Remove gcc abstraction for expression statement

The gcc abstraction contained a method of turning expressions into
statements which used to contain their own types like Bstatement,
Bexpression this produced awkward interfaces which we no longer require.

This is part of a patch series to introduce the CPP front-end
convert_to_void to port over the support for the nodiscard attribute which
maps nicely over to Rust's must_use attribute.

7 files changed, 29 insertions, 70 deletions

diff --git a/gcc/rust/backend/rust-compile-base.cc b/gcc/rust/backend/rust-compile-base.cc
index 33e4c26..3fc7360 100644
--- a/gcc/rust/backend/rust-compile-base.cc
+++ b/gcc/rust/backend/rust-compile-base.cc
@@ -262,9 +262,7 @@ HIRCompileBase::compile_function_body (Context *ctx, tree fndecl,
       auto compiled_expr = CompileStmt::Compile (s.get (), ctx);
       if (compiled_expr != nullptr)
 	{
-	  tree compiled_stmt
-	    = ctx->get_backend ()->expression_statement (fndecl, compiled_expr);
-	  ctx->add_statement (compiled_stmt);
+	  ctx->add_statement (compiled_expr);
 	}
     }
 
@@ -289,10 +287,8 @@ HIRCompileBase::compile_function_body (Context *ctx, tree fndecl,
 	    }
 	  else
 	    {
-	      tree final_stmt
-		= ctx->get_backend ()->expression_statement (fndecl,
-							     compiled_expr);
-	      ctx->add_statement (final_stmt);
+	      // FIXME can this actually happen?
+	      ctx->add_statement (compiled_expr);
 	    }
 	}
     }
diff --git a/gcc/rust/backend/rust-compile-expr.cc b/gcc/rust/backend/rust-compile-expr.cc
index bf47661..6d50c3f 100644
--- a/gcc/rust/backend/rust-compile-expr.cc
+++ b/gcc/rust/backend/rust-compile-expr.cc
@@ -63,8 +63,6 @@ CompileExpr::visit (HIR::ArithmeticOrLogicalExpr &expr)
 void
 CompileExpr::visit (HIR::CompoundAssignmentExpr &expr)
 {
-  fncontext fn = ctx->peek_fn ();
-
   auto op = expr.get_expr_type ();
   auto lhs = CompileExpr::Compile (expr.get_left_expr ().get (), ctx);
   auto rhs = CompileExpr::Compile (expr.get_right_expr ().get (), ctx);
@@ -82,10 +80,7 @@ CompileExpr::visit (HIR::CompoundAssignmentExpr &expr)
 	= resolve_operator_overload (lang_item_type, expr, lhs, rhs,
 				     expr.get_left_expr ().get (),
 				     expr.get_right_expr ().get ());
-      auto assignment
-	= ctx->get_backend ()->expression_statement (fn.fndecl,
-						     compound_assignment);
-      ctx->add_statement (assignment);
+      ctx->add_statement (compound_assignment);
 
       return;
     }
@@ -94,7 +89,7 @@ CompileExpr::visit (HIR::CompoundAssignmentExpr &expr)
     = ctx->get_backend ()->arithmetic_or_logical_expression (op, lhs, rhs,
 							     expr.get_locus ());
   tree assignment
-    = ctx->get_backend ()->assignment_statement (fn.fndecl, lhs, operator_expr,
+    = ctx->get_backend ()->assignment_statement (lhs, operator_expr,
 						 expr.get_locus ());
   ctx->add_statement (assignment);
 }
@@ -304,8 +299,10 @@ CompileExpr::visit (HIR::MatchExpr &expr)
 	{
 	  tree result_reference
 	    = ctx->get_backend ()->var_expression (tmp, arm_locus);
-	  tree assignment = ctx->get_backend ()->assignment_statement (
-	    fnctx.fndecl, result_reference, kase_expr_tree, arm_locus);
+	  tree assignment
+	    = ctx->get_backend ()->assignment_statement (result_reference,
+							 kase_expr_tree,
+							 arm_locus);
 	  ctx->add_statement (assignment);
 	}
 
diff --git a/gcc/rust/backend/rust-compile-expr.h b/gcc/rust/backend/rust-compile-expr.h
index 3cc51d4..8aeb703 100644
--- a/gcc/rust/backend/rust-compile-expr.h
+++ b/gcc/rust/backend/rust-compile-expr.h
@@ -169,7 +169,6 @@ public:
 
   void visit (HIR::AssignmentExpr &expr) override
   {
-    fncontext fn = ctx->peek_fn ();
     auto lvalue = CompileExpr::Compile (expr.get_lhs (), ctx);
     auto rvalue = CompileExpr::Compile (expr.get_rhs (), ctx);
 
