ty = ty;
+    d.kind = kind;
+    d.drop_place = drop_place;
+    d.locus = locus;
+    return d;
+  }
+  static Datum new_lvalue (tree val, TyTy::BaseType *ty, DropPlace *drop_place,
+			   location_t locus)
+  {
+    return new_datum (val, ty, DatumKind::Lvalue, drop_place, locus);
+  }
+  static Datum new_rvalue (tree val, TyTy::BaseType *ty, location_t locus)
+  {
+    return new_datum (val, ty, DatumKind::Rvalue, nullptr, locus);
+  }
+
+  bool is_lvalue () const { return kind == DatumKind::Lvalue; }
+  bool is_rvalue () const { return kind == DatumKind::Rvalue; }
+  bool is_valid () const
+  {
+    return check_node (val) && ty != nullptr && kind != DatumKind::Invalid;
+  }
+  void set_not_valid ()
+  {
+    val = error_mark_node;
+    ty = nullptr;
+    kind = DatumKind::Invalid;
+  }
+
+  bool needs_drop (DropContext *drop_ctx) const
+  {
+    if (!is_valid ())
+      return false;
+    return drop_ctx->needs_drop (ty);
+  }
+
+  Datum get_field (Context *ctx, size_t field_index, location_t locus);
+  tree raw_tree () const { return val; }
+
+  void add_clean_if_rvalue (Context *ctx, HirId expr_id);
+  Datum to_lvalue (Context *ctx, HirId expr_id);
+  Datum to_rvalue (Context *ctx);
+  void store_to (Context *ctx, tree dest_ptr);
+  void post_store (Context *ctx);
+};
+} // namespace Compile
+} // namespace Rust
+#endif // RUST_COMPILE_DATUM_H