[gcc r17-2249] gccrs: Refactor CompileDrop and add DropBuilder

https://gcc.gnu.org/g:0461510c487b4df2a07e6c479f00b45b5c9c0cc1

commit r17-2249-g0461510c487b4df2a07e6c479f00b45b5c9c0cc1
Author: Lishin <[email protected]>
Date:   Tue Jun 16 15:44:11 2026 +0000

    gccrs: Refactor CompileDrop and add DropBuilder
    
    Refactor CompileDrop to keep Context as a member
    instead of passing it to each method.
    
    Move the drop candidate note/peek operations from
    Context to DropBuilder. This keeps the drop-specific
    API off the compile Context.
    
    gcc/rust/ChangeLog:
    
            * Make-lang.in: Add rust-compile-drop-builder.o.
            * backend/rust-compile-base.cc
            (HIRCompileBase::compile_function_body):
            Update CompileDrop calls.
            * backend/rust-compile-block.cc (CompileBlock::visit):
            Update CompileDrop calls.
            * backend/rust-compile-context.h (Context): Allow
            DropBuilder to access drop candidate storage and move
            drop candidate APIs to DropBuilder.
            * backend/rust-compile-drop.cc (CompileDrop::CompileDrop):
            Add constructor.
            (CompileDrop::type_has_drop_impl): Use stored Context member.
            (CompileDrop::compile_drop_call): Likewise.
            (CompileDrop::emit_current_scope_drop_calls): Use stored
            Context member and get drop candidates from DropBuilder.
            * backend/rust-compile-drop.h: Store Context as a member.
            * backend/rust-compile-pattern.cc (CompilePatternLet::visit):
            Use DropBuilder and update CompileDrop calls.
            * backend/rust-compile-drop-builder.cc: New file.
            * backend/rust-compile-drop-builder.h: New file.
    
    Signed-off-by: Lishin <[email protected]>

Diff:
---
 gcc/rust/Make-lang.in                         |  1 +
 gcc/rust/backend/rust-compile-base.cc         |  4 +--
 gcc/rust/backend/rust-compile-block.cc        |  2 +-
 gcc/rust/backend/rust-compile-context.h       | 15 ++-------
 gcc/rust/backend/rust-compile-drop-builder.cc | 42 +++++++++++++++++++++++++
 gcc/rust/backend/rust-compile-drop-builder.h  | 44 +++++++++++++++++++++++++++
 gcc/rust/backend/rust-compile-drop.cc         | 16 ++++++----
 gcc/rust/backend/rust-compile-drop.h          | 12 +++++---
 gcc/rust/backend/rust-compile-pattern.cc      | 10 ++++--
 9 files changed, 118 insertions(+), 28 deletions(-)

diff --git a/gcc/rust/Make-lang.in b/gcc/rust/Make-lang.in
index d8093dad66b5..a56db9241b38 100644
--- a/gcc/rust/Make-lang.in
+++ b/gcc/rust/Make-lang.in
@@ -226,6 +226,7 @@ GRS_OBJS = \
     rust/rust-compile-struct-field-expr.o \
     rust/rust-constexpr.o \
     rust/rust-compile-base.o \
+    rust/rust-compile-drop-builder.o \
     rust/rust-compile-drop.o \
     rust/rust-tree.o \
     rust/rust-compile-context.o \
diff --git a/gcc/rust/backend/rust-compile-base.cc b/gcc/rust/backend/rust-compile-base.cc
index 9678ad482d89..1a6ce99f42f2 100644
--- a/gcc/rust/backend/rust-compile-base.cc
+++ b/gcc/rust/backend/rust-compile-base.cc
@@ -708,7 +708,7 @@ HIRCompileBase::compile_function_body (tree fndecl,
 	  return_value = coercion_site (id, return_value, actual, expected,
 					lvalue_locus, rvalue_locus);
 
-	  CompileDrop::emit_current_scope_drop_calls (ctx);
+	  CompileDrop (ctx).emit_current_scope_drop_calls ();
 
 	  tree return_stmt
 	    = Backend::return_statement (fndecl, return_value, locus);
@@ -732,7 +732,7 @@ HIRCompileBase::compile_function_body (tree fndecl,
       // errors should have occurred
       location_t locus = function_body.get_locus ();
       tree return_value = unit_expression (locus);
-      CompileDrop::emit_current_scope_drop_calls (ctx);
+      CompileDrop (ctx).emit_current_scope_drop_calls ();
       tree return_stmt
 	= Backend::return_statement (fndecl, return_value, locus);
       ctx->add_statement (return_stmt);
diff --git a/gcc/rust/backend/rust-compile-block.cc b/gcc/rust/backend/rust-compile-block.cc
index 245c16c52e85..e35d02e52a06 100644
--- a/gcc/rust/backend/rust-compile-block.cc
+++ b/gcc/rust/backend/rust-compile-block.cc
@@ -85,7 +85,7 @@ CompileBlock::visit (HIR::BlockExpr &expr)
 					 expr.get_locus ());
       ctx->add_statement (assignment);
     }
-  CompileDrop::emit_current_scope_drop_calls (ctx);
+  CompileDrop (ctx).emit_current_scope_drop_calls ();
 