@@ -191,7 +190,7 @@ public:
 		       expr.get_rhs ()->get_locus ());
 
     tree assignment
-      = ctx->get_backend ()->assignment_statement (fn.fndecl, lvalue, rvalue,
+      = ctx->get_backend ()->assignment_statement (lvalue, rvalue,
 						   expr.get_locus ());
 
     ctx->add_statement (assignment);
@@ -594,9 +593,7 @@ public:
       = CompileBlock::compile (expr.get_loop_block ().get (), ctx, nullptr);
     tree loop_expr
       = ctx->get_backend ()->loop_expression (code_block, expr.get_locus ());
-    tree loop_stmt
-      = ctx->get_backend ()->expression_statement (fnctx.fndecl, loop_expr);
-    ctx->add_statement (loop_stmt);
+    ctx->add_statement (loop_expr);
 
     if (tmp != NULL)
       {
@@ -645,9 +642,7 @@ public:
       = CompileExpr::Compile (expr.get_predicate_expr ().get (), ctx);
     tree exit_expr
       = ctx->get_backend ()->exit_expression (condition, expr.get_locus ());
-    tree break_stmt
-      = ctx->get_backend ()->expression_statement (fnctx.fndecl, exit_expr);
-    ctx->add_statement (break_stmt);
+    ctx->add_statement (exit_expr);
 
     tree code_block_stmt
       = CompileBlock::compile (expr.get_loop_block ().get (), ctx, nullptr);
@@ -659,14 +654,11 @@ public:
 
     tree loop_expr
       = ctx->get_backend ()->loop_expression (loop_block, expr.get_locus ());
-    tree loop_stmt
-      = ctx->get_backend ()->expression_statement (fnctx.fndecl, loop_expr);
-    ctx->add_statement (loop_stmt);
+    ctx->add_statement (loop_expr);
   }
 
   void visit (HIR::BreakExpr &expr) override
   {
-    fncontext fnctx = ctx->peek_fn ();
     if (expr.has_break_expr ())
       {
 	tree compiled_expr
@@ -676,8 +668,10 @@ public:
 	tree result_reference = ctx->get_backend ()->var_expression (
 	  loop_result_holder, expr.get_expr ()->get_locus ());
 
-	tree assignment = ctx->get_backend ()->assignment_statement (
-	  fnctx.fndecl, result_reference, compiled_expr, expr.get_locus ());
+	tree assignment
+	  = ctx->get_backend ()->assignment_statement (result_reference,
+						       compiled_expr,
+						       expr.get_locus ());
 	ctx->add_statement (assignment);
       }
 
@@ -721,9 +715,7 @@ public:
 	tree exit_expr = ctx->get_backend ()->exit_expression (
 	  ctx->get_backend ()->boolean_constant_expression (true),
 	  expr.get_locus ());
-	tree break_stmt
-	  = ctx->get_backend ()->expression_statement (fnctx.fndecl, exit_expr);
-	ctx->add_statement (break_stmt);
+	ctx->add_statement (exit_expr);
       }
   }
 
@@ -761,9 +753,7 @@ public:
 	  }
       }
 
-    tree goto_label
-      = ctx->get_backend ()->goto_statement (label, expr.get_locus ());
-    ctx->add_statement (goto_label);
+    translated = ctx->get_backend ()->goto_statement (label, expr.get_locus ());
   }
 
   void visit (HIR::BorrowExpr &expr) override;
diff --git a/gcc/rust/backend/rust-compile-stmt.h b/gcc/rust/backend/rust-compile-stmt.h
index 2dfb520..0f69fb0 100644
--- a/gcc/rust/backend/rust-compile-stmt.h
+++ b/gcc/rust/backend/rust-compile-stmt.h
@@ -90,9 +90,8 @@ public:
     auto fnctx = ctx->peek_fn ();
     if (ty->is_unit ())
       {
-	tree expr_stmt
-	  = ctx->get_backend ()->expression_statement (fnctx.fndecl, init);
-	ctx->add_statement (expr_stmt);
+	// FIXME this feels wrong
+	ctx->add_statement (init);
       }
     else
       {
diff --git a/gcc/rust/backend/rust-compile.cc b/gcc/rust/backend/rust-compile.cc
index fcbfc05..6aec050 100644
--- a/gcc/rust/backend/rust-compile.cc
+++ b/gcc/rust/backend/rust-compile.cc
@@ -82,10 +82,7 @@ CompileBlock::visit (HIR::BlockExpr &expr)
       auto compiled_expr = CompileStmt::Compile (s.get (), ctx);
       if (compiled_expr != nullptr)
 	{
-	  tree compiled_stmt
-	    = ctx->get_backend ()->expression_statement (fnctx.fndecl,
-							 compiled_expr);
-	  ctx->add_statement (compiled_stmt);
+	  ctx->add_statement (compiled_expr);
 	}
     }
 