   ctx->pop_block ();
   translated = new_block;
diff --git a/gcc/rust/backend/rust-compile-context.h b/gcc/rust/backend/rust-compile-context.h
index c86ac349f850..9fe39e5572d7 100644
--- a/gcc/rust/backend/rust-compile-context.h
+++ b/gcc/rust/backend/rust-compile-context.h
@@ -51,6 +51,8 @@ struct CustomDeriveInfo
   std::vector<std::string> attributes;
 };
 
+class DropBuilder;
+
 class Context
 {
 public:
@@ -136,18 +138,6 @@ public:
 
   void add_statement (tree stmt) { statements.back ().push_back (stmt); }
 
-  std::vector<DropCandidate> &peek_block_drop_candidates ()
-  {
-    rust_assert (!block_drop_candidates.empty ());
-    return block_drop_candidates.back ();
-  }
-
-  void note_simple_drop_candidate (HirId hirid, location_t locus)
-  {
-    rust_assert (!block_drop_candidates.empty ());
-    block_drop_candidates.back ().emplace_back (hirid, locus);
-  }
-
   void insert_var_decl (HirId id, ::Bvariable *decl)
   {
     compiled_var_decls[id] = decl;
@@ -436,6 +426,7 @@ public:
   }
 
 private:
+  friend class DropBuilder;
   Context ();
 
   Resolver::TypeCheckContext *tyctx;
diff --git a/gcc/rust/backend/rust-compile-drop-builder.cc b/gcc/rust/backend/rust-compile-drop-builder.cc
new file mode 100644
index 000000000000..e0947a787ca4
--- /dev/null
+++ b/gcc/rust/backend/rust-compile-drop-builder.cc
@@ -0,0 +1,42 @@
+// Copyright (C) 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-drop-builder.h"
+#include "rust-compile-context.h"
+
+namespace Rust {
+namespace Compile {
+
+DropBuilder::DropBuilder (Context &ctx) : ctx (ctx) {}
+
+void
+DropBuilder::note_simple_drop_candidate (HirId hirid, location_t locus)
+{
+  rust_assert (!ctx.block_drop_candidates.empty ());
+  ctx.block_drop_candidates.back ().emplace_back (hirid, locus);
+}
+
+std::vector<DropCandidate> &
+DropBuilder::peek_block_drop_candidates ()
+{
+  rust_assert (!ctx.block_drop_candidates.empty ());
+  return ctx.block_drop_candidates.back ();
+}
+
+} // namespace Compile
+} // namespace Rust
\ No newline at end of file
diff --git a/gcc/rust/backend/rust-compile-drop-builder.h b/gcc/rust/backend/rust-compile-drop-builder.h
new file mode 100644
index 000000000000..36e3cdc1e356
--- /dev/null
+++ b/gcc/rust/backend/rust-compile-drop-builder.h
@@ -0,0 +1,44 @@
+// Copyright (C) 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_DROP_BUILDER_H
+#define RUST_COMPILE_DROP_BUILDER_H
+
+#include "rust-compile-drop-candidate.h"
+
+namespace Rust {
+namespace Compile {
+
+class Context;
+
+class DropBuilder
+{
+public:
+  DropBuilder (Context &ctx);
+
+  void note_simple_drop_candidate (HirId hirid, location_t locus);
+  std::vector<DropCandidate> &peek_block_drop_candidates ();
+
+private:
+  Context &ctx;
+};
+
+} // namespace Compile
+} // namespace Rust
+
+#endif // RUST_COMPILE_DROP_BUILDER_H
\ No newline at end of file
diff --git a/gcc/rust/backend/rust-compile-drop.cc b/gcc/rust/backend/rust-compile-drop.cc
index e15eb320dd63..5cb4db0e4798 100644
--- a/gcc/rust/backend/rust-compile-drop.cc
+++ b/gcc/rust/backend/rust-compile-drop.cc
@@ -17,6 +17,7 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-compile-drop.h"
+#include "rust-compile-drop-builder.h"
 #include "rust-compile-base.h"
 #include "rust-compile-context.h"
 #include "rust-compile-implitem.h"
@@ -29,8 +30,10 @@
 namespace Rust {
 namespace Compile {
 
+CompileDrop::CompileDrop (Context *ctx) : ctx (ctx) {}
+
 bool
-CompileDrop::type_has_drop_impl (Context *ctx, TyTy::BaseType *ty)
+CompileDrop::type_has_drop_impl (TyTy::BaseType *ty)
 {
   auto drop_lang_item
     = ctx->get_mappings ().lookup_lang_item (LangItem::Kind::DROP);
@@ -53,8 +56,8 @@ CompileDrop::type_has_drop_impl (Context *ctx, TyTy::BaseType *ty)
 
 // Find the Drop trait, look for the drop method, and build the function call.
 tree
-CompileDrop::compile_drop_call (Context *ctx, Bvariable *var,
-				TyTy::BaseType *ty, location_t locus)
+CompileDrop::compile_drop_call (Bvariable *var, TyTy::BaseType *ty,
+				location_t locus)
 {
   auto drop_lang = ctx->get_mappings ().lookup_lang_item (LangItem::Kind::DROP);
   if (!drop_lang.has_value ())
@@ -88,9 +91,10 @@ CompileDrop::compile_drop_call (Context *ctx, Bvariable *var,
 }
 
 void
-CompileDrop::emit_current_scope_drop_calls (Context *ctx)
+CompileDrop::emit_current_scope_drop_calls ()
 {
-  auto &drop_candidates = ctx->peek_block_drop_candidates ();
+  DropBuilder drop_builder (*ctx);
+  auto &drop_candidates = drop_builder.peek_block_drop_candidates ();
 
   for (auto it = drop_candidates.rbegin (); it != drop_candidates.rend (); ++it)
     {
@@ -103,7 +107,7 @@ CompileDrop::emit_current_scope_drop_calls (Context *ctx)
       ok = ctx->lookup_var_decl (it->hirid, &var);
       rust_assert (ok);
 
-      tree drop_call = CompileDrop::compile_drop_call (ctx, var, ty, it->locus);
+      tree drop_call = compile_drop_call (var, ty, it->locus);
       if (drop_call != NULL_TREE)
 	ctx->add_statement (convert_to_void (drop_call, ICV_STATEMENT));
     }
diff --git a/gcc/rust/backend/rust-compile-drop.h b/gcc/rust/backend/rust-compile-drop.h
index 2a710d6ceb96..55a09c5dd9ed 100644
--- a/gcc/rust/backend/rust-compile-drop.h
+++ b/gcc/rust/backend/rust-compile-drop.h
@@ -27,12 +27,16 @@ namespace Compile {
 class CompileDrop
 {
 public:
-  static bool type_has_drop_impl (Context *ctx, TyTy::BaseType *ty);
+  CompileDrop (Context *ctx);
 
-  static tree compile_drop_call (Context *ctx, Bvariable *var,
-				 TyTy::BaseType *ty, location_t locus);
+  bool type_has_drop_impl (TyTy::BaseType *ty);
 
-  static void emit_current_scope_drop_calls (Context *ctx);
+  void emit_current_scope_drop_calls ();
+
+private:
+  tree compile_drop_call (Bvariable *var, TyTy::BaseType *ty, location_t locus);
+
+  Context *ctx;
 };
 
 } // namespace Compile
diff --git a/gcc/rust/backend/rust-compile-pattern.cc b/gcc/rust/backend/rust-compile-pattern.cc
index 2179916d5c1d..e2f54d7ac624 100644
--- a/gcc/rust/backend/rust-compile-pattern.cc
+++ b/gcc/rust/backend/rust-compile-pattern.cc
@@ -17,6 +17,7 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-compile-pattern.h"
+#include "rust-compile-drop-builder.h"
 #include "print-tree.h"
 #include "rust-compile-drop.h"
 #include "rust-compile-expr.h"
@@ -1356,12 +1357,15 @@ CompilePatternLet::visit (HIR::IdentifierPattern &pattern)
       drop_ty = ref_ty->get_base ();
     }
 
-  if (!CompileDrop::type_has_drop_impl (ctx, drop_ty))
+  if (!CompileDrop (ctx).type_has_drop_impl (drop_ty))
     return;
 
   if (!pattern.has_subpattern () && !pattern.get_is_ref ())
-    ctx->note_simple_drop_candidate (pattern.get_mappings ().get_hirid (),
-				     pattern.get_locus ());
+    {
+      DropBuilder drop_builder (*ctx);
+      drop_builder.note_simple_drop_candidate (
+	pattern.get_mappings ().get_hirid (), pattern.get_locus ());
+    }
   else
     rust_sorry_at (pattern.get_locus (),
 		   "drop trait not supported for subpatterns and ref patterns");