@@ -98,10 +95,7 @@ CompileBlock::visit (HIR::BlockExpr &expr)
 	{
 	  if (result == nullptr)
 	    {
-	      tree final_stmt
-		= ctx->get_backend ()->expression_statement (fnctx.fndecl,
-							     compiled_expr);
-	      ctx->add_statement (final_stmt);
+	      ctx->add_statement (compiled_expr);
 	    }
 	  else
 	    {
@@ -109,8 +103,7 @@ CompileBlock::visit (HIR::BlockExpr &expr)
 		result, expr.get_final_expr ()->get_locus ());
 
 	      tree assignment
-		= ctx->get_backend ()->assignment_statement (fnctx.fndecl,
-							     result_reference,
+		= ctx->get_backend ()->assignment_statement (result_reference,
 							     compiled_expr,
 							     expr.get_locus ());
 	      ctx->add_statement (assignment);
diff --git a/gcc/rust/rust-backend.h b/gcc/rust/rust-backend.h
index fe809c9..fca09b2 100644
--- a/gcc/rust/rust-backend.h
+++ b/gcc/rust/rust-backend.h
@@ -292,16 +292,13 @@ public:
 
   // Statements.
 
-  // Create an expression statement within the specified function.
-  virtual tree expression_statement (tree, tree) = 0;
-
   // Create a variable initialization statement in the specified
   // function.  This initializes a local variable at the point in the
   // program flow where it is declared.
   virtual tree init_statement (tree, Bvariable *var, tree init) = 0;
 
   // Create an assignment statement within the specified function.
-  virtual tree assignment_statement (tree, tree lhs, tree rhs, Location) = 0;
+  virtual tree assignment_statement (tree lhs, tree rhs, Location) = 0;
 
   // Create a return statement, passing the representation of the
   // function and the list of values to return.
diff --git a/gcc/rust/rust-gcc.cc b/gcc/rust/rust-gcc.cc
index 812fd55..dfdfe8a5 100644
--- a/gcc/rust/rust-gcc.cc
+++ b/gcc/rust/rust-gcc.cc
@@ -249,11 +249,9 @@ public:
 
   // Statements.
 
-  tree expression_statement (tree, tree);
-
   tree init_statement (tree, Bvariable *var, tree init);
 
-  tree assignment_statement (tree, tree lhs, tree rhs, Location);
+  tree assignment_statement (tree lhs, tree rhs, Location);
 
   tree return_statement (tree, const std::vector<tree> &, Location);
 
@@ -1837,14 +1835,6 @@ Gcc_backend::call_expression (tree, // containing fcn for call
   return ret;
 }
 
-// An expression as a statement.
-
-tree
-Gcc_backend::expression_statement (tree, tree expr)
-{
-  return expr;
-}
-
 // Variable initialization.
 
 tree
@@ -1880,8 +1870,7 @@ Gcc_backend::init_statement (tree, Bvariable *var, tree init_tree)
 // Assignment.
 
 tree
-Gcc_backend::assignment_statement (tree bfn, tree lhs, tree rhs,
-				   Location location)
+Gcc_backend::assignment_statement (tree lhs, tree rhs, Location location)
 {
   if (lhs == error_mark_node || rhs == error_mark_node)
     return error_mark_node;
@@ -1896,8 +1885,7 @@ Gcc_backend::assignment_statement (tree bfn, tree lhs, tree rhs,
       || int_size_in_bytes (TREE_TYPE (lhs)) == 0
       || TREE_TYPE (rhs) == void_type_node
       || int_size_in_bytes (TREE_TYPE (rhs)) == 0)
-    return this->compound_statement (this->expression_statement (bfn, lhs),
-				     this->expression_statement (bfn, rhs));
+    return this->compound_statement (lhs, rhs);
 
   rhs = this->convert_tree (TREE_TYPE (lhs), rhs, location);
 
@@ -2527,8 +2515,7 @@ Gcc_backend::temporary_variable (tree fndecl, tree bind_tree, tree type_tree,
   if (init_tree != NULL_TREE
       && (this->type_size (type_tree) == 0
 	  || TREE_TYPE (init_tree) == void_type_node))
-    *pstatement = this->compound_statement (
-      this->expression_statement (fndecl, init_tree), *pstatement);
+    *pstatement = this->compound_statement (init_tree, *pstatement);
 
   return new Bvariable (var);
 